Current Sensor

Abstract

The rate of change of current sensor includes two measurement coils arranged such that the turns of the first and second measurement coils are interleaved. The rate of change of current sensor further includes two return coils arranged to travel in opposite directions to the measurement coils. The coils form a loop and travel substantially around the target measurement conductor. This ensures that both of the two measurement coils experience the same capacitive coupling from an external conductor that is not the target of the measurement operation. Furthermore, the two measurement coils are arranged such that the first coil and the second coil are, on average, the same distance to the current carrying conductor of interest.

Description

[Technical Field]

[0001] The present disclosure relates to current sensors, and more particularly to differential current sensors. [Background technology]

[0002] Current sensors detect and measure electrical current passing through a conductor. They are used in many different applications, for example, to provide accurate current measurements in utility meters.

[0003] One type of current sensor uses a shunt resistor in series with a current-carrying conductor. The voltage drop across the resistor can be measured, and through knowledge of the shunt's resistance, the current through the resistor can be calculated. However, higher currents can increase the temperature of the shunt, changing its resistance and thus providing inaccurate current measurements. Furthermore, because the shunt is located directly in the measured current path, isolation circuitry may be required between the shunt and the sensitive measurement and processing electronics.

[0004] Another type of current sensor uses an electromagnetic transducer to detect changes in the magnetic field generated by a current-carrying conductor. These field current rate-of-change sensors, e.g., Rogowski coils, do not require any physical connection to the current-carrying conductor and are therefore isolated from the current-carrying conductor without the need for any additional insulating components.

[0005] However, because rate-of-change sensors rely on magnetic field coupling, they are susceptible to interference generated by other changing magnetic fields around the sensor. For example, a second current-carrying conductor that is not the target of the measurement operation may pass close to the Rogowski coil. Some of the magnetic field generated by this second current-carrying conductor may be coupled into the Rogowski coil, affecting the coil's measurement accuracy.

[0006] A compensation wire, compensation conductor, or return wire, which starts at the end of the coil and returns so that both terminals of the Rogowski coil are at the same end, can be used to cancel the effects of external transverse magnetic fields. The compensation conductor forms a loop opposite the helical measuring coil, canceling the effects of the external field. However, even with a compensation conductor to help eliminate the external magnetic field, the Rogowski coil can still be subject to external interference due to capacitive coupling of conductors into the coil.

[0007] The main challenge of the Rogowski coil is its sensitivity to capacitive or capacitive coupling from nearby AC conductors. For example, in utility meters, capacitive coupling can be prevalent due to the positioning of the AC busbars that carry the current being measured, but also carry the phase voltage, typically 240V. With capacitive coupling, the busbar voltage couples to the coil through stray capacitance, and just a small stray capacitance can result in an erroneous signal from the sensor due to the high voltage on the conductor.

[0008] The sensitivity of this coupling to changes in the relative position of the coil with respect to the conductor and to the environment is also important to consider and algorithmically nullify, which is often practically impossible due to fluctuations and drift, making it necessary to reduce sensitivity to capacitive coupling.

[0009] To reduce the effects of external electrostatic interference, shielding may be provided around the measurement coil, however, shielding the coil not only increases the size of the measurement device but may also result in excessive manufacturing requirements. Summary of the Invention [Means for solving the problem]

[0010] There is a need to provide an improved current measurement means that reduces the effect of external fields on measurement accuracy and / or reduces the effect of capacitive coupling to the coil under all conditions of position of the conductor under test.

[0011] The present disclosure provides an improved rate-of-change sensor, e.g., a Rogowski coil, designed to reduce the effects of electrostatic noise coupling. The rate-of-change sensor, arranged to measure current in a current-carrying conductor, includes two measurement coils that may be formed on a printed circuit board. The measurement coils may substantially surround the current-carrying conductor, which may reduce sensitivity to the position of the current-carrying conductor and may provide common-mode coupling of noise fields so that each measurement coil receives the same amount of electrostatic coupling. This common electrostatic coupling may then be easily canceled or eliminated.

[0012] In a first aspect of the present disclosure, a rate of change sensor is provided, the rate of change sensor comprising: a path for at least one current carrying conductor; a first measurement coil, the first measurement coil traveling around the path in a first circumferential direction, the first measurement coil having a first end and a second end; and a first return coil, the first end of the first return coil being coupled to the second end of the first measurement coil, the first return coil traveling in a direction opposite the first circumferential direction. The measuring coil includes a first return coil that travels around the path in a circumferential direction; a second measuring coil that travels around the path in a second circumferential direction, the second measuring coil having a first end and a second end; and a second return coil that has a first end and a second end, the first end of the second return coil being coupled to the second end of the second measuring coil, the second return coil traveling around the path in a circumferential direction opposite to the second circumferential direction.

[0013] The first circumferential direction and the second circumferential direction may be the same circumferential direction, or the first circumferential direction may be the opposite circumferential direction.

[0014] The first measurement coil, the second measurement coil, the first return coil, and the second return coil may travel to substantially encircle the path.

[0015] The rate of change of current sensor may be a differential rate of change of current sensor providing a differential output signal, wherein a first end of the first measurement coil provides a first signal of the differential output signal, a first end of the second measurement coil provides a second signal of the differential output signal, and a second end of the first return coil is coupled to a second end of the second return coil and further coupled to a common reference signal.

[0016] The first measurement coil may comprise a first measurement coil segment and a second measurement coil segment, the first return coil may comprise a first return coil segment and a second return coil segment, the first measurement coil segment may be coupled to the first return coil segment, the second measurement coil segment may be coupled to the second return coil segment, the second measurement coil may comprise a third measurement coil segment and a fourth measurement coil segment, the second return coil may comprise a third return coil segment and a fourth return coil segment, the third measurement coil segment is coupled to the third return coil segment, and the fourth measurement coil segment is coupled to the fourth return coil segment, each coil segment progressing substantially 180° circumferentially around the path.

[0017] An electrostatic shield may be provided around the path, between the path and the measurement coil.

[0018] The first measurement coil and the second measurement coil may be formed on an inner layer of the substrate, and the electrostatic shield may be formed on an outer layer of the substrate.

[0019] The current change rate sensor may further comprise a first connecting conductor and a second connecting conductor, wherein a first end of the first measuring coil is suitable for coupling to a first node of the current measurement circuit using the first connecting conductor and a first end of the second measuring coil is suitable for coupling to a second node of the current measurement circuit using the second connecting conductor, and the first connecting conductor and the second connecting conductor are arranged using a twisted pair arrangement.

[0020] In a second aspect of the present disclosure, a rate of change sensor is provided, the rate of change sensor comprising: a substrate including a path for at least one current-carrying conductor; a first measurement coil formed on the substrate, the first measurement coil progressing around and substantially surrounding the path in a first circumferential direction, the first measurement coil having a first end and a second end; and a first return coil formed on the substrate, the first return coil having a first end and a second end, the first end of the first return coil being coupled to the second end of the first measurement coil, the first return coil progressing around and substantially surrounding the path in a circumferential direction opposite the first circumferential direction.

[0021] The first return coil may be arranged to follow the same circumferentially extending path as the first measurement coil.

[0022] The rate of change of current sensor may further comprise a path for the current carrying conductor, the path passing through the center of the first measurement coil and the first return coil.

[0023] In a third aspect of the present disclosure, a current change rate sensor is provided, the current change rate sensor comprising: a substrate including a path for at least one current carrying conductor; a first measurement coil formed on the substrate, the first measurement coil progressing around the path in a first circumferential direction; and a second measurement coil formed on the substrate, the second measurement coil progressing around the path in a second circumferential direction.

[0024] The first measurement coil and the second measurement coil may be interleaved on the substrate such that they both have the same average capacitive coupling to the current-carrying conductor under measurement, the current-carrying conductor following the path.

[0025] The first measurement coil and the second measurement coil may be interleaved in a radial plane perpendicular to the surface of the substrate so that the first turn of the first measurement coil and the first turn of the second measurement coil are located in the same radial plane perpendicular to the surface of the substrate.

[0026] The first turn of the first measurement coil may be formed on the first and third layers of the substrate, and the first turn of the second measurement coil may be formed on the second and fourth layers of the substrate.

[0027] The first measurement coil and the second measurement coil may be interleaved such that a first turn of the first measurement coil is located in a first radial plane perpendicular to the surface of the substrate and a first turn of the second measurement coil is located in a second radial plane perpendicular to the surface of the substrate, and the first radial plane and the second radial plane are adjacent to each other in the circumferential direction.

[0028] The current change rate sensor may further include a first compensation conductor formed on the substrate and coupled to the first measurement coil, the first compensation conductor progressing around a path in a circumferential direction opposite to the first circumferential direction, and a second compensation conductor formed on the substrate and coupled to the second measurement coil, the second compensation conductor progressing around a path in a circumferential direction opposite to the second circumferential direction.

[0029] The first circumferential direction and the second circumferential direction may be the same circumferential direction.

[0030] The first measurement coil may travel an integer multiple of 360° around the path, and the second measurement coil may travel the same integer multiple of 360° around the path.

[0031] The current change rate sensor may further comprise a twisted pair arrangement formed on the substrate, the twisted pair comprising a first connecting conductor and a second connecting conductor, the first connecting conductor coupled to the first measurement coil and a first node, the second connecting conductor coupled to the second measurement coil and a second node, the first connecting conductor and the second conductor arranged on the substrate to alternately cross each other, and the first and second nodes being outputs from the current change rate sensor.

[0032] In a fourth aspect of the present disclosure, a rate of change sensor is provided comprising: a substrate including a first layer and a second layer, the substrate including a path for at least one current-carrying conductor; a first plurality of measurement conductors formed on the first layer of the substrate; a second plurality of measurement conductors formed on the second layer of the substrate; and a first plurality of vias formed in the substrate, the first plurality of vias being arranged to connect ends of the first plurality of measurement conductors with respective ends of the second measurement conductors to form a first current measurement coil progressing around the path in a first circumferential direction and a second current measurement coil progressing around the path in a second circumferential direction, wherein each measurement conductor on the first layer of the substrate is aligned with a respective measurement conductor on the second layer of the substrate in a radial plane perpendicular to a surface of the substrate.

[0033] The first measurement coil and the second measurement coil may be interleaved such that a first turn of the first measurement coil comprises a measurement conductor of the first plurality of measurement conductors and a measurement conductor of the second plurality of measurement conductors located in a first radial plane, and such that a first turn of the second measurement coil comprises a measurement conductor of the first plurality of measurement conductors and a measurement conductor of the second plurality of measurement conductors located in a second radial plane.

[0034] The first circumferential direction and the second circumferential direction may be the same circumferential direction.

[0035] The first circumferential direction and the second circumferential direction may be opposite circumferential directions.

[0036] The current change rate sensor may further comprise a third plurality of measurement conductors formed on the first layer of the substrate, a fourth plurality of measurement conductors formed on the second layer of the substrate, and a second plurality of vias arranged to connect ends of the third plurality of measurement conductors to respective ends of the fourth plurality of measurement conductors to form a first return coil and a second return coil, a first end of the first return coil coupled to a second end of the first measurement coil, the first return coil traveling around the path in a direction opposite to the first circumferential direction, the first end of the second return coil coupled to a second end of the second measurement coil, the second return coil traveling around the path in a direction opposite to the second circumferential direction, the first end of the first measurement coil suitable for coupling to a measurement circuit, and the first end of the second measurement coil suitable for coupling to a measurement circuit.

[0037] The first measurement coil, the first return coil, the second measurement coil, and the second return coil may be interleaved such that a first turn of the first return coil comprises a measurement conductor of the third plurality of measurement conductors and a measurement conductor of the fourth plurality of measurement conductors located in a third radial plane, and a first turn of the second return coil comprises a measurement conductor of the third plurality of measurement conductors and a measurement conductor of the fourth plurality of measurement conductors located in a fourth radial plane, and the first radial plane, the third radial plane, the second radial plane, and the fourth radial plane are arranged circumferentially adjacent in that order.

[0038] A first end of the first measurement coil may be suitable for coupling to a measurement circuit, and a first end of the second measurement coil may be suitable for coupling to a measurement circuit, the first measurement circuit being configured to determine a current passing through the current-carrying conductor under measurement.

[0039] The current change rate sensor may further comprise a first connecting conductor for connecting a first end of the first measurement coil to a measurement circuit, and a second connecting conductor for connecting a first end of the second measurement coil to the measurement circuit, the first connecting conductor and the second connecting conductor being arranged to form a twisted pair arrangement on the substrate.

[0040] The first measurement coil and the second measurement coil can be coupled to the measurement circuit using a first layer and a measurement layer of the substrate, and a dielectric distance between the first layer and the measurement layer is smaller than a dielectric distance between the first layer and the second layer.

[0041] The substrate may include more than two layers, wherein a first layer of the substrate and a second layer of the substrate are internal layers of the substrate such that the current measurement coil is located on the internal layer of the substrate, and the substrate includes a third layer and a fourth layer, the third layer and the fourth layer being located external to the first and second layers of the substrate, and the third and fourth layers including a shield configured to reduce electrostatic coupling to the current measurement coil.

[0042] The vias may be through-holes in the substrate, which may be plated to provide shielding for the through-holes.

[0043] The first plurality of vias may comprise a first circle of vias at inner ends of measurement conductors of the first and second plurality of measurement conductors, the vias of the first circle of vias being alternately used to form first and second measurement coils by connecting measurement conductors of the first and second plurality of measurement conductors, and the second plurality of vias may comprise a second circle of vias concentric with the first circle of vias at inner ends of measurement conductors of the third and fourth plurality of measurement conductors, the vias of the second circle of vias being alternately used to form first and second return coils by connecting measurement conductors of the third and fourth plurality of measurement conductors, the first circle and second circle being concentric circles.

[0044] The current change rate sensor may further include a first compensation conductor coupled to the first measurement coil, the first compensation conductor progressing around the path in a circumferential direction opposite to the first circumferential direction, and a second compensation conductor coupled to the second measurement coil, the second compensation conductor progressing around the path in a circumferential direction opposite to the second circumferential direction.

[0045] Current carrying conductors may be provided on the substrate and routed on an outer layer of the substrate and then routed through the center of the first current measuring coil and the second current measuring coil.

[0046] In a fifth aspect of the present disclosure, there is provided a rate of change of current sensor, the rate of change of current sensor comprising: a substrate, the substrate including a first layer, a second layer, a third layer, and a fourth layer, the substrate including a path for at least one current-carrying conductor; a first plurality of measurement conductors formed on the first layer of the substrate; a second plurality of measurement conductors formed on the second layer of the substrate; a third plurality of measurement conductors formed on the third layer of the substrate; a fourth plurality of measurement conductors formed on the fourth layer of the substrate; and a first plurality of vias formed in the substrate, the first plurality of vias being arranged around the path in a first circumferential direction. and a first plurality of vias arranged to connect respective ends of the first, second, third, and fourth plurality of measurement conductors to form a first current measurement coil traveling in a first circumferential direction and a second current measurement coil traveling around the path in a second circumferential direction, wherein each measurement conductor on the first layer of the substrate is aligned with each measurement conductor on the second, third, and fourth layers of the substrate such that the respective measurement conductors form a radial plane substantially perpendicular to the surface of the substrate.

[0047] The first measurement coil and the second measurement coil may be interleaved such that a first turn of the first measurement coil comprises a measurement conductor of the first plurality of measurement conductors and a measurement conductor of the third plurality of measurement conductors located in a first radial plane, and such that a first turn of the second measurement coil comprises a measurement conductor of the second plurality of measurement conductors and a measurement conductor of the fourth plurality of measurement conductors located in the first radial plane.

[0048] The rate of change of current sensor may further include a fifth plurality of measurement conductors formed on a first layer of the substrate, a sixth plurality of measurement conductors formed on a second layer of the substrate, a seventh plurality of measurement conductors formed on a third layer of the substrate, an eighth plurality of measurement conductors formed on a fourth layer of the substrate, and a second plurality of vias formed on the substrate, the second plurality of vias connecting respective ends of the fifth plurality of measurement conductors, the sixth plurality of measurement conductors, the seventh plurality of measurement conductors, and the eighth plurality of measurement conductors to form a first return coil and a second return coil. wherein a first end of the first return coil is coupled to a second end of the first measurement coil, the first return coil traveling around the path in a direction opposite to the first circumferential direction, a first end of the second return coil is coupled to a second end of the second measurement coil, the second return coil traveling around the path in a direction opposite to the second circumferential direction, the first end of the first measurement coil is suitable for coupling to a measurement circuit, and the first end of the second measurement coil is suitable for coupling to a measurement circuit.

[0049] The first return coil and the second return coil may be interleaved such that the first turn of the first return coil comprises a measurement conductor of the fifth plurality of measurement conductors and a measurement conductor of the seventh plurality of measurement conductors located in a second radial plane, and the first turn of the second return coil comprises a measurement conductor of the sixth plurality of measurement conductors and a measurement conductor of the eighth plurality of measurement conductors located in the second radial plane, the second radial plane being circumferentially adjacent to the first radial plane.

[0050] The current change rate sensor may further include a first compensation conductor coupled to the first measurement coil, the first compensation conductor progressing around the path in a circumferential direction opposite to the first circumferential direction, and a second compensation conductor coupled to the second measurement coil, the second compensation conductor progressing around the path in a circumferential direction opposite to the second circumferential direction.

[0051] In a sixth aspect of the present disclosure, a current change rate sensor is provided, comprising: a substrate, the substrate including a path for a current carrying conductor; a first measurement coil formed on the substrate, the first measurement coil positioned to surround the path in a first plane of the substrate; and a second measurement coil formed on the substrate, the second measurement coil positioned to surround the path in the first plane of the substrate, the first measurement coil being interleaved with the second measurement coil in a circumferential direction around the path. [Brief explanation of the drawings]

[0052] Aspects of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which like reference numerals refer to like parts and in which: [Figure 1] 1 is a schematic representation of a Rogowski coil. [Figure 2a] 1 is a schematic representation of a Rogowski coil with a compensation or return conductor. [Figure 2b] 1 is a schematic representation of a split or differential Rogowski coil with compensation or return conductors. [Figure 3] 1 is a schematic representation of the parasitic impedance that exists between a rate of change of current sensor and the current-carrying conductor under measurement. [Figure 4] 4 is a simplified schematic representation of the parasitic impedances of FIG. 3. [Figure 5a] FIG. 1 is a schematic diagram of a coil with a rate of change of current sensor, with the measurement coils wound in opposite directions. [Figure 5b] FIG. 10 is a schematic diagram of another coil of the rate of change of current sensor, where the measurement coil is wound in the opposite direction. [Figure 5c] FIG. 5B is a schematic diagram of a rate of change of current sensor including the coil of FIGS. 5a and 5b. [Figure 6a] FIG. 5b is a simplified circuit diagram of the coil of FIG. 5a. [Figure 6b] FIG. 5c is a simplified circuit diagram of the coil of FIG. 5b. [Figure 6c] FIG. 5c is a simplified circuit diagram of FIG. 5c including the coils of FIGS. 6a and 6b. [Figure 7a] FIG. 1 is a schematic diagram of a coil with a rate of change of current sensor, with the measurement coils wound in the same direction. [Figure 7b] FIG. 10 is a schematic diagram of another coil of the rate of change of current sensor, with the measurement coils wound in the same direction. [Figure 7c] FIG. 7B is a schematic diagram of a rate of change of current sensor including the coil of FIGS. 7a and 7b. [Figure 8a] FIG. 7b is a simplified circuit diagram of the coil of FIG. 7a. [Figure 8b] FIG. 7b is a simplified circuit diagram of the coil of FIG. [Figure 8c] FIG. 7c is a simplified circuit diagram of FIG. 7c including the coils of FIGS. 8a and 8b. [Figure 9a] FIG. 1 is a schematic diagram of a coil with a rate of change of current sensor provided with a return coil. [Figure 9b] FIG. 10 is a schematic diagram of another coil of the rate of change of current sensor, provided with a return coil. [Figure 9c] FIG. 9C is a schematic diagram of a rate of change of current sensor including the coil of FIGS. 9a and 9b. [Figure 10a] FIG. 9b is a simplified circuit diagram of the coil of FIG. 9a. [Figure 10b] FIG. 9c is a simplified circuit diagram of the coil of FIG. 9b. [Figure 10c] FIG. 9c is a simplified circuit diagram of FIG. 9c including the coils of FIGS. 10a and 10b. [Figure 11] 5a-5c are four-layer current change rate sensor schematics. FIG. [Figure 12] FIG. 12 is a three-dimensional view of the four-layer current change rate sensor of FIG. 11. [Figure 13a]12 is a subsection of the four-layer rate of change of current sensor of FIG. 11 showing only the conductors associated with the first measurement coil. [Figure 13b] 12 is a subsection of the four-layer rate of change of current sensor of FIG. 11 showing only the conductors associated with the second measurement coil. [Figure 13c] 12 is a subsection of the four-layer rate of change of current sensor of FIG. 11 showing conductors associated with both the first and second measurement coils. [Figure 14a] 12 is a schematic representation of a first coil of the current sensor of FIG. 11; [Figure 14b] 12 is a schematic representation of a second coil of the current sensor of FIG. 11. [Figure 14c] 14a and 14b show schematic representations of variations of the current sensor according to FIG. 11, including both the first and second coils of FIGS. 14a and 14b; [Figure 15a] 5b is a schematic representation of a two-layer implementation of the first coil of the current sensor of FIG. 5a; [Figure 15b] 5b is a schematic representation of a two-layer representation of the second coil of the current sensor of FIG. [Figure 15c] 15a and 15b. FIG. 15c is a schematic representation of a two-layer implementation of the rate of change of current sensor according to FIG. 5c, including both the first and second coils of FIGS. 15a and 15b. [Figure 16a] 7b is a schematic representation of the first coil and the second coil of the current sensor of FIG. 7a in a two-layer implementation; [Figure 16b] 7b is a schematic representation of the second coil of the current sensor of the two-layer implementation of FIG. [Figure 16c] 16a and 16b. FIG. 16b is a schematic representation of a rate of change of current sensor according to FIG. 7c, including both the first and second coils of FIGS. [Figure 17] FIG. 9B is a plan view of the two-layer current change rate sensor according to FIGS. 9a to 9c. [Figure 18] FIG. 18 is a plan view of the measurement coil of FIG. 17. [Figure 19] FIG. 18 is a plan view of the return coil of FIG. 17. [Figure 20a] 19 is a schematic representation of the measurement coil of FIG. 18. [Figure 20b]20 is a schematic representation of the return coil of FIG. 19. [Figure 20c] 20a and 20b are schematic representations of the measurement coil and return coil of FIG. 20b. [Figure 21] FIG. 18 is a plan view of the via arrangement on the inner circumference of the measurement conductor of FIG. 17. [Figure 22] FIG. 18 is a plan view of the twisted pair connection from the rate of change of current sensor of FIG. 17. [Figure 23] FIG. 18 is a plan view of an alternative connection from the rate of change of current sensor of FIG. 17. [Figure 24] 18 is a representation of the rate of change of current sensor of FIG. 17 including an additional electrostatic shield. [Figure 25] 1 is an alternative implementation of a rate of change of current sensor constructed from multiple coil segments. [Figure 26] FIG. 26 is a diagram of a measurement circuit and the connection of the rate of change of current sensor of FIG. 25 to the measurement circuit. DETAILED DESCRIPTION OF THE INVENTION

[0053] Known Rogowski coils can be negatively affected by both capacitively coupled noise and magnetically coupled noise, e.g., noise from other current-carrying conductors near the Rogowski coil. Capacitively coupled noise into a differential Rogowski coil can be different for each differential coil, meaning it cannot be easily canceled or removed. Furthermore, solutions to remove magnetically coupled noise, e.g., using compensation or return conductors, can be difficult to implement in printed circuit board implementations of the Rogowski coil.

[0054] 1 is a diagram of a known Rogowski coil. A measurement coil 102 is positioned so that the current-carrying conductor 100 passes through it to measure the current I(t) flowing through the current-carrying conductor 100. The measurement coil 102 is wound as a helix, such that the loops or turns of the helix enclose a cross-sectional area 104, A. The current-carrying conductor 100 can be, for example, a bus bar.

[0055] As the current I(t) in the current-carrying conductor 100 changes, so does the field generated by the current. Positioning the measurement coil induces a voltage in the measurement coil 102 that is proportional to the rate of change of the current dI / dt. Thus, integrating the measurement coil output v(t) provides a value proportional to the current. Each turn or loop of the coil defines a measurement area 104 in a plane perpendicular to the direction of travel of the current-carrying conductor.

[0056] However, the voltage induced in the measurement coil may be affected by external conductors that the user is not intending to measure. As well as the loops of the coil forming multiple measurement zones 104, the course of the coil itself also effectively forms a single loop in the plane of the current-carrying conductors. To address the coupling of magnetic fields into this single loop, compensation conductors may be included.

[0057] A Rogowski coil including a compensation conductor is shown in Figure 2a. A measurement coil 200 is formed as a nearly complete loop with an external circuit connection node 204 at one end of the coil. The other end of the coil is attached to a compensation conductor 202 at node 206. The compensation conductor 202 returns to a second external circuit connection node 208 along the loop path formed by the measurement coil 200. In some instances, the compensation conductor may be referred to as a return conductor or return wire.

[0058] The compensation conductor 202 forms a single turn loop in the opposite circumferential direction to the measurement coil 200, such that the compensation conductor 202 returns along or through the loop path formed by the measurement coil 200. This effectively results in the magnetic coupling in the compensation conductor 202 being opposite to the magnetic coupling in the large single turn area of ​​the measurement coil 200.

[0059] 2b shows a differential coil (or split / segmented coil) that can be used to reduce the effects of capacitive coupling. The Rogowski coil is provided as two half coils 210, 212, with each half coil advanced by approximately 180°. The first half coil 210 may be referred to as coil P, and the second half coil 212 may be referred to as coil N.

[0060] A first end of first half coil 210 is coupled to connection node 216. A second end of first half coil 210 is coupled to a first end of compensation conductor 214 at connection node 218. A second end of compensation conductor 214 is coupled to a first end of second half coil 212 at connection node 220. A second end of second half coil 212 is coupled to connection node 222. Nodes 218 or 220 may be connected to ground or a common reference.

[0061] Each half coil is designed to sense current differentially, but capacitive coupling is common mode. Capacitive coupling can be eliminated by using a differential amplifier connected to the coil outputs. However, any difference in the amount of capacitive coupling between the two coil halves can lead to errors in the differential amplifier output. For example, any offset in the position of current-carrying conductor 100 (a current-carrying conductor not centered between the two half coils) can cause the capacitive coupling in coil P210 to differ from the capacitive coupling in coil N212. Capacitive coupling can be from an AC voltage present on the current-carrying conductor or from a nearby conductor with an AC voltage (dv / dt) signal.

[0062] Figure 3 shows an example of the parasitic capacitance that exists between a current carrying conductor, i.e., a busbar, and a turn of a current measuring coil. The coil P304 has several turns, or loops, POS 巻き1 ~POS 巻きN Coil N306 consists of several turns, or loops, NEG 巻き1 ~NEG 巻きNDue to the physical proximity of the measurement coil and the current-carrying conductors, parasitic capacitance exists between the current-carrying conductor 302 and the measurement coils 304, 306. If an AC voltage is present on the current-carrying conductors, for example, AC voltage 308, unwanted voltages can be injected into the current-measurement coils through the parasitic capacitance.

[0063] Each turn of coil P, POS 巻き1 ~POS 巻きN are the respective parasitic resistances, R P1 ~R PN , and their respective parasitic capacitances, C P1 ~C PN The parasitic resistance is caused by the resistance of the measurement coil or, if the measurement coil is mounted on a PCB, the resistance of the copper traces that make up the measurement coil. As mentioned above, the parasitic capacitance is caused by the proximity of the measurement coil to the current-carrying conductor or busbar 302. Similarly, the parasitic capacitance of the coils N, NEG 巻き1 ~NEG's 巻きN Each winding of has its own parasitic resistance, R N1 ~R NN , and their respective parasitic capacitances, C N1 ~C NN Includes.

[0064] Figure 4 shows a simplified equivalent electrostatic model of the parasitic capacitance between the current-carrying conductor and the measurement coil. P1 ~C PN and C N1 ~C NN is C P represents the total parasitic capacitance between the coil P 304 and the current-carrying conductor 302, and C N and C respectively, so that C represents the total parasitic capacitance between the coil N 306 and the current-carrying conductor 302. P and C N Resistance, R P1 ~R PN and R N1 ~R NN is R P represents the total resistance of the coil P304, and R N represents the total resistance of coil N, respectively. P and R NThese parasitic impedances are the Thévenin impedances at the frequency of interest.

[0065] The noise (spurious signals from the voltages on the conductors) coupled into the coils P304 and N306 can be determined by the impedance divider between the corresponding parasitic components. P ≠C N or R P ≠R N Whenever the AC voltage 308 is applied, the noise induced in coil P 304 and coil N 306 will be different. Any offset such that the current carrying conductor or bus bar 302 is not centered on coil P 304 and coil N 306 will result in a different parasitic capacitance C P and C N This can cause differences in the capacitance of the coils. This results in different couplings of the measurement coils. Similarly, any differences in the parasitic resistance of the coils can result in coupling to different coils. Capacitive coupling can be from AC voltages present on current-carrying conductors or from nearby conductors with AC voltage (dv / dt) signals.

[0066] Providing a differential coil that includes two complete coils, i.e., coils that each travel 360° or approximately 360°, can significantly reduce sensitivity to the position of the current-carrying conductor 100 by providing a closer match of the parasitic capacitance between each coil and the current-carrying conductor 302, regardless of the position of the current-carrying conductor 302. 360° wiring can allow the two coils to be positioned so that they are both the same distance, on average, from the current-carrying conductor. This also ensures that each coil follows the same path and therefore experiences the same common-mode capacitive coupling.

[0067] However, it may still be important to provide a current measurement coil that improves the balance of the capacitive coupling while providing a coil that rejects external magnetic fields.

[0068] Therefore, several rate of change sensor layouts have been proposed to provide balanced capacitive noise coupling that can be cancelled in the external measurement circuitry.

[0069] 5a, 5b, and 5c show diagrams of a differential rate-of-change sensor 502 for measuring current in a current-carrying conductor 500. Paths, holes, or openings may be provided in the current-carrying conductor 500. FIG. 5c shows a complete rate-of-change sensor, including coil P, coil N, and their respective compensation conductors. FIG. 5a shows a first measurement coil, coil P 504, and its respective first compensation conductor 506. FIG. 5b shows a second measurement coil, coil N 508, and its respective second compensation conductor 510. The forward path of measurement coil P 504 is in an opposite circumferential direction to the forward path of measurement coil N 508, such that the first and second measurement coils travel in substantially opposite directions.

[0070] A first end of the first measurement coil P504 begins at a terminal or node 512, travels or moves in a counterclockwise direction (or in an alternative implementation, a clockwise direction) relative to the current-carrying conductor 500, and terminates at a second end or node 514. The first compensation conductor 506 travels or moves in the opposite direction relative to the coil P504, from node 514 to node 516, in the example depicted in FIG. 5a, clockwise relative to the current-carrying conductor 500. The first end 514 of the compensation conductor 506 is coupled to the second end 514 of the measurement coil P504.

[0071] A first end of the second measurement coil N508 begins at terminal 518, travels or moves in a clockwise direction (or in an alternative implementation, a counterclockwise direction) relative to the current-carrying conductor 500, and terminates at a second end or node 520. The second compensation conductor 510 travels or moves in the opposite direction relative to the coil N508, from node 520 to node 522, counterclockwise relative to the current-carrying conductor 500 depicted in FIG. 5b. The first end 514 of the compensation conductor 510 is coupled to the second end 520 of the measurement coil N508.

[0072] The schematic diagrams of FIGS. 5a-5c show that both coil P 504 and coil N travel substantially around the current-carrying conductor 500 to surround the path for the current-carrying conductor. Surrounding the path may be defined as a measurement coil traveling between 180° and 360° around the path. For example, traveling substantially 360° may provide excellent balanced coupling, as shown in FIG. 4. Depending on the pitch of the radially extending measurement conductor, substantially 360° may be slightly less than 360°. Traveling more than 180° may still provide improved coupling with a larger common-mode component than a circuit in which the coil does not travel more than 180°. The measurement coil may travel more than 360°, for example, N*360°, where N is a positive integer. In this way, the capacitive coupling to each coil remains the same. By providing a sensor with two measurement coils traveling across substantially the same area of ​​the substrate, the parasitic capacitance C P and C N may be similar or the same. In some examples, nodes 516 and 522 may be coupled together to a common reference, for example, ground (although this may be any suitable reference voltage). A further differential measurement circuit may enable common capacitively coupled noise in the first measurement coil 504 and the second measurement coil 508 to be cancelled.

[0073] Simplified circuit diagrams of the coils of Figures 5a-5c are shown in Figures 6a-6c. In particular, the second end 516 of the first compensating conductor 506 may be coupled to the second end 522 of the second compensating conductor 510. The sensor may further be coupled to a circuit for converting the rate of change of current detected by the current measurement coil into a current measurement by coupling the differential terminals 512 and 518 to a current measurement circuit. The current measurement circuit is not the subject of this disclosure and will not be described further herein. Those skilled in the art will understand that there are many known differential current measurement circuits that may be used.

[0074] The first end 512 of the first measurement coil 504 may provide a first signal of the rate of change of current sensor differential output signal, and the first end 518 of the second measurement coil 508 may provide a second signal of the differential output signal, which may be provided to or coupled to a further differential circuit.

[0075] Although Figures 5a-6c show sensors in which the current measuring coils travel in substantially opposite circumferential directions, sensors in which the current measuring coils travel in substantially the same circumferential direction may be implemented.

[0076] For example, Figures 7a, 7b, and 7c show diagrams of a differential rate-of-change sensor 702 for measuring current in a current-carrying conductor 500. Figure 7c shows the complete rate-of-change sensor, including coil P, coil N, and their respective compensation conductors. Figure 7a shows a first measurement coil, coil P 704, and its respective first compensation conductor 706. Figure 7b shows a second measurement coil, coil N 708, and its respective second compensation conductor 710. The forward path of measurement coil P 704 is in the same circumferential direction as the forward path of measurement coil N 708.

[0077] A first end of the first measurement coil P704 begins at a terminal or node 712, travels or moves in a counterclockwise direction (or in an alternative implementation, a clockwise direction) relative to the current-carrying conductor 500, and terminates at a second end or node 714. The first compensation conductor 706 travels or moves in the opposite direction relative to the coil P704, from node 714 to node 716, in the example depicted in FIG. 7a, clockwise relative to the current-carrying conductor 500. The first end 714 of the compensation conductor 706 is coupled to the second end 714 of the measurement coil P704.

[0078] A first end of the second measurement coil N708 begins at terminal 718, travels or moves in a counterclockwise direction (or in an alternative implementation, a clockwise direction) relative to the current-carrying conductor 500, and terminates at a second end or node 720. The second compensation conductor 710 travels or moves in the opposite direction relative to coil N708, from node 720 to node 722, clockwise relative to the current-carrying conductor 500 depicted in FIG. 7b. The first end 714 of the compensation conductor 710 is coupled to the second end 720 of the measurement coil N708.

[0079] First and second measurement coils traveling in the same direction may improve the capacitive coupling balance compared to measurement coils traveling in opposite directions. Starting both coils in the same direction relative to the coil center (both clockwise or both counterclockwise) ensures that each turn of each coil remains the same proximity to the current-carrying conductor.

[0080] Simplified circuit diagrams of the coils of Figures 7a-7c are shown in Figures 8a-8c. In particular, the second end 716 of the first compensating conductor 706 may be coupled to the second end 722 of the second compensating conductor 710. The sensor may further be coupled to a circuit for converting the rate of change of current detected by the current measurement coil into a current measurement by coupling the differential terminals 712 and 718 to a current measurement circuit. The current measurement circuit is not the subject of this disclosure and will not be described further herein. Those skilled in the art will understand that there are many known differential current measurement circuits that may be used.

[0081] The first end 712 of the first measurement coil 704 may provide a first signal of the rate of change of current sensor differential output signal, and the first end 718 of the second measurement coil 708 may provide a second signal of the differential output signal, which may be provided to or coupled to a further differential circuit.

[0082] 5a-8c may provide a sensor with improved capacitive coupling balance due to the provision of two coils traveling together in substantially the same routing around the path for the current-carrying conductor 500. Additionally, the sensor should have good magnetic cancellation through the provision of two compensation wires. However, in some situations, it may be desirable to provide a sensor with improved current sensing sensitivity while still retaining the magnetic cancellation provided by the compensation wires.

[0083] For example, Figures 9a, 9b, and 9c show a diagram of a differential rate-of-change of current sensor 902 for measuring current in a current-carrying conductor 500. The rate-of-change of current sensor includes four current measurement coils, which may be referred to as two forward coils and two return coils. Figure 9c shows the complete rate-of-change of current sensor, including coil P, coil N, and their respective return coils. Figure 9a shows a first measurement coil, coil P 904, and its respective first return coil 906. Figure 9b shows a second measurement coil, coil N 908, and its respective second return coil 910.

[0084] Although the return coils have been so referred to for clarity, it should be understood that the return coils act to measure the current in the current-carrying conductor in the same manner as the measurement coils, and therefore the return coils may also be considered measurement coils, or they may be considered to be part of the respective measurement coils.

[0085] The compensating return wire is replaced with a secondary coil, called a return coil or reverse coil. As with the previous design, the first and second measurement coils begin their circumferential progression in the same direction (counterclockwise in this example). These coils move together, maintaining spatial symmetry, for a complete progression. They then each connect to a respective return or reverse coil, which returns clockwise along the same progression path. The turns of the first and second measurement coils and the first and second return coils are interleaved along the progression path, as seen in Figures 9a-9c. In total, this creates essentially four individual coils that combine to generate the desired Rogowski coil.

[0086] A first end of the first measurement coil P904 begins at a terminal or node 912, travels or moves in a counterclockwise direction (or in an alternative implementation, a clockwise direction) around the path for the current-carrying conductor 500, and terminates at a second end or node 914. The first return coil 906 travels or moves in the opposite direction relative to coil P904, clockwise around the path for the current-carrying conductor or current-carrying conductor 500, from node 914 to node 916, in the example depicted in FIG. 9 a. The first end 914 of the first return coil 906 is coupled to the second end 914 of the measurement coil P904. A rate of change of current sensor may be provided that includes a measurement coil and a return coil to provide increased coil turns while still providing magnetic field cancellation.

[0087] A first end of the second measurement coil N908 begins at terminal 918, travels or moves in a clockwise direction (or in an alternative implementation, a counterclockwise direction) around the path for the current-carrying conductor 500, and terminates at a second end or node 920. The second return coil 910 travels or moves in the opposite direction relative to coil N908, from node 920 to node 922, counterclockwise around the path for the current-carrying conductor 500 depicted in FIG. 9b. The first end 914 of the second return coil 910 is coupled to the second end 920 of the measurement coil N908.

[0088] In this implementation, the measurement coils travel in the same circumferential direction relative to each other, although alternatively, the coils may travel in opposite directions relative to each other. The schematic diagrams of Figures 9a-9c show that both coil P 904 and coil N 908 travel substantially around the path for current-carrying conductor 500 so as to encircle the path. By providing a sensor with two measurement coils, the parasitic capacitance C P and C N may be similar or the same. In some examples, nodes 916 and 922 may be coupled together and to a common reference, e.g., ground. Similarly, return coils 906, 910 may travel substantially around the path for current-carrying conductor 500 so as to encircle the path.

[0089] Simplified circuit diagrams of Figures 9a-9c are shown in Figures 10a-10c. In particular, the second end 916 of the first return coil 906 may be coupled to the second end 922 of the second return coil 910. The sensor may further be coupled to circuitry configured to convert the rate of change of current detected by the current measurement coil into a current measurement by coupling the differential terminals 912, 918 to a current measurement circuit.

[0090] By providing a return coil instead of a compensation conductor, more turns can be provided in the same amount of space, which can improve the coil's sensitivity to the rate of change of current in the current-carrying conductor under measurement. The first measurement coil and the second measurement coil can have a balanced capacitive coupling, and the first return coil and the second return coil can have a balanced capacitive coupling, so that the capacitive coupling can be canceled in a further measurement circuit. Furthermore, the first return coil can function as a compensation conductor for the first measurement coil as it travels in the opposite circumferential direction to the first measurement coil, and the second return coil can function as a compensation conductor for the second measurement coil.

[0091] Due to the increased number of turns (the return coil also acts to sense the current in the current-carrying conductor), the output voltage at the output terminals 912, 918 may be larger than a system that provides a compensation conductor instead of a return coil.

[0092] Printed circuit board implementation of current change rate sensor The rate of change of current sensor may be mounted on a printed circuit board (PCB) or substrate. Advantageously, providing the rate of change of current sensor on a printed circuit board may allow the rate of change of current sensor to be provided on the same circuit board as other parts of the current measurement device, for example, the current measurement circuitry, amplifier, comparator, integrator.

[0093] However, when attempting to implement current measurement coils such as those shown in Figures 5a-10c on a PCB, it can be difficult to wire the two coils so that they are, on average, the same distance from the current-carrying conductor. Therefore, it can be difficult to ensure that the capacitive coupling provided between each coil and the measurement conductor is the same, as outlined in Figures 3 and 4. It is necessary to provide current measurement coils implemented on a PCB that achieve the desired balance of parasitic capacitances, so that the capacitive coupling to each coil is equal and the coupling can be canceled by a differential amplifier stage. If the coils were in different regions, the capacitive coupling might not be the same and might not be completely canceled or eliminated at the output. Furthermore, this becomes even more difficult because, while attempting to create a coil that improves the balance of capacitive coupling, it is still desirable to provide a coil that rejects external magnetic fields.

[0094] 4-layer implementation: 5a-6c show a rate of change of current sensor 502 comprising two current measuring coils 504, 508 and two compensating conductors 506, 510, the current measuring coils traveling in opposite directions, which may be implemented across four layers of a substrate or printed circuit board (PCB).

[0095] FIG. 11 shows a two-dimensional top view of a printed circuit board implementation of a rate of change sensor 502, including two measurement coils (coil P and coil N) that travel substantially together around a path for a current-carrying conductor 500. Traveling substantially around the current-carrying conductor 500 can result in the current measurement coils traveling substantially around the path so as to surround the path. Each measurement coil is formed, in part, by several conductive measurement coil tracks / traces (also called measurement conductors) 1102. The measurement conductors 1102 can be radial elements in that they can extend radially from the center of the printed circuit board, from the current-carrying conductor 500, or from the location of the path or opening. The plane in which they extend is perpendicular to the surface or main surface of the board. A Rogowski coil-like structure can include a hole, opening, or path in the board / circuit board at the center of the coil, allowing the current-carrying conductor to pass through the path. Multiple measurement conductors 1102 are arranged to circumferentially surround the path. Circumferential progression of the coil may be accomplished on the outer circumference using circumferential progression conductors, or "twists," 1106. These circumferential progression conductors allow the measurement coil to progress circumferentially relative to the current-carrying conductors 500, as outlined in the discussion of Figures 5a-5c.

[0096] FIG. 12 shows a three-dimensional view of the PCB traces and vias of the rate of change of current sensor of FIG. 11. The radial measurement conductors are distributed across four layers of the PCB substrate. For example, a first plurality of measurement conductors 1202 are located on the first layer of the substrate. In this example, the first layer is the top layer represented. A second plurality of measurement conductors 1204 are located on the second layer of the circuit board, which in this example is the layer below the first layer (perpendicular or perpendicular to the plane of the PCB substrate). A third plurality of measurement conductors 1206 are located on the third layer of the circuit board, which in this example is the layer below the second layer (perpendicular or perpendicular to the plane of the PCB substrate). A fourth plurality of measurement conductors 1208 are located on the fourth layer of the circuit board, which in this example is the layer below the third layer (perpendicular or perpendicular to the plane of the PCB substrate) and is the lowest layer represented.

[0097] Although the radial elements are distributed across four layers of the circuit board, the circuit board itself is not necessarily a four-layer circuit board. For example, the circuit board may have more than four layers, such as a circuit board having six, eight, or ten layers.

[0098] Each respective measurement conductor of the first plurality of measurement conductors 1202 is aligned with a respective measurement conductor from the second, third, and fourth plurality of measurement conductors 1204, 1206, 1208. These respective measurement conductors are aligned in a radial plane that is perpendicular to the surface of the substrate, which is the major surface of the substrate. Conceptually, the plane passing through each measurement conductor of the plurality of measurement conductors 702, 704, 706, and 708 is sometimes referred to as the "radial plane" throughout this disclosure, as it extends radially through the coil and is perpendicular / perpendicular to the plane of the substrate.

[0099] The rate of change of current sensor 502 further comprises a first plurality of vias including a plurality of outer circumferential vias 1210 and a plurality of inner circumferential vias 1214, 1216. Each measurement conductor of the first, second, third, and fourth plurality of measurement conductors is connected to a respective via of the plurality of outer circumferential vias 1210. The outer circumferential vias 1210 are formed around the outer circumference of the measurement conductors. The outer circumferential vias 1210 may include at least a conductive lining (and optionally may be completely filled with conductive material) and may couple measurement conductors on one layer of the circuit board with measurement conductors on another layer of the circuit board by circumferentially traveling conductors 1212.

[0100] Each measurement conductor is also connected to an inner circumferential via 1214, 1216. The inner circumferential vias may be provided in two circles, with the vias 1214 in the first circle having a first diameter and the vias 1216 in the second circle having a second diameter, and the first and second circles being concentric. The diameter of the vias 1214 in the first circle may be smaller than the diameter of the vias 1216 in the second circle. In this example, the vias 1214 in the first circle are formed closer to the center of the circle formed by the group of measurement conductors than the vias 1216 in the second circle, although "first" and "second" are merely labeling terms. The vias 1214 in the first circle and the vias 1216 in the second circle may each include at least a conductive lining (and optionally be completely filled with a conductive material) and may couple a respective measurement conductor of one of the plurality of measurement conductors to a respective measurement conductor of a second of the plurality of measurement conductors.

[0101] 1 , each coil turn is formed by two measurement conductors on different layers of the circuit board from different measurement conductors of the plurality of measurement conductors, connected by one of the first circle vias 1214 or the second circle vias 1216. For example, measurement conductors from the first plurality of measurement conductors 1202, the second plurality of measurement conductors 1204, the third plurality of measurement conductors 1206, and the fourth plurality of measurement conductors 1208, together with vias from the first circle vias 1214, the second circle vias 1216 (on the inner circumference of the coil), and the outer circumference vias 1210 (on the outer circumference of the coil), form part of a turn of the first measurement coil (coil P) 504 and the second measurement coil (coil N) 508. Circumferential progression of the coils is alternatively provided on the outer circumference using connection regions 1212, known as "twists" or circumferentially extending conductors.

[0102] Simply mounting the two measurement coils separately, for example by mounting coil P on layers 1 and 2 of the printed circuit board and coil N on layers 3 and 4 of the circuit board, can lead to imbalances. The coils will be located in different areas (for example the average midpoints of the two coils in the direction perpendicular to the plane of the board will be different), which will lead to different parasitic capacitances as described with reference to Figures 3 and 4. The same is true if coil N is mounted on a first circuit board and coil P on a second circuit board.

[0103] Instead, Coil N and Coil P are interleaved, meaning that Coil N and Coil P are, on average, the same distance from the current-carrying conductor or busbar of interest, the capacitive coupling to each coil is the same (e.g., the average midpoint of the two coils in the direction perpendicular to the pane of the substrate is substantially the same), and they have the same average capacitive coupling.

[0104] 13a-13c show subsections of FIG. 12. For ease of illustration, FIG. 13a shows only the measurement conductors that form part of the second measurement coil N, and FIG. 13b shows only the measurement conductors that form part of the first measurement coil P. FIG. 13c shows the measurement conductors of both coils N and P (and is therefore a true subsection of FIG. 12). Furthermore, FIGS. 14a, 14b, and 14c show simplified schematic diagrams of PCB implementations of FIGS. 13a, 13b, and 13c. Although FIGS. 14a-14c show linearly arranged coils (i.e., progressing linearly from right to left or left to right, as if the coils were straight rather than surrounding a central opening), this is done solely for ease of presentation. It will be appreciated that the radial conductor elements are in fact arranged in a circle around the central opening, and the vias located on the inner and outer edges are also arranged in a circle, such that the vias mark the inner and outer circumferences of the measurement conductor, as in Figures 11 and 12.

[0105] The first turn of coil N (as seen in FIG. 13 a) includes measurement conductors 1302 formed on the first layer of the PCB for the first plurality of measurement conductors 1202 and measurement conductors 1304 formed on the third layer of the PCB for the third plurality of measurement conductors 1206, connected at their first ends (the ends closer to the openings, paths, or current-carrying conductors) by inner circumferential vias 1306 of the first circular vias 1214. The second turn of coil N includes measurement conductors 1308 formed on the second layer of the PCB for the second plurality of measurement conductors 1204 and measurement conductors 1310 formed on the fourth layer of the PCB for the fourth plurality of measurement conductors 1208, connected by inner circumferential vias 1312 of the second circular vias 1216. The third turn of coil N includes measurement conductors 1314 formed on the first layer of the PCB of the first plurality of measurement conductors 1202 and measurement conductors 1316 formed on the third layer of the PCB of the third plurality of measurement conductors 1206, which are connected by inner circumferential vias 1318 of the first circle of vias 1204. In particular, the measurement conductors that form part of the turns of coil N lie in the same plane perpendicular to the surface of the circuit board. For example, measurement conductors 1302 and 1304 are centered on the same radially extending plane, which is perpendicular to the surface of the board. Vias are also connected to the second ends of each of the measurement conductors (outer circumferential vias 1210 in FIG. 12 ) so that the second ends of the radial elements are coupled to the outer circumferential vias. However, these outer circumferential vias are not shown in this figure for ease of understanding.

[0106] The first turn of coil P (as seen in FIG. 13b) includes measurement conductors 1320 formed on the second layer of the PCB for the second plurality of measurement conductors 1204 and measurement conductors 1322 formed on the fourth layer of the PCB for the fourth plurality of measurement conductors 1208, which are connected by inner circumferential vias 1324 of the second circle vias 1216. The second turn of coil P includes measurement conductors 1326 formed on the first layer of the PCB for the first plurality of measurement conductors 1202 and measurement conductors 1328 formed on the third layer of the PCB for the third plurality of measurement conductors 1206, which are connected by inner circumferential vias 1330 of the first circle vias 1214. The third turn of coil P includes measurement conductors 1332 formed on the second layer of the PCB of the second plurality of measurement conductors 1204 and measurement conductors 1334 formed on the fourth layer of the PCB of the fourth plurality of measurement conductors 1208, which are connected by inner circumferential vias 1336 of the second circle of vias 1216. As with coil N, the measurement conductors forming each turn of coil P lie in the same radial plane. The outer circumferential vias are not shown in Figure 13b for ease of understanding.

[0107] As shown in FIG. 13c, when these two measurement coils are implemented on a four-layer circuit board, they are arranged so that the turns of coil N (FIG. 13a) lie in the same radially extending plane as the turns of coil P (FIG. 13b), thereby interleaving the coils. For example, a first group of measurement conductors includes measurement conductors 1302, 1304, 1320, and 1322. This group of measurement conductors lies in a first radial plane perpendicular to the main surface of the circuit board or substrate. A second group of measurement conductors includes measurement conductors 1308, 1310, 1326, and 1328. This second group of measurement conductors lies in a second radial plane perpendicular to the main surface of the circuit board or substrate. A third group of measurement conductors includes measurement conductors 1314, 1316, 1332, and 1334, which lies in a third radial plane perpendicular to the main surface of the circuit board or substrate. Each group of measurement conductors includes two measurement conductors that form part of the coil N and two measurement conductors that form part of the coil P.

[0108] A portion of the turns of coil P and a portion of the turns of coil N are located in the same plane. Measurement conductor 1302, mounted on the first layer of the circuit board, and measurement conductor 1304, mounted on the third layer of the circuit board, form a portion of coil N. Measurement conductor 1320, mounted on the second layer of the circuit board, and measurement conductor 1322, mounted on the fourth layer of the circuit board, form a portion of coil P. With each successive turn, the layer occupied by coil N and the layer occupied by coil P are interchanged. For example, the second turn of coil N includes measurement conductor 1308, mounted on the second layer of the circuit board, and measurement conductor 1310, mounted on the fourth layer of the circuit board. The second turn of coil P includes measurement conductor 1326, mounted on the first layer of the circuit board, and measurement conductor 1328, mounted on the third layer of the circuit board.

[0109] This arrangement results in a portion of the first turn of coil N being located on layers 1 and 3, and a portion of the first turn of coil P being located on layers 2 and 4. For the second turn, the measurement conductors of coil N are located on layers 2 and 4, and the measurement conductors of coil P are located on layers 1 and 3. This alternating pattern of layers used to alternately wire each coil continues as the coils progress around the circuit board. In other words, for the first turns of coils N and P, coil N comprises a first plurality of measurement conductors 1202 and a third plurality of measurement conductors 1206, while coil P comprises a second plurality of measurement conductors 1204 and a fourth plurality of measurement conductors 1208. For the second turns of coils N and P, coil N comprises a second plurality of measurement conductors 1204 and a fourth plurality of measurement conductors 1208, while coil P comprises a first plurality of measurement conductors 1202 and a third plurality of measurement conductors 1206. With each turn of the coil, the measurement conductor used alternates.

[0110] This interleaved arrangement can provide improved capacitive coupling performance. For example, there may be external interfering AC voltage-carrying (dv / dt) conductors near the top surface of the PCB, or generally undesirable fields present directly above the PCB. Because both coils contain the same number of turns on the first layer of the PCB, the same capacitive coupling should occur in each coil.

[0111] Compensating conductors 1206, 1210 may be included around the circuit board. For example, the compensating conductors may take the form of serpentine conductors located near and wound between the outer circumferential vias 1210 of the coil.

[0112] The vias on the inner circumference may be arranged in two concentric circles 1214, 1216 to allow the four measurement conductors forming a group of measurement conductors to be connected in the same radial plane as the group of measurement conductors. Coil N alternates between vias 1214 on the first circle and vias 1216 on the second circle of inner circumference vias. Coil P alternates between vias 1214 on the first circle and vias 1216 on the second circle of inner circumference vias.

[0113] For example, measurement conductors 1302, 1304 of coil N are connected using via 1306 of vias 1214 in the first circle, and measurement conductors 1320, 1322 of coil P are connected using via 1324 of vias 1216 in the second circle. Measurement conductors 1308, 1310 of coil N are connected using via 1312 of vias 1216 in the second circle, and measurement conductors 1326, 1328 of coil P are connected using via 1330 of vias 1214 in the first circle. In general, measurement conductors of the first plurality of measurement conductors 1202 and the third plurality of measurement conductors 1206 can be connected using the first circle via 1214. Measurement conductors of the second plurality of measurement conductors 1204 and the fourth plurality of measurement conductors 1208 can be connected using the second circle via 1216. Although the vias are described in this manner, they could also be connected in the opposite manner; for example, the measurement conductors of the first plurality of measurement conductors 1202 and the third plurality of measurement conductors 1206 could be connected using the second circular via 1216, and the measurement conductors of the second plurality of measurement conductors 1204 and the fourth plurality of measurement conductors 1208 could be connected using the first circular via 1214. Because each coil, i.e., Coil N and Coil P, uses the same number of first circular vias and second circular vias in this alternating manner, the area enclosed by the coils remains the same, on average. This ensures that the coils can provide balanced coupling from the current-carrying conductors under measurement.

[0114] FIG. 14a shows the conductive PCB traces that make up Coil N and its respective first compensation conductor. FIG. 14b shows the conductive PCB traces that make up Coil P and its respective second compensation conductor. FIG. 14c shows how Coil N and Coil P can be combined to form a differential rate of change sensor. Many of the features in FIGS. 14a-14c are the same as those in FIGS. 13a-13c, but FIGS. 14a-14c more clearly show the connections at the outer circumference of the coils and the placement of the compensation conductors. A legend is provided in the figures, and measurement conductors on different layers of the board are represented using different line formats. For ease of understanding, the measurement conductors are represented as adjacent to each other rather than directly in the same radial plane.

[0115] On the outer circumference, the circumferential progression of the coil P can be provided using circumferential progression elements that connect the measurement conductors to the respective outer circumferential vias. These circumferential progression conductors allow the measurement coil to proceed circumferentially from the connection node and connect to further measurement conductors.

[0116] For example, coil P504 uses circumferentially extending conductors 1402 to travel counterclockwise from connection node 512 to node 514. Outer circumferential vias 1404 connect circumferentially extending conductors on one layer of the circuit board to conductors on another layer of the circuit board, allowing circumferentially extending conductors 1402 to connect measurement conductors in one plane perpendicular to the major surface of the circuit board to measurement conductors in another plane.

[0117] Coil N travels from connecting node 518 to node 520 in a clockwise direction relative to the current carrying conductors using a circumferentially extending conductor 1406 connected to an outer circumferential via 1408 .

[0118] A first compensation conductor 506 and a second compensation conductor 510 are also provided on the schematic diagrams of Figures 14a-14c. The first compensation conductor is provided such that it snakes adjacent to the circumferential conductor 1402 of coil P in the opposite circumferential direction to coil P, from node 514 back to node 516. The second compensation conductor is provided such that it snakes adjacent to the circumferential conductor 1406 of coil N. In this manner, by closely following the circumferentially extending elements of the respective measurement coils, it is ensured that the single loop formed by the compensation conductors is the same as, or as similar as possible to, the single loop formed by the measurement coil.

[0119] The compensation conductors are formed across the four layers of the circuit board, alternating between these layers. The compensation conductors are formed from conductive traces on the circuit board 1410 that run in a circumferential direction. The compensation conductor traces 1410 run across the four layers of the circuit board, alternating between first outer circumferential vias 1412 and second outer circumferential vias 1414.

[0120] Although the above four-layer implementation is described with the current measurement coils traveling in opposite directions, the current measurement coils can also be implemented so that they travel in the same direction, as outlined in Figures 7a-7c.

[0121] Two-layer implementation Similar to the rate of change of current sensors described above in which the measurement coils are implemented in opposite directions or senses across four layers of a circuit board, differential current sensors can also be implemented across two layers of a circuit board. For example, the implementations of Figures 5a-5c can be implemented across two layers of a circuit board such that Coil N and Coil P are interleaved in a plane parallel to the major surface of the circuit board, rather than being interleaved in a plane perpendicular to the major surface of the circuit board as in Figures 11-14. Beneficially, a two-layer circuit board implementation may offer simplified manufacturing requirements compared to a four-layer circuit board implementation, and may reduce the cost of producing a rate of change of current sensor while still maintaining good performance in terms of rejection of noise coupling.

[0122] 15a-15c are schematic representations of subsections of a two-layer implementation of the rate of change of current sensor according to FIGS. 5a-5c, in which first and second measurement coils travel in opposite directions around a central path for the current-carrying conductor 500. While FIGS. 15a-15c show the coils arranged linearly (i.e., traveling linearly from right to left or left to right, as if the coils were straight, rather than surrounding a central opening), this is done solely for ease of presentation. It will be understood that the radial conductor elements are actually arranged circularly around the central opening or path, and that the vias located on the inner and outer edges are also arranged circularly, so that the vias mark the inner and outer circumferences of the measurement conductor. Some aspects of the two-layer implementation are the same as those of the four-layer implementation, and the discussion regarding FIGS. 11-14 should also be kept in mind when considering the discussion of the two-layer implementation.

[0123] FIG. 15a shows a schematic diagram of a subsection of a first measurement coil P 504 and its first compensation conductor 506. FIG. 15b shows a schematic diagram of a subsection of a second measurement coil N 508 and its second compensation conductor 510. FIG. 15c shows a schematic diagram including features of both FIG. 15a and FIG. 15b implemented across two layers of a circuit board. A legend is provided in the figure, and measurement conductors on different layers of the board are represented using different line formats. For ease of understanding, the measurement conductors are represented as adjacent to each other rather than directly in the same radial plane.

[0124] Coil N and Coil P are disposed across two layers of the circuit board and are interleaved such that the turns of Coil N are formed in a radially extending plane perpendicular to the surface of the circuit board, followed by the turns of Coil P formed in a different radially extending plane perpendicular to the surface of the circuit board. For example, a first turn of Coil P1 502 is formed on two layers of the circuit board, then a first turn of Coil N1 504 is formed on two layers of the circuit board in a radial plane adjacent to the first turn of Coil P, and then a second turn of Coil P1 506 is formed on two layers of the circuit board in a radial plane adjacent to the first turn of Coil N. Interleaving the turns of the measurement coils in this manner allows both measurement coils to travel substantially around the path for the current-carrying conductor 500 while still maintaining, on average, the same distance from the current-carrying conductor of interest. The turns of Coil P and the turns of Coil N are adjacent such that the turns of Coil P lie in different but adjacent radially extending planes relative to the turns of Coil N.

[0125] The first plurality of measurement conductors may be located on a first layer of a substrate or circuit board, and the second plurality of measurement conductors may be located on a second layer of the circuit board. Each respective measurement conductor of the first plurality of measurement conductors is aligned with a respective measurement conductor of the second plurality of measurement conductors in a plane perpendicular to the surface of the substrate, the plane extending in a radial direction. The winding of the first measurement coil P504 may include a measurement conductor 1508 of the first plurality of measurement conductors and a measurement conductor 1510 of the second plurality of measurement conductors. These measurement conductors 1508, 1510 are formed in the same radially extending plane (i.e., a plane perpendicular to the surface of the circuit board). The measurement conductor 1508 on the first layer and the measurement conductor 1510 on the second layer may be connected by an inner circumferential via 1512.

[0126] The winding of the second measurement coil N508 may include a measurement conductor 1514 of the first plurality of measurement conductors and a measurement conductor 1516 of the second plurality of measurement conductors. The measurement conductor 1514 on the first layer and the measurement conductor 1516 on the second layer may be connected by an inner circumferential via 1518.

[0127] On the outer circumference, the circumferential progression of the coil P can be provided using circumferential progression elements that connect the measurement conductors to the respective outer circumferential vias. These circumferential progression conductors allow the measurement coil to proceed circumferentially from the connection node and connect to further measurement conductors.

[0128] For example, first measurement coil P504 uses circumferentially extending conductors 1520 to travel in a counterclockwise direction around the path for current-carrying conductors 500 from connection node 512 to node 514. Outer circumferential vias 1522 connect circumferentially extending conductors on one layer of the circuit board to conductors on another layer of the circuit board, allowing circumferentially extending conductors 1520 to connect measurement conductors in one radial plane to measurement conductors in an adjacent radial plane.

[0129] The second measurement coil N 508 travels in a clockwise direction around the path for the current-carrying conductor 500 from the connection node 518 to the node 520 .

[0130] First compensation conductor 506 and second compensation conductor 510 are also provided in the schematic diagrams of Figures 15a-15c. The first compensation conductor is provided in a circumferential direction opposite coil P, snaking adjacent to the circumferential conductor 1520 of coil P, from node 514 back to node 516. The second compensation conductor is provided in a circumferential direction opposite coil N, snaking adjacent to the circumferential conductor of coil N, from node 520 back to node 522. In this way, closely following the circumferential elements of the respective measurement coils can ensure that the single loop formed by the compensation conductors is the same as, or as similar as possible to, the single loop formed by the measurement coil.

[0131] The compensation conductors are formed across two layers of the circuit board, alternating between the layers. The compensation conductors are formed from conductive traces on the circuit board 1524 that run in a circumferential direction. The compensation conductor traces 1524 run across the two layers of the circuit board, alternating between a first outer circumferential via 1526 and a second outer circumferential via 1528.

[0132] The compensation conductor may be formed across two layers of a circuit board such that the compensation conductor comprises conductor segments formed in alternating order across the first and second layers of the circuit board. This is seen in Figures 15a-15c, where first compensation conductor segments 1524 are formed in an alternating pattern on the first layer of the circuit board and the second layer of the circuit board. This pattern continues such that the compensation conductor is formed from multiple circumferentially progressing segments 1524 disposed on alternating layers of the circuit board.

[0133] The second compensation coil is formed in a similar manner using segments 1530 on the first and second layers of the circuit board.

[0134] Figures 11-15 relate to implementations of rate of change of current sensors in which the two measurement coils are arranged to travel in opposite circumferential directions, as in Figures 5a-5c, but they can also be implemented with the measurement coils traveling in the same circumferential direction, as in Figures 7a-7c.

[0135] Counter-direction measurement coils may not completely eliminate capacitive coupling that can be caused by imperfect matching of the parasitic impedances shown in Figures 3 and 4 due to interfering conductors that are not symmetrically centered on the coil. 巻き1 The parasitic impedance of NEG 巻き1 If the parasitic impedance of coil P is equal to the parasitic impedance of coil N, and the same is true for all turns of coil P and coil N up to turn N, there should be perfect impedance balance so that there is no differential voltage between the first and second measuring coils. However, if the current-carrying conductors are connected to the NEG 巻き1 than POS 巻き1 If the coils are off-center, such as if they were physically closer to each other, the parasitic capacitance to the current-carrying conductors of each turn will be slightly different, which will result in an impedance mismatch in the equivalent circuit of Figure 4. Wiring the coils in opposite directions can cause the coils to follow different paths.

[0136] Therefore, a potential solution to further improve the balance of parasitic impedances is to wire both coils in approximately the same fashion from the terminals of the differential measurement circuit that may be connected to the coils' connection nodes. Starting both coils to follow the same circumferential direction around the coil's center (e.g., Coil N and Coil P both traveling clockwise, or Coil N and Coil P both traveling counterclockwise) may keep each turn of the coil the same distance from current-carrying conductors or interference sources, and may keep the coils' terminals or connection nodes (e.g., 718, 712, 716, and 722) close to each other.

[0137] Advancing both coils in the same direction may allow them to follow the same path while maintaining spatial symmetry for the complete advancement of the coils, in that both coils move together. It may also allow the connection nodes 712, 716, 718, and 722 to be positioned on the same side of the coils, which may make it easier to connect measurement circuitry since all connection nodes are close to each other.

[0138] 16a-16c show schematic diagrams of the two-layer co-directional mounting arrangement according to FIGS. 7a-7c. FIG. 16a shows the conductive traces that make up both the first measurement coil P 704 and the second measurement coil N 708. FIG. 16b shows the conductive traces that make up the compensation conductors for Coil N and Coil P. FIG. 16c shows the complete rate of change of current sensor, including both Coil N, Coil P, and their respective compensation conductors. A legend is provided in the figures, where measurement conductors on different layers of the substrate are represented using different linear forms. For ease of understanding, the measurement conductors are represented as adjacent to each other rather than directly in the same radial plane.

[0139] 16a-16c depict the coils arranged linearly (i.e., progressing linearly from right to left or left to right, as if the coils were straight, rather than surrounding a central opening or path 500), this is done solely for ease of presentation. It will be understood that the radial conductor elements are actually arranged in a circle around the path for the current-carrying conductors 500, and that the vias located on the inner and outer edges are also arranged in a circle, such that the vias mark the inner and outer circumferences of the measurement conductors. Some aspects of the two-layer implementation are the same as in the four-layer and two-layer opposite-direction implementations, and the discussion regarding FIGS. 11-15 should also be kept in mind when considering the discussion of the two-layer same-direction implementations.

[0140] Coil N and Coil P are arranged across two layers of the circuit board, interleaved such that the first turn of Coil N is formed in a radially extending plane perpendicular to the surface of the circuit board, followed by the first turn of Coil P, also formed in a radially extending plane perpendicular to the surface of the circuit board and circumferentially adjacent to the first turn of Coil N. For example, the first turn of Coil P1602 may be formed on two layers of the circuit board, then the turn of Coil N1604 may be formed circumferentially adjacent to the first turn of Coil P1602 on two layers of the circuit board, and then the second turn of Coil P1606 may be formed circumferentially adjacent to the first turn of Coil N on two layers of the circuit board. Interleaving the turns of the measurement coils in this manner allows the measurement coils to travel together around the path or circuit board while still maintaining, on average, the same distance from the current-carrying conductor of interest, e.g., travel substantially 360° around the path. The turns of Coil P and the turns of Coil N are circumferentially adjacent such that the turns of Coil P lie in a different, but circumferentially adjacent, radially extending plane relative to the turns of Coil N.

[0141] The first plurality of measurement conductors may be located on a first layer of a substrate or circuit board, and the second plurality of measurement conductors may be located on a second layer of the circuit board. The first plurality of measurement conductors and the second plurality of measurement conductors are located in the same radially extending plane perpendicular to the surface of the substrate. A winding of the coil P includes a measurement conductor 1608 of the first plurality of measurement conductors and a measurement conductor 1610 of the second plurality of measurement conductors. These measurement conductors are formed in the same radially extending plane (i.e., a plane perpendicular to the surface of the circuit board). The measurement conductor 1608 of the first plurality of measurement conductors and the measurement conductor 1610 of the second plurality of measurement conductors may be connected by an inner circumferential via 1612, which may be located in the same radial plane as the measurement conductors.

[0142] A turn of coil N includes a measurement conductor 1614 of the first plurality of measurement conductors and a measurement conductor 1616 of the second plurality of measurement conductors. The measurement conductor 1614 on the first layer and the measurement conductor 1616 on the second layer may be connected by an inner circumferential via 1618, which lies in the same radial plane as the measurement conductor.

[0143] On the outer circumference, the circumferential progression of the coil P can be provided using circumferential progression elements that connect the measurement conductors to the respective outer circumferential vias. These circumferential progression conductors allow the measurement coil to proceed circumferentially from the connection node and connect to further measurement conductors.

[0144] For example, coil P704 travels in a counterclockwise direction around the current-carrying conductors from connection node 712 to node 714 using circumferentially extending conductor 1620. The circumferentially extending conductors are connected to vias at the outer circumference, which allow measurement conductors in one radially extending plane to be connected to radially extending elements in a different radially extending plane. Coil N travels in a counterclockwise direction around the current-carrying conductors from connection node 718 to node 720. While this diagram shows both measurement coils traveling in a counterclockwise direction, the measurement coils could alternatively both travel in a clockwise direction.

[0145] A first compensation conductor 706 and a second compensation conductor 710 are also provided in the schematic diagrams of Figures 16a-16c. The first compensation conductor is provided in a circumferential direction opposite coil P, snaking adjacent to the circumferentially traveling conductor 1620 of coil P from node 714 back to node 716. The second compensation conductor is provided in a circumferential direction opposite coil P, snaking adjacent to the circumferentially traveling conductor 1620 of coil N. In this manner, closely following the circumferentially extending elements of the respective measurement coils may mean that the single loop formed by the compensation conductors is the same as, or as similar as possible to, the single loop formed by the measurement coil.

[0146] The compensation conductors are formed across two layers of the circuit board, alternating between these layers. The compensation conductors are formed from conductive traces on the circuit board 1622 that run in a circumferential direction. The compensation conductor traces 1622 run across the two layers of the circuit board.

[0147] The compensating conductor may provide at least some magnetic immunity to external transverse fields by forming a canceling loop that opposes the advance of the coil. This compensating conductor may replace the secondary or return coil without sacrificing magnetic immunity. Thus, in some implementations, the rate of change of current sensor may not include a compensating conductor, but instead may include an additional coil, as shown in FIGS. 9a-9c. Providing an additional coil in this manner may allow more turns to be included in the current sensor, since the return coil turns also provide current measurement. Including more coil turns may provide improved sensitivity to the current under measurement, providing a larger output voltage for the same current being measured.

[0148] Figure 17 shows a two-dimensional top view of a printed circuit board implementation of rate of change of current sensor 902. Similar to Figures 9a-9c, the rate of change of current sensor includes a first measurement coil (coil P) 904, a second measurement coil (coil N) 908, a first return coil 906, and a second return coil 910. Figures 18 and 19 show subsections of Figure 17, with Figure 18 showing the conductors forming the first measurement coil 904 and the second measurement coil 908. Figure 19 shows the conductors forming the first return coil 906 and the second return coil 910. Measurement conductors on a first layer of the board are represented as solid lines, and measurement conductors on a second layer of the board are represented as dashed lines.

[0149] The measurement coil and return coil travel around, e.g., substantially around, e.g., surrounding, the current-carrying conductor or path 500. Each measurement coil is formed in part by several conductive measurement coil tracks / traces, measurement conductors 1702. The measurement conductors or measurement coil tracks 1702 may be radial elements in that they may extend radially from the path for the current-carrying conductor 500 of the sensor. Additional measurement conductors 1706 are provided that form part of the return coils 904, 908. The multiple measurement conductors 1702, 1706 are arranged to circumferentially surround the current-carrying conductor 500. Circumferential travel of the coils may be achieved on the outer circumference using circumferential travel conductors, or "twists," 1704. These circumferential travel conductors allow the measurement coils to travel circumferentially relative to the current-carrying conductor or path 500, as outlined in the discussion of Figures 9a-9c.

[0150] 18 shows a plurality of measurement conductors 1702 constituting the first and second measurement coils. The measurement conductors 1702 include a first plurality of measurement conductors formed on a first layer of a substrate and a second plurality of measurement conductors formed on a second layer of the substrate. The first and second plurality of measurement conductors are located in the same radially extending plane perpendicular to the surface of the substrate. Since FIG. 18 shows a top-down perspective view of the measurement coil, only the first plurality of measurement conductors located on the first layer are visible, and the view of the second plurality of measurement conductors located in the same radial plane is obscured.

[0151] FIG. 19 shows a plurality of measurement conductors 1704 that constitute the first and second return coils. The measurement conductors 1704 include a third plurality of measurement conductors formed on a first layer of the substrate and a fourth plurality of measurement conductors formed on a second layer of the substrate. The third and fourth plurality of measurement conductors are located in the same radially extending plane perpendicular to the surface of the substrate. Because FIG. 19 shows a top-down perspective view of the measurement coil, only the third plurality of measurement conductors located on the first layer are visible, and the fourth plurality of measurement conductors located in the same radial plane are obscured.

[0152] The measurement conductors of the first plurality of measurement conductors are coupled to the measurement conductors of the second plurality of measurement conductors using a first plurality of vias 1802 that form a first circle, and the measurement conductors of the third plurality of measurement conductors are coupled to the measurement conductors of the fourth plurality of measurement conductors using a second plurality of vias 1902 that form a second circle.

[0153] 20a-20c show schematic diagrams of two-layer mounting arrangements including return coils according to FIGS. 9a-9c. FIG. 20a shows both the first measurement coil P and the second measurement coil N, as in FIG. 18. FIG. 20b shows the first return coil and the second return coil, as in FIG. 19. FIG. 20c shows the complete rate of change of current sensor, including both the first measurement coil 904, the second measurement coil 908, the first return coil 906, and the second return coil 910. A legend is provided in the figures, and measurement conductors on different layers of the substrate are represented using different linear forms. For ease of understanding, the measurement conductors are represented as adjacent to each other rather than directly in the same radial plane.

[0154] Although Figures 20a-20c show the coils arranged linearly (i.e., progressing linearly from right to left or left to right, as if the coil were straight, rather than surrounding a central opening), this is done solely for ease of presentation. It will be understood that the radial conductor elements are actually arranged in a circle around the central opening or path, and that the vias located on the inner and outer edges are also arranged in a circle, such that the vias mark the inner and outer circumferences of the measurement conductors, as in Figures 17 and 19. Some aspects of this two-layer implementation are the same as other PCB implementations, and the discussion regarding Figures 11-16 should also be kept in mind when considering the discussion of two-layer implementations.

[0155] Coils N and P are arranged across two layers of the circuit board and are interleaved such that a first measurement coil turn is formed in a first radially extending plane perpendicular to the surface of the circuit board, followed by a circumferentially adjacent turn of the second measurement coil formed in a second radially extending plane. Interleaving the measurement coil turns in this manner allows the measurement coils to travel together around the circuit board while still maintaining, on average, the same distance from the current-carrying conductors.

[0156] The turns of Coil N and Coil P are provided in a repeating pattern around the path for the current-carrying conductor or current-carrying conductor 500, with a turn of Coil P followed by a turn of Coil N. However, the return coils may be further interleaved in this repeating pattern. The first turn 2008 of the first return coil 906 is provided adjacent to the first turn 2010 of the second return coil 910. This provides a repeating interleaved pattern such that, circumferentially around the sensor, the turn 2002 of the first measurement coil 904 is adjacent to the turn 2008 of the first return coil 906, which is adjacent to the turn 2004 of the second measurement coil 908, which is adjacent to the turn 2010 of the second return coil 910, which is adjacent to the next turn of the first measurement coil 904, and so on.

[0157] A turn of the first measurement coil P904 may include a measurement conductor 2012 from the first plurality of measurement conductors and a measurement conductor 2014 from the second plurality of measurement conductors. The measurement conductors that form part of the turns of the coil lie in the same radially extending plane perpendicular to the surface of the substrate. The measurement conductor 2012 on the first layer and the measurement conductor 2014 on the second layer may be connected by vias 2016, the vias 2016 connecting the measurement conductors of the turns lying in the same plane as the measurement conductors.

[0158] A turn of the second measurement coil 908 may include a measurement conductor 2018 of the first plurality of measurement conductors and a measurement conductor 2020 of the second plurality of measurement conductors. The measurement conductor 2018 on the first layer and the measurement conductor 2020 on the second layer may be connected by a via 2022, which is located in the same plane as the measurement conductors 2018, 2020.

[0159] The turns of the first return coil 906 may include a third plurality of measurement conductors 2024 and a fourth plurality of measurement conductors 2026. The measurement conductors 2024 on the first layer and the measurement conductors 2026 on the second layer may be connected by vias 1728.

[0160] The turns of the second return coil 910 may include a measurement conductor 2030 of the first plurality of measurement conductors and a measurement conductor 2032 of the fourth plurality of measurement conductors. The measurement conductor 2030 on the first layer and the measurement conductor 2032 on the second layer may be connected by a via 2034.

[0161] In particular, the first measurement coil 904, the first return coil 906, the second measurement coil 908, and the second return coil 910 are interleaved in the plane of the substrate such that a turn of the first measurement coil is circumferentially followed or preceded by a turn of the first return coil, then a turn of the second measurement coil, then a turn of the second return coil.

[0162] The turns can be wired so that each turn adds to the combined coil output voltage. The first turn 2002 of the first measurement coil 904 can enter a turn on the first layer and exit a turn on the second layer, resulting in an EMF of a specific polarity being induced in the turn resulting from measuring the desired magnetic field. The first turn 2004 of the second measurement coil 908 can enter a turn on the second layer and exit a turn on the first layer, resulting in an EMF of opposite polarity to that induced in the first turn 2002 of the first measurement coil 904. These opposite polarities result in a differential mode voltage at terminals 912 and 918. Each turn of each coil can be wired in this manner from terminals 912 and 918, increasing the differential mode voltage of each turn added. The return coil turns are wired to further add the differential mode voltage.

[0163] The first measurement coil 904, the second measurement coil 908, the first return coil 906, and the second return coil 910 travel circumferentially around the path 500 using a circumferentially traveling element or conductor 1704. All circumferential travel of the coils occurs at the outer end of the measurement conductor. This may ensure that the travel rings of the measurement coil and return coil occur in the same area of ​​the substrate, and that the magnetic noise induced in each forward coil is canceled by the magnetic noise induced in the respective return coil. Each coil travel has the same loop area, resulting in approximately the same magnetic pickup due to undesired magnetic fields.

[0164] The measurement conductors of the first and second plurality of measurement conductors are coupled using vias at the inner circumference of the measurement conductors, closer to the path or current-carrying conductor 500. The vias coupling the first and second plurality of measurement conductors may be arranged to form a first circle of vias 1708. The vias coupling the third and fourth plurality of measurement conductors may be arranged to form a second circle of vias 1710. In this manner, the first measurement coil 904 and the second measurement coil 908 are formed using the vias of the first circle of vias 1708, and the first return coil 906 and the second return coil 910 are formed using the vias of the second circle of vias 1710.

[0165] The vias on the inner circumference of the measurement conductor may be staggered, with the forward coils 904 and 908 using vias from a first circle 1708 and the return coils 906, 910 using vias from a second circle 1710. This means that the turns of the first measurement coil 904 are the same size as the turns of the second measurement coil 908, and the turns of the first return coil 906 are the same size as the turns of the second return coil 910, so that the coupling to the first and second measurement coils is balanced and the coupling to the first and second return coils is balanced. The vias in the first circle 1708 have a first diameter and the vias in the second circle 1710 have a second diameter, the first diameter being smaller than the second diameter, and the vias in the first and second circles are concentric.

[0166] This results in the inner ends of the measurement conductors constituting the first measurement coil 904 and the second measurement coil 908 being at the same distance from each other to the current-carrying conductors, and the inner ends of the measurement conductors constituting the first return coil 906 and the second return coil 910 being at the same distance from each other to the current-carrying conductors.

[0167] This arrangement results in the measurement coils 904, 908 being positioned in such a way that they are spatially equivalent because they both share the same proportion of the measurement conductors on each layer of the circuit board and are coupled using the same circle of vias, which means that the measurement conductors are the same length. This also results in the coils encircling the same area as they travel around the circuit board. The same applies to the return coils.

[0168] Staggering the vias in this manner balances the parasitic capacitances of the first and second measurement coils and the first and second return coils, respectively. This also allows more turns to be provided for all coils, since the inner circumference is smaller than the outer circumference and therefore may provide a limit on the number of vias / turns that can be achieved. Providing two inner circumferences increases the number of vias that can be placed on the inner circumference, and therefore the number of turns that the coils can have.

[0169] FIG. 21 shows the first circle via and second circle via arrangements of FIG. 17. The arrangement of FIG. 21 further includes a current-carrying conductor 2102. Typically, in prior art arrangements, the current-carrying conductor is off-centered so that it is not located at the center of the coil, which would result in unbalanced capacitive coupling to the coil, as described in connection with FIGS. 3 and 4. However, by alternating the vias in the first circle to connect alternate turns of the measurement conductor of the first and second measurement coils, the capacitive coupling between the first and second measurement coils and the current-carrying conductor under test should be approximately equal.

[0170] Similarly, by alternating the vias in the second circle to alternately connect the measurement conductors of the turns of the first and second return coils, the capacitive coupling to the first and second return coils should be approximately equal.

[0171] For example, via 2016 of the first circular vias forms part of a turn of the first measurement coil 906, and via 2022 of the first circular vias forms part of a turn of the second measurement coil 908. Due to their positions, the capacitive coupling to the turns of the first and second measurement coils should be the same or similar. Staggering the vias in this way allows the wiring of the turns of the first measurement coil 904 and the second measurement coil 908 to be spatially equal, which should mean that only common-mode noise pickup from external magnetic and electrostatic fields will occur.

[0172] Both the first and second measurement coils may share the same proportion of time between the top and bottom layers and may enclose the same square area with each turn as they move around the front. This ensures that each measurement coil (and the return coil to which they are provided) utilizes the same amount of conductive traces or conductors on each layer of the circuit board.

[0173] Although the return coil concept has been described with reference to FIGS. 17-21 for a two-layer PCB implementation, it should be apparent that it can also be implemented across four layers of a circuit board. For example, in the implementation of FIGS. 14a-14c, the compensation conductors can be replaced with first and second return coils. To implement the first and second return coils across four layers, a fifth plurality of measurement conductors can be provided on the first layer of the board, a sixth plurality of measurement conductors can be provided on the second layer of the board, a seventh plurality of measurement conductors can be provided on the third layer of the board, and an eighth plurality of measurement conductors can be provided on the fourth layer of the board. The first and second return coils can be formed using the fifth through eighth plurality of measurement conductors in the same manner as the first and second measurement coils are formed using the first through fourth plurality of measurement conductors. The first and second return coils may be interleaved with the first and second measurement coils in the plane of the substrate such that a first radial plane includes the measurement conductors of the first measurement coil and the second measurement coil, and an adjacent second radial plane includes the measurement conductors of the first and second return coils.

[0174] Terminals 912, 916, 918, and 922 of the rate of change of current sensor of Figure 9 may be connected to a further measurement circuit. As shown in Figures 10a-10c, terminals 916 and 922 of the return coil may be coupled to a common reference, for example, ground. Terminals 912, 918 of the first and second measurement coils may be coupled to a differential amplifier. This may allow the common capacitive coupling signal of the first and second measurement coils to be cancelled by the amplifier.

[0175] However, the connection from the coil to the amplifier or other measurement circuitry can be a potential source of additional unwanted electromagnetic pickup due to the unintended loop area formed by this connection.

[0176] 22 illustrates one way in which unwanted electromagnetic pickup can be reduced. First ends 912, 918 of a first measurement coil 904 and a second measurement coil 908 can be coupled to measurement circuitry at nodes 2202 and 2204 using a substrate or PCB-mounted twisted pair arrangement. The loop formed by the twisted pair is arranged so that each conductor of the twisted pair is, on average, the same distance from any interference source and therefore receives the same amount of noise coupling, which can be canceled by taking the signal difference. Conductors on the first layer of the substrate are represented by shaded lines, and conductors on the second layer of the substrate are represented as clear lines.

[0177] The twisted pair arrangement is constructed on the substrate using a plurality of connecting conductors 2206 and coupled using a plurality of connecting vias 2208. The connecting conductors 2206 are arranged to alternate between the first and second layers of the substrate using connecting vias 2208. The connecting conductors are arranged in a zigzag pattern and cross each other across the first and second layers of the substrate to form the twisted pair.

[0178] In particular, the twisted pair arrangement may be implemented in any of the PCB arrangements described and in any of the schematic diagrams of Figures 5-10. For example, when implemented in the four-layer rate of change current sensor of Figures 11-14, the twisted pair arrangement may alternate between the first and fourth layers, between the second and third layers, or any combination thereof.

[0179] Alternatively, or in combination with, the twisted pair arrangement described with respect to FIG. 22, connections to the outer measurement circuitry may be routed on a layer of the board with a small dielectric distance, thereby reducing the size of the loop created by the connection. This results in a negligible loop area and reduced electromagnetic noise pickup. For example, if the rate of change of current sensor is implemented across the first and second layers of the PCB, connections to the further current measurement circuitry may be implemented across the first and further "connection" layers of the PCB, with the dielectric distance between the first and connection layers being small relative to the dielectric distance between the first and second layers of the PCB.

[0180] For example, in a four-layer PCB, the first and second layers may be internal layers of the PCB and may be used for the first and second coils (i.e., the two layer design described above). Connection to an external measurement circuit may be made using the external layer (which may be called the "connection" layer in this example) and one of the first and second layers.

[0181] FIG. 22 shows a rate of change of current sensor mounted on a PCB or substrate including four layers 2302, 2304, 2306, and 2308. The measurement coil is mounted across two of the four layers; for example, the first layer depicted in FIGS. 17-20 could be layer 2304, and the second layer depicted in FIGS. 17-20 could be layer 2306. Connections to external measurement circuitry can be the same as the ends of the measurement / return coil shown in FIG. 9, including nodes 912, 918, 916, and 922. Nodes 916 and 922 can be tied together to a common reference or ground.

[0182] 23, nodes 916, 922 may be wired to the measurement circuitry using the first layer 2304, and nodes 912 and 918 may be wired to a common reference using the second layer 2306, but instead may be wired using layers 2302 and 2304. For example, as depicted in FIG. 23, nodes 916, 922 may be wired to the measurement circuitry using the first layer 2304, and nodes 912 and 918 may be wired to a common reference using layer 2302 (with vias used to couple nodes 912 and 918 to layer 2306). Alternatively, nodes 916, 922 may be wired to the measurement circuitry using layer 2308 (with vias used to couple nodes 916, 922 to layer 2308), and nodes 912 and 918 may be wired to a common reference using layer 2306. The dielectric distance between layers 2302 and 2304 (and between layers 2306 and 2308) is smaller than the dielectric distance between layers 2304 and 2306. This reduces the size of the loop formed by the connections of nodes 912, 918, 916, and 922 to the measurement circuitry. This also allows for a larger dielectric distance between the layers of the substrate used to route the measurement coil, increasing the area of ​​each coil turn, thereby improving the sensitivity of the coil and increasing the voltage output.

[0183] In general, a four-layer PCB stack-up can be chosen to have wide dielectric layers between the copper layers used for the measurement and return coil turns, but thin dielectric layers between layers used for connections to further measurement circuitry. This concept applies to any of the PCB designs referenced above, in that connections to external measurement circuitry are routed using layers with smaller dielectric distances than those used to route the majority of the coil turns.

[0184] To improve the sensitivity of the coils, the area enclosed by each turn of each coil may be made as large as possible while keeping the area enclosed by the turns of the first measurement coil substantially the same as the area enclosed by the turns of the second measurement coil.

[0185] For example, an eight-layer board may be provided, and a four-layer implementation may be provided, with measurement coils mounted on layers 1, 2, 7, and 8 of the board. This increases the area of ​​each coil turn, but the coils may still be arranged in an interleaved fashion across the layers. Similarly, if the circuit is a two-layer implementation, the two layers may be layers 1 and 8 of the circuit board to maximize the area enclosed by the turns.

[0186] Furthermore, shielding from external capacitive coupling may be implemented using a board with more layers than necessary to implement the measurement coils. Providing two measurement coils that essentially travel around the current-carrying conductor or path provides improved capacitive coupling in that the coils experience balanced coupling, but capacitive coupling can be further reduced by adding shielding layers to the PCB. For example, measurement coils can be implemented on inner layers of a multilayer PCB, and shielding can be implemented on outer layers of the PCB. In a six-layer board, a four-layer measurement coil can be implemented on layers 2, 3, 4, and 5 in the same alternating interleaved arrangement described above. Shielding can be implemented on layers 1 and 6 by coating layers 1 and 6 in a conductive material. Similarly, a two-layer measurement coil can be implemented on layers 2 and 3 of a four-layer board, and shielding can be implemented on layers 1 and 4.

[0187] For example, Figure 24 shows a rate of change of current sensor implemented on a four-layer PCB. First electrostatic shielding layer 2402 and second electrostatic shielding layer 2404 may be provided on layers of the board that are external to the layers used to implement the coils of the rate of change of current sensor.

[0188] PCB via technologies can involve different levels of manufacturing complexity, which affects the cost and complexity of developing a current measurement coil on a PCB. Through-hole vias are vias that extend through the entire PCB stack, starting on one surface layer and ending on another surface layer. Blind vias start on a surface layer and extend partially through the PCB stack. Buried vias do not extend through a surface layer, but instead begin and end on an internal layer of the PCB stack. Blind and buried vias tend to be more complex to manufacture than through-hole vias, but allow for the design of denser PCBs. All implementations of the current measurement coil described herein may be manufactured using blind or buried vias, although this may be undesirable due to increased manufacturing complexity; all implementations designed herein may use through-hole vias.

[0189] If the circuit board uses non-blind vias, e.g., through-hole vias 2406 as in FIG. 24, the shielding conductor material may not cover the entire outer layer because the vias reach the surface of the circuit board. Therefore, the shielding may extend to cover all areas of the shielding layer that do not contain through-hole vias. For example, the outer layer of the board may be coated with a conductor over the entire area except for etched areas 2408 surrounding each of the inner and outer vias to insulate them from the shielding layer.

[0190] The through-hole vias may be provided with sufficient spacing so that the shielding layer can be fabricated by spilling from the outermost circumference of the coil or substrate to the center of the substrate.

[0191] A hole, opening, or via 500, 2410 may be included on the substrate in the center of the current measurement coil to allow a current-carrying conductor to rest on or pass through the substrate in the center of the current measurement coil. The inner circumference of the hole may be electrostatically shielded 2412 across all layers of the circuit board by plating the inner circumference of the via. Alternatively, rather than a single shield, multiple shielding vias may be located around the inner circumference between the holes and vias at the inner circumference of the measurement conductor, extending across all layers of the circuit board. This may provide shielding for the inside of the coil.

[0192] The measurement coil can be implemented on an inner layer of a multi-layer PCB, so that outer layers can be used to route the current-carrying conductors. This eliminates the need for separate physical wire-based conductors and allows for a more compact implementation of the current measurement coil. Instead, the system can simply include contacts to which the current-carrying conductors can be connected. On a six-layer PCB, a four-layer current change rate sensor can be implemented on layers 2, 3, 4, and 5, with routing for the current-carrying conductors provided on layers 1 and 6, with vias connecting the current-carrying conductors on layers 1 and 6 to the center of the measurement coil.

[0193] If the rate of change of current sensor is implemented on a PCB with eight or more layers, shielding may be implemented between the PCB-based current-carrying conductors and the measurement coil. For example, a four-layer rate of change of current sensor may be implemented on layers 3-6, with shielding implemented on layers 2 and 7, and input current-carrying PCB traces implemented on layers 1 and 8.

[0194] Although only a few examples of shields and wiring current-carrying conductors are described here, it will be apparent that if the printed circuit board has six, eight, or more layers, multiple combinations of measurement coil, shield, and current-carrying conductor connections may be implemented across different layers of the circuit board.

[0195] The rate of change of current sensor may be implemented such that the measurement coil travels substantially 360° around the hole or current-carrying conductor, e.g., as in Figures 5-10. However, the rate of change of current sensor may be implemented using a combination of shorter coils, each of which travels less than 360°. For example, the first measurement coil may be implemented as two 180° coils, and the second measurement coil may be implemented as two 180° coils.

[0196] For example, Figure 25 shows a rate of change of current sensor including 180° coil segments. The first measurement coil is made up of two 180° measurement coil segments and two 180° return coil segments.

[0197] The first measurement segment begins at node 2502 and travels 180° to node 2504, which is also connected to a first return segment that travels 180° from node 2504 to node 2506. The second measurement segment begins at node 2508 and travels 180° to node 2510, which is also connected to a second return segment that travels 180° from node 2510 to node 2512. In this manner, a first measurement coil that travels 360° is formed from the first measurement segment and the second measurement segment. Similarly, a first return coil that travels 360° is formed from the first return segment and the second return segment.

[0198] The third measurement segment begins at node 2514 and travels 180° to node 2516, which is also connected to a third return segment that travels 180° from node 2516 to node 2518. The fourth measurement segment begins at node 2520 and travels 180° to node 2522, which is also connected to a fourth return segment that travels 180° from node 2522 to node 2524. In this manner, a second measurement coil that travels 360° is formed from the third measurement segment and the fourth measurement segment. Similarly, a second return coil that travels 360° is formed from the third return segment and the fourth return segment.

[0199] This arrangement provides a system in which the first and second measurement and return coils still provide a balanced coupling while leaving a gap above the measurement coils, which may allow the rate of change of current sensor to be provided across multiple, e.g., two, boards or circuit boards.

[0200] The individual measurement coil segments may be located on the same printed circuit board, or alternatively, on separate circuit boards, which may be useful for clamp-on types of current sensors or brownfield applications where it is not possible to pass current carrying wires through the sensor due to disassembly constraints.

[0201] Furthermore, each measurement coil or return coil may be composed of two or more segments, for example, a first measurement coil may be implemented using four measurement segments, each providing a 90° progression, six measurement segments, each providing a 60° progression, or eight measurement segments, each providing a 45° progression.

[0202] The first and second measurement coils in FIG. 25 are identical in structure, except that the layers may be reversed on the second measurement coil relative to the first measurement coil. In other words, the first measurement coil may start on the first layer, and the second measurement coil may start on the second layer. Reversing the layers may result in the desired signal, which is magnetic coupling to a current-carrying conductor, having opposite polarity between the two coils, and the undesired signal from an external magnetic or electrostatic field having the same polarity between the two coils. Thus, in the circuit, the undesired signal may be canceled, and the desired signal may be constructively added.

[0203] Figure 26 shows an example of how each node of the circuit of Figure 25 can be connected to further measurement circuitry. A first differential amplifier 2602 receives signals from nodes 2502 and 2514 as inputs. Nodes 2506 and 2518 can be connected to a common reference, such as ground. A second differential amplifier 2604 receives signals from nodes 2508 and 2520 as inputs. Nodes 2512 and 2524 can be connected to a common reference, such as ground. The outputs of the first differential amplifier 2602 and the second differential amplifier 2604 can be connected to a third differential amplifier 2606. The output of the third differential amplifier 2608 can be a current measurement signal.

[0204] Various modifications may be made to the above examples to provide further examples, whether by adding, deleting, or substituting features, any and all of which are intended to be encompassed by the appended claims.

Claims

1. A current change rate sensor, the current change rate sensor comprising: a path for at least one current-carrying conductor; a first measurement coil, the first measurement coil traveling around the path in a first circumferential direction, the first measurement coil having a first end and a second end; a first return coil having a first end and a second end, the first end of the first return coil coupled to the second end of the first measurement coil, the first return coil traveling around the path in a circumferential direction opposite the first circumferential direction; a second measurement coil, the second measurement coil traveling around the path in a second circumferential direction, the second measurement coil having a first end and a second end; a second return coil having a first end and a second end, the first end of the second return coil being coupled to the second end of the second measurement coil, the second return coil traveling around the path in a circumferential direction opposite the second circumferential direction; the first measurement coil and the second measurement coil are interleaved in a radial plane perpendicular to the surface of the substrate such that a first turn of the first measurement coil and a first turn of the second measurement coil lie in the same radial plane perpendicular to the surface of the substrate; or a current change rate sensor, wherein the first measurement coil and the second measurement coil are interleaved such that a first turn of the first measurement coil lies in a first radial plane perpendicular to a surface of the substrate and a first turn of the second measurement coil lies in a second radial plane perpendicular to the surface of the substrate, and the first radial plane and the second radial plane are adjacent to each other in the circumferential direction.

2. 2. The rate of change of current sensor of claim 1, wherein said first circumferential direction and said second circumferential direction are the same circumferential direction.

3. 3. The rate of change of current sensor of claim 1, wherein the first measurement coil, the second measurement coil, the first return coil, and the second return coil each travel substantially around the path.

4. the rate of change of current sensor is a differential rate of change of current sensor providing a differential output signal; the first end of the first measurement coil provides a first one of the differential output signals; the first end of the second measurement coil provides a second one of the differential output signals; 4. The rate of change of current sensor of claim 1, wherein the second end of the first return coil is coupled to the second end of the second return coil and is further coupled to a common reference signal.

5. the first measurement coil comprises a first measurement coil segment and a second measurement coil segment; the first return coil comprises a first return coil segment and a second return coil segment, the first measurement coil segment is coupled to the first return coil segment, and the second measurement coil segment is coupled to the second return coil segment; the second measurement coil comprises a third measurement coil segment and a fourth measurement coil segment; the second return coil comprises a third return coil segment and a fourth return coil segment, the third measurement coil segment is coupled to the third return coil segment, and the fourth measurement coil segment is coupled to the fourth return coil segment; 2. The rate of change sensor of claim 1 wherein each coil segment travels substantially 180 degrees circumferentially around said path.

6. A rate of change of current sensor according to any preceding claim, wherein an electrostatic shield is provided around the path between the path and the measurement coil.

7. 7. The current change rate sensor according to claim 1, wherein the first measurement coil and the second measurement coil are formed on an inner layer of a substrate, and an electrostatic shielding portion is formed on an outer layer of the substrate.

8. Further comprising a first connecting conductor and a second connecting conductor; 8. The rate of change of current sensor of claim 1, wherein the first end of the first measurement coil is suitable for coupling to a first node of a current measurement circuit using the first connecting conductor, and the first end of the second measurement coil is suitable for coupling to a second node of the current measurement circuit using the second connecting conductor, and the first and second connecting conductors are arranged using a twisted pair arrangement.

9. A current change rate sensor, the current change rate sensor comprising: a substrate, the substrate including a path for at least one current-carrying conductor; a first measurement coil formed on the substrate, the first measurement coil traveling around the path in a first circumferential direction; a second measurement coil formed on the substrate, the second measurement coil progressing around the path in a second circumferential direction; the first measurement coil and the second measurement coil are interleaved in a radial plane perpendicular to the surface of the substrate such that a first turn of the first measurement coil and a first turn of the second measurement coil lie in the same radial plane perpendicular to the surface of the substrate; or a current change rate sensor, wherein the first measurement coil and the second measurement coil are interleaved such that a first turn of the first measurement coil lies in a first radial plane perpendicular to a surface of the substrate and a first turn of the second measurement coil lies in a second radial plane perpendicular to the surface of the substrate, and the first radial plane and the second radial plane are adjacent to each other in the circumferential direction.

10. 10. The rate of change of current sensor of claim 9, wherein the first measurement coil and the second measurement coil are interleaved on the substrate such that they both have the same average capacitive coupling to a current-carrying conductor under measurement, the current-carrying conductor following the path.

11. 10. The rate of change of current sensor of claim 9, wherein the first turn of the first measurement coil is formed on the first and third layers of the substrate, and the first turn of the second measurement coil is formed on the second and fourth layers of the substrate.

12. a first compensation conductor formed on the substrate and coupled to the first measurement coil, the first compensation conductor traveling around the path in a circumferential direction opposite the first circumferential direction; and 12. The rate of change of current sensor of claim 9, further comprising: a second compensation conductor formed on the substrate and coupled to the second measurement coil, the second compensation conductor traveling around the path in a circumferential direction opposite the second circumferential direction.

13. 13. The current change rate sensor according to claim 9, wherein the first circumferential direction and the second circumferential direction are the same circumferential direction.

14. 14. The rate of change sensor of claim 9, wherein the first measurement coil travels an integer multiple of 360 degrees around the path and the second measurement coil travels the same integer multiple of 360 degrees around the path.

15. 15. The current change rate sensor of claim 9, further comprising a twisted pair arrangement formed on the substrate, the twisted pair comprising a first connecting conductor and a second connecting conductor, the first connecting conductor coupled to the first measurement coil and a first node, the second connecting conductor coupled to the second measurement coil and a second node, the first connecting conductor and the second connecting conductor arranged on the substrate to alternately cross each other, and the first and second nodes being outputs from the current change rate sensor.

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