Four-terminal current measurement shunt resistor assembly

Abstract

The present invention relates to a four-terminal current measurement shunt resistor assembly comprising a shunt resistor portion, a sensing loop and a PCB portion, where the shunt resistor portion comprises two low resistance portions connected by a high resistance portion, and where the PCB portion connects the two low resistance portions to each other via two contact points.

Description

Technical Field

[0001] The present invention relates to a four-terminal current measuring shunt resistor assembly, which includes a shunt resistor portion, a sensing loop, and a PCB portion. Wherein, the shunt resistor portion includes two low-resistance portions connected by a high-resistance portion, and wherein the PCB portion connects the two low-resistance portions to each other via two contact points. Background Art

[0002] Shunt resistor assemblies are used for current measurement. Such measurements may occur at high frequencies, at which problematic inductive effects and skin effects dominate the characteristics and output of the shunt resistor, and degrade the performance of the shunt resistor. Known shunt resistors may include a coaxial shunt structure made of a U-shaped component. Such known shunt resistors can perform well technically, but they are complex, difficult to mass-produce, and expensive. Summary of the Invention

[0003] The object of the present invention is to provide an improved resistor system that overcomes the above problems and ensures that the shunt resistor functions correctly even at high frequencies.

[0004] This object is achieved by a four-terminal current measuring shunt resistor according to claim 1. Advantageous embodiments of the present invention are subject to the dependent claims.

[0005] Claim 1 relates to a four-terminal current measuring shunt resistor assembly, which includes a shunt resistor portion, a sensing loop, and a PCB portion. Wherein, the shunt resistor portion includes two low-resistance portions connected to each other by a high-resistance portion, and wherein the PCB portion connects the two low-resistance portions to each other via two contact points. The two contact points are the sensing terminals of the shunt resistor assembly.

[0006] Therefore, the core of the present invention lies in the use of a special geometry of the components in the claimed potential measuring circuit and its implementation as a printed circuit board structure. This printed circuit board structure facilitates the addition of other possible compensating components and other components. The present invention allows the use of strip-shaped shunt resistors to improve behavior during high-frequency current measurement. The present invention provides a simple and cost-effective solution to the above problems, is easy to mass-produce, and provides a good frequency response. In addition, the present invention allows the expansion of the usable frequency range.

[0007] In a preferred embodiment of the present invention, the low-resistance portion is made of copper, and / or the high-resistance portion is made of manganin alloy, which is an alloy containing 84.2% ± 2.0% copper, 12.1% ± 2.0% manganese, and 3.7% ± 2.0% nickel.

[0008] In another preferred embodiment of the present invention, the sensing loop is arranged symmetrically. In particular, the sensing loop may have a rectangular shape.

[0009] In another preferred embodiment of the present invention, the PCB part is preferably directly mounted to the shunt resistor part via a contact point located in the middle of the shunt resistor part, and / or the conductor within the PCB part is routed across the shunt resistor part at a distance corresponding to 20% ± 5% of the width of the shunt resistor part from the edge of the shunt resistor part.

[0010] In another preferred embodiment of the present invention, the PCB part includes the sensing loop, a high-frequency compensation network, a Delta-Sigma AD converter, a current measurement electronic circuit, an IGBT driver, and / or a driving device.

[0011] In another preferred embodiment of the present invention, the shunt resistor part includes a self-inductive part serially coupled to a resistive shunt part.

[0012] In a particularly preferred embodiment of the present invention, the shunt resistor part includes a voltage sensing inductive part serially coupled to the high-frequency compensation network.

[0013] In another particularly preferred embodiment of the present invention, the high-frequency compensation network includes an RC filter for blocking a specific output frequency. The blocked frequency can be selected according to the actual requirements of the current shunt resistor assembly.

[0014] In another preferred embodiment of the present invention, the shunt resistor part has a substantially rectangular shape, wherein the outer edge of the shunt resistor part is preferably continuous and straight.

[0015] In another preferred embodiment of the present invention, one of the contact points is aligned with the sensing loop. The alignment of the contact point with the sensing loop provides a symmetric arrangement of the components, thereby improving the performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other details and advantages of the present invention are described with reference to the embodiments shown in the accompanying drawings, the features of which may be part of the present invention in any possible combination. The drawings show:

[0017] Figure 1 : The principle of the optimal potential lead placement of the current measurement shunt resistor assembly;

[0018] Figure 2 : The model of the current measurement shunt resistor assembly; and

[0019] Figure 3 : Perspective view of a model of a current measurement shunt resistor assembly. DETAILED DESCRIPTION

[0020] Figure 1 Illustrates the principle of the optimal potential lead placement of the currently described current measurement shunt resistor assembly. The current measurement shunt resistor assembly includes four terminals and a shunt resistor section 10, sense loops 3, b, a, 2, d, c, 3, and a PCB section 13 shown as a gray shaded area. The shunt resistor section 10 includes two low-resistance sections 11 connected by a high-resistance section 12. The PCB section 13 connects the two low-resistance sections 11 to each other via two contact points 1, 2.

[0021] The low-resistance sections 11 can be made of copper or some other metal such as aluminum. The high-resistance section 12 can be made of manganin, which is an alloy containing 84.2% ± 2.0% copper, 12.1% ± 2.0% manganese, and 3.7% ± 2.0% nickel. Alternative high-resistance materials can also be used.

[0022] Electron beam welding EBW can be used as an economical way to manufacture the entire shunt resistor section 10 including the low-ohm shunt resistor sections 11 and the high-resistance section 12. During the manufacturing process, two copper strips and one manganin strip are fed from the reels to the welding machine as a continuous process. After welding, typically by a stamping process, the welded strips are cut to a certain length to form the individual shunt resistor sections 10.

[0023] Typical physical parameters of such shunt resistor sections 10 can be on the order of 85 mm x 36 mm in size and have a resistance of, for example, 50 μΩ. The pin terminals 1, 2 are used for voltage sensing and for mounting the PCBA 13 to the low-resistance sections 11 of the shunt resistor section 10. Each low-resistance section 11 can include another terminal. The shunt resistor section 10 can be easily used with a bus bar structure and corresponding bolt connections.

[0024] This wide-strip-shaped resistor exhibits more complex high-frequency behavior than the case of a small symmetric round-bar resistor. At higher frequencies, the current increasingly concentrates at the sharp corners of the strip-shaped resistor. This results in a phase shift of the current distribution and a phase shift of the magnetic field around the shunt.

[0025] By providing a shunt structure with a high-resistance section 12, the high-frequency behavior can be significantly improved. In this shunt structure, the current return conductor is located on the other side of the strip, i.e., below the high-resistance section 12, and preferably opposite to the PCBA 13 and as close as possible to the shunt resistor section 10. The high-resistance section 12 can be a U-shaped structure, in which the current is very evenly distributed in the manganin alloy section. Since this geometry also causes a field cancellation effect around the structure, the mutual inductance of the voltage sensing part (i.e., Figure 2 the voltage sensing inductance part L shown se ) is greatly reduced.

[0026] To minimize production costs, the shunt can be directly mounted between two straight busbar structures. In this case, by making the voltage measurement loop or its potential leads as small as possible and pressing them tightly against the shunt metal, the mutual coupling can be minimized. This can minimize the noise voltage caused by stray fields. In this case, with single-pole compensation, phase shift may occur.

[0027] Therefore, by making the sensing loop larger and farther away from the shunt surface, the behavior of the sensing loop can be improved. However, making the loop larger purposefully conflicts with minimizing the stray field effect of the circuit. The reference numeral 1 referring to one of the contact points represents the optimal position of the potential lead structure. From the viewpoints of both inductance and skin effect, it provides good compensation.

[0028] The actual potential measurement contact points 1 and 2 of the resistor are located in the middle of the strip, and the wire connected to point 2 crosses the resistor wiring at a distance of about 20% of the strip width from the edge. The output signals are taken from points 1 and 3.

[0029] The error voltage present in the voltage between points 1 and 2 is cancelled by the voltages induced in the d-c part and a-b part of the path. Any voltage induced in the 2-d part or 2-a part is cancelled in the c-3 part or in the b-3 part respectively by the symmetric structure. The wires of the sensing loop 3, b, a, 2, d, c, 3 are located at a distance of 20% of the strip width from the edge, close to the point where the imaginary component of the flux density intersects the zero line. The a, b regions and c, d regions (i.e., the regions between the a-b part and the edge of the strip, and the regions between the c-d part and the opposite edge of the strip) give good possibilities for fine-tuning the frequency response by changing the distance from the edge. In Figure 1 it, this distance is expressed as about 0.2 of the total width W of the strip.

[0030] The components of the shunt resistor assembly can be arranged such that there is no net flux through the total loop 3 - b - a - 2 - d - c - 3 in the direction normal to the surface. Thus, no corresponding current component flows in the loop.

[0031] Even in the case of an asymmetric geometry 2 - a - b - 3 or 2 - d - c - 3, the compensation can work well. However, a symmetric structure is beneficial because it has a canceling effect on both the normal direction field from the shunt and the stray fields from other circuits besides the shunt itself.

[0032] The sensing loop 3, b, a, 2, d, c, 3 can be arranged symmetrically. In particular, the sensing loop 3, b, a, 2, d, c, 3 can have a rectangular shape. It can be symmetric about the direction of current flow, which is the Figure 1 vertical direction in, which is perpendicular to the width direction indicated by the large arrow W.

[0033] The PCB part 13 can be directly mounted to the shunt resistor part 10 via the contact points 1, 2 located in the middle of the shunt resistor part 10. The PCB part 13 is indicated by the Figure 1 gray area in. The middle of the shunt resistor part 10 can refer to its vertical center line with respect to its width direction. The conductors of the PCB 13 can be routed across the shunt resistor part 10 at a distance corresponding to 20% ± 5% of the width of the shunt resistor part 10 from the side edges of the shunt resistor part 10 (as shown by the two small arrows W). The side edges are the edges that define the width of the shunt resistor assembly.

[0034] The PCB part can include the sensing loop 3, b, a, 2, d, c, 3, a high - frequency compensation network, a Delta - Sigma AD converter, current measurement electronic circuits, an IGBT driver, and / or a driving device, which are not shown in detail in the drawings. The shunt resistor part 10 can have a substantially rectangular shape, where the outer edges of the shunt resistor part 10 are preferably continuous and / or straight. At least one of the contact points 1, 2 can be aligned with the sensing loop 3, b, a, 2, d, c, 3. The alignment of the contact points 1, 2 with the sensing loop 3, b, a, 2, d, c, 3 provides a symmetric arrangement of the components, thus improving the performance of the device. For example, the c - 3 - b part of the loop can be aligned with pin 1, making them all on the same line for better symmetry, as will be shown in Figure 3 as shown. To achieve this, the c - 3 - b part of the loop can include a bent part, and pin 1 can be positioned within this bent part.

[0035] Key points of the present invention include the geometry of the potential lead structure, namely the geometry of the sensing loop 3, b, a, 2, d, c, 3. The shape of the sensing loop 3, b, a, 2, d, c, 3 can be implemented as printed circuit board (PCB) traces in a board, where the PCB is directly mounted to the shunt.

[0036] The present invention provides an economical shunt resistor assembly design with very good tolerances. Since the sensing terminals are arranged in the middle of the strip, it is easily implemented into commercially available resistors.

[0037] The shape of the shunt can deviate from Figure 1 the exact shape presented in to further optimize the function of the device. Since different metals are involved in the EBW shunt, the shape can be further optimized. The sensing loop 3, b, a, 2, d, c, 3 can be mounted as close as possible to the shunt surface. This means that there can be no gap between the PCB including the sensing loop 3, b, a, 2, d, c, 3 and the shunt. Therefore, the loop area in the normal direction of the shunt surface is minimized, and the voltage induced by the stray field in this direction is greatly reduced.

[0038] The center line of the strip-shaped shunt resistor is at the optimal placement of the signal takeout because the normal direction field has a zero point in the middle of the shunt resistor (i.e., at the vertical center line in the middle between the two vertical sides of the shunt resistor part 10 shown in Figure 1 ). This shunt resistor assembly is beneficial for its connection to connectors, amplifiers, AD converters, and other front-end electronic circuits, and for the placement of these components relative to the shunt resistor part. The position of the copper part or the low-resistance part 11 also helps to improve the performance of the device. Due to the higher conductivity of copper, more current accumulates at the corners of the strip-shaped shunt resistor rather than in the manganin part or the high-resistance part 12, and thus the field strength tends to be lower.

[0039] The present invention also enhances compensation and frequency response. The overall system may or may not include Figure 2 the compensation poles of the compensation network. In many cases, some residual inductance is beneficial: although the compensation poles straighten the measured frequency response, they attenuate the unwanted noise signals induced from the stray field to the system. Additional filtering can also be provided, for example, for anti-aliasing purposes. By changing the Figure 1 distance of the a-b line and the d-c line shown in from the edge of the shunt resistor, the frequency response of the device can be adjusted. Depending on the application, the placement of the loop can be selected so that the device is purposefully tuned from the optimal flat response point. The total compensation can include both analog filtering and digital filtering.

[0040] The principle of the device described currently can be used with resistance materials and material combinations other than manganin alloys (including pure copper). Therefore, the a-b / d-c distance from the edge of the shunt resistor can vary according to the material selection.

[0041] A U-shaped shunt resistor with a return conductor can also be used with the proposed potential lead structure. In addition to the current measurement electronic circuit, other electronic circuits can also be included for the PCB, such as IGBT drivers, preferably complete drive devices in a relatively small current range, where the main current-carrying traces are also arranged in the same PCBA and / or multi-layer structure to distinguish the potential measurement structure and the main current part of the device.

[0042] Figure 2 A model of the currently described current measurement shunt resistor assembly is shown. The basic model for a four-terminal current measurement shunt assembly can include a frequency compensation network. The resistor model consists of a resistor R s , a self-inductance L s , and a voltage sensing circuit inductance L se . Therefore, the voltage U s1 has both a resistive component and an inductive component.

[0043] Due to the inductance involved, the system transfer function from I1 to U s1 is zero at the frequency f z = R s / 2πL M , where L M is the mutual inductance or effective inductance between the L s circuit and the L se circuit. Above the zero frequency, the amplitude response rises infinitely. Therefore, if this region belongs to the frequency range of interest, measures must be taken. To limit the power consumption in the resistor, it is desirable to use as low a resistance value as possible. When the measurement range is from several hundred amperes to several thousand amperes, a resistance value in the order of several tens of micro-ohms is practical. The inductance value can be in the nH range, so the zero of the system transfer function tends to occur at relatively low frequencies, and phase shift errors will be generated even at the fundamental frequency of the output of the drive device of the shunt resistor assembly.

[0044] By adding a compensation network to the signal path, the transfer function zero can be cancelled. A corresponding RC circuit can add a pole to the transfer function, and by satisfying R c C c = L M / R s , the voltage U s2 can have a completely flat frequency response. Instead of an RC network, a dedicated compensation coil can also be inserted near the resistor structure to eliminate the mutual inductance.

[0045] If the mechanical dimensions of the shunt resistor are less frequency-dependent and the structure is mechanically or geometrically symmetric, such as being circular, then the idealized model of the compensation network having Figure 2 works well. For example, if the shunt resistor (Rs) is made of a round bar and the diameter of the shunt resistor is small enough such that the skin effect can be neglected or has only a minimal effect.

[0046] The shunt resistor section 10 may include a self-inductance section Ls serially coupled to the resistive shunt section Rs. The shunt resistor section 10 may include a voltage-sensing inductance section Lse serially coupled to a high-frequency compensation network indicated by the dashed line. The high-frequency compensation network includes an RC filter Rc, Cc for blocking a specific output frequency. The frequency to be blocked can be selected according to the actual requirements of the current shunt resistor assembly.

[0047] Figure 3 is a perspective view of the current-measuring shunt resistor assembly. The external solder points 14 provide a mechanical connection means for connecting the shunt resistor section 10 to the PCB section 13 or other components. The internal solder points 15 provide a signal connection between the shunt resistor section 10 and the sensing loop 3, b, a, 2, d, c, 3. The internal solder points 15 coincide with the loop points 1 and 2. The output points 16 correspond to the loop points 3 and the contact point 1. These output points 16 are provided for capturing the measurement signal. The signal can continue from these points to, for example, a compensation network and an AD converter.

Claims

1. A four-terminal current measurement shunt resistor assembly, comprising: A shunt resistor section (10); A sensing loop (3, b, a, 2, d, c, 3); And A PCB section (13), wherein The shunt resistor section (10) includes two low-resistance sections (11) connected by a high-resistance section (12), and wherein the PCB section (13) connects the two low-resistance sections (11) to each other via two contact points (1, 2).

2. The four-terminal current measurement shunt resistor component according to claim 1, characterized in that, The low-resistance section (11) is made of copper, and / or the high-resistance section (12) is made of manganin alloy, which is an alloy containing 84.2% ± 2.0% copper, 12.1% ± 2.0% manganese, and 3.7% ± 2.0% nickel.

3. The four-terminal current measuring shunt resistor assembly according to any one of the preceding claims, characterized in that, The sensing loop (3, b, a, 2, d, c, 3) is arranged symmetrically.

4. The four-terminal current measuring shunt resistor assembly according to any one of the preceding claims, characterized in that, The PCB section (13) is preferably directly mounted to the shunt resistor section (10) via contact points (1, 2) located in the middle of the shunt resistor section (10), and / or is characterized in that conductors are routed across the shunt resistor section (10) at a distance corresponding to 20% ± 5% of the width of the shunt resistor section (10) from the edge of the shunt resistor section (10).

5. The four-terminal current measuring shunt resistor assembly according to any one of the preceding claims, characterized in that, The PCB section (13) includes the sensing loop (3, b, a, 2, d, c, 3), a high-frequency compensation network, a Delta-Sigma AD converter, a current measurement electronic circuit, an IGBT driver, and / or a driving device.

6. The four-terminal current shunt resistor assembly according to any one of the preceding claims, characterized in that, The shunt resistor section (10) includes a self-inductance section (Ls) serially coupled to a resistive shunt section (Rs).

7. The four-terminal current shunt resistor assembly according to at least claims 5 and 6, characterized in that, The shunt resistor section (10) includes a voltage sensing inductance section (Lse) serially coupled to the high-frequency compensation network.

8. The four-terminal current shunt resistor component according to claim 7, characterized in that, The high-frequency compensation network includes an RC filter (R C , Cc) for blocking a specific output frequency.

9. The four-terminal current measuring shunt resistor assembly according to any one of the preceding claims, characterized in that The shunt resistor section (10) has a substantially rectangular shape, wherein the outer edge of the shunt resistor section (10) is preferably continuous and straight.

10. The four-terminal current measuring shunt resistor assembly according to any one of the preceding claims, characterized in that, One of the contact points (1) is aligned with the sensing loop (3, b, a, 2, d, c, 3).

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