Compensation current sensor arrangement

Abstract

Current sensor arrangement based on the compensation principle with a primary conductor (6) designed to generate a primary magnetic field dependent on a current flowing through it, which is to be measured, a first secondary winding (21) which is designed to generate a first secondary magnetic field dependent on a first compensation current (is1) flowing through it, a second secondary winding (22) which is designed to generate a second secondary magnetic field dependent on a second compensation current (is2) flowing through it, a magnetic field sensor (58) designed to generate a measurement signal representing a magnetic field detected by it, a magnetic core (54) made of soft magnetic material, which is designed and arranged to magnetically couple the primary conductor (6), first secondary winding (21), second secondary winding (22) and magnetic field sensor (58) together, a first evaluation circuit (8) connected downstream of the magnetic field sensor (58) and upstream of the first secondary winding (21), which is configured to generate a first compensation current (is1) corresponding to the measurement signal of the magnetic field sensor (58) and to supply the first secondary winding (21), and a second evaluation circuit (10) connected upstream of the second secondary winding (22), which is designed to generate a second compensation current (is2) corresponding to the first compensation current (is1) and to supply the second secondary winding (22), wherein the magnetic field detected by the magnetic field sensor (58) is the magnetic field in the magnetic core resulting from the superposition of the primary magnetic field, the first secondary magnetic field and the second secondary magnetic field, the first compensation current (is1) and the second compensation current (is2) are adjusted by the first evaluation circuit (8) and the second evaluation circuit (10) so that the resulting magnetic field detected by the magnetic field sensor (58) approaches zero, the first or second compensation current (is1, is2) represents the current (ip) flowing in the primary conductor (6) to be measured and the second evaluation circuit (10) has a device that evaluates the first compensation current (is1) and sets the second compensation current (is2) proportionally to the measured first compensation current (is1).

Description

[0001] The invention relates to a current sensor arrangement based on the compensation principle.

[0002] Current sensor assemblies are used to determine the electric current intensity of a current being measured and are specialized measuring transducers that operate according to different principles. Current sensor assemblies that operate on the compensation principle, also called compensation current sensor assemblies or simply compensation current sensors, typically have a magnetic core made of soft magnetic material that surrounds a primary conductor carrying the current to be measured. The current to be measured flows through the primary conductor and generates a (primary) magnetic field in the magnetic core, which is compensated by a (secondary) magnetic field generated by a compensating current in a secondary winding wound around the core.For this purpose, the magnetic flux in the magnetic core is measured using a magnetic field sensor and regulated towards zero by means of an evaluation circuit. This is achieved by feeding a suitable compensation current into the compensation winding, which, when the resulting magnetic flux in the magnetic core is zero, is proportional to the primary current being measured. Publication DE 100 52 171 A1 describes a compensation current sensor with a floating load. Its reference potential is actively regulated to a freely selectable level, thereby reducing power loss.

[0003] However, during the operation of such compensation current sensors, short-term peak currents can occur that are significantly higher than the rated current (continuous current). With conventional compensation current sensors, the ratio of permissible peak current to rated current is less than two. However, a ratio greater than two, and often greater than three, is advantageous in many cases. At the same time, the transformation ratio should be high, for example, 1:5000, while minimizing power loss. A corresponding improvement of known compensation current sensors is therefore desirable.

[0004] This is achieved by a current sensor arrangement based on the compensation principle. This arrangement comprises a primary conductor configured to generate a primary magnetic field dependent on the current flowing through it, which is to be measured. Furthermore, a first secondary winding is provided, configured to generate a first secondary magnetic field dependent on a first compensation current flowing through it, and a second secondary winding is provided, configured to generate a second secondary magnetic field dependent on a second compensation current flowing through it.The arrangement further comprises: a magnetic field sensor configured to generate a measurement signal representing a magnetic field detected by it; a magnetic core made of soft magnetic material, configured and arranged to magnetically couple the primary conductor, first secondary winding, second secondary winding, and magnetic field sensor; a first evaluation circuit connected downstream of the magnetic field sensor and upstream of the first secondary winding, configured to generate a first compensation current corresponding to the measurement signal of the magnetic field sensor and thereby supplying the first secondary winding; and a second evaluation circuit connected upstream of the second secondary winding, configured to generate a second compensation current corresponding to the first compensation current and thereby supplying the second secondary winding.The magnetic field detected by the magnetic field sensor is the magnetic field in the magnetic core resulting from the superposition of the primary, first secondary, and second secondary magnetic fields. The first and second compensation currents are adjusted by the first and second evaluation circuits, respectively, so that the resulting magnetic field detected by the magnetic field sensor becomes zero. The first or second compensation current represents the current flowing in the primary conductor that is to be measured, and the second evaluation circuit includes a device that evaluates the first compensation current and adjusts the second compensation current proportionally to the measured first compensation current.

[0005] The invention is explained in more detail below with reference to the exemplary embodiments shown in the figures of the drawing, where identical elements are provided with the same reference numerals. The drawing shows: Fig. 1 in a simplified schematic representation the mechanical construction and electrical wiring of an exemplary improved compensation current sensor with two compensation windings. Fig. 2 in a circuit diagram a first exemplary design of the compensation current sensor according to Fig. 1 each with a driver for the compensation windings. Fig. 3 in a circuit diagram a second exemplary embodiment of the compensation current sensor according to Fig. 1 with two drivers in full bridge configuration and two measuring resistors in series with the two secondary windings. Fig. 4 in a circuit diagram a third exemplary embodiment of the compensation current sensor according to Fig. 1 with two drivers in full bridge configuration and two measuring resistors each connected between two partial windings of the two secondary windings. Fig. 5 in a circuit diagram a fourth exemplary embodiment of the compensation current sensor according to Fig. 1 with two drivers in full bridge configuration and four measuring resistors leading to ground and each connected in pairs between two partial windings of the two secondary windings. Fig. Figure 6 in a circuit diagram shows an exemplary linear driver that generates a linear output voltage that depends on the input voltage. Fig. Figure 7 in a circuit diagram shows an exemplary pulsed driver that generates a pulse-width modulated output voltage that depends on the input voltage. Fig. Figure 8 in a circuit diagram shows an exemplary linear driver that generates a linear output current that depends on the input voltage. Fig. 9 in a schematic representation a ring-shaped magnetic core for use in the in Fig. 1 compensation current sensor shown. Fig. 10 in a circuit diagram a fifth exemplary embodiment of the compensation current sensor according to Fig. 1 with a driver in full bridge configuration and two ground-leading measuring resistors connected in pairs between two partial windings of the first secondary winding and a half bridge with measuring resistor for the second compensation winding.

[0006] Fig. Figure 1 shows a schematic representation of an example of an improved compensation current sensor. The compensation current sensor has four windings 1, 2, 3, and 4 wound on a closed magnetic core 5 made of a soft magnetic material such as iron or iron alloys. In this case, the magnetic core 5 has the form of a toroidal core with a rectangular base structure and rectangular cross-section (not visible from the figure). Fig. 1) Due to its rectangular shape, the magnetic core 5 has four legs, two of which are opposite each other and each contains two of the windings 1, 2, 3, and 4. Windings 1 and 2 are wound around one of these two legs, while windings 3 and 4 are wound around the other. To achieve this, winding 1 or 3 is first applied to the respective legs, and then winding 2 or 4 is wound over them. Windings 1 and 3 are electrically connected in series and together form a first secondary winding 21. Similarly, windings 2 and 4 are electrically connected in series and together form a second secondary winding 22.

[0007] Instead of the magnetic core 5 with rectangular base structure and rectangular cross-section, any shapes can be used for the base structure and cross-section, such as round ones (see below). Fig. 9), oval, square, or polygonal basic structures and cross-sections, provided that the basic structure of the magnetic core 5 is a closed shape with a central opening. A closed basic structure is understood to mean that the central opening completely encloses the core or almost completely, except for a narrow air gap relative to the overall circumference of the magnetic core, with a small gap width relative to the circumference of the central opening. Any combination of different basic structures and cross-sections of the magnetic core 5 is possible. Furthermore, instead of windings 1 and 2 or 3 and 4 wound one on top of the other, windings wound inside each other or alternating sections wound along the circumference of the magnetic core can also be provided.

[0008] A primary conductor 6 is guided through the central opening of the magnetic core 5 in a largely straight line, carrying a current to be measured, hereinafter referred to as the primary current ip. Instead of guiding the primary conductor 6 more or less straight through the central opening, it can also be wound around the magnetic core 5 as a further winding, i.e., as a primary winding.

[0009] Furthermore, a magnetic field sensor 7 is provided, which in this case is housed in an almost completely enclosed recess in the magnetic core 5 beneath the winding 1. For example, electromagnetically operating sensors, which in the simplest case consist only of a single winding, or semiconductor sensors utilizing the so-called Hall effect can be used as the magnetic field sensor 7. Alternatively, the magnetic field sensor 7 can also be arranged on the outside of the magnetic core 5, in an outwardly opening indentation, or—if an air gap is present—within it.

[0010] A first evaluation circuit 8 is connected downstream of the magnetic field sensor 7. This circuit processes a measurement signal supplied by the magnetic field sensor 7 and provides a corresponding current. This current represents the compensation current is1 and is controlled by the magnetic field sensor 7 in conjunction with the first evaluation circuit 8 such that the resulting magnetic flux in the magnetic core 5 is approximately zero, and thus the compensation current is1 is proportional to the primary current ip. The compensation current is1 is conducted to ground G (reference potential) via the series connection of winding 1 and winding 3 (first secondary winding 21) and the input circuit of a second evaluation circuit 10.The second evaluation circuit 10 measures the first compensation current is1 and generates a second compensation current is2 proportional to the first compensation current is1. This second compensation current is2 is routed to ground G through the series connection of winding 2 and winding 4 (second secondary winding 22) and a series-connected ohmic resistor 9. The second compensation current is2 is proportional to the first compensation current is1 and smaller than it. Due to its proportionality to the first compensation current is1, it also represents the current flowing in the primary conductor, the primary current ip, which is to be measured. Consequently, a voltage Um can be tapped across the resistor 9, which is proportional to the second compensation current is2. This second compensation current is, in turn, is proportional to the first compensation current is1 and thus proportional to the primary current ip to be measured.

[0011] The number of turns w21 of the first secondary winding 21 is higher than the number of turns w22 of the second secondary winding 22 (w21 > w22). Since, in this example, the first and second secondary windings 21 and 22 are each formed from two identical (partial) windings 1 and 3, respectively, it is provided that windings 1 and 3 have the same number of turns w1 = w3 = 0.5·w21, and windings 2 and 4 have the same number of turns w2 = w4 = 0.5·w22. The winding direction of windings 1 to 4 is such that, in conjunction with the currents flowing through them in the magnetic core 5, they generate magnetic fluxes in the same direction. Furthermore, the wire gauges of the two secondary windings 21 and 22 can each be selected so that the current densities in both are (approximately) the same.

[0012] Fig. Figure 2 shows an example of a possible further electrical wiring of the compensation current sensor in a circuit diagram. Fig. 1. The primary current ip to be measured is therefore passed through the primary conductor 6, which is located in the Fig. In the example shown in Figure 2, the primary winding is represented. The first secondary winding 21 and the second secondary winding 22 are magnetically coupled to each other via the magnetic core 5 by the primary conductor 6. The magnetic flux in the magnetic core 5 is measured by the magnetic field sensor 7 and evaluated by the first evaluation circuit 8, which generates the first compensation current is1 based on this measurement. This current is then passed through the first secondary winding 21 to the second evaluation circuit 10, which generates the second compensation current is2 from it, as explained above. The second compensation current is2 is passed through the second secondary winding 22 and the resistor 9 connected in series with it. The voltage drop Um across the resistor 9 caused by the second compensation current is2 then forms the output quantity, i.e., the quantity representing the primary current ip.

[0013] In this example, the evaluation circuit is formed by a differential input stage 13, which is connected downstream of the magnetic field probe 7 and which generates a corresponding output signal referenced to ground G – in this case, an output voltage – from the floating output signal of the magnetic field probe 7. The input stage 13 is designed in the usual manner according to the type of magnetic field sensor used (for example, Hall sensor or magnetic sensor), so its design will not be discussed in detail here. However, it is characteristic of the input stage 13 that it outputs a signal representing, and in particular proportional to, the magnetic flux occurring at it.This can be, for example, a voltage proportional to the magnetic flux, as is assumed for further considerations, but any other suitable quantity can be used, such as current, frequency, duty cycle, or appropriately coded digital signals such as binary words.

[0014] The output signal of the differential input stage 13 is fed to a first driver amplifier 14, which, depending on its design, generates an output voltage or current sufficient to drive the first secondary winding 21. In the example shown... Fig. 2. This is a voltage-to-voltage amplifier, but a voltage-to-current amplifier can also be used in the same way. The first driver amplifier 14 can provide a unipolar output voltage or current, or a bipolar output voltage or current, depending on the application. A unipolar output voltage or current has only one polarity, while a bipolar output voltage or current can have two opposite polarities.

[0015] The second evaluation circuit 10 comprises a resistive load 11 connected to ground G and a second driver amplifier 12 controlled by the voltage across the resistor 11. In this case, the second driver amplifier 12 is implemented as a voltage-to-current amplifier; however, a suitably dimensioned voltage-to-voltage amplifier can also be used. The first driver amplifier 14 can provide a unipolar output voltage or current, or a bipolar output voltage or current, depending on the application. In the example shown, the first compensation current is1 is converted into a voltage proportional to it by means of the resistor 11, and this voltage is then converted by the second driver amplifier 12 into a proportional current, the second compensation current is2.Resistor 11 and the second driver amplifier 12 together form a current-controlled current source (with a gain of less than one), such as a current-to-current amplifier or a current mirror, in which the output current and input current are in a specific ratio to each other. Since, in the present case, the output current of such a current-to-current amplifier or current mirror is equal to the second compensation current is2 and its input current is equal to the first compensation current is1, where the first compensation current is1 is greater than the second compensation current is2, the following relationship results: is1=x⋅is2 with x>1.

[0016] For example, x > 1.2 or x > 1.5 or x > 2.

[0017] If a voltage-to-voltage amplifier is used instead of the voltage-to-current amplifier shown, it and resistor 11 would have to be dimensioned such that the second compensation current is2 is always smaller than the first compensation current is1. This can be easily achieved, for example, by appropriately dimensioning resistor 11. Alternatively, instead of the voltage across resistor 11, the voltage at the output of the first driver amplifier 14 could be used to control the second driver amplifier 12.

[0018] When using driver amplifiers 12 and 14 powered by bipolar supply voltage sources, i.e., by two voltage sources with opposite polarities connected in series, the driver amplifiers 12 and 14 can be operated in reverse to each other in order to load the supply voltage sources with opposite polarities somewhat evenly, so that the second compensation current is2 is always taken from the supply voltage source with the opposite polarity to the one that supplies the first compensation current is1.

[0019] Furthermore, it can be provided that the wire gauges of the two compensation windings 21 and 22 are each designed such that the current densities in both compensation windings 21 and 22 are approximately equal during operation. Although it is equally possible to tap the output voltage Um across resistor 11 in the circuit of the first compensation current is1, in the circuits shown, it is taken across resistor 9 in the circuit of the second compensation current is2. In this way, a virtual turns ratio can be generated that is significantly smaller than the nominal turns ratio. The nominal turns ratio results from the number of turns wp of the primary winding and the numbers of turns w1, w2, w3, and w4 of the secondary (partial) windings 1, 2, 3, and 4 as follows: N=wp / (w1+w2+w3+w4)>Nv, Whereas the virtual conversion ratio Nv undergoes a further reduction, which is primarily determined by the ratio of the first compensation current is1 to the second compensation current is2. In this process, the primary-side ampere-turn number and the sum of the secondary-side ampere-turn numbers cancel each other out. ip⋅wp=is1⋅(w1+w3)+is2⋅(w2+w4).

[0020] The in Fig. The circuit shown in Figure 2, including all the variations described above, can also be implemented with full-bridge circuits instead of half-bridge circuits, which are frequently used in conjunction with bipolar-fed driver amplifiers. A corresponding example is shown in Figure 2. Fig. 3 shown. Compared to the one in Fig. In the circuit shown in Figure 2, a third driver amplifier 16, identical to the first driver amplifier 14, is connected downstream of the first driver amplifier 14 via an inverter 15. An inverting driver amplifier could also be used instead of the combination of inverter 15 and third driver amplifier 16. Due to the interposed inverter 15, inverse, i.e., out-of-phase, output signals are present at the outputs of the driver amplifiers 14 and 16. If the first secondary winding 21 is now connected between the outputs of the driver amplifiers 14 and 16 (full bridge circuit), the voltage across it doubles compared to a half-bridge circuit (as, for example, in the circuit shown in Figure 2). Fig. 2) and consequently, assuming a constant load, also the electricity generated by it.

[0021] However, the series connection of the first secondary winding 21 and resistor 11 is then no longer referenced to ground G, but "floats" between the outputs of the driver amplifiers 14 and 16. In the case of the Fig. In the example shown in Figure 3, resistor 11 is directly connected to the output of the third driver amplifier 16 and, via the first secondary winding 21, to the output of the first driver amplifier 14. In the example shown in Figure 3, the resistor 11 is directly connected to the output of the third driver amplifier 16 and, via the first secondary winding 21, to the output of the first driver amplifier 14. Fig. In example 4, partial winding 3 is directly connected to the output of the third driver amplifier 16, and partial winding 1 is directly connected to the output of the first driver amplifier 14. The two partial windings 1 and 3 are connected to each other via resistor 11. This applies to both examples. Fig. 3, as well as in the example after Fig. 4. The floating voltage across resistor 11 is detected by a differential input stage 17 and fed as a corresponding output voltage referenced to ground G to a fourth driver amplifier 18. A third driver amplifier 16, identical to the first driver amplifier 14, is connected downstream of the first driver amplifier 14 via an inverter 15.

[0022] In the present case, all driver amplifiers 14, 16, 18 and 20 are identical; however, other configurations, up to four different driver amplifiers, are possible in the same way. In the case of the Fig. In the example shown in Figure 3, resistor 9 is directly connected to the output of the fifth driver amplifier 20 and, via the second secondary winding 22, to the output of the fourth driver amplifier 18. In the example shown in Figure 3, resistor 9 is directly connected to the output of the fifth driver amplifier 20 and to the output of the fourth driver amplifier 18 via the second secondary winding 22. Fig. In example 4, partial winding 4 of the second secondary winding 22 is directly connected to the output of the fifth driver amplifier 20, and partial winding 2 is directly connected to the output of the fourth driver amplifier 18. The two partial windings 2 and 4 are connected to each other via resistor 9. In both examples, Fig. 3, as well as in the example after Fig. 4 The voltage Um is tapped by floating across the resistor 9.

[0023] In the example after Fig. 4 indicates that, firstly, the winding direction of the two partial windings 2 and 4 is reversed compared to partial windings 1 and 3, because the control of partial windings 2 and 4 is also reversed compared to partial windings 1 and 3, i.e., partial windings 2 and 4 are operated in the opposite direction to the example shown. Fig. 3 are driven with inverse voltages. Note the different wiring of the outputs of the driver amplifiers 18 and 20 with the second compensation winding 22.

[0024] Based on the one in Fig. The example shown in 3 is the circuit of the one in Fig. The compensation current sensor shown in Figure 5 has been modified such that the resistors 9 and 11 are each designed as resistor pairs with the identical resistors 9a, 9b and 11a, 11b respectively, which are all connected to ground G on one side and to one terminal of the windings 2 and 4 and the windings 1 and 3 on the other.

[0025] The other terminal of winding 1 is connected to the output of the first driver amplifier 14, the other terminal of winding 3 is connected to the output of the third driver amplifier 16, the other terminal of winding 4 is connected to the output of the fourth driver amplifier 18, and the other terminal of winding 2 is connected to the output of the fifth driver amplifier 20. The terminals connected to resistors 9a, 9b and 11a, 11b, respectively, are the terminals facing each other of windings 1 and 3 and 2 and 4, respectively, so that the connection of the first and second compensation windings 21, 22 is similar to that in Fig. The circuit shown in Figure 4 is identical except that resistors 9 and 11 are connected to ground (G). This connection is formed at the junction of resistors 9a and 9b, and 11a and 11b, respectively. The corresponding voltages are therefore taken across the series connections of resistors 9a and 9b, and 11a and 11b, respectively.

[0026] In Fig. Figure 6 shows a circuit diagram illustrating an example of a linear driver amplifier, which can be used, for example, as driver amplifiers 14, 16, 18, and 20. The core of the linear driver amplifier shown there is an operational amplifier 23, which is fed from the positive supply voltage Vp via a resistor 24 and from the negative supply voltage Vn via a resistor 25. The output of the operational amplifier 23 is connected to the positive supply voltage Vp via a resistor 26 and to the negative supply voltage Vn via a resistor 27. A pnp bipolar transistor 28 and an npn bipolar transistor 29 serve as the output stage, their collectors being connected to each other and to the output OUT of the driver amplifier. The emitter of transistor 28 is connected to the positive supply voltage Vp, and its base is connected to the junction of resistor 24 and operational amplifier 23.Accordingly, transistor 29 is connected with its emitter to the negative supply voltage Vn and with its base to the junction of resistor 25 and operational amplifier 23. The output OUT is protected against reverse polarity voltages by two diodes 30 and 31, which lead from the output OUT to the positive supply voltage Vp and the negative supply voltage Vn, respectively. The operational amplifier 23 is negatively fed by a voltage divider comprising two resistors 32 and 33, which is connected between the output of the operational amplifier 23 and ground G. The tap of the voltage divider, i.e., the junction between resistors 32 and 33, is connected to the inverting input of the operational amplifier 23. The non-inverting input of the operational amplifier 23 forms the input IN of the driver amplifier.Instead of bipolar transistors, (MOS) field-effect transistors can be used in the same way.

[0027] Alternatively to one mentioned above in connection with Fig. In addition to the linear driver amplifier described in Figure 6, a pulsed driver amplifier can also be used, in which the output voltage can be varied, for example, by pulse-width modulation. The pulsed voltage is converted into linear voltage changes by means of a low-pass filter, which in this case is formed by an RL element comprising the inductance of the respective compensation winding 21 or 22 and the resistor 9 or 11 connected in series with it. An example of such a pulse-width modulated driver amplifier is shown in Figure 6. Fig. Figure 7 shows the core of the pulse-width modulated driver amplifier depicted there. A comparator 34 (for example, with hysteresis) is fed via a resistor 35 from the positive supply voltage Vp and via a resistor 36 from the negative supply voltage Vn. The output of the comparator 34 is connected via a resistor 37 to the positive supply voltage Vp and via a resistor 28 to the negative supply voltage Vn. A pnp bipolar transistor 39 and an npn bipolar transistor 40 serve as the output stage, their collectors being connected to each other and to the output OUT of the driver amplifier. The emitter of transistor 39 is connected to the positive supply voltage Vp, and its base is connected to the junction of resistor 35 and comparator 34.Accordingly, transistor 40 is connected with its emitter to the negative supply voltage Vn and with its base to the junction of resistor 36 and comparator 34. The output OUT is protected against reverse polarity voltages by two diodes 41 and 42, which lead from the output OUT to the positive supply voltage Vp and the negative supply voltage Vn, respectively. Comparator 34 receives a triangular reference voltage at its inverting input from the reference voltage source 43, which is referenced to ground G. The non-inverting input of comparator 34 forms the input IN of the driver amplifier. Here, too, (MOS) field-effect transistors can readily be used instead of the bipolar transistors.

[0028] The ones related to the Fig. 6 and Fig. The driver amplifiers described in section 7 generate an output voltage that depends on the input voltage (voltage-to-voltage amplifiers). However, voltage-to-current amplifiers, i.e., amplifiers where the output current depends on the input voltage, are equally applicable. Such a driver amplifier is used, for example, as a second driver amplifier 12 in the Fig. The circuit shown in section 2 is used, but can be used with any other circuit shown in the Fig. 3, Fig. 4 and Fig. The driver amplifiers 14, 16, 18, and 20 shown in Figure 5 are used. An example of a driver amplifier implemented as a voltage-current amplifier is shown in Figure 5. Fig. 8 shown.

[0029] The in Fig. The driver amplifier shown in Figure 8 comprises an operational amplifier 44, which is fed via a resistor 45 from the positive supply voltage Vp and via a resistor 46 from the negative supply voltage Vn. The output of operational amplifier 44 is connected directly to its inverting input and also to ground G via a resistor 47. Furthermore, two operational amplifiers 48 and 51 are provided, the non-inverting inputs of which are connected to the junction between resistor 45 and operational amplifier 44 and to the junction between resistor 46 and operational amplifier 44, respectively. Operational amplifier 48 is connected directly to the positive supply voltage Vp and ground G via its supply lines, while operational amplifier 51 is connected directly to the negative supply voltage Vn and ground G via its supply lines.The base of a PNP bipolar transistor 49 is connected to the output of operational amplifier 48. The emitter of this transistor is directly connected to the inverting input of operational amplifier 48 and, via a resistor 50, to the positive supply voltage Vp. The base of an NPN bipolar transistor 53 is connected to the output of operational amplifier 51. The emitter of this transistor is directly connected to the inverting input of operational amplifier 51 and, via a resistor 52, to the negative supply voltage Vn. The collectors of transistors 49 and 53 are connected together to form the output OUT of the driver amplifier.

[0030] In Fig. Figure 9 shows an example of a round, ring-shaped, closed magnetic core 54, which replaces the one shown in the example. Fig. 1. A rectangular, ring-shaped, closed magnetic core 5 can be used. The magnetic core 54 is completely wound by a first compensation winding 55, which is then also completely wound over by a second compensation winding 56. Alternatively, the two compensation windings 55 and 56 can also be wound together or alternately wound section by section. The magnetic core 54 has a recess 57 in which a magnetic field sensor 58 is housed, and which, when the magnetic field sensor 58 is inserted into the recess 57, is wound over by the two compensation windings 55 and 56.

[0031] Based on the one in Fig. The example shown in 3 is the circuit of the one in Fig. The compensation current sensor shown in Figure 10 is modified such that resistor 11 is configured as a resistor pair with identical resistors 11a and 11b, which are connected to ground G on one side and to one terminal of windings 1 and 3 on the other. The other terminal of winding 1 is connected to the output of the first driver amplifier 14, the other terminal of winding 3 is connected to the output of the third driver amplifier 16, the other terminal of winding 4 is connected to the output of the fourth driver amplifier 18, and the other terminal of winding 2 is connected to resistor 9, which is also connected to ground G. The terminals connected to resistors 11a and 11b are the terminals facing each other of windings 1 and 3, so that the connection of the first compensation winding 21 is similar to that shown in Figure 10. Fig.The circuit shown in Figure 4 is identical except that resistors 11 are provided with a tap connected to ground G. This tap is formed at the junction of resistors 11a and 11b. The corresponding voltages are therefore taken across the series connection of resistors 11a and 11b.

Claims

[1] Current sensor arrangement based on the compensation principle with a primary conductor (6) designed to generate a primary magnetic field dependent on a current flowing through it, which is to be measured, a first secondary winding (21) which is designed to generate a first secondary magnetic field dependent on a first compensation current (is1) flowing through it, a second secondary winding (22) which is designed to generate a second secondary magnetic field dependent on a second compensation current (is2) flowing through it, a magnetic field sensor (58) designed to generate a measurement signal representing a magnetic field detected by it, a magnetic core (54) made of soft magnetic material, which is designed and arranged to magnetically couple the primary conductor (6), first secondary winding (21), second secondary winding (22) and magnetic field sensor (58) together, a first evaluation circuit (8) connected downstream of the magnetic field sensor (58) and upstream of the first secondary winding (21), which is configured to generate a first compensation current (is1) corresponding to the measurement signal of the magnetic field sensor (58) and to supply the first secondary winding (21), and a second evaluation circuit (10) connected upstream of the second secondary winding (22), which is designed to generate a second compensation current (is2) corresponding to the first compensation current (is1) and to supply the second secondary winding (22), wherein the magnetic field detected by the magnetic field sensor (58) is the magnetic field in the magnetic core resulting from the superposition of the primary magnetic field, the first secondary magnetic field and the second secondary magnetic field, the first compensation current (is1) and the second compensation current (is2) are adjusted by the first evaluation circuit (8) and the second evaluation circuit (10) so that the resulting magnetic field detected by the magnetic field sensor (58) approaches zero, the first or second compensation current (is1, is2) represents the current (ip) flowing in the primary conductor (6) to be measured and the second evaluation circuit (10) has a device that evaluates the first compensation current (is1) and sets the second compensation current (is2) proportionally to the measured first compensation current (is1). [2] Current sensor arrangement according to claim 1, wherein the second compensation current (is2) is smaller than the first compensation current (is1). [3] Current sensor arrangement according to claim 2, in which the output signal representing the current to be measured flowing in the primary conductor (6) is generated from the first or second compensation current (is1, is2). [4] Current sensor arrangement according to one of claims 1-3, wherein the first compensation winding (21) and the second compensation winding (22) have wires with wire diameters dimensioned such that the current densities are equal when the first compensation current (is1) and the second compensation current (is2) respectively flow through them. [5] Current sensor arrangement according to one of claims 1-4, wherein the first secondary winding (21) and the second secondary winding (22) have different numbers of turns. [6] Current sensor arrangement according to one of claims 1-5, wherein the first evaluation circuit (8) and the second evaluation circuit (10) each have a driver circuit which generates the first compensation current (is1) and the second compensation current (is2) in the first compensation winding (21) and the second compensation winding (22), respectively. [7] Current sensor arrangement according to claim 6, wherein at least one of the driver circuits has an output-side half-bridge circuit. [8] Current sensor arrangement according to claim 6, wherein at least one of the driver circuits has an output-side full bridge circuit. [9] Current sensor arrangement according to claim 6, wherein one of the driver circuits has an output-side half-bridge circuit and one of the driver circuits has an output-side full-bridge circuit. [10] Current sensor arrangement according to one of claims 6-9, wherein at least one of the driver circuits is a linear driver circuit. [11] Current sensor arrangement according to one of claims 6-9, wherein at least one of the driver circuits is a pulse width modulated driver circuit. [12] Current sensor arrangement according to one of claims 6-9, wherein one of the driver circuits is a linear driver circuit and one of the driver circuits is a pulse width modulated driver circuit. [13] Current sensor arrangement according to one of claims 6-12, wherein at least one of the driver circuits is a driver circuit supplied with bipolar supply voltages. [14] Current sensor arrangement according to one of claims 6-13, wherein at least one of the driver circuits behaves like a current source on the output side. [15] Current sensor arrangement according to one of claims 1-14, wherein the magnetic core (54) is a round, closed, ring-shaped magnetic core with at least one air gap or probe pocket. [16] Current sensor arrangement according to one of claims 1-14, wherein the magnetic core (54) is a rectangular or polygonal, closed, annular magnetic core (54) with at least four legs and at least one air gap or probe pocket. [17] Current sensor arrangement according to claim 16, wherein the number of ampere turns is the same on each of the wound legs. [18] Current sensor arrangement according to one of claims 15-17, wherein the first compensation winding (21) and the second compensation winding (22) are wound in symmetrically arranged sections. [19] Current sensor arrangement according to one of claims 15-17, in which the magnetic core (54) is wound by first compensation winding (21) and second compensation winding (22) evenly distributed over the entire magnetic core (54). [20] Current sensor arrangement according to claim 18 or 19, wherein the first compensation winding (21) and the second compensation winding (22) are wound together. [21] Current sensor arrangement according to claim 18 or 19, wherein the first compensation winding (21) and the second compensation winding (22) are wound one over the other. [22] Current sensor arrangement according to one of claims 1-21, wherein the second compensation current (is2) is at least 20% smaller than the first compensation current (is1).

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