Position-Compensated Current Measuring Device

Abstract

The present disclosure relates to a current measuring transducer for measuring an electric current in an electrical conductor that can be arranged so as to extend through the current measuring transducer, comprising a housing base portion and a housing mating portion coupled to one another, wherein the electrical conductor can be arranged in a central through opening between the housing base portion and the housing mating portion, wherein the housing base portion comprises a first part of a probe ring and the housing mating portion comprises a second part thereof, and comprises at least two sensors for simultaneously measuring the electric current in the electrical conductor, and further comprises an evaluation device in the current measuring transducer for simultaneously evaluating sensor signals and for outputting a corrected output signal.

Claims

1. A current measuring transducer for measuring an electric current in an electrical conductor that can be arranged so as to extend through the current measuring transducer, comprising: a housing, comprising: a housing base portion and at least one housing mating portion which can be coupled with the housing base portion; wherein, in a closed state, the housing base portion is coupled to the housing mating portion and a central through opening is defined, and wherein the electrical conductor can be arranged in the central through opening between the housing base portion and the housing mating portion so that the electrical conductor extends through the housing; wherein the housing base portion comprises a first part of a probe ring and the housing mating portion comprises a second part thereof, so that in the closed state of the housing a closed loop probe ring is formed around the conductor when the conductor is arranged inside the current measuring transducer; at least two sensors for simultaneously measuring the electric current in the electrical conductor and generating first and second sensor signals; and an evaluation device in the current measuring transducer, configured for simultaneously evaluating the first and second sensor signals and for outputting a corrected output signal.

2. The current measuring transducer of claim 1, wherein the evaluation device is accommodated in the housing mating portion; and/or wherein the evaluation device comprises a microcontroller; and/or wherein the current measuring transducer is configured to process both DC voltage signals and AC voltage signals.

3. The current measuring transducer as claimed in claim 2, wherein the evaluation device simultaneously reads in and processes the first sensor signal and the second sensor signal so as to perform signal balancing between the first sensor signal and the second sensor signal.

4. The current measuring transducer as claimed in claim 3, comprising automatic position compensation so that the first and second sensor signals are correctable with respect to a position of the electrical conductor in the current measuring transducer.

5. The current measuring transducer as claimed in claim 4, wherein installation deviations when assembling the current measuring transducer on the electrical conductor are compensated for by signal balancing between the first sensor signal and the second sensor signal.

6. The current measuring transducer of claim 5, wherein the evaluation device is configured for achieving signal balancing between the at least two sensor signals by averaging over the sensor signals.

7. The current measuring transducer as claimed in claim 6, wherein the housing base portion and the housing mating portion have interengagable latching means for latching the housing mating portion to the housing base portion.

8. The current measuring transducer as claimed in claim 7, wherein the housing base portion and the housing mating portion each have first and second probe ring end faces, and wherein in the closed state of the housing, the probe ring end faces of the housing base portion and of the housing mating portion adjoin one another.

9. The current measuring transducer as claimed in claim 8, wherein in the closed state of the housing, the respective first and second probe ring end faces define a common end face plane such that the probe ring end faces of the housing base portion and of the housing mating portion are located on opposite sides of the electrical conductor and in a common plane intersecting the electrical conductor, wherein, preferably, the end face plane intersects the electrical conductor, for example through the center thereof.

10. The current measuring transducer as claimed in claim 9, wherein the first sensor is arranged on the first probe ring end face and the second sensor is arranged on the second probe ring end face.

11. The current measuring transducer as claimed in claim 10, wherein the probe ring defines first and second sensor accommodation areas on the probe ring end faces for receiving the sensors on the probe ring end faces.

12. The current measuring transducer according to claim 11, wherein the first and second sensor accommodation areas are each adapted to receive at least two sensors per probe ring end face.

13. The current measuring transducer as claimed in claim 12, further comprising: a third sensor which is arranged adjacent to the first sensor; and a fourth sensor which is arranged adjacent to the second sensor; wherein, for example, the first and third sensors are arranged in a first accommodation area in the probe ring; wherein, for example, the second and fourth sensors are arranged in a second accommodation area in the probe ring; and wherein the evaluation device reads in and evaluates the sensor signals of the plurality of sensors in order to calculate a position compensation for the position of the electrical conductor.

14. The current measuring transducer as claimed in claim 13, wherein the sensors are in the form of magnetoresistive sensors or Hall sensors.

15. The current measuring transducer according to claim 14, wherein the housing base portion comprises fixing means for fixing the current measuring transducer on a mounting rail or on a wall.

16. The current measuring transducer as claimed in claim 15, wherein the housing mating portion has electrical connectors for measuring voltage signals and for outputting the corrected output signal, for example in the form of power and energy values.

17. The current measuring transducer as claimed in claim 16, further comprising at least one temperature sensor connected to the evaluation device for temperature compensation of the first and second sensor signals.

18. The current measuring transducer as claimed in claim 13, further comprising a for tool-free attachment on the electrical conductor at both of its connection ends for position-compensated measurement of the current flowing in the electrical conductor.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0041] FIG. 1 shows a first embodiment of the current measuring transducer;

[0042] FIG. 2 shows a further embodiment of the current measuring transducer;

[0043] FIG. 3 shows yet another embodiment of the current measuring transducer, where an electrical conductor is installed with an offset;

[0044] FIG. 4 shows an embodiment of the current measuring transducer with an incorrectly installed sensor;

[0045] FIG. 5 shows an embodiment of the current measuring transducer in an open state;

[0046] FIG. 6 shows the embodiment of the current measuring transducer of FIG. 5 in the closed state.

DETAILED DESCRIPTION

[0047] Referring to FIG. 1, a first embodiment of a current measuring transducer 10 is shown with an electrical conductor 50 arranged therein. Current measuring transducer 10 comprises a housing base portion 12 comprising a first part 16 of the probe ring 15. The current (_primary flowing through the electrical conductor 50 induces a magnetic field flux 52 in probe ring 15.

[0048] A housing mating portion 14 comprises a second part 18 of probe ring 15. It also comprises an evaluation device 20, which can be used to evaluate and compensate the sensor signals from field sensors 62, 64, 66, and 68. In this example, fixing means 32, 34 are provided which are interengagable in order to close the probe ring 15 and to bring the housing 11 into the closed state.

[0049] Field sensors 62, 64 are arranged next to one another in a first accommodation area 38. Field sensors 66, 68 are arranged next to one another in a second accommodation area 39. In the case of a perfect set up in which the housing 11 as a whole is assembled without errors and the electrical conductor 50 is placed perfectly in the center, each field sensor 62, 64, 66, 68 will experience the same field flux 52 in the probe ring 15 and therefore deliver identical measurement results Out 1.1, Out 2.1, Out 1.2, Out 2.2. In this embodiment of FIG. 1, the field sensors 62, 64 and 66, 68, respectively, which are disposed jointly in a respective accommodation area 38, 39, are each installed in the same direction. Therefore, if the current measuring transducer 10 is installed correctly, the measured magnetic field will not only have the same absolute value but also the same direction. The direction of field flux is indicated by the arrow designated by 52.

[0050] The current measuring transducer is able to measure alternating currents and direct currents up to 600 A, for example, without saturating. Especially in the case of alternating currents, the frequency of the primary current may lead to magnetization reversals in the core material of the probe ring 15. The resulting forces may cause the probe ring 15 to oscillate or vibrate, so that the height of the accommodation areas 38, 39 may fluctuate. However, the height of accommodation areas 38, 39 will usually have a considerable impact on the probe signal obtained. With a change of just a few micrometers, the magnetic flux to be detected at the sensor will change in the single-digit percentage range. The correction calculation by evaluation device 20 is able to also suppress such interferences and to operate at lower error rates even in the case of high alternating currents such as between 400 and 600 amperes, i.e. to achieve an error tolerance of less than 1% of the measured value.

[0051] The use of sensors pairs 62, 68 and 64, 66 may be exploited for a further refinement of the present disclosure. If the sensors of the respective pairs differ, i.e. for example sensors 62, 68 and sensors 64, 66, it is possible to additionally sense in different measuring ranges. When a measuring range of sensor 62 is exceeded or undershot, a switch can then be made to the measuring range of sensor 64, etc.

[0052] Because of the high currents to be detected, the core material preferably used for the probe ring 15 is wound silicon iron. Once the winding process has been completed, the core is divided into two halves of equal size, for example. In order to limit the magnetic flux through sensors 62, 64, 66, 68, the height of the accommodation area 38, 39 can be adjusted to 2.2 millimeters, for example. In this way, settings can be made such that the measuring ranges of the sensor elements are not exceeded even in the case of the intended current of 600 amperes AC, for example. This allows to use sensors with a measuring range of up to 200 mT, for example.

[0053] Referring to FIG. 2, a current measuring transducer 10 is shown in which the housing 11 was not correctly fitted together or connected. Rather, the current measuring transducer 10 was plugged together with an assembly error 42, and in order to improve the understanding, the assembly error 42, i.e. the radial offset between housing base portion 12 and housing mating portion 14 is exaggerated in the illustration. The fixing means 36 provided on the housing base portion 12 and intended to be introduced into an opening (not shown) in the housing mating portion 14, were not correctly introduced in this example, but rather extend alongside the housing mating portion 14.

[0054] In the embodiment shown in FIG. 2, field sensors 62, 64, 66, and 68 will sense field strengths of different absolute values. However, the sensor signals from field sensors 62, 64, 66, 68 are then forwarded to the evaluation device 20 and compensated. For example, the evaluation device 20 is able to perform signal transformations or signal calculations using a microcontroller 22. For example, the evaluation device 20 has an analog-to-digital converter (ADC) 24. The incoming analog signals from field sensors 62, 64, 66, 68 are then converted into digital signals in evaluation device 20 so that digital arithmetic operations can be performed on the signals. For example, the evaluation device 20 is able to calculate a mean value from the plurality of digital sensor signals from the field sensors 62, 64, 66, 68. The mean value will then have a significantly smaller error than the individual measured value. Evaluation device 20 may also perform such averaging over a longer period of time, for example, so that fluctuations over time can also be eliminated. In the case of a direct current flowing through the electrical conductor 50, for example, this allows, in a simple manner, to compensate for external electrical or magnetic alternating fields as well.

[0055] Referring to FIG. 3, an embodiment of the current measuring transducer 10 is shown in which the electrical conductor 50 is arranged eccentrically. Although, in principle, this does not cause a change in the field flux direction 52, the absolute value of the induced field strength at field sensors 62, 64 will differ from that sensed by field sensors 66, 68. In other words, the magnetic field strength prevailing in the first accommodation area 38 will be different from that in the second accommodation area 39.

[0056] The sensor data are processed by evaluation device 20, for example converted into digital data by ADC 24 and, for example, a mean value is calculated from the sensor data. The mean value calculated by evaluation device 20, i.e. the output signal of evaluation device 20, represents a position-compensated signal, in which the relative position of the electrical conductor 50 in current measuring transducer 10 has been compensated for with regard to the electric current.

[0057] Therefore, time-consuming adjustments of the current measuring transducer 10 can be dispensed with, and a change in position of the electrical conductor 50 in the current measuring transducer 10 can be compensated for without having to recalibrate or realign the current measuring transducer 10.

[0058] Referring to FIG. 4, yet another embodiment of a current measuring transducer 10 is shown, in which the sensor 62 is dislocated, in the present case it is installed in a rotated orientation (the rotation is shown exaggerated for greater clarity). Since sensors such as Hall sensors detect the magnetic flux perpendicular across the sensor, the magnitude measured by sensor 62 will be smaller than the magnitude measured at sensor 66. Evaluation device 20 averages the sensor signals 62, 66 so that the resulting measurement error is significantly reduced.

[0059] The common circuit board for evaluation device 20 may, for example, also provide wiring for a power supply 28 unit and for output interface 26. The latter is integrated into the housing mating portion 14, for example parallel to the second core half 18. The sensors are electrically connected at an angle of 90° relative to the circuit board, for example. Especially the positioning of four Hall sensors allows to detect position-related deviations also by furthermore comparing to one another and accounting for the output signals of the respective sensor pairs in the calculation. At the same time, the circuit becomes more robust against external magnetic fields that might couple into one of the two air gaps or accommodation areas 38, 39.

[0060] FIG. 5 shows an embodiment of a current measuring transducer 10 in an open state. Features described for previous embodiments of the present disclosure are designated by the same reference numerals.

[0061] The housing base portion 12 shown in FIG. 5 is fixed on a mounting rail 70 by brackets 72. The evaluation device 20 is accommodated in housing mating portion 14. The evaluation device 20 outputs the position-compensated output signal via output interface 26. Housing base portion 12 can be coupled to housing mating portion 14 through latching means 33, 35. The current measuring transducer 10 may furthermore have a power supply 28 including a power source for supplying electric power to the electronics of current measuring transducer 10.

[0062] Referring to FIG. 6, the embodiment of current measuring transducer 10 shown in FIG. 5 is illustrated in its closed state. In the closed state of housing 11, the probe ring 15 completely surrounds the electrical conductor 50 circumferentially. The position-compensated output signal can be tapped at output interface 26.

[0063] It will be obvious for a person skilled in the art that the embodiments described above are to be understood as examples and that the invention is not limited thereto, but rather can be varied in various ways without departing from the scope of the claims. Furthermore, it will be appreciated that the features, regardless of whether they are disclosed in the description, the claims, the figures or otherwise, also individually define components of the present disclosure, even if they are described together with other features. In all figures, the same reference numerals designate the same items, so that descriptions of items that are possibly only mentioned in conjunction with one or at least not with all figures can also be transferred to those figures, for which such subject matter is not explicitly described in the description.