Current measuring device for electric machine
Through the current measurement device combining Hall sensor and flux conduction element, the problems of high current measurement cost and large structure in the prior art are solved, accurate and economical current measurement is achieved, and flexible adaptability and non-invasive installation are provided.
Patent Information
- Application Number
- CN202380070053.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-09-30
- Filing Date
- 2023-09-27
- Publication Date
- 2025-05-06
AI Technical Summary
The prior art is difficult to effectively and economically measure high currents (such as excitation current on the rotor of a synchronous machine) and stator currents, and traditional measurement methods have problems such as high cost, large structure, and non-equal potential shortcomings.
The current measuring device using a Hall sensor combined with a flux conduction element and a spacer element is used to measure the current indirectly by measuring the magnetic field to achieve measurement of high current. The device is variability to adapt to different currents and field strengths by replacing the spacer elements and flux conducting elements.
Accurate measurement of high currents, reduces cost and reduces structural size, and the potentialless design is suitable for high current or high voltage environments, with non-invasive installation and flexible adaptability.
Smart Images
Figure CN119948344A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a current measuring device for a motor or a current measuring method for a motor. Background Art
[0002] For electric machines, operating parameters and / or test parameters of electric machines can be measured. Examples of such parameters are current or voltage. Such measured values (i.e., actual current or actual voltage) can be used for regulating, controlling and / or monitoring electric machines. Monitoring of electric machines can also be referred to as condition monitoring. Electric machines are, for example, motors or generators. Electric machines can be synchronous machines or asynchronous machines. If such electric machines have a power in the range of megawatts (MW), correspondingly high currents and voltages are also obtained. For example, for the purpose of condition monitoring and test fields, the current on the rotor of a synchronous machine is measured and transmitted by means of a slip ring transmitter or a contactless telemetry system. Since the excitation current can be assumed to be of the order of magnitude of>1000A, a special measuring instrument for its measurement is required, which should be as cost-effective as possible. In addition to the specific problem of current measurement on the rotor, there are also problems with the stator current, which should be included in the monitoring system. Shunts can be used to measure the excitation current in synchronous machines. For the observed current range of>1000A, these components are large and very costly in individual manufacturing. Alternatively, current converters can be used as shunts, which are however also large and expensive. Furthermore, for rotating applications, such as rotors of electric machines, a robust design suitable for centrifugal forces is required.
[0003] In the case of direct current, current transformers or Rogowski coils are not suitable, since they are not suitable for direct current. Special LEM current transformers for direct current have difficulty in achieving the desired measuring range and are also very expensive. Measurement via shunts also has the disadvantage of non-equipotentiality.
[0004] The current measurement of the stator alternating current can be carried out via equipotential current transformers, since voltages of up to several kilovolts are used there. Current transformers require a certain amount of installation space and are also relatively expensive components. For example, it is usually not feasible to additionally insert a monitoring system into an existing protective circuit or measuring circuit. Then, an additional transformer is a non-negligible expense item. Summary of the invention
[0005] An object of the present invention is to provide a simple current measurement device for an electric machine. Another object of the present invention is to provide a simple method for current measurement of an electric machine.
[0006] The solution to this problem is provided according to claim 1 or according to claim 9. For example, an embodiment is derived from at least one of claims 2 to 8 and 10.
[0007] A current measuring device for an electric motor has a sensor. In particular, the sensor is a Hall sensor, also referred to as a Hall effect sensor or Hall current sensor or Hall sensor. The Hall sensor measures a magnetic field and thereby indirectly measures a current via the law of magnetic flux. However, the Hall sensor is often also referred to as a current sensor. The Hall current sensor can be used to measure direct currents and alternating currents, wherein the direct currents and alternating currents are in particular in the range between 1000A and 10000A. The current measuring device has a first flux conducting element and a first spacing element. Therefore, the current measuring device has at least one flux conducting element and at least one spacing element. In the current measuring device, the first spacing element spaces the end regions of the first flux conducting element, or the first spacing element spaces the first flux conducting element from the second flux conducting element. In one embodiment of the current measuring device, the first spacing element is also spaced from the end regions of the first flux conducting element. In another embodiment of the current measuring device, the first spacing element also spaces the first flux conducting element from the second flux conducting element.
[0008] The measurement of current can be carried out using Hall effect sensors (Hall sensors) for measuring the magnetic field caused by a current-carrying conductor. In particular, the sensor is integrated in the chip. The sensor is therefore in particular an integrated component. The measurement is carried out in particular in the chip plane. For this purpose, there are various sensors that can measure the magnetic field in one or more spatial axes. The sensor must be arranged in a suitable manner in the spacing element. The magnetic field passes through the sensor, wherein the material can also be used in a targeted manner to conduct the magnetic field in the immediate vicinity of the chip.
[0009] By using flux conducting elements and spacing elements, almost arbitrarily high currents can be measured with the chip. Thus, chips with limited magnetic field measurement ranges can be used.
[0010] In one embodiment of the current measuring device, the structure is based on the fact that the magnetic field surrounding the current-carrying conductor is measured. Since the Hall sensor has a specific field direction and a maximum evaluable field strength, the structure can be designed so that the field strength can be easily adjusted and secondly, there is a relatively uniform field distribution in the area of the sensor so as to be particularly insensitive to tolerances.
[0011] In one embodiment of the current measuring device, the current measuring device is of potential-free construction and comprises in particular digital signal processing which enables the sensor signal to be transmitted over longer distances with little or no interference.
[0012] In one embodiment of the current measuring device, at least one flux conducting element surrounds the current conductor together with at least one spacing element. In this case, at least an air gap can also be produced. This arrangement makes it possible to guide the magnetic field of the current-carrying conductor.
[0013] In one embodiment of the current measuring device, at least one flux conducting element and / or at least one spacing element can be exchanged.
[0014] In one embodiment of the current measuring device, its adaptation to different currents or field strengths is achieved by variably using (i.e. replacing) one or more spacer elements and / or one or more flux conducting elements. The spacer elements can be regarded as variable inserts between the flux conducting elements. The flux conducting elements can be realized, for example, by electrical sheets or by a plurality of electrical sheets stacked one above the other. This results in a guide plate structure.
[0015] In one embodiment of the current measuring device, the flux conducting element is made of a material having a particularly narrow hysteresis loop, for example mu metal. As a result, the achievable measurement accuracy can be influenced (in particular advantageously increased).
[0016] In one embodiment of the current measuring device, the flux conducting element or elements are designed geometrically, in particular in the region surrounding the electrical conductor, so that their geometry follows the magnetic field lines around the electrical conductor. In other words, the field essentially follows the magnetic conductor.
[0017] In one embodiment of the current measuring device, a sensor carrier with a sensor is used with flux-conducting elements of different geometry and / or with spacing elements of different geometry, the flux-conducting elements and / or the spacing elements being exchanged. The sensor carrier is, for example, an electronic circuit board or a carrier of an electronic circuit board for placing a sensor.
[0018] In one embodiment of the current measuring device, the current measuring device has at least one connecting element which connects the spacing element to the flux-conducting element, wherein the connecting element comprises in particular a non-magnetic material. The connecting element is, for example, a clamp, a cable tie, a screw, etc. For example, copper or a synthetic material can be used as material.
[0019] In one embodiment of the current measuring device, the sensor is arranged in the spacing region. Thus, for example, the sensor and / or the sensor carrier can be held or positioned in the spacing region by the spacing element.
[0020] In one embodiment of the current measuring device, the sensor is arranged in the region of the uniform magnetic field lines. This allows for improved measurement accuracy.
[0021] In one embodiment of the current measuring device, the sensor is arranged at the minimum distance from the conductor (electrical conductor). This makes it possible to better position the sensor in an area where the magnetic field is uniformly distributed.
[0022] In one embodiment of the current measuring device, at least one flux conducting element is embodied as a sheet material. This therefore enables eddy currents to be reduced or eliminated.
[0023] In one embodiment of the current measuring device, the current measuring device has a radio device for wireless transmission of the measurement signal recorded by the sensor.
[0024] In a method for measuring the current of an electrical machine, a current measuring device according to one of the described exemplary embodiments is used.
[0025] In one embodiment of the method, the rotor current or the stator current of the electric machine is measured. The variability of the current measuring device enables the same sensor to be used for different electric machines with different powers.
[0026] In one embodiment of the method, at least one spacing element is replaced in order to measure different currents, in particular different maximum currents. Thus, the current measuring device can be used flexibly.
[0027] The variability of the current measuring device enables relatively low costs compared to shunts. In addition, a relatively very compact structure can be produced. Another advantage of the current measuring device enables non-invasive installation (without opening the circuit). Another advantage of the current measuring device can be achieved by the potential-free structure of the current measuring device. It is precisely in the case of high currents or high voltages that potential-free is important. The feasible use of the combination of the integrated Hall sensor in conjunction with a microcontroller (especially an inexpensive microcontroller) and / or simple components (for example: metal sheets for flux-conducting elements, 3D-printed plastic structures or brass screws for spacing elements) is very low cost, flexible and robust in structure.
[0028] In one embodiment of the current measuring device or method, savings can be obtained compared to the shunts used hitherto and further savings potentials can be obtained if the sensor is also used for current measurement in other areas (eg condition monitoring systems or the like). BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The features of the various claimed or described embodiments can be easily combined with each other. Hereinafter, the invention is described and explained in more detail by way of example by means of the accompanying drawings. In different figures, the same reference numerals represent similar elements. A person skilled in the art can combine the features shown in the figures to form new embodiments without departing from the invention. They show:
[0030] Figure 1 shows a motor,
[0031] Figure 2 shows the current measurement device and
[0032] Figures 3 to 8 A further current measuring arrangement is shown. DETAILED DESCRIPTION
[0033] according to Figure 1 The illustration of shows an electric machine 1 having a stator 2 and a rotor 3. The electric machine 1 has an electrical connection to current conductors (conductors) 5, 5', 5". A current measuring device 4 is provided for measuring the current in the conductors 5.
[0034] according to Figure 2 The illustration in FIG. 4 shows a current measuring device 4 for a current conductor (electric conductor) 5. Figure 2 The electrical conductor 5 in the embodiment has a circular cross section. The current flowing through the electrical conductor 5 is indicated by the reference 15. The reference 15 has a circle and has a cross located in the circle. The current measuring device 4 has a first flux conducting element 9, which has end regions 19, 19' and a magnetically conductive region 21 located between the end regions. The magnetically conductive region 21 of the flux conducting element 9 guides the magnetic field according to the course of the magnetic field around the conductor. To this end, the end regions 19, 19' serve to homogenize or parallelize the magnetic field in a defined area. This area is a spacing area 26, which is created by the first spacing element 11. In this area 26, parallel-extending magnetic field lines 20 can be formed. In this area where the parallel-extending magnetic field lines 20 can be formed, the sensor 6 is located on the circuit board 7. For example, the sensor 6 can be pushed or positioned together with the circuit board 7 into a recess of the spacing element 11.
[0035] according to Figure 3 The illustration in FIG. 4 shows a current measuring device 4 for an electrical conductor 5. Figure 3 The electrical conductor 5 in also has a circular cross section. Figure 3 In the example, the current flowing through the conductor 5 is indicated by the reference numeral 15'. The reference numeral 15' has a circle and a dot located in the circle. In this context, the dot and the cross (see Figure 1 ) point to different current directions. Figure 3 , the conductor 5 has an insulating layer 8 of thickness 16. The electrical conductor 5 and the insulating layer 8 form a cable 27, the cross section of which is shown. The spacing element 11 is directly adjacent to the insulating layer 8 of the conductor 5. The sensor 6 has a first distance 17 to the cable 27. The sensor 6 has a second distance 18 to the electrical conductor 5. The distances 17, 18 are large so that the sensor 6 is located in a region with magnetic field lines running in parallel. This situation must be ensured in particular for different current intensities.
[0036] according to Figure 4 The illustration in FIG. 4 shows a current measuring device 4 for a current conductor (electric conductor) 5. Figure 4 The electrical conductor 5 in has a rectangular cross section. Furthermore, a first flux conducting element 9 and a second flux conducting element 10 are shown. The first flux conducting element 9 has end regions 19 and 19″. The second flux conducting element 10 has end regions 19′ and 19′″. The first flux conducting element 9 is spaced apart from the second flux conducting element 10 in the end regions 19 and 19′ by a first spacing element 11. Furthermore, the first flux conducting element 9 is also spaced apart from the second flux conducting element 10 in the end regions 19″ and 19′″ by a second spacing element 12. In the first spacing element 11, the sensor 6 is located on the circuit board 7. A first spacing region 26 having a distance 25 between the end regions 19 and 19′ is produced by the first spacing element 11. A second spacing region 26″ with a distance 25′ between the end regions 19″ and 19″′ is produced by the second spacing element 12. The first spacing element 11 is connected to the first flux conducting element 9 and the second flux conducting element 10 in the spacing region 26 by means of the connecting element 24. The first spacing element 11 is connected to the first flux conducting element 9 and the second flux conducting element 10 in the spacing region 26′ by means of the connecting element 24′. The flux conducting elements 9, 10 have magnetically conductive regions 21, 21′. In the conductive region, the respective flux conducting element has an arc shape or a circular shape.
[0037] according to Figure 5 The illustration shows a current measuring device 4 for a current conductor 5. The flux conducting elements 9, 10 are designed as sheets, wherein according to Figure 5 , each flux conducting element 9, 10 shows two sheets 22, 22', 23, 23', respectively. Eddy current losses can thus be reduced.
[0038] according to Figure 6 The illustration in FIG. 4 shows a current measuring device 4 for a current conductor 5. Figure 6 The electrical conductor 5 in the embodiment has a rectangular cross section with an insulating layer 8 .
[0039] according to Figure 7 The illustration of FIG. 4 shows a current measuring device 4 for a current conductor 5. Figure 7 The current conductor 5 in the current measuring device 4 is separated from the spacing elements 11, 12 by the separation elements 13, 14. The current conductor 5 is positioned in the current measuring device 4 by the first separation element 13 and the second separation element 14, which are both insulators.
[0040] according to Figure 8The illustration of FIG. 4 shows a current measuring device 4 for a current conductor 5. The spacing elements 12, 13 have recesses 30, 31, 32 and 33 into which the flux conducting elements 9, 10 protrude. The recesses are adjacent to the location of the sensor 6. Figure 8 Sensor 6 in has Figures 2 to 7 The sensor 6 in the embodiment of the invention has different geometries. This case shows that different geometries can be used for the sensor. The mounting position of the sensor is selected or rotated so that the measurement can be successfully performed. Thus, for example, different sensors are rotated (e.g. 90 degrees) to achieve a suitable measurement. The sensor is oriented according to the direction of the magnetic field in the measurement environment and in the sensor.
Claims
1. A current measuring device (4) for an electric machine, comprising a sensor (6), a first flux conducting element (9) and a first spacing element (11), wherein: The first spacing element (11) spaces apart an end region of the first flux conducting element (9), or wherein the first spacing element (11) spaces apart the first flux conducting element (9) from a second flux conducting element (10).
2. The current measuring device (4) according to claim 1, wherein: At least one flux conducting element (9, 10) surrounds a current conductor (5, 5', 5") together with at least one spacing element (11, 12).
3. The current measuring device (4) according to claim 1 or 2, wherein: At least one flux conducting element (9, 10) and / or at least one spacing element (11, 12) can be replaced.
4. The current measuring device (4) according to any one of claims 1 to 3, wherein: The current measuring device has a connecting element (24, 24') which connects a spacing element (11, 12) to a flux-conducting element (9, 10), wherein the connecting element (24, 24') comprises, in particular, a non-magnetic material.
5. The current measuring device (4) according to any one of claims 1 to 4, wherein: The sensor (6) is arranged in the spacing area (26, 26').
6. The current measuring device (4) according to any one of claims 1 to 5, wherein: The sensor (6) is arranged in the region of uniform magnetic field lines (20).
7. The current measuring device (4) according to any one of claims 1 to 6, wherein: The sensor (6) is arranged at a minimum distance (18) from the current conductor (5, 5', 5'').
8. The current measuring device (4) according to any one of claims 1 to 7, wherein: At least one flux conducting element (9, 10) is embodied as a metal plate.
9. A method for measuring the current of an electric machine (1), wherein: Use is made of a current measuring device (4) according to any one of claims 1 to 8.
10. The method according to claim 9, wherein: At least one of the spacing elements (11, 12) is replaced to measure different currents.