Method for observing insulation state of stator coil and system for observing insulation state of stator coil

Abstract

To provide a technique capable of appropriately carrying out a finite insulation life test of a stator coil under an electric environment similar to the case where a rotary electric machine is in a normal running state.SOLUTION: A method for observing an insulation state of a stator coil comprises the steps of: connecting an inverter INV to N-phase coils, and connecting a voltage application device GS for applying a test voltage to the N-phase coils and the inverter INV to the N-phase coils; connecting a first test conductor 11 to a first phase coil, and connecting a second test conductor 12 to a second phase coil in a state in which the first test conductor 11 and the second test conductor 12, both being the same structure as a conductor for coils, are brought into contact to each other; carrying out, in a testing state, running-state voltage application processing for applying an AC voltage with the same amplitude and phase as a normal running state to the N-phase coils using the voltage application device GS; and carrying out, while executing the running-state voltage application processing, first discharge detection processing for detecting a partial discharge between the first test conductor 11 and the second test conductor 12.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a technique for observing the insulation state of a stator coil. [Background technology]

[0002] IEC Standard 60034-18-41, established by the International Electrotechnical Commission in 2007, covers the insulation life of stator coils in AC rotating electrical machines. This standard applies to AC rotating electrical machines with an effective AC voltage of approximately 300 to 700 volts. The standard requires that no partial discharge occurs when an impulse voltage is applied to a test conductor (twisted pair TP shown in Figure 1) that uses the same conductor as the stator coil. In other words, this standard specifies an infinite insulation life.

[0003] Meanwhile, as rotating electrical machines are required to produce higher output, the effective value of AC voltages also increases. In 2017, the International Electrotechnical Commission established IEC Standard 60034-18-42 as a standard for AC voltages with an effective value of 700 volts or higher. This standard requires that an impulse voltage be applied to a test conductor (parallel coupling bar CB shown in Figure 2) that uses the same conductor as the stator coil, and that no more than a specified number of discharges occur within a specified time. This standard specifies the relationship between the specified number of discharges and the insulation life, taking into account that the more discharges occur, the more the insulation performance deteriorates. In other words, this standard specifies a finite life as the insulation life.

[0004] Both of these standards are provisions for testing the insulation life of a stator coil in an offline state, where no current flows through the stator coil. However, when a rotating electric machine rotates, currents for driving the rotating electric machine (currents for generating a rotating magnetic field) and currents associated with the back electromotive force generated by the rotor rotation flow through the stator coil. Because offline testing is performed with no current flowing through the stator coil, there is a possibility that the insulation life of the actual stator coil cannot be accurately evaluated. For this reason, it is considered to test the insulation life of a stator coil in an online state, where current flows through the stator coil.

[0005] The papers by Toshiba and Toshiba Mitsubishi-Electric Industrial Systems, cited below, mention online testing as well as offline testing. For example, Fig. 4 of the paper (reproduced in Fig. 30 attached to this specification) illustrates a test device in which an inverter 502 using IGBTs is connected to a rotating electric machine 501 equipped with a three-phase stator coil, and a partial discharge detector 503 is provided between the inverter 502 and the rotating electric machine 501. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Satoshi Hiroshima et al., Toshiba Corporation and Toshiba Mitsubishi-Electric Industrial Systems Corporation, “Off-line and On-line Detection of PD in Inverter-Fed Random-Wound Motor Considering IEC Technical Specifications”, 2012 Annual Report IEEE Conference on Electrical Insulation and Dielectric Phenomena, 14-17 October 2012, Conference in Montreal, QC, Canada Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, currently, offline testing for stator coil insulation life is standardized, such as in IEC Standard 60034-18-41 and IEC Standard 60034-18-42. However, offline testing does not apply switching pulses (switching pulses used to drive an inverter) equivalent to those used to drive an actual rotating electric machine to the stator coil. Furthermore, offline testing does not change the operating conditions of the rotating electric machine, such as the modulation factor. For example, if the rotating electric machine is used as a driving power source for a vehicle, the operating conditions of the vehicle are not properly reflected. Furthermore, offline testing does not allow current to flow through the stator coil. As such, offline testing is performed under conditions that differ from actual usage conditions, which poses challenges in evaluating the insulation life of stator coils.

[0008] The aforementioned paper proposes an online test using an actual rotating electric machine. However, as mentioned above, the finite life test requires that the number of discharges during the test be less than a specified number. Furthermore, accelerated testing that takes environmental conditions into account is often performed during the test to improve test efficiency (shorten test time) and ensure accuracy (ensure the reliability of insulation life depending on the number of discharges). For example, accelerated testing may involve placing the rotating electric machine in a high-temperature environment. However, this may cause demagnetization of the permanent magnets arranged in the rotor, which may result in inaccurate testing. On the other hand, removing the rotor and testing only the stator and stator coils may not adequately take into account the back electromotive force associated with rotor rotation, which may also result in inaccurate testing.

[0009] Additionally, online testing may involve the use of a dynamo bench, a testing machine used to operate a test specimen (in this case, a rotating electrical machine) and conduct performance tests. Partial discharges are often detected by using an antenna to detect the electromagnetic waves generated by partial discharges, but dynamo benches tend to generate noise, resulting in a lot of background noise in the testing environment. This means that it is difficult to distinguish between the electromagnetic waves generated by partial discharges and background noise, and the electromagnetic waves in question may not be detected properly.

[0010] As mentioned above, there are standardized specifications for offline testing for both infinite and finite life. However, there are currently no standardized specifications for online testing that specifies finite life. In other words, there are still challenges to be overcome in order to properly perform online testing for stator coils in permanent magnet rotating electrical machines.

[0011] In view of the above background, it is desirable to provide a technique that can appropriately perform a limited insulation life test on a stator coil in an electrical environment similar to that in which a rotating electric machine is in normal operation. [Means for solving the problem]

[0012] In view of the above, one aspect of a method for observing an insulation state of a stator coil is a method for observing an insulation state of a coil conductor having an insulating coating in a stator for a rotating electric machine having an N-phase coil (N is any natural number), the method comprising: An inverter is connected to the N-phase coil, and a voltage application device is connected to apply a test voltage to the N-phase coil; using a first test conductor and a second test conductor having the same structure as the coil conductor, and connecting the first test conductor to a first phase coil in the N-phase coil and the second test conductor to a second phase coil in the N-phase coil while the first test conductor and the second test conductor are in contact with each other; A rotor is disposed at a predetermined position facing the stator, and a state in which the rotor is driven to rotate by a magnetic field generated by a voltage applied to the N-phase coil is defined as a normal operating state, In a test state in which the rotor has stopped rotating or the rotor is not facing the stator, an operating state voltage application process is performed in which the voltage application device applies an AC voltage having the same amplitude and phase as the normal operating state to the N-phase coil; During the execution of the operating state voltage application process, a first discharge detection process is performed to detect partial discharge between the first test conductor and the second test conductor.

[0013] Another aspect of the stator coil insulation state observation method is a method for observing an insulation state of a coil conductor having an insulating coating in a stator for a rotating electric machine having an N-phase coil (N is any natural number), the method comprising: An inverter is connected to the N-phase coil, and a voltage application device is connected to apply a test voltage to the N-phase coil; A rotor is disposed at a predetermined position facing the stator, and a state in which the rotor is driven to rotate by a magnetic field generated by a voltage applied to the N-phase coil is defined as a normal operating state, In a test state in which the rotor has stopped rotating or the rotor is not facing the stator, an operating state voltage application process is performed in which the voltage application device applies an AC voltage having the same amplitude and phase as the normal operating state to the N-phase coil; During the execution of the operating state voltage application process, at least one of a second discharge detection process for detecting partial discharge between coils of different phases in the N-phase coil and a third discharge detection process for detecting partial discharge between the N-phase coil and ground is performed.

[0014] In addition, in one aspect, the insulation state monitoring system for a stator coil in consideration of the above includes: an inverter connected to the N-phase coil; a voltage application device that applies a test voltage to the N-phase coil; a control device that controls the voltage application device; a discharge detection device for detecting discharge; a test conductor pair in which a first test conductor and a second test conductor, which have the same structure as the coil conductors, are in contact with each other, the first test conductor being connected to a first phase coil in the N-phase coil, and the second test conductor being connected to a second phase coil in the N-phase coil; A rotor is disposed at a predetermined position facing the stator, and a state in which the rotor is driven to rotate by a magnetic field generated by a voltage applied to the N-phase coil is defined as a normal operating state, the control device performs an operating state voltage application process in which, in a test state in which the rotor has stopped rotating or the rotor is not facing the stator, the voltage application device applies an AC voltage having the same amplitude and phase as in the normal operating state to the N-phase coil; The discharge detection device detects partial discharge occurring between the first test conductor and the second test conductor during the execution of the operating state voltage application process.

[0015] In addition, in another aspect, the insulation state monitoring system for a stator coil in consideration of the above includes: an inverter connected to the N-phase coil; a voltage application device that applies a test voltage to the N-phase coil; a control device that controls the voltage application device; a discharge detection device that detects discharge, A rotor is disposed at a predetermined position facing the stator, and a state in which the rotor is driven to rotate by a magnetic field generated by a voltage applied to the N-phase coil is defined as a normal operating state, the control device performs an operating state voltage application process in which, in a test state in which the rotor has stopped rotating or the rotor is not facing the stator, the voltage application device applies an AC voltage having the same amplitude and phase as in the normal operating state to the N-phase coil; The discharge detection device detects at least one of partial discharges occurring between coils of different phases in the N-phase coil and partial discharges occurring between the N-phase coil and ground during execution of the operating state voltage application process.

[0016] These methods and systems can reproduce current and voltage conditions in the stator of a rotating electric machine similar to those observed when the rotor is rotated, without actually rotating the rotor. Therefore, whether using the first and second test conductors or not, the insulation state of the coil conductors can be relatively easily observed in an environment similar to that of an actual rotating electric machine. Instead of actually rotating the rotor, a voltage application device applies an AC voltage of the same amplitude and phase as that observed under normal operating conditions to the N-phase coil. This allows the insulation state to be observed without being affected by noise that may occur when the rotor is rotated. Therefore, even weak physical phenomena (e.g., generation of electromagnetic waves, generation of minute currents, etc.) caused by partial insulation breakdown can be measured with high accuracy. Thus, these methods and systems can appropriately perform a finite insulation life test of a stator coil in an electrical environment similar to that observed under normal operating conditions of a rotating electric machine.

[0017] Further features and advantages of the method and system for monitoring the insulation condition of a stator coil will become apparent from the following description of exemplary, non-limiting embodiments, which are illustrated with reference to the drawings. [Brief explanation of the drawings]

[0018] [Figure 1] Schematic diagram of test conductor (twisted pair) [Figure 2] Schematic diagram of test conductor (parallel bar) [Figure 3] Figure showing the impulse voltage waveform applied in offline testing (infinite life) [Figure 4] Figure showing the impulse voltage waveform applied in offline testing (infinite life) [Figure 5] Figure showing the impulse voltage waveform applied in offline testing (infinite life) [Figure 6] Figure showing the impulse voltage waveform applied in offline testing (finite life) [Figure 7] A diagram showing an example of a pulse waveform including a surge voltage in an offline test (limited life) [Figure 8] FIG. 1 is a diagram showing an example of a modulated pulse waveform including a surge voltage in an actual rotating electrical machine. [Figure 9] Equivalent circuit block diagram showing an example of the system configuration for turn-to-turn short circuit testing in a single inverter system [Figure 10] Equivalent circuit block diagram showing an example of the system configuration for turn-to-turn short circuit testing in a dual inverter system [Figure 11] Equivalent circuit block diagram showing an example of a system configuration for a ground fault test (or phase-to-phase short circuit test) in a single inverter system [Figure 12] Equivalent circuit block diagram showing an example of a system configuration for earth fault testing (or phase-to-phase short circuit testing) in a dual inverter system [Figure 13] A diagram showing the current and voltage waveforms of a stator coil in a single inverter system. [Figure 14] 1 is a diagram showing current and voltage waveforms of a stator coil in a dual inverter system; [Figure 15] Comparison of voltage waveforms between single inverter system and dual inverter system [Figure 16] Block diagram showing an example of the system configuration for turn-to-turn short circuit testing in a single inverter system [Figure 17] Block diagram showing an example of the system configuration for turn-to-turn short circuit testing in a dual inverter system [Figure 18] Block diagram showing an example of a system configuration for a ground fault test (or phase-to-phase short circuit test) in a single inverter system [Figure 19] Block diagram showing an example of a system configuration for a ground fault test (or phase-to-phase short circuit test) in a dual inverter system [Figure 20] Voltage vector diagram of a rotating electric machine with a rotor [Figure 21] Voltage vector diagram correcting the amplitude of the back electromotive force of a rotating electric machine without a rotor (air rotor) [Figure 22] Voltage vector diagram correcting the amplitude and phase of the back electromotive force of a rotating electric machine without a rotor (air rotor) [Figure 23] Control block diagram of inverter and grid simulator [Figure 24] Control block diagram of inverter and grid simulator [Figure 25] 20 to 22 are waveform diagrams showing the U-phase current and U-phase voltage at low rotation speeds, respectively. [Figure 26] 20 to 22 are waveform diagrams showing the U-phase current and U-phase voltage at high rotation speeds, respectively. [Figure 27] Graph showing the relationship between applied voltage and time to breakdown [Figure 28] Graph showing the relationship between voltage application time and capacitance change [Figure 29] Graph showing the relationship between voltage application time and the number of partial discharges [Figure 30]A diagram showing an example of a conventional online testing system. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a method and system for observing the insulation state of a stator coil, which observes the insulation state of a coil conductor with an insulating coating, in a stator for a rotating electric machine having an N-phase coil (N is any natural number, N=3 in this embodiment) will be described with reference to the drawings. First, two standards defined by the International Electrotechnical Commission will be briefly described. The two standards are an offline infinite life test and an offline finite life test. Here, "offline" refers to a state in which no current flows through the stator coil. The infinite life test is a test whose passing condition is that no dielectric breakdown occurs (no partial discharge occurs) even when an impulse voltage is applied multiple times, and the finite life test is a test whose passing condition is that partial discharge occurs no more than a specified number of times when an impulse voltage is applied multiple times.

[0020] 1 and 2 show an example of a test conductor pair 1 formed using a first test conductor 11 and a second test conductor 12, which have the same structure as a coil conductor (stator coil) with an insulating coating. Fig. 1 illustrates the test conductor pair 1 configured as a twisted pair TP in which two conductors called round wires 13 (sometimes called round bundle windings) with a conductive core wire coated are wound in a spiral shape. Fig. 2 also illustrates the test conductor pair configured as a parallel coupled bar CB in which two conductors called rectangular bar windings with a conductive core wire coated and rectangular in cross section are bundled together. As shown in Fig. 2, the parallel coupling bar CB is formed by bundling rectangular wires 15, each of which has a copper wire 16 (core wire) covered with an insulating coating 17, with the rectangular wires 15 spaced apart at both ends of the bundling insulating coating 18, with the space between them being filled with a non-conductive filler 19. These test conductor pairs 1 are used in the standard specifications mentioned above.

[0021] The standard specifies offline infinite life tests, including a turn-to-turn (TT) test to check for partial discharges in the twisted pair TP, a phase-to-ground (PG) test to check for partial discharges between one phase of a multi-phase stator coil and ground, and a phase-to-phase (PP) test to check for partial discharges between phases of a multi-phase stator coil. The infinite life test requires that no partial discharges occur during multiple impulse voltage applications. Each impulse voltage application covers one electrical cycle. Figure 3 shows the impulse voltage waveform during the turn-to-turn short circuit test, Figure 4 shows the impulse voltage waveform during the ground fault test, and Figure 5 shows the impulse voltage waveform during the phase-to-phase short circuit test.

[0022] This infinite life test is intended for rotating electric machines with an AC voltage root mean square (RMS) value of 300 to 700 volts. Generally, AC rotating electric machines are connected to a DC power source via an inverter that converts power between DC and AC. The peak value of the impulse voltage described above is specified based on the DC side voltage of the inverter (DC link voltage Vdc). The amplitude of the impulse voltage in the turn-to-turn short circuit test is set to 1.71 times the DC link voltage (Vdc), which is the DC side voltage of the inverter connected to the AC rotating electric machine. The peak value of the impulse voltage in the ground fault test is set to 1.45 times the DC link voltage (Vdc), and the peak value of the impulse voltage in the phase-to-phase short circuit test is set to 2.44 times the DC link voltage (Vdc).

[0023] The standard specifies offline finite life tests, including a turn-to-turn short-circuit test (TT) to test for partial discharges in the parallel coupling bars (CB), a ground fault test (PG) to test for partial discharges between one phase of a multi-phase stator coil and ground, and a phase-to-phase short-circuit test (PP) to test for partial discharges between phases of a multi-phase stator coil. The finite life test requires that partial discharges occur no more than a specified number of times when an impulse voltage is applied multiple times within a specified time. Multiple impulse voltage cycles, as shown in Figures 6 and 7, are repeatedly applied. This finite life test is intended for rotating electrical machines with an AC voltage root mean square (rms) value of 700 volts or greater. The peak value of the impulse voltage is set according to the insulation life for each test (i.e., the relationship between the time and voltage at which dielectric breakdown occurs).

[0024] However, offline finite life testing in accordance with the standard has the following problems (a) to (c). (a) In offline testing, it was not possible to apply modulated pulses to the stator coil that were similar to those used in an actual inverter. (b) In offline testing, no current flows through the stator coil. (c) In the offline test, the modulation rate is not changed in accordance with the operation of the actual rotating electrical machine, and the duty of the modulation pulse applied to the stator coil is not changed.

[0025] For example, Fig. 7 shows an example of a pulse waveform including a surge voltage in an offline test, and Fig. 8 shows an example of a modulated pulse waveform including a surge voltage in an actual rotating electric machine. As shown in Fig. 7, the peak value of the amplitude of the surge voltage applied in the offline test is K times the DC link voltage Vdc and is almost constant. In contrast, as shown in Fig. 8, in an actual rotating electric machine, the peak value of the surge voltage is not constant and often exceeds K times the DC link voltage Vdc.

[0026] The finite insulation life test in the standard has the issues (a) to (c) mentioned above, and it cannot be said that the test accurately reflects the effects of surges in actual rotating electrical machines. In other words, it cannot be said that the finite insulation life is being tested correctly, and it is required to test the insulation life of the stator coil with current flowing through it, that is, in an online state.

[0027] For example, Fig. 30 shows an example of such an online test system. In this test system, an inverter 502 using IGBTs is connected to a rotating electric machine 501 equipped with a three-phase stator coil, and a partial discharge detector 503 is provided between the inverter 502 and the rotating electric machine 501.

[0028] In this way, in online testing using an actual rotating electric machine 501, a dynamo bench, which is a testing machine for operating a test specimen (here, a rotating electric machine) to conduct performance tests, may be used. The occurrence of partial discharge is often detected by detecting the electromagnetic waves generated by the partial discharge using an antenna, but dynamo benches tend to generate noise, which increases the background noise in the testing environment. In other words, it is sometimes impossible to distinguish between the electromagnetic waves generated by partial discharge and background noise, and the electromagnetic waves in question cannot be detected.

[0029] As described above, a finite life test requires that discharges occur no more than a specified number of times during the test to pass. Accelerated testing, which takes environmental conditions into account, is often performed during testing to improve test efficiency (shorten test time) and ensure accuracy (ensure reliability of insulation life depending on the number of discharges). For example, accelerated testing may involve placing a rotating electrical machine in a high-temperature environment. However, this may result in demagnetization of the permanent magnets disposed in the rotor, potentially preventing accurate testing. On the other hand, removing the rotor and testing only the stator and stator coils makes it impossible to consider the back electromotive force that accompanies rotor rotation, which may also result in inaccurate testing.

[0030] In other words, existing online exams have the following issues (d) and (e). (d) It is difficult to measure the voltage of partial discharges while rotating the rotor of a rotating electrical machine using a dynamo bench (in many cases, electromagnetic waves are detected using an antenna) due to the influence of background noise. (e) In the case of a finite insulation life test, an accelerated test is performed by raising the environmental temperature. However, if a rotor equipped with a permanent magnet is placed in a high-temperature environment, problems such as demagnetization may occur, making it difficult to perform an accelerated test.

[0031] In view of the above problems (a) to (e), the inventors have proposed a new testing method and testing system (a method and system for observing the insulation state of a stator coil) as described in this specification. These methods and systems will be described in detail below.

[0032] 9 to 12 are schematic block diagrams of a test system (insulation state observation system) according to this embodiment. Figures 9 and 10 show the test system when the above-mentioned turn-to-turn short circuit test (TT) is performed, and Figures 11 and 12 show the test system when the above-mentioned ground fault test (PG) or phase-to-phase short circuit test (PP) is performed.

[0033] 9 and 11 illustrate a test system for testing the stator coils of a rotating electrical machine having a so-called star-connected stator coil, in which multiple phases (here, three phases) of stator coils are connected to each other at a neutral point. One ends of the multiple phase stator coils are connected to each other at a neutral point, and the other ends of the multiple phase stator coils are connected to arms of each phase of a single inverter INV that converts power between direct current and multiple phase alternating current. In this specification, this system may be referred to as a single inverter system as appropriate.

[0034] 10 and 12 illustrate a test system for testing a stator coil of a rotating electrical machine having open windings of multiple phases (three phases in this example). A first inverter INV1 that converts power between direct current and multiple phase alternating current is connected to one end of the open windings of multiple phases, and a second inverter INV2 that converts power between direct current and multiple phase alternating current is connected to the other end of the open windings of multiple phases. In this specification, this system may be referred to as a dual inverter system as appropriate. When there is no need to distinguish between the two inverters in a dual inverter system, they are collectively referred to simply as inverter INV.

[0035] As shown in Figures 9 to 12, the rotor is removed from the rotating electric machine. In other words, in the online test proposed by the inventors, the electrical state of the stator coil is maintained as if the rotor were rotating, without actually rotating the rotor. Not only is a drive voltage applied to the stator coil via the inverter INV, but a back electromotive force (back electromotive force, induced electromotive force, or induced electromotive force) generated by the rotor rotation is also applied. To apply the back electromotive force induced in the stator coil by the rotor rotation to the stator coil without the rotor, a voltage application device GS (a power supply generating an arbitrary voltage waveform, e.g., a grid simulator) is connected to the stator coil. In other words, in the online test proposed by the inventors, in a test state in which the rotor stops rotating or is not facing the stator, the voltage application device performs an operating state voltage application process in which an AC voltage of the same amplitude and phase as in the normal operating state is applied to the N-phase coil. Note that in this specification, a rotor that does not generate a back electromotive force in the test state, including when the rotor is not facing the stator, is sometimes referred to as an "air rotor."

[0036] Because the rotor is removed from the rotating electric machine, the rotor is not rotated using a dynamo bench or the like. The occurrence of partial discharge is detected, for example, by receiving electromagnetic waves generated by discharge using an antenna (not shown in Figures 9 to 12) (antenna 4 in Figures 16 to 19). By not using a dynamo bench, background noise is suppressed, allowing the occurrence of partial discharge to be properly detected. For example, if a test is performed while gradually increasing the applied voltage, the partial discharge inception voltage (PDIV) can also be properly determined. In this way, the system illustrated in Figures 9 to 12 has a system configuration that addresses the above-mentioned issue (d).

[0037] Furthermore, since the rotor does not rotate or does not need to be present, demagnetization of the permanent magnets when the environmental temperature changes is not an issue. For example, accelerated deterioration tests can be performed under high environmental temperatures. In other words, the systems illustrated in Figures 9 to 12 have a system configuration that also addresses the issue (e) above.

[0038] Figure 13 shows the current and voltage waveforms of the stator coil in a single inverter system, and Figure 14 shows the current and voltage waveforms of the stator coil in a dual inverter system. In both Figures 13 and 14, the left side shows the waveforms when the rotating electric machine is equipped with a rotor, and the right side shows the waveforms when the rotating electric machine is equipped with an air rotor, i.e., when a grid simulator is connected to the stator coil.

[0039] In the single inverter system shown in Fig. 13, the peak value of the surge voltage when the grid simulator is connected is only 2.0% higher than the peak value of the surge voltage when there is a rotor, so the peak values ​​of the surge voltage can be said to be almost the same. Furthermore, the average value of the surge voltage when the grid simulator is connected is only 0.2% higher than the value when there is a rotor, so the average values ​​of the surge voltage can also be said to be almost the same.

[0040] Similarly, in the dual inverter system shown in Fig. 14, the peak surge voltage value when the grid simulator is connected is only 0.5% higher than the peak surge voltage value when the rotor is present, so the peak surge voltage values ​​can be said to be roughly equivalent. Also, the average surge voltage value when the grid simulator is connected is only 0.8% higher than the value when the rotor is present, so the average surge voltage values ​​can also be said to be roughly equivalent.

[0041] In the case of an air rotor, the detailed configuration for applying the same back electromotive force to the stator coil as when a rotor is present will be described later. In this way, with the stator coil insulation state observation method and stator coil insulation state observation system according to this embodiment, it is possible to properly carry out a finite insulation life test on the stator coil in an electrical environment similar to that when the rotating electric machine is in normal operating condition.

[0042] In a dual inverter system, by setting the output of one inverter to positive and the output of the other inverter to negative, it is possible to apply to the stator coil a voltage with an amplitude twice that of a single inverter. Therefore, as shown in Figure 15, the dual inverter system can reduce surge voltage and peak value relatively compared to a single inverter system. According to experiments and simulations conducted by the inventors, it was confirmed that the rate at which a surge voltage reaching twice the DC link voltage (Vdc) occurs in response to one modulated pulse is reduced to about 20% in a dual inverter system, compared to nearly 100% in a single inverter system.

[0043] If the number of high surge voltages that occur is small, the partial discharge inception voltage (PDIV) may be higher even if the insulation capacity is the same.Conversely, if a dual inverter system is designed to ensure the same partial discharge inception voltage (PDIV) as a single inverter system, the insulation performance can be kept low, which makes it possible to reduce costs.

[0044] The specific configuration of the stator coil insulation state monitoring system according to this embodiment will be described below. The block diagrams of Figures 16 and 17 show an example of the system configuration of an insulation state monitoring system 100 (insulation state monitoring system 101 for turn-to-turn short circuit testing) that performs a turn-to-turn short circuit test, and the block diagrams of Figures 18 and 19 show an example of the system configuration of an insulation state monitoring system (insulation state monitoring system 102 for ground fault and phase-to-phase short circuit testing) that performs a ground fault test (or phase-to-phase short circuit test). The block diagrams of Figures 16 and 18 show an example of the system configuration of the insulation state monitoring system 100 in a single inverter system, and the block diagrams of Figures 17 and 19 show an example of the system configuration of the insulation state monitoring system 100 in a dual inverter system.

[0045] First, we will explain the insulation condition observation system 101 for turn-to-turn short circuit testing. The block diagram in Fig. 16 shows an example of the system configuration of a first insulation condition observation system 101S that performs a turn-to-turn short circuit test in a single inverter system, and the block diagram in Fig. 17 shows an example of the system configuration of a second insulation condition observation system 101D that performs a turn-to-turn short circuit test in a dual inverter system.

[0046] 16 and 17, the insulation status observation system 101 for turn-to-turn short circuit testing includes an inverter INV (first inverter INV1 and second inverter INV2 in a dual inverter system) connected to the N-phase coil (stator coil), a voltage application device GS that applies a test voltage to the N-phase coil, a control device 2 that controls the voltage application device GS, a test conductor pair 1, and a discharge detection device 5 that detects discharge. As described above, the test conductor pair 1 is configured such that the first test conductor 11 and the second test conductor 12, which have the same structure as the coil conductors, are in contact with each other, with the first test conductor 11 connected to the first phase coil of the N-phase coil and the second test conductor 12 connected to the second phase coil of the N-phase coil.

[0047] The control device 2 is configured with a logic operation device such as a DSP (Digital Signal Processor) or a microcomputer at its core. The control device 2 performs an operating-state voltage application process in which, in a test state in which the rotor stops rotating or the rotor does not face the stator, the voltage application device GS applies an AC voltage of the same amplitude and phase as in a normal operating state to the N-phase coil. Here, the "rotor stops rotating" state refers to a state in which the rotor does not rotate in a rotating electric machine with a normal configuration including a rotor and a stator. The "rotor does not face the stator" state refers to a state in which the rotor is detached from the rotating electric machine. The "normal operating state" refers to a state in which the rotor is positioned facing the stator at a specified position and is driven to rotate by a magnetic field generated by a voltage applied to the N-phase coil. To distinguish the rotor in the test state (including when it is detached and not present) from the rotor in the normal operating state, the rotor is referred to as an "air rotor" as described above.

[0048] In a normal operating state, when the rotor is rotating, a back electromotive force is induced in the stator coil. However, in a test state where the rotor is stopped rotating or the rotor is not facing the stator, this back electromotive force does not occur. Therefore, in order to reproduce the "normal operating state" in the "test state," a voltage equivalent to the back electromotive force must be separately applied to the stator coil. The insulation state observation system 100 (including the insulation state observation method) of this embodiment is characterized by performing an "operating state voltage application process" in which a voltage equivalent to this back electromotive force is applied to the stator coil. The "operating state voltage application process" will be described in detail later.

[0049] The discharge detection device 5 detects partial discharges occurring between the first test conductor 11 and the second test conductor 12 during the running-state voltage application process. That is, the insulation status observation system 101 for turn-to-turn short circuit testing performs a first discharge detection process to detect partial discharges between the first test conductor 11 and the second test conductor 12 during the running-state voltage application process. The discharge detection device 5 for detecting discharges includes an antenna 4 that receives electromagnetic waves generated by discharges and an oscilloscope OS as a recorder that displays and records the signals received by the antenna 4. To record single-shot signals generated by discharges, as in this embodiment, the oscilloscope OS is preferably a device capable of recording using a one-shot trigger rather than a sweep trigger. The oscilloscope OS records the signals triggered by the signal received by the antenna 4. The recorder is not limited to the oscilloscope OS, but may also be a data acquisition device (DAQ) such as a memory high-coder or a waveform recorder.

[0050] It is known that partial discharge not only generates electromagnetic waves but also increases the current flowing through the stator coil. Therefore, instead of or in addition to the antenna 4 and oscilloscope OS, a current detector (current sensor) capable of detecting the current increased by partial discharge can be used as the discharge detection device 5. This current sensor may also serve as a current sensor (for example, current sensor 79 shown in FIG. 23) that detects the current flowing through the stator coil for feedback control of the inverter INV.

[0051] The insulation condition observation system 101 for turn-to-turn short circuit testing may further include a temperature-humidity chamber 9 that can maintain the environmental temperature and humidity at a predetermined constant temperature and humidity regardless of the outside air temperature and humidity and can accommodate the test conductor pair 1. The turn-to-turn short circuit test can be performed with the test conductor pair 1 accommodated in the temperature-humidity chamber 9. By setting stricter environmental conditions, such as the environmental temperature, an accelerated test can be performed, thereby shortening the time required to perform the finite insulation life test. The environmental temperature set for the turn-to-turn short circuit test is a temperature (e.g., 40 to 50°C) higher than room temperature (approximately 20 to 25°C) or a temperature (-20 to 40°C) lower than room temperature (approximately 20 to 25°C), and the environmental humidity is, for example, 20 to 30% for low humidity and 80 to 90% for high humidity. For example, accelerated testing can be performed appropriately by conducting tests under so-called high temperature conditions (conditions where the temperature is maintained at a constant temperature (40-50°C) higher than the outside air temperature (room temperature) at a constant humidity) or high temperature and high humidity conditions (conditions where the temperature is maintained at a constant temperature (40-50°C) higher than the outside air temperature (room temperature) and a constant humidity (80 to 90%) higher than the outside air temperature).

[0052] In other words, the insulation condition observation system 101 for turn-to-turn short circuit testing includes a thermo-humidistat chamber 9 that can maintain a constant humidity and a constant temperature higher than the outside air temperature and can accommodate the test conductor pair 1 (first test conductor 11 and second test conductor 12), and performs the operating state voltage application process and the first discharge detection process with the test conductor pair 1 (first test conductor 11 and second test conductor 12) placed in the thermo-humidistat chamber 9 that is maintained at a constant humidity and a constant temperature higher than the outside air temperature. Naturally, the insulation condition observation system 101 for turn-to-turn short circuit testing may be configured without including the thermo-humidistat chamber 9.

[0053] Next, we will explain the insulation status monitoring system 102 for ground fault and phase-to-phase short circuit testing. The block diagram of Fig. 18 shows an example of the system configuration of a third insulation status monitoring system 102S that performs a ground fault test (or a phase-to-phase short circuit test) in a single inverter system, and the block diagram of Fig. 19 shows an example of the system configuration of a fourth insulation status monitoring system 102D that performs a ground fault test (or a phase-to-phase short circuit test) in a dual inverter system.

[0054] 18 and 19, the insulation condition observation system 102 for ground fault and phase-to-phase short circuit testing includes an inverter INV (first inverter INV1 and second inverter INV2 in a dual inverter system) connected to the N-phase coil (stator coil), a voltage application device GS that applies a test voltage to the N-phase coil, a control device 2 that controls the voltage application device GS, and a discharge detection device 5 that detects discharge. Unlike the insulation condition observation system 101 for turn-to-turn short circuit testing that includes a test conductor pair 1, the insulation condition observation system 102 for ground fault and phase-to-phase short circuit testing does not include a test conductor pair 1.

[0055] The control device 2, which is configured with a logic operation unit as its core, performs an operating-state voltage application process in which the voltage application device GS applies an AC voltage of the same amplitude and phase as in the normal operating state to the N-phase coil during a test state in which the rotor stops rotating or the rotor is not facing the stator. The test state and normal operating state are as described above. During the operating-state voltage application process, the discharge detection device 5 detects at least one of partial discharges occurring between different-phase coils in the N-phase coil and partial discharges occurring between the N-phase coil and ground. That is, during the operating-state voltage application process, the insulation status observation system 102 for ground fault and phase-to-phase short circuit testing performs at least one of a second discharge detection process for detecting partial discharges between different-phase coils in the N-phase coil and a third discharge detection process for detecting partial discharges between the N-phase coil and ground. The configuration of the discharge detection device 5 is similar to that of the insulation status observation system 101 for turn-to-turn short circuit testing, and therefore a description thereof will be omitted.

[0056] Like the insulation condition observation system 101 for turn-to-turn short circuit testing, the insulation condition observation system 102 for ground fault and phase-to-phase short circuit testing may further include a temperature-humidity chamber 9 capable of maintaining a constant environmental temperature and humidity regardless of the ambient temperature and humidity, and capable of housing a stator coil (N-phase coil). The ground fault test (or phase-to-phase short circuit test) may be performed with the N-phase coil housed in the temperature-humidity chamber 9. By setting stricter environmental conditions, such as the ambient temperature, an accelerated test may be performed, thereby shortening the time required to perform a finite insulation life test. The ambient temperature set for the ground fault test (or phase-to-phase short circuit test) may be a temperature (e.g., 40 to 50°C) higher than room temperature (approximately 20 to 25°C) or a temperature (-20 to 40°C) lower than room temperature (approximately 20 to 25°C), and the ambient humidity may be, for example, 20 to 30% for low humidity and 80 to 90% for high humidity. For example, accelerated testing can be performed appropriately by conducting tests under so-called high temperature conditions (conditions where the temperature is maintained at a constant temperature (40-50°C) higher than the outside air temperature (room temperature) at a constant humidity) or high temperature and high humidity conditions (conditions where the temperature is maintained at a constant temperature (40-50°C) higher than the outside air temperature (room temperature) and a constant humidity (80 to 90%) higher than the outside air temperature).

[0057] In other words, the insulation state observation system 102 for ground fault and phase-to-phase short circuit testing further includes a thermo-humidistat chamber 9 that can maintain a constant humidity and a constant temperature higher than the outside air temperature and can accommodate a stator coil (N-phase coil), and performs the operating state voltage application process and at least one of the second discharge detection process and the third discharge detection process with the stator coil (N-phase coil) placed in the thermo-humidistat chamber 9 that is maintained at a constant humidity and a constant temperature higher than the outside air temperature. Naturally, the insulation state observation system 102 for ground fault and phase-to-phase short circuit testing may be configured without including the thermo-humidistat chamber 9.

[0058] In this embodiment, a grid simulator is used as the voltage application device GS, which is common to both the insulation status observation system 101 for turn-to-turn short circuit testing and the insulation status observation system 102 for ground fault and phase-to-phase short circuit testing. However, the voltage application device GS is not limited to a grid simulator, and may be configured using an arbitrary voltage waveform generating power supply (AWG: Arbitrary Waveform Generator). The arbitrary voltage waveform generating power supply is a power supply device that outputs an arbitrary waveform set by a program or the like.

[0059] The "operating state voltage application process" will be described in detail below. In this embodiment, the rotating electric machine is controlled by executing current feedback control using a current vector control method in an orthogonal vector space (orthogonal vector coordinate system) of two axes that rotate in synchronization with the rotation of the rotating electric machine. In the current vector control method, for example, current feedback control is performed in a dq axis vector coordinate system with a d axis along the direction of the field magnetic flux of a permanent magnet and a q axis electrically leading π / 2 from this d axis. The control device 2 calculates a torque command T based on the target torque of the rotating electric machine to be controlled. * is determined, and the d-axis current command Id * and q-axis current command Iq * Determine.

[0060] In a steady state where the current on the dq axes can be considered constant, the time differential term in the voltage equation becomes zero, so the voltage on the dq axes can be simplified to the following equation (1).

[0061]

number

[0062] where V d , V q are the d-axis voltage and q-axis voltage, respectively, and i d , i q are the d-axis current and q-axis current, respectively, R is the resistance of the stator coil (winding resistance), ω is the angular velocity, and L d , L qare the d-axis inductance and q-axis inductance, respectively, and φ m is the magnetic flux linkage of the permanent magnet (magnetic flux).

[0063] Fig. 20 shows a voltage vector diagram for a typical rotating electric machine with a rotor. In the dq-axis vector coordinate system, as mentioned above, the d-axis is set along the direction of the field magnetic flux generated by the permanent magnet, so the magnetic flux φ m is on the d axis. L d i d and L q i q are the magnetic flux φ of the magnet as the interlinkage magnetic flux components of the d-axis and q-axis, respectively. m is added to the total magnetic flux, φ t This becomes:

[0064] Armature current i a is the d-axis current i d and q-axis current i q And the q-axis and armature current i a The angle with the back electromotive force ωMif (=ωφ m ) corresponds to the current phase angle β based on the armature voltage V a is the back electromotive force ωMif plus the voltage ωL due to the armature reaction of the d-axis and q-axis q i q , ωL d i d The inductive voltage V0 is added to the voltage drop Ri due to the winding resistance R. a The voltage is the sum of the q-axis and armature voltage V a The angle with the back electromotive force ωMif (=ωφ m ) as a reference. As shown in Figure 20, the inductive voltage V0 is t It is 90° ahead in phase.

[0065] FIG. 21 shows a voltage vector diagram in which the amplitude of the back electromotive force of a rotating electric machine without a rotor (air rotor) is corrected. d2 , L q2indicate the d-axis inductance and q-axis inductance in an air rotor rotating electric machine. d2 <L d1 ","L q2 <L q1 " and the total magnetic flux φ t The air rotor is smaller than the rotating electrical machine with a rotor. d2 =L q2 "

[0066] In comparison with a rotating electric machine with a rotor, the d-axis inductance and q-axis inductance of an air rotor are smaller, so the voltage (ωL q2 i q , ωL d2 i d ) also becomes smaller, and the armature voltage V a2 In other words, the amplitude of the output voltage becomes smaller. For example, if the counter electromotive force ωMif is corrected by the gain "K a " and correct the back electromotive force ωMif, the armature voltage V in the air rotor a2 The magnitude of the armature voltage V a This gain "K a " can be calculated as follows:

[0067] Armature voltage V a is the effective value of the AC voltage, and the modulation factor Midx, which indicates the ratio of the effective value of the AC voltage to the DC voltage (DC link voltage Vdc), can be expressed by the following formula (2), as is clear from the vector diagrams in Figures 20 and 21. a As the rotation speed increases, it can be ignored, so on the right side of equation (2) we use "V a =V0".

[0068]

number

[0069] In order to simplify the calculation formula, we use the fixed value "ωL q i q " to "K1", "ωL d i d " is replaced with "K2" and "ωMif" with "K3". Also, in the case of a rotating electric machine with a rotor, "K1" is replaced with "K 11 (=ωL q1 i q1 ) and "K2" to "K 21 (=ωL d1 i d1 ) and "K1" in the case of a rotating electric machine without a rotor (air rotor) is set to "K 12 (=ωL q2 i q2 ) and "K2" to "K 22 (=ωL d2 i d2 )"

[0070] Here, the armature voltage V in the case of an air rotor is a2 The magnitude of the armature voltage V a In order to make the magnitude of the correction gain "K a " is used to make equation (2) for the air rotor equal to equation (2) for the rotating electrical machine with a rotor.

[0071] K 11 2 +(K 21 +K3) 2 = K 12 2 +(K 12 +K3·K a ) 2 ···(3)

[0072] Rearranging equation (3) gives the following equation (4), which is solved to give the following equation (5).

[0073] (K3 2 )K a 2 +(2·K 22 ·K3)K a + (K 22 2 +K 12 2 -K 11 2 -K 21 2 -2·K 12 K3-K3 2 )···(4)

[0074]

number

[0075] In this way, the correction gain "K a ", the armature voltage V in the case of an air rotor a2 The magnitude of the armature voltage V when the rotor is present a However, as is clear from a comparison of Figure 20 and Figure 21, the voltage phase changes from "α" to "α'". This causes the power factor to change as well. In order to perform accurate testing, the armature voltage V a2 In addition to correcting the magnitude of the voltage, it is also necessary to adjust the phase so that the voltage phase becomes "α" in the case of an air rotor. q2 i q , ωL d2 i d Since the phase of the counter electromotive force ωMif cannot be changed, the phase of the counter electromotive force ωMif is changed.

[0076] When a rotor is present, as shown in Figure 20, the back electromotive force ωMif only has a q-axis component. In order to change the phase of the back electromotive force ωMif, a d-axis component is also required. Figure 22 shows a voltage vector diagram in which the amplitude and phase of the back electromotive force of a rotating electric machine without a rotor (air rotor) is corrected. As shown in Figure 22, the magnetic flux φ m By changing the phase of "δ", the magnetic flux of the magnet φ m The phase of the back electromotive force ωMif, which leads by 90 degrees, is changed. This "δ" and the gain of the amplitude of the back electromotive force ωMif when the phase is changed, "K a2 " can be calculated as follows:

[0077] The following equations (6) and (7) are the voltage equations for the dq axes when there is a rotor, and the following equations (8) and (9) are the voltage equations for the dq axes when there is an air rotor. Note that the voltage drop due to the winding resistance R is omitted because it is offset in the following equations (10) and onwards.

[0078] V d1 =-ωL q1 i q -ωMif·sin(0) ···(6) V q1 = ωL d1 i d +ωMif·cos(0) ···(7) V d2 =-ωL q2 i q -ωMif·K a sin(δ) (8) V q2 = ωL d2 i d +ωMif·K a cos(δ) (9)

[0079] Here, "V d2 =V d1 "," "V q2 =V q1 ", "sin(0)=0", "cos(0)=1", so the following formula (10) holds from formulas (6) and (8), which can be rearranged to give the following formula (11). Furthermore, the following formula (12) holds from formulas (7) and (9), which can be rearranged to give the following formula (13).

[0080] -ωL q2 i q -ωMif·K a sin(δ)=-ωL q1 i q ···(10) K a sin(δ)=(L q1 i q -L q2 i q ) / Mif ···(11)

[0081] ωLd2 i d +ωMif·K a cos(δ)=ωL d1 i d +ωMif ···(12) K a cos(δ)=(L d1 i d -L d2 i d ) / Mif+1 ···(13)

[0082] From equations (11) and (13), the following equation (14) is established, and therefore the correction phase δ can be obtained as in equation (15).

[0083] tan(δ) = sin(δ) / cos(δ) = K a sin(δ) / K a cos(δ) (14) δ=tan -1 (δ) =tan -1 ((L q1 i q -L q2 i q ) / (L d1 i d -L d2 i d +Mif)) =tan -1 ((L q1 -L q2 )i q / ((L d1 -L d2 )i d +Mif))···(15)

[0084] The gain for correcting the amplitude of the back electromotive force ωMif is shown in the vector diagram of FIG. a ", but "K a2 When the correction phase δ is specified, the gain "K a2 " can also be calculated.

[0085]

number

[0086] As shown in Figures 20 and 22, the armature voltage V a and the corrected armature voltage in the case of an air rotor, "V a3 This allows the modulation factor to be the same as that in the case of a rotor, even in the case of an air rotor, without changing the power factor.

[0087] Furthermore, this gain "K a2 " corresponds to the "back electromotive force correction gain" and "correction phase δ" corresponds to the "back electromotive force correction phase." As described above, the normal operating state is the AC voltage (V a ) is applied to the N-phase coil to rotate the rotor. In the operation state voltage application process, the control device 2 applies the test state AC voltage (V a3 ) amplitude is the AC voltage (V a The back EMF correction gain (K a2 ) and AC voltage under test (V a3 ) phase (α) of the AC voltage (V a The back electromotive force vector in the orthogonal vector coordinate system is corrected using the back electromotive force correction phase (δ) which is the phase of the back electromotive force (ωMif) that coincides with the phase (α) of the AC voltage (V a3 ) and calculate the amplitude and phase.

[0088] Fig. 23 shows a control block diagram for controlling the inverter INV and the voltage application device GS so as to apply the above-mentioned voltage to the stator coil and cause current to flow in the operating state voltage application process. Fig. 23 shows an example of a control block diagram for a first insulation state observation system 101S that performs a turn-to-turn short circuit test in a single inverter system, but the same applies to a second insulation state observation system 101D that performs a turn-to-turn short circuit test in a dual inverter system, a third insulation state observation system 102S that performs a ground fault test (or a phase-to-phase short circuit test) in a single inverter system, and a fourth insulation state observation system 102D that performs a ground fault test (or a phase-to-phase short circuit test) in a dual inverter system.

[0089] The calculation unit 20 of the control device 2 includes a drive calculation unit 21 for driving the inverter INV and the voltage application device GS, and a parameter setting unit 22 for setting parameters for driving and controlling the inverter INV and parameters for driving the voltage application device GS.

[0090] The parameter setting unit 22 includes a first lookup table (LUT1) 24, a second lookup table (LUT2) 25, and a third lookup table (LUT3) 26. The first lookup table 24 and the second lookup table 25 are tables for setting parameters that define the relationship between the rotation speed and torque (current) of the rotating electric machine, and can also be called a rotating electric machine drive parameter setting unit 23. The first lookup table 24 sets the torque command T * (d-axis current command Id * , q-axis current command Iq * ) is defined. The second lookup table 25 is a table in which the magnetic pole position θ is defined in correspondence with the speed at each time. The third lookup table (LUT3) 26 can also be called a voltage application device drive parameter setting unit that sets parameters for driving the voltage application device GS. The third lookup table 26 also contains the above-mentioned back electromotive force correction gain (K a2 ) and the back electromotive force correction phase (δ) are set.

[0091] The drive calculation unit 21 includes a low-pass filter (LPF) 71, a coordinate conversion unit 72, a proportional-integral control unit (PI) 73, a modulation factor calculation unit 74, a modulation unit 75, and a DA converter (digital-to-analog converter) 77. The low-pass filter (LPF) 71, the coordinate conversion unit 72, the proportional-integral control unit (PI) 73, the modulation factor calculation unit 74, and the modulation unit 75 constitute an inverter drive calculation unit for driving the inverter INV. The DA converter 77 is a voltage application device drive calculation unit for driving the voltage application device GS.

[0092] The low-pass filter (LPF) 71 is a filter that removes high-frequency noise from the detection results of a current sensor 79 that detects the current flowing through each phase of the stator coil (N-phase (here, three-phase) coil). The coordinate conversion unit 72 converts the three-phase current values ​​that have passed through the low-pass filter 71 into current values ​​in a dq-axis vector coordinate system. The proportional-integral control unit 73 converts the current command (id * , IQ * ) and the actual current after coordinate transformation (i d , i q ) and performs current feedback control based on the deviation. The modulation factor calculation unit 74 is a calculation unit that calculates the modulation factor. The modulation unit 75 is a calculation unit that generates a modulated pulse by pulse width modulation, for example. The DA converter 77 sets the voltage to be output by the voltage application device GS based on the parameters of the third lookup table 26.

[0093] By setting the rotor magnetic pole position θ corresponding to each time in the second lookup table 25 in advance in this way, even if there is no rotor, such as an air rotor, the inverter INV can be driven by a switching pulse corresponding to the rotor rotation, and a voltage corresponding to the switching pulse can be applied to the stator coil and a current corresponding to the switching pulse can be passed through the stator coil. Also, because the voltage to be output by the voltage application device GS at each time is set in the third lookup table 26, the calculation load on the calculation unit 20 in the control device 2 can be reduced.

[0094] In this way, in the insulation state observation system 100 (insulation state observation method) of this embodiment, even in the test state, it is possible to apply a voltage to the stator coil equivalent to that in the state in which the rotor is driven to rotate in the normal operation state, and to pass an equivalent current through the stator core. In other words, it is possible to conduct an insulation life test under the same conditions as in the normal operation state.

[0095] In addition, in the insulation state observation system 100 (insulation state observation method) of this embodiment, when a point determined by a combination of the output torque and rotation speed of the rotor in the rotating electrical machine is set as an operating point and an operating state voltage application process corresponding to each of a plurality of operating points is performed, a back electromotive force correction gain (K a2 ) and the back electromotive force correction phase (δ) are used to correct the back electromotive force vector in the orthogonal vector coordinate system.

[0096] A rotating electric machine operates in various operating states. The voltage applied to and current flowing through the stator coil differs depending on the operating state. By performing the operating state voltage application process and the discharge detection process for each of the multiple operating points of the rotating electric machine, it is possible to appropriately perform a finite insulation life test on the stator coil while taking into account the various operating states of the rotating electric machine.

[0097] When a rotating electric machine is used as a driving power source for a vehicle, it is preferable to set the operating point in accordance with the WLTC mode (a driving mode based on the World Widely Harmonized Light Vehicles Test Cycle). The WLTC mode is a driving mode that is similar to actual driving, and is configured with an average usage time distribution for driving in urban areas, suburban areas, and highways, making it possible to realize testing that is similar to the environment in which a rotating electric machine is actually used.

[0098] As described above, the back electromotive force correction gain K a2and the correction phase δ of the back electromotive force, and controlling the voltage application device GS using a look-up table is not limited to the method of calculating the dq-axis voltage when there is no rotor, and calculating the missing dq-axis voltage from the parameters of the rotating electric machine when there is a rotor, and performing two-phase to three-phase conversion to control the voltage application device GS. The voltage equation for the rotating electric machine in the normal operating state is expressed by the following equation (17).

[0099]

number

[0100] where L d_motor , L q_motor are the d-axis and q-axis inductances of a normal rotating electric machine (a rotating electric machine with a rotor), respectively. The first term on the right-hand side is the voltage drop (drop voltage) due to the winding resistance, the second term is the induced electromotive force in the non-steady state (first induced electromotive force), and the third term on the right-hand side is the induced electromotive force in the steady state (second induced electromotive force).

[0101] In addition, the d-axis inductance and q-axis inductance of a rotating electric machine without a rotor (air rotor), that is, a rotating electric machine with only a stator, are respectively defined as L d_air , L q_air Then, the fluctuation of the d-axis and q-axis inductance due to the removal of the rotor is expressed as the d-axis differential inductance L as shown in the following equations (18) and (19): d ', q-axis differential inductance L q ' becomes.

[0102] L d '=L d_motor -L d_air ···(18) L q '=L q_motor -L q_air ···(19)

[0103] Therefore, the AC voltage (V a3 ) is the output voltage of the voltage application device GS required to obtain d_GS , V q_GS" is expressed by the following equation (20). m " is the back electromotive force, and "ωφ m =ωMif".

[0104]

number

[0105] The voltage equation for the entire system is given by the following equation (21).

[0106]

number

[0107] In equation (21), the first term on the right-hand side is the voltage drop (drop voltage) due to the winding resistance, the second term is the induced voltage in the unsteady state (first induced voltage during test), the third term on the right-hand side is the output voltage (correction voltage) of the voltage application device GS, and the fourth term on the right-hand side is the induced voltage in the steady state (second induced voltage during test).

[0108] Here, a difference occurs in the induced voltage in the unsteady state (the second term on the right side) compared to the normal operating state. The output voltage of the voltage application device GS may be a value that also compensates for the change in the induced voltage in the unsteady state, as shown in the following equation (22).

[0109]

number

[0110] Furthermore, when the counter electromotive force of a rotating electrical machine contains harmonics, it is preferable to adjust the output voltage of the voltage application device GS in a similar manner.

[0111] Since the output voltage of the voltage application device GS calculated by equations (21) and (22) is a value in the dq-axis vector coordinate system, it is converted into three-phase voltages of U, V, and W as shown in equation (23) below and output from the voltage application device GS.

[0112]

number

[0113] As described above with reference to the block diagram of FIG. 23, the calculation load on the control device 2 can be reduced by storing the parameters that determine the output voltage of the voltage application device GS in advance in a lookup table (third lookup table 26). However, if the calculation capacity of the control device 2 is high or there is room for the calculation load, the value of the voltage application device GS may be calculated each time. FIG. 24 shows an example of a control block diagram in this case. The function of each block will be obvious to those skilled in the art from the above description using equations (17) to (23), and therefore a detailed description will be omitted.

[0114] As explained above, in the voltage equation under normal operating conditions, the voltage of the stator coil (N-phase coil (here, three-phase coil)) is expressed as the sum of the voltage drop due to the resistance component of the N-phase coil (voltage drop due to winding resistance), the first induced voltage which is the induced voltage in the non-steady state based on the d-axis inductance and q-axis inductance under normal operating conditions, and the second induced voltage which is the induced voltage in the steady state based on the field flux by the permanent magnet, the d-axis inductance and q-axis inductance under normal operating conditions (see equation (17)). Here, the d-axis inductance (L d_motor ) and the d-axis inductance (L d_air ) is the d-axis differential inductance (L d ') (see equation (18)). Also, the q-axis inductance (L q_motor ) and the q-axis inductance (L q_air ) is the q-axis differential inductance (L q '). The permanent magnet field flux (φ m ), d-axis differential inductance (L d '), and q-axis differential inductance (L q The voltage calculated based on the second induced voltage (φ ') is used as the correction voltage (see the third term on the right side of equation (21)).m ) is not used, and the d-axis inductance (L d_air ) and the q-axis inductance (L q_air The voltage calculated based on the second induced voltage is the second induced voltage during the test (see the fourth term on the right side of equation (21)). d_air ) and the q-axis inductance (L q_air ) is used as the first induced electromotive force during test (see the second term on the right side of equation (21)). In the operating state voltage application process, a voltage equation showing the voltage of the N-phase coil is calculated as the sum of the drop voltage, the first induced electromotive force during test, the second induced electromotive force during test, and the correction voltage (see equation (21)).

[0115] In this way, in the insulation state observation system 100 (insulation state observation method) of this embodiment, even in the test state, it is possible to apply a voltage to the stator coil equivalent to that in the state in which the rotor is driven to rotate in the normal operation state, and to pass an equivalent current through the stator core. In other words, it is possible to conduct an insulation life test under the same conditions as in the normal operation state.

[0116] 25 and 26 show the armature voltage V in a rotating electric machine with a rotor (normal rotor) and a rotating electric machine without a rotor (air rotor). a When only the amplitude of the air rotor is compensated (air rotor + amplitude compensation), the armature voltage V a The figure compares the U-phase current and U-phase voltage (U-phase voltage) when the amplitude and phase of the rotor are compensated (air rotor + phase compensation + amplitude compensation). Figure 26 shows an example of a rotating electric machine with a relatively high rotational speed, compared to Figure 25. As shown in Figures 25 and 26, by performing phase compensation and amplitude compensation, the air rotor achieves voltage and current similar to that of a conventional rotor. Although the air rotor exhibits a higher current ripple than the conventional rotor, this has almost no effect on the test. This is due to the fact that the air rotor has a smaller inductance than the conventional rotor.

[0117] When an insulation life test is performed, the following test conditions are set: DC link voltage Vdc, switching frequency of inverter INV, temperature of test conductor pair 1 (in the case of insulation condition observation system 101 for turn-to-turn short circuit test), and temperature of the stator (temperature of stator coil (N-phase coil)) (in the case of insulation condition observation system 102 for ground fault and phase-to-phase short circuit test). As described above with reference to FIG. 15 , the DC link voltage Vdc differs between a single inverter system and a dual inverter system. It is preferable to set the DC link voltage Vdc appropriately depending on the system configuration. Note that the DC link voltage Vdc may be set lower and the temperature higher than those in the environment in which the rotating electric machine is actually used.

[0118] In addition, there are several ways to measure the finite insulation life, such as measuring the elapsed time until insulation breakdown depending on the applied voltage (Figure 27), measuring the change in capacitance of test conductor pair 1 (Figure 28), and measuring the number of partial discharge occurrences depending on the elapsed time (Figure 29).

[0119] The graph in Figure 27 shows the relationship between the applied voltage and the time elapsed until breakdown. It can be seen that the higher the applied voltage, the shorter the time elapsed until breakdown. The graph shown in Figure 27 can be created by conducting tests until breakdown occurs. If the elapsed time is taken as the required lifespan, the tolerable voltage can be identified.

[0120] However, if the test is continued until a breakdown occurs, an overcurrent may flow through the inverter INV, potentially destroying the inverter INV. Therefore, if a breakdown occurs, it is preferable to stop applying voltage from that point onward and terminate the test. As shown in FIGS. 16 to 19 , in this embodiment, the determination unit 29 is configured to determine the end of the test based on an external trigger signal (condition 1) from the oscilloscope OS, which is turned on when a breakdown occurs and a discharge occurs. Furthermore, if a breakdown occurs and a short-circuit current flows through the inverter INV, the determination unit 29 is configured to determine the end of the test by detecting that the current exceeds a threshold (condition 2).

[0121] In one aspect, the control device 2 outputs parameters set in the third lookup table 26 based on time information output from a timer (or counter), causing the voltage application device GS to output a voltage. For example, by resetting the value of the timer (or counter), the parameters are no longer output from the third lookup table 26. As a result, the voltage application device GS no longer outputs a voltage. In such a configuration, the timer (or counter) corresponds to the determination unit 29.

[0122] Furthermore, instead of continuing the test until actual breakdown occurs, the lifespan may be determined from, for example, the change in capacitance of the test conductor pair 1. The graph in Figure 28 shows the relationship between the voltage application time and the change in capacitance. A graph like the one shown in Figure 28 can be created by measuring the capacitance of one test conductor pair 1 while repeatedly applying voltage at regular intervals using, for example, an LCR meter (a measuring instrument that measures circuit constants such as resistance, capacitance, and inductance). The insulation lifespan can be determined based on the change in capacitance.

[0123] Furthermore, repeated application of voltage gradually deteriorates the insulation performance. Therefore, the number of partial discharges increases over time. Therefore, as shown in Figure 29, the insulation life can be determined based on the relationship between the voltage application time and the number of partial discharges.

[0124] As described above, according to this embodiment, it is possible to appropriately carry out a limited insulation life test on a stator coil in an electrical environment similar to that in which a rotating electrical machine is in a normal operating state. [Explanation of symbols]

[0125] 1: Test conductor pair, 2: Control device, 4: Antenna (discharge detection device), 5: Discharge detection device, 9: Constant temperature and humidity chamber, 11: First test conductor, 12: Second test conductor, 17: Insulation coating, 100: Insulation state observation system, GS: Voltage application device, INV: Inverter, Ka2 : Back electromotive force compensation gain, L d ': d-axis differential inductance, L q ': q-axis differential inductance, R: winding resistance (resistance component of N-phase coil), Ri a : voltage drop (drop voltage), δ: correction phase, ωMif: back electromotive force

Claims

1. A method for observing an insulation state of a stator coil, the method comprising: observing an insulation state of a coil conductor having an insulating coating in a stator for a rotating electric machine having N-phase coils (N is any natural number); an inverter is connected to the N-phase coil, and a voltage application device is connected to apply a test voltage to the N-phase coil; using a first test conductor and a second test conductor having the same structure as the coil conductor, and connecting the first test conductor to a first phase coil in the N-phase coil and the second test conductor to a second phase coil in the N-phase coil while the first test conductor and the second test conductor are in contact with each other; A rotor is disposed so as to face the stator at a predetermined position, and a state in which the rotor is rotationally driven by a magnetic field generated by a voltage applied to the N-phase coil is defined as a normal operation state, In a test state in which the rotor has stopped rotating or the rotor is not facing the stator, an operating state voltage application process is performed in which the voltage application device applies an AC voltage having the same amplitude and phase as the normal operating state to the N-phase coil; a first discharge detection process for detecting partial discharge between the first test conductor and the second test conductor during execution of the operating state voltage application process;

2. 2. The method for observing the insulation state of a stator coil according to claim 1, wherein the operating state voltage application process and the first discharge detection process are performed while the first test conductor and the second test conductor are placed in a constant temperature and humidity chamber in which the environmental temperature and humidity are maintained at predetermined constant temperatures and humidity.

3. A method for observing an insulation state of a stator coil, the method comprising: observing an insulation state of a coil conductor having an insulating coating in a stator for a rotating electric machine having N-phase coils (N is any natural number); an inverter is connected to the N-phase coil, and a voltage application device is connected to apply a test voltage to the N-phase coil; A rotor is disposed so as to face the stator at a predetermined position, and a state in which the rotor is rotationally driven by a magnetic field generated by a voltage applied to the N-phase coil is defined as a normal operation state, In a test state in which the rotor has stopped rotating or the rotor is not facing the stator, an operating state voltage application process is performed in which the voltage application device applies an AC voltage having the same amplitude and phase as the normal operating state to the N-phase coil; A method for observing the insulation state of a stator coil, wherein, during execution of the operating state voltage application process, at least one of a second discharge detection process for detecting partial discharge between coils of different phases in the N-phase coil and a third discharge detection process for detecting partial discharge between the N-phase coil and ground is performed.

4. 4. The method for observing the insulation state of a stator coil according to claim 3, wherein the operating state voltage application process and at least one of the second discharge detection process and the third discharge detection process are performed while the N-phase coil is placed in a constant temperature and humidity chamber in which the environmental temperature and environmental humidity are maintained at predetermined constant temperatures and humidity.

5. the normal operation state is a state in which an AC voltage having an amplitude and a phase calculated by current feedback control in an orthogonal vector coordinate system having a d-axis along the direction of a field magnetic flux generated by a permanent magnet provided in the rotor and a q-axis perpendicular to the d-axis is applied to the N-phase coil, thereby driving the rotor to rotate; 5. The insulation state observation method for a stator coil according to claim 1, wherein in the operating state voltage application process, a back electromotive force vector in the orthogonal vector coordinate system is corrected and an amplitude and a phase of the AC voltage are calculated using a back electromotive force correction gain that is a gain of the back electromotive force such that the amplitude of the AC voltage in the test state matches the amplitude of the AC voltage in the normal operating state, and a back electromotive force correction phase that is a phase of the back electromotive force such that the phase of the AC voltage in the test state matches the phase of the AC voltage in the normal operating state.

6. A point determined by a combination of the output torque and rotation speed of the rotor in the rotating electric machine is defined as an operating point, 6. The insulation state observation method for a stator coil according to claim 5, wherein, when performing the operating state voltage application process corresponding to each of the plurality of operating points, the back electromotive force vector in the orthogonal vector coordinate system is corrected using the back electromotive force correction gain and the back electromotive force correction phase calculated in advance for the torque of each of the plurality of operating points.

7. the normal operation state is a state in which an AC voltage having an amplitude and a phase calculated by current feedback control in an orthogonal vector coordinate system having a d-axis along the direction of a field magnetic flux generated by a permanent magnet provided in the rotor and a q-axis perpendicular to the d-axis is applied to the N-phase coil, thereby driving the rotor to rotate; In the voltage equation in the normal operating state, the voltage of the N-phase coil is expressed as follows: a voltage drop due to a resistance component of the N-phase coil; a first induced voltage that is an induced voltage in a non-steady state based on the d-axis inductance and the q-axis inductance in the normal operation state; is expressed as the sum of a field magnetic flux by the permanent magnet, a second induced electromotive force which is an induced electromotive force in a steady state based on the d-axis inductance and the q-axis inductance in the normal operation state, a difference between the d-axis inductance in the normal operating state and the d-axis inductance in the test state is defined as a d-axis differential inductance, and a difference between the q-axis inductance in the normal operating state and the q-axis inductance in the test state is defined as a q-axis differential inductance, a voltage obtained by calculating the second induced voltage based on the field magnetic flux of the permanent magnet, the d-axis differential inductance, and the q-axis differential inductance is set as a correction voltage; a voltage obtained by calculating the second induced voltage based on the d-axis inductance in the test state and the q-axis inductance in the test state without using the field magnetic flux of the permanent magnet, and the voltage is set as the second induced voltage during test; a voltage obtained by calculating the first induced voltage based on the d-axis inductance in the test state and the q-axis inductance in the test state is defined as a test-time first induced voltage; In the operating state voltage application process, a voltage equation showing the voltage of the N-phase coil is expressed as follows: the voltage drop; the first induced voltage during test; the second induced voltage during test; the correction voltage; The insulation state monitoring method for a stator coil according to claim 1 , wherein the insulation state monitoring method is performed by calculating the sum of the above.

8. A stator coil insulation state monitoring system for monitoring an insulation state of a coil conductor having an insulating coating in a stator for a rotating electric machine having N-phase coils (N is any natural number), comprising: an inverter connected to the N-phase coil; a voltage application device that applies a test voltage to the N-phase coil; a control device that controls the voltage application device; a discharge detection device for detecting discharge; a test conductor pair in which a first test conductor and a second test conductor, which have the same structure as the coil conductors, are in contact with each other, the first test conductor being connected to a first phase coil in the N-phase coil, and the second test conductor being connected to a second phase coil in the N-phase coil; A rotor is disposed so as to face the stator at a predetermined position, and a state in which the rotor is rotationally driven by a magnetic field generated by a voltage applied to the N-phase coil is defined as a normal operation state, the control device performs an operating state voltage application process in which, in a test state in which the rotor has stopped rotating or the rotor is not facing the stator, the voltage application device applies an AC voltage having the same amplitude and phase as in the normal operating state to the N-phase coil; The discharge detection device detects partial discharge occurring between the first test conductor and the second test conductor while the operating state voltage application process is being performed.

9. 9. The stator coil insulation state monitoring system according to claim 8, further comprising a constant temperature and humidity chamber capable of maintaining a predetermined constant environmental temperature and humidity and capable of accommodating the first test conductor and the second test conductor.

10. A stator coil insulation state monitoring system for monitoring an insulation state of a coil conductor having an insulating coating in a stator for a rotating electric machine having N-phase coils (N is any natural number), comprising: an inverter connected to the N-phase coil; a voltage application device that applies a test voltage to the N-phase coil; a control device that controls the voltage application device; a discharge detection device that detects discharge, A rotor is disposed so as to face the stator at a predetermined position, and a state in which the rotor is rotationally driven by a magnetic field generated by a voltage applied to the N-phase coil is defined as a normal operation state, the control device performs an operating state voltage application process in which, in a test state in which the rotor has stopped rotating or the rotor is not facing the stator, the voltage application device applies an AC voltage having the same amplitude and phase as in the normal operating state to the N-phase coil; The discharge detection device detects at least one of partial discharges occurring between coils of different phases in the N-phase coil and partial discharges occurring between the N-phase coil and ground during execution of the operating state voltage application process.

11. 11. The stator coil insulation state monitoring system according to claim 10, further comprising a constant temperature and humidity chamber capable of maintaining a constant humidity and a constant temperature higher than the ambient temperature, and capable of accommodating the N-phase coil.

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