Diagnostic devices, systems, methods, and storage media for power converters

Abstract

Embodiments of the present invention relate to a diagnostic apparatus, diagnostic system, and diagnostic method for power converters, as well as a storage medium. The problem to be solved by the present invention is to provide a diagnostic apparatus, diagnostic system, and diagnostic method for power converters that appropriately determines the degradation state of semiconductor elements without causing short-circuit current in the power converter, as well as a storage medium. According to an embodiment, a diagnostic apparatus for a power converter is provided, which drives a motor by outputting converted AC power to the motor. The diagnostic apparatus includes an output control unit and a degradation determination unit. The output control unit controls the operation of multiple semiconductor elements of the power converter to provide a constant voltage output to the motor in a target voltage mode, thereby enabling power to be output from the power converter to the motor. The degradation determination unit determines the degradation state of one or more semiconductor elements based on the current flowing through the motor in the constant voltage output from the power converter to the motor.

Description

Technical Field

[0001] Embodiments of the present invention relate to diagnostic devices, diagnostic systems, diagnostic methods, and storage media for power converters. Background Technology

[0002] In the drive control of an electric motor, in the power converter forming the inverter circuit, direct current (DC) power is converted into multi-phase AC power, such as three-phase AC power, and the converted multi-phase AC power is output to the motor from the power converter. At this time, by controlling the operation of multiple semiconductor elements installed in the power converter through a drive control device, the output from the power converter to the motor is controlled, thereby controlling the motor drive. In this system for driving and controlling the motor, the power converter is diagnosed by determining the degradation state and lifespan of the semiconductor elements. In one example, a short-circuit current that does not flow through the motor is generated in the power converter, and the degradation state of the semiconductor elements is determined based on the generated short-circuit current.

[0003] Here, in the power converter, the allowable time for the aforementioned short-circuit current to flow is strictly limited. Therefore, it is required to diagnose the power converter without causing a short-circuit current to be generated. Furthermore, in diagnosing the power converter, it is required to appropriately determine the degradation state of the semiconductor elements installed in the power converter without causing a short-circuit current to be generated. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a diagnostic device, diagnostic system, diagnostic method, and storage medium for a power converter that can appropriately determine the degradation state of semiconductor elements without causing a short-circuit current in the power converter.

[0005] According to one embodiment, a diagnostic device for a power converter is provided, which drives a motor by outputting converted AC power to the motor. The diagnostic device includes an output control unit and a degradation determination unit. The output control unit controls the operation of multiple semiconductor elements of the power converter to provide a constant voltage output to the motor in a target voltage mode, thereby enabling power to be output from the power converter to the motor. The degradation determination unit determines the degradation state of one or more semiconductor elements based on the current flowing through the motor in the constant voltage output from the power converter to the motor.

[0006] Based on the diagnostic device, diagnostic system, diagnostic method, and storage medium of the power converter described above, the degradation state of semiconductor components can be appropriately determined without causing a short-circuit current in the power converter. Attached Figure Description

[0007] Figure 1This is a schematic diagram illustrating an example of the configuration for controlling the drive of an electric motor.

[0008] Figure 2 This is a schematic diagram illustrating the characteristics of the semiconductor element located on the power converter that outputs power to the electric motor.

[0009] Figure 3 This is a schematic diagram illustrating an example of the relationship between the ambient temperature and saturation voltage of a semiconductor device when it has been unpowered for an extended period of time.

[0010] Figure 4 This is a schematic diagram illustrating an example of how the saturation voltage of a semiconductor element changes over time, with the ambient temperature as a reference temperature, as a correction (conversion) of the saturation voltage.

[0011] Figure 5 This is a schematic diagram illustrating an example of the temperature characteristics of the winding resistance of an electric motor.

[0012] Figure 6 It is a schematic diagram illustrating the changes in current flowing through the power converter and motor in an output where the multiphase output voltages are each kept constant at a fixed voltage value, caused by the degradation of semiconductor elements.

[0013] Figure 7 This is a schematic diagram illustrating an example of a diagnostic system for a power converter according to an implementation method.

[0014] Figure 8 This is a schematic diagram illustrating six target voltage modes for constant voltage output to the motor during the diagnosis of the power converter in the embodiment.

[0015] Figure 9 This is a schematic diagram showing the target voltage values ​​of the three-phase output voltage for each of the six target voltage modes for constant voltage output to the motor in the diagnostics of the power converter in the implementation.

[0016] Figure 10 It means Figure 9 The diagram shown illustrates the current flowing through the power converter and the motor in the constant voltage output to the motor in each of the six target voltage modes.

[0017] Figure 11 This is a schematic diagram illustrating an example of the time-dependent variation of the three-phase output voltage from the power converter to the motor during the diagnostic process of the power converter in this embodiment.

[0018] Figure 12 This is a flowchart that schematically illustrates an example of the processing performed by the processor or the like of the diagnostic device in the embodiment.

[0019] Figure 13 It is a general expression about Figure 12 The flowchart shown is an example of a diagnostic process for a power converter.

[0020] Figure 14 This is a schematic diagram showing the time-dependent change of the current flowing through the U-phase of the motor under constant voltage output conditions in six target voltage modes for two different diagnostic times of the first verification.

[0021] Figure 15 This is a schematic diagram showing the relationship between the number of power cycles and the current flowing through the U-phase of the motor in the constant voltage output of the corresponding target voltage mode, which is the result of the first verification.

[0022] Figure 16 It means according to Figure 15 The diagram shown is a schematic representation of the result of correcting the detected U-phase current to the corrected value when the motor temperature is 20°C.

[0023] Figure 17 It means to Figure 14 The diagram shows a schematic representation of the voltage signal generated by amplifying and converting the time-dependent changes in the current of phase U, followed by A / D conversion and then D / A conversion.

[0024] Figure 18 This is a schematic diagram showing the relationship between the corrected current at the detection point and the number of power cycles in the constant voltage output of each of the six target voltage modes, serving as the verification result of the second verification. Detailed Implementation

[0025] Hereinafter, the implementation methods will be described with reference to the accompanying drawings.

[0026] (Control configuration for driving an electric motor)

[0027] First, the configuration of the drive for controlling the electric motor will be explained as a matter related to the implementation method. Figure 1 An example of the configuration for controlling the drive of an electric motor is shown. In Figure 1In one example, the drive of motor 1, which is a three-phase synchronous motor, is controlled. The system controlling the drive of motor 1 includes a power converter 2, which acts as an inverter. DC power is supplied to the power converter 2 from a DC power supply 3, which serves as the drive power source. The power converter 2 includes multiple semiconductor elements 5, such as IGBTs (Insulated Gate Bipolar Transistors). In the power converter 2, a multi-phase half-bridge circuit is formed by the semiconductor elements 5, and each half-bridge circuit includes a positive-side semiconductor element 5p and a negative-side semiconductor element 5m. The multi-phase half-bridge circuits are electrically connected in parallel between the positive-side power lines and the negative-side power lines. Figure 1 In one example, there are six semiconductor elements 5, and a three-phase half-bridge circuit is formed in parallel with each other.

[0028] In each semiconductor element 5 of the power converter 2, a return-current diode 6 is connected between the collector and emitter. Each return-current diode 6 is electrically connected in parallel to a corresponding semiconductor element 5. Furthermore, in each half-bridge circuit, an output terminal is formed between the positive-side semiconductor element 5p and the negative-side semiconductor element 5m. The motor 1 has a number of windings (stator windings) 7 equal to the number of phases in the half-bridge circuit. The output terminal of each half-bridge circuit is connected to a corresponding winding 7 of the motor 1. Figure 1 In one example, the output terminals of the three-phase half-bridge circuits of phases U, V, and W are each connected to one of the corresponding windings 7.

[0029] In the system for controlling the drive of the electric motor 1, a drive control device 8 is provided. The drive control device 8 controls the drive of the electric motor 1 by controlling the operation of the power converter 2. The drive control device 8 is equipped with an integrated circuit including a processor and a storage medium. The processor of the integrated circuit includes a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), or a FPGA (Field Programmable Gate Array). In the drive control device 8, the processor controls the operation of the power converter 2 by executing a program stored in the storage medium. The drive control device 8 controls the operation of the power converter 2 by controlling the timing of the turn-on and turn-off of each of the semiconductor elements 5. Furthermore, the drive control device 8 uses pulse signals such as PWM (Pulse Width Modulation) signals to control the timing of the turn-on and turn-off of each of the semiconductor elements 5. In each semiconductor element 5, the pulse signal from the drive control device 8 is input to the gate, for example.

[0030] The power converter 2 is controlled by the drive control device 8 to convert the DC power from the DC power supply 3 into multiphase AC power. Figure 1 In one example, direct current (DC) power is converted into three-phase alternating current (AC). Power converter 2 outputs the converted multiphase AC power to motor 1, thereby driving motor 1 and causing its rotor to rotate. While motor 1 is driven, multiphase AC voltages with different phases are output as output voltages from power converter 2 to motor 1. Figure 1 In one example, the three-phase AC voltages (U-phase, V-phase, and W-phase) are output from the power converter 2 to the motor 1 with different phases. Furthermore, the phase of the U-phase AC voltage is offset by 120° relative to the phases of the V-phase and W-phase AC voltages, respectively, and the phase of the V-phase AC voltage is also offset by 120° relative to the phase of the W-phase AC voltage. Additionally, while the motor 1 is driven by the multi-phase AC power supply, the output voltage from the power converter 2 to the motor 1, i.e., the applied voltage in the motor 1, varies over time, with one cycle of the AC power supply as one period.

[0031] In addition, Figure 1 In one example, a current detection circuit 11 is provided. The current detection circuit 11 detects the current flowing through the motor 1 while it is driven by a multi-phase (three-phase) AC power supply. Figure 1In one example, the current detection circuit 11 includes a shunt resistor located at a point on the power supply line on the negative side of the power converter 2, and detects the current flowing through the motor 1 based on the voltage across the shunt resistor. In another example, in each multi-phase (three-phase) half-bridge circuit, a shunt resistor is provided between the semiconductor element 5m on the negative side and the power supply line on the negative side, and multiple (three) shunt resistors are provided in the power converter 2. Furthermore, the current detection circuit detects the current flowing through the motor 1 based on the voltage across each of the multiple shunt resistors.

[0032] In addition, Figure 1 In one example, the analog signal representing the current detection result in the current detection circuit 11 is amplified by amplifier 12, and the amplified analog signal is transmitted to the drive control device 8. The analog signal representing the current detection result is converted into a digital signal using an A / D (Analog to Digital) converter in the drive control device 8. Thus, the drive control device 8 obtains a digital signal representing the current detection result flowing through the motor 1. Based on the current detection result flowing through the motor 1, the drive control device 8 generates pulse signals such as PWM signals to control the operation of each of the semiconductor elements 5, and uses the generated pulse signals to control the operation of each of the semiconductor elements 5. Therefore, based on the current detection result flowing through the motor 1, the multi-phase (three-phase) output voltage is controlled separately. In one example, the drive control device 8 adjusts the magnitude of the multi-phase output voltage of the motor 1 by performing PI control on the current flowing through the motor 1.

[0033] As previously described, in the system controlling the drive of the motor 1, each semiconductor element 5 of the power converter 2 repeatedly turns on and off in short cycles. Therefore, in each semiconductor element 5, self-heating during on-time and cooling during off-time are repeatedly induced and caused in short cycles. Since, as previously described, self-heating and cooling of each semiconductor element 5 are repeatedly induced and caused in short cycles, it is necessary to appropriately determine, for each semiconductor element 5, the occurrence of cracks at the connection points of components with different coefficients of thermal expansion, and appropriately determine the deterioration state. Furthermore, it is necessary to appropriately diagnose the power converter 2 by appropriately determining the deterioration state of each semiconductor element 5.

[0034] (Matters related to determining the degradation state of semiconductor devices)

[0035] The following explains matters related to determining the deterioration state of semiconductor elements, such as semiconductor element 5, used in the aforementioned power converter 2. Figure 2 The diagram shows parameters representing the characteristics of semiconductor devices. Figure 2In this diagram, the saturation voltage Vce(sat) between the collector and emitter is shown as a parameter representing the characteristics of a semiconductor device. In the following explanation, the saturation voltage Vce(sat) between the collector and emitter will be simply referred to as the "saturation voltage". In semiconductor devices such as IGBTs, the saturation voltage increases as the degree of degradation increases. However, in semiconductor devices, the difference between the saturation voltage in a highly degraded state and the saturation voltage in a non-degraded state is relatively small. In an example semiconductor device, the difference between the saturation voltage after 16,000 power cycles (16,000 cycles) under specified conditions and the saturation voltage before the power cycles is approximately 100mV (0.1V). Therefore, in determining the degradation state of a semiconductor device, it is necessary to appropriately detect the small change in saturation voltage between the highly degraded state and the non-degraded state.

[0036] Furthermore, in semiconductor devices such as IGBTs, the aforementioned saturation voltage varies with the temperature of the junction surface of the semiconductor device's constituent components with respect to the chip, i.e., the junction temperature Tj. In one example, when the junction temperature changes by 50°C, the saturation voltage of the semiconductor device changes by 0.14V. In this case, the change in saturation voltage caused by the change in junction temperature is about the same magnitude as the difference in saturation voltage between a state with a higher degree of degradation and a state without degradation. Therefore, when determining the degradation state of a semiconductor device based on the saturation voltage, the influence of the junction temperature Tj needs to be considered. As shown in calculation formula (1), the junction temperature Tj is calculated using the ambient temperature Ta of the environment in which the semiconductor device is located, the thermal resistance Rth(ja) between the junction surface (junction) of the chip and the environment in which the semiconductor device is located, and the power P supplied to the semiconductor device.

[0037] Formula 1

[0038] Tj=Ta+Rth(ja)×P (1)

[0039] However, the thermal resistance Rth(ja) changes according to the time it takes for a voltage to be applied to the semiconductor element. Furthermore, in situations such as driving a motor with power supplied from a power converter, the individual semiconductor elements repeatedly turn on and off for short periods, as described above. Therefore, in situations such as driving a motor with power supplied from a power converter, it is difficult to properly determine the effect of the power supplied to the semiconductor elements on the thermal resistance Rth(ja), and it is difficult to properly derive the thermal resistance Rth(ja). Consequently, it is difficult to consider the thermal resistance Rth(ja) and calculate the junction temperature Tj.

[0040] Here, in situations where the semiconductor device has been unpowered for an extended period, such as when the motor has not been driven for a long time, the junction temperature of the semiconductor device is considered to be the same as the ambient temperature of the environment where the semiconductor device is located, i.e., the ambient temperature of the power converter. Therefore, for situations where the semiconductor device has been unpowered for a long time, the ambient temperature of the semiconductor device can be used instead of the junction temperature to correct the detected saturation voltage of the semiconductor device. For example, in cases where the degradation state of the semiconductor device is determined before the motor starts driving, the ambient temperature of the semiconductor device can be used to correct the detection result of the semiconductor device's saturation voltage.

[0041] Figure 3 This illustrates an example of the relationship between the ambient temperature Ta and the saturation voltage Vce(sat) of a semiconductor device when it is not powered on for an extended period. Figure 3 In the diagram, the horizontal axis represents the ambient temperature Ta of the semiconductor device (power converter), and the vertical axis represents the saturation voltage Vce(sat). Under conditions where the semiconductor device is not powered for an extended period, based on... Figure 3 Using an example relationship and the detection results of ambient temperature Ta, the detected saturation voltage can be corrected to the saturation voltage under conditions where ambient temperature Ta becomes the reference temperature Tarref. Here, the reference temperature Tarref is, for example, 20°C.

[0042] Furthermore, when determining the degradation state of a semiconductor device after it has been unpowered for an extended period, the degradation state of the semiconductor device can be appropriately determined based on the correction result of the saturation voltage at the ambient temperature Ta and the reference temperature Taref, indicating whether the semiconductor device has experienced a fault or other degradation conditions. Figure 4 This illustrates an example of the change over time in the corrected (converted) saturation voltage of a semiconductor device, with ambient temperature Ta as the reference temperature Taref. Figure 4 In the graph, the horizontal axis represents time referenced to the start of use of the semiconductor device (power converter), and the vertical axis represents the correction result for the saturation voltage at the reference temperature Taref. Figure 4 In one example, at time ta, the correction result for the saturation voltage at the reference temperature Taref exceeds the threshold Vce(sat)th and becomes high. Therefore, after time ta, it is determined that the semiconductor device has malfunctioned, etc.

[0043] Furthermore, in the power converter that drives the electric motor, as previously described, each multiphase half-bridge circuit is connected to a corresponding winding of the electric motor, and each semiconductor element is connected to a corresponding winding of the electric motor. Therefore, the aforementioned saturation voltage of each semiconductor element is affected by the winding of the connected electric motor. Each motor winding has a winding resistance, and the winding resistance of each winding varies corresponding to the temperature of the electric motor. Figure 5 An example of the temperature characteristics of the winding resistance of an electric motor is shown. Figure 5 In the diagram, the horizontal axis represents the motor temperature T, and the vertical axis represents the winding resistance of the motor windings. For example... Figure 5 As shown in one example, the winding resistance of a motor increases with rising temperature. Furthermore, in one example, the winding resistance R of the motor's windings increases with temperature T. T It can be calculated as shown in equation (2). In equation (2), the winding resistance R of the motor is the case where the reference temperature Tref is the reference temperature. Tref The winding resistance R is specified and relative to temperature T. T Inclination α T It is stipulated.

[0044]

Formula 2

[0045] R T =R Tref {1+α T (T-Tref)} (2)

[0046] In one example, at the reference temperature Tref of 20°C, the winding resistance of the motor is 1.70Ω. Furthermore, based on calculations such as formula (2), the winding resistance of the motor at 100°C is 2.24Ω. In this case, when the current flowing through the motor is 5A, as the motor temperature changes from 20°C to 100°C, the voltage applied to the motor winding resistance changes from 8.5V to 11.2V, a change of approximately 3V. Therefore, the change in voltage applied to the winding resistance caused by the change in motor temperature is larger than the difference in saturation voltage between a highly degraded state and a non-degraded state. In conclusion, when determining the degradation state of semiconductor elements in a power converter based on saturation voltage, it is important to consider the influence of the motor winding resistance on the saturation voltage of the semiconductor element.

[0047] Furthermore, each semiconductor element of the power converter, as described above, is connected to a corresponding one of the windings of the motor. Therefore, the current flowing through and connected to the winding becomes saturated, allowing the saturation voltage of each semiconductor element to be detected. In one example, the winding resistance of the motor connected to the semiconductor element is 1.7Ω, and the inductance is 0.027H. In this case, the winding time constant is 0.016s. In the motor being driven and controlled, the winding time constant is not significantly different from the previous example. Therefore, in the motor, the current flowing through the winding becomes saturated after approximately 0.1s of energization. Thus, by continuously flowing current through the semiconductor element and the connected winding for approximately 0.1s, the saturation voltage of the semiconductor element can be detected.

[0048] Since the saturation voltage of a semiconductor device can be detected by applying power for approximately 0.1 seconds, the power-on time of the semiconductor device can be shortened during saturation voltage detection. By shortening the power-on time, the rise in junction temperature of the semiconductor device caused by power-on is suppressed during saturation voltage detection. Therefore, the ambient temperature of the semiconductor device (power converter) can be considered to be consistent with the junction temperature, and the aforementioned determination of semiconductor device degradation status based on saturation voltage can be performed.

[0049] In systems that control the drive of electric motors, the aforementioned changes in the saturation voltage of semiconductor elements can be detected using the output voltage of the power converter to the motor in a control system that aims to achieve a target current flow through the motor. For example, the saturation voltage of each semiconductor element in the power converter can be detected using the output voltage of the power converter to the motor in a PI control system that controls the current flowing through the motor. However, in controls that aim to achieve a target current flow through the motor, it is necessary to detect the current flowing through the motor in real time. Therefore, when detecting the saturation voltage of each semiconductor element in a control system that aims to achieve a target current flow through the motor, the accuracy of current detection will be significantly affected, which will have a significant impact on current control.

[0050] Furthermore, the aforementioned change in the saturation voltage of the semiconductor element can be detected by measuring the current flowing through the motor when the output voltage of each phase from the power converter to the motor is constant over time at a fixed voltage value. Here, if the output voltage of each phase from the power converter to the motor is constant at a fixed voltage value, then when the saturation voltage of a certain semiconductor element rises due to degradation, the current flowing through the winding (winding resistance) connected to the degraded semiconductor element and the winding of the degraded semiconductor element decreases. Figure 6The diagram illustrates the variation in current flowing through the power converter and motor due to semiconductor element degradation in an output where the multiphase output voltages are each kept constant at a fixed value. Figure 6 In the example, regarding one phase of the multiphase system, semiconductor element 5α, which is one of the two semiconductor elements 5, and the winding resistance Rα of the motor winding are shown.

[0051] In the output of the power converter to the motor, where the output voltages are each kept constant at a fixed value, in each phase of the multiphase circuit, the voltages transmitted and applied to the corresponding one of the two semiconductor elements and the winding resistance of the motor are kept constant at a fixed value. At this time, in Figure 6 In one phase shown, a fixed voltage value V0 is transmitted and applied to the semiconductor element 5α and the winding resistor Rα. In the undegraded state of the semiconductor element 5α, in the aforementioned output condition where the output voltage to the motor is kept constant at a fixed value, the saturation voltage of the semiconductor element 5α is Vα, and the voltage applied to the winding resistor Rα is V0-Vα. Furthermore, the current flowing through the semiconductor element 5α and the winding resistor Rα is Iα.

[0052] On the other hand, when the semiconductor element 5α is highly degraded, its saturation voltage increases compared to its undegraded state. Furthermore, even in the case of highly degraded semiconductor element 5α, in an output where the output voltage from the power converter to the motor is kept constant at a fixed value, a fixed voltage value V0 is applied to both the semiconductor element 5α and the winding resistor Rα. Therefore, in the case of highly degraded semiconductor element 5α, in the aforementioned output where the output voltage to the motor is kept constant at a fixed value, the saturation voltage of the semiconductor element 5α becomes Vα + ΔV, and the voltage applied to the winding resistor Rα becomes V0 - Vα - ΔV. When the semiconductor element 5α degrades, as described above, since the voltage applied to the winding resistor Rα decreases to V0 - Vα - ΔV, the current flowing through the semiconductor element 5α and the winding resistor Rα decreases to Iα - ΔI.

[0053] As described above, based on the current flowing through the motor in the output of power from a power converter that maintains a constant output voltage for each of the multiphase phases of the motor, the change in current corresponding to the change in the saturation voltage of each semiconductor element of the power converter can be detected, and the degradation state of the semiconductor elements can be determined. Here, the resistance value of the aforementioned winding resistor Rα is set to 1.7Ω, and the fixed voltage value V0 transmitted and applied to the semiconductor element 5α and the winding resistor Rα is set to 10V. Furthermore, due to the degradation of the semiconductor element 5α, the saturation voltage of the semiconductor element 5α is set to increase from 1.5V to 1.6V. In this case, in the output where the output voltage to the motor is maintained at a constant constant value, the current flowing through the semiconductor element 5α and the winding resistor Rα decreases from 5.00A in the undegraded state to 4.94A in the more degraded state, a change of about 0.06A. In determining the degradation state of each semiconductor element of the power converter that outputs power to the motor, such as the semiconductor element 5α, it is necessary to appropriately detect the aforementioned change in current of about 0.06A.

[0054] In one example, in a system controlling the drive of a motor, the resolution of the detected current is determined by the maximum current that the system can detect and the number of bits in the A / D converter that converts the analog signal of the detected current into a digital signal. For example, suppose the maximum current that the system can detect is 37.5A and the A / D converter has 12 bits. In this case, the resolution of the detected current is 0.018A. Therefore, if the change in current caused by the degradation of the semiconductor element is approximately 0.06A, as mentioned above, then theoretically, the change in current caused by the degradation of the semiconductor element can be detected.

[0055] However, the lower-order digits in an A / D converter are affected by errors in the conversion to a digital signal. Therefore, when detecting current changes of approximately 0.06A, the analog signal of the detected current needs to be amplified at a higher amplification rate before being input into the A / D converter to improve the resolution of the detected current. Consequently, when detecting current changes caused by semiconductor component degradation, compared to detecting current in a motor driven by AC power, the analog signal of the detected current needs to be amplified at a higher amplification rate before being input into the A / D converter.

[0056] (Diagnostic devices, diagnostic systems, diagnostic methods, and diagnostic procedures)

[0057] Hereinafter, considering the foregoing matters, the diagnostic apparatus, diagnostic system, diagnostic method, and diagnostic procedure of the embodiments will be described. In the embodiments, the degradation state of multiple semiconductor elements of the power converter is determined as follows. Figure 7 Diagnostic system 10 is shown as an example of a diagnostic system for a power converter as an implementation method. Figure 7 Diagnostic system 10 and Figure 1 Similarly, in another example, a device includes a motor 1, a power converter 2, a DC power supply 3, a drive control device 8, a current detection circuit 11, and an amplifier 12. In the power converter 2, which functions as an inverter, a three-phase (multi-phase) half-bridge circuit is formed using six semiconductor elements 5. Furthermore, with... Figure 1 Similarly, in the power converter 2, each return diode 6 is electrically connected in parallel with a corresponding one of the semiconductor elements 5, and the output terminals of each of the three-phase half-bridge circuits are connected to a corresponding one of the three windings (stator windings) 7 of the motor 1. In this embodiment, the drive control device 8 is also connected to... Figure 1 Similarly, by controlling the operation of the power converter 2, the output voltage from the power converter 2 to the motor 1 is controlled, and the drive of the motor 1 is controlled.

[0058] In addition, Figure 7 In this embodiment, the diagnostic system 10 includes a diagnostic device 15, an amplifier 16, and temperature sensors 17 and 18. The diagnostic device 15 includes an A / D converter 21, an output control unit 22, a degradation determination unit 23, a correction unit 25, and a storage unit 26. The diagnostic device 15 performs diagnostics on the power converter 2, for example, determining the degradation state of each of the plurality of semiconductor elements 5 of the power converter 2. In the diagnostic device 15, an analog signal is input to the A / D converter 21, and the analog signal is converted into a digital signal by the A / D converter 21. Here, the number of bits of the A / D converter 21 is, for example, the same as the number of bits of the A / D converter mounted on the drive control device 8.

[0059] The diagnostic device 15 is equipped with an integrated circuit including a processor and a storage medium. The processor in the integrated circuit in the diagnostic device 15 may be a CPU, ASIC, or FPGA. Furthermore, in the diagnostic device 15, the processor executes programs stored in the storage medium to perform diagnostic-related processing for the power converter 2. In the diagnostic device 15, the output control unit 22, the degradation determination unit 23, and the correction unit 25 each perform a portion of the processing by the processor, and the storage unit 26 functions as a storage medium.

[0060] In the diagnostic device 15, the output control unit 22 controls the operation of each semiconductor element 5 of the power converter 2 and controls the power output from the power converter 2 to the motor 1. During diagnostics using the diagnostic device 15, the output control unit 22 controls the operation of the power converter 2 to achieve a constant voltage output to the motor 1 in a target voltage mode, thus outputting power from the power converter 2 to the motor 1. In the constant voltage output from the power converter 2 to the motor 1, the applied voltage of the three phases (multi-phase) of the power converter 2 to the motor 1, i.e., the voltage in the motor 1, becomes constant or approximately consistent over time. Therefore, in the constant voltage output of the motor 1, the output voltages of the three phases—U-phase, V-phase, and W-phase—each become constant or approximately constant over time at a target voltage value (fixed voltage value). Furthermore, similarly to the drive control device 8, the output control unit 22 inputs pulse signals, etc., to the gates of each semiconductor element 5 to control the operation of each semiconductor element 5.

[0061] In this embodiment, during the diagnostics of the power converter 2, the output control unit 22 sequentially executes a constant voltage output that maintains a constant output voltage to the motor 1 under multiple target voltage modes. In these multiple target voltage modes, the applied state to the motor 1 from the output voltage of the power converter 2 differs from one another. Therefore, between these multiple target voltage modes, the target voltage value (fixed voltage value) of the output voltage from the power converter 2 to the motor 1 differs in at least one phase of the three-phase (multi-phase) power converter. Preferably, the number of target voltage modes for maintaining a constant voltage output voltage to the motor 1 is greater than the number of semiconductor elements 5 provided in the power converter 2. Figure 7 In one example, during the diagnosis of the power converter 2, under each of the six target voltage modes γ1 to γ6, which are the same number as the number of semiconductor elements 5, the power converter 2 outputs a constant voltage to the motor 1.

[0062] Here, using Figure 8 The six target voltage modes γ1 to γ6 for constant voltage output of motor 1 during diagnosis are explained. Figure 8 The image shows the voltage waveforms of the three-phase AC voltages (U-phase, V-phase, and W-phase). As previously described, the phases of the three-phase AC voltages are offset by 120° from each other. Figure 8 In the diagram, the horizontal axis represents the phase of the U-phase AC voltage, and the vertical axis represents the voltage itself. Figure 8 In the three-phase AC voltage, the AC voltages of phase U, phase V and phase W are set to peak value - peak value of 2Vq, and change periodically.

[0063] When performing a diagnostic test, the six target voltage modes γ1 to γ6 with constant voltage output are used. Figure 8When comparing the three-phase AC voltages, in the target voltage mode γ1 Figure 8 When the AC voltage of phase U in the three-phase AC voltage is phase θ1, the applied voltage state of motor 1 is consistent. Furthermore, the applied voltage state of motor 1 is consistent in the following cases, including: in target voltage mode γ2... Figure 8 In the case where the AC voltage of phase U in the three-phase AC voltage becomes phase θ2, in the target voltage mode γ3... Figure 8 In the case where the AC voltage of phase U in the three-phase AC voltage becomes phase θ3, in the target voltage mode γ4... Figure 8 In the case where the AC voltage of phase U in the three-phase AC voltage becomes phase θ4, in the target voltage mode γ5... Figure 8 In the case where the AC voltage of phase U in the three-phase AC voltage becomes phase θ5, in the target voltage mode γ6... Figure 8 In a three-phase AC voltage, the AC voltage of phase U becomes phase θ6. Additionally, Figure 8 In the U-phase AC voltage, phases θ1 to θ6 are offset from each other by 60°.

[0064] Figure 9 This represents the target voltage value for the three-phase output voltage of each of the six target voltage modes γ1 to γ6 for constant voltage output to motor 1. Figure 7 In one example, in the constant voltage output of the target voltage modes γ1 to γ6 respectively, the output voltage of each of the three phases is adjusted to achieve the following: Figure 9 The target voltage value shown is kept constant. For example... Figure 9 As shown, the target voltage values ​​for the output voltage of phase U are set as follows: Vq in target voltage mode γ1, Vq / 2 in target voltage mode γ2, -Vq / 2 in target voltage mode γ3, -Vq in target voltage mode γ4, -Vq / 2 in target voltage mode γ5, and Vq / 2 in target voltage mode γ6. Similarly, the target voltage values ​​for the output voltage of phase V are set as follows: -Vq / 2 in target voltage mode γ1, Vq / 2 in target voltage mode γ2, Vq in target voltage mode γ3, Vq / 2 in target voltage mode γ4, -Vq / 2 in target voltage mode γ5, and -Vq in target voltage mode γ6. Furthermore, the target voltage values ​​of the output voltage of phase W are set as follows: -Vq / 2 in target voltage mode γ1, -Vq in target voltage mode γ2, -Vq / 2 in target voltage mode γ3, Vq / 2 in target voltage mode γ4, Vq in target voltage mode γ5, and Vq / 2 in target voltage mode γ6.

[0065] Figure 10This represents the current flowing through the power converter 2 and the motor 1 in the constant voltage output of each of the target voltage modes γ1 to γ6 to the motor 1. Figure 10 In the diagram, the flow of current is indicated by arrows. Furthermore, regarding the three windings 7, the U phase is represented as winding 7U, the V phase as winding 7V, and the W phase as winding 7W. Also, regarding the three positive-side semiconductor elements 5p, the U phase is represented as semiconductor element 5Up, the V phase as semiconductor element 5Vp, and the W phase as semiconductor element 5Wp; regarding the three negative-side semiconductor elements 5m, the U phase is represented as semiconductor element 5Um, the V phase as semiconductor element 5Vm, and the W phase as semiconductor element 5Wm.

[0066] like Figure 10 As shown, in the constant voltage output of target voltage mode γ1, current flows from the positive power line through semiconductor element 5Up to motor 1. Furthermore, current flows from motor 1 through one of semiconductor elements 5Vm and 5Wm to the negative power line. In addition, in the constant voltage output of target voltage mode γ1, the voltage transmitted and applied to semiconductor element 5Up and the winding resistance of winding 7U is a fixed voltage value corresponding to the target voltage value Vq of phase U, becoming constant or approximately constant. Furthermore, in the constant voltage output of target voltage mode γ2, current flows from the positive power line through one of semiconductor elements 5Up and 5Vp to motor 1. Furthermore, current flows from motor 1 through semiconductor element 5Wm to the negative power line. Furthermore, in the constant voltage output of target voltage mode γ2, the voltage transmitted and applied to the winding resistance of winding 7W and semiconductor element 5Wm is a fixed voltage value corresponding to the target voltage value -Vq of phase W, becoming constant or approximately constant.

[0067] In the constant voltage output of target voltage mode γ3, current flows from the positive power line through semiconductor element 5Vp to motor 1. Furthermore, current flows from motor 1 through one of semiconductor elements 5Um and 5Wm to the negative power line. In addition, in the constant voltage output of target voltage mode γ3, the voltage transmitted and applied to semiconductor element 5Vp and the winding resistance of winding 7V is a fixed voltage value corresponding to the target voltage value Vq of phase V, becoming constant or approximately constant. In the constant voltage output of target voltage mode γ4, current flows from the positive power line through one of semiconductor elements 5Vp and 5Wp to motor 1. Furthermore, current flows from motor 1 through semiconductor element 5Um to the negative power line. In addition, in the constant voltage output of target voltage mode γ4, the voltage transmitted and applied to the winding resistance of winding 7U and semiconductor element 5Um is a fixed voltage value corresponding to the target voltage value Vq of phase U, becoming constant or approximately constant.

[0068] In the constant voltage output of target voltage mode γ5, current flows from the positive power line through semiconductor element 5Wp to motor 1. Furthermore, current flows from motor 1 through one of semiconductor elements 5Um and 5Vm to the negative power line. In addition, in the constant voltage output of target voltage mode γ5, the voltage applied to semiconductor element 5Wp and the winding resistor of winding 7W is a fixed voltage value corresponding to the target voltage value Vq of phase W, becoming constant or approximately constant. In the constant voltage output of target voltage mode γ6, current flows from the positive power line through one of semiconductor elements 5Up and 5Wp to motor 1. Furthermore, current flows from motor 1 through semiconductor element 5Vm to the negative power line. In addition, in the constant voltage output of target voltage mode γ6, the voltage applied to the winding resistor of winding 7V and semiconductor element 5Vm is a fixed voltage value corresponding to the target voltage value Vq of phase V, becoming constant or approximately constant.

[0069] In the diagnostics of the power converter 2, the current detection circuit 11 detects the current flowing through the motor 1 in the constant voltage output of each of the aforementioned target voltage modes γ1 to γ6. In the constant voltage output of the target voltage mode γ1, the current equivalent to the current IUp flowing through the semiconductor element 5Up and the winding 7U is detected by detecting the current flowing through the shunt resistor of the current detection circuit 11. Similarly, by detecting the current flowing through the shunt resistor of the current detection circuit 11, the following currents are detected respectively, which include: in the constant voltage output of the target voltage mode γ2, the current IWm corresponding to the current flowing through the semiconductor element 5Wm and the winding 7W; in the constant voltage output of the target voltage mode γ3, the current IVp corresponding to the current flowing through the semiconductor element 5Vp and the winding 7V; in the constant voltage output of the target voltage mode γ4, the current IUm corresponding to the current flowing through the semiconductor element 5Um and the winding 7U; in the constant voltage output of the target voltage mode γ5, the current IWp corresponding to the current flowing through the semiconductor element 5Wp and the winding 7W; and in the constant voltage output of the target voltage mode γ6, the current IVm corresponding to the current flowing through the semiconductor element 5Vm and the winding 7V.

[0070] Furthermore, in this embodiment, the analog signal representing the current detection result of the current detection circuit 11 in the aforementioned constant voltage output is amplified by amplifier 12 and then by amplifier 16. The analog signal amplified by amplifier 16 is then input to the A / D converter 21 of the diagnostic device 15. In contrast, when the motor 1 is driven by three-phase AC power from the power converter 2, the analog signal representing the current detection result of the current detection circuit 11 is amplified by amplifier 12 but not by amplifier 16, and is input to the A / D converter (not shown) of the drive control device 8. Therefore, the analog signal representing the current detection result in the constant voltage output is amplified at a higher amplification rate than the analog signal representing the current detection result when the motor 1 is driven. The analog signal amplified at the higher amplification rate is then transmitted to the diagnostic device 15.

[0071] In the diagnostic device 15, the A / D converter 21 converts the analog signal representing the current detection result into a digital signal and inputs it to the degradation determination unit 23 and the correction unit 25. Furthermore, the degradation determination unit 23 and the correction unit 25 process the current detection result represented by the digital signal. Here, in Figure 7 In one example, the number of bits in the A / D converter 21 is the same as the number of bits in the A / D converter of the drive control device 8. The analog signal transmitted to the diagnostic device 15 as the current detection result in the current detection circuit 11 is amplified with a higher amplification rate compared to the analog signal transmitted to the drive control device 8 as the current detection result in the current detection circuit 11. Therefore, in constant voltage output, the resolution of the current detected by the current detection circuit 11 is higher than that in the state where the motor 1 is driven by AC power. That is, the degradation determination unit 23 and the correction unit 25 obtain the detection result of the current flowing through the motor 1 in constant voltage output with a higher resolution than the detection result of the current flowing through the motor 1 in the state where the motor 1 is driven.

[0072] Figure 11 This illustrates an example of the time-dependent variation in the three-phase output voltage from power converter 2 to motor 1 during diagnostics of power converter 2. Figure 11 In the diagram, the horizontal axis represents time from the start of the diagnostic test, and the vertical axis represents voltage. Figure 11In one example, during a diagnostic test of the power converter 2, the aforementioned constant voltage output is performed sequentially in the order of target voltage modes γ1, γ2, γ3, γ4, γ5, and γ6. During the diagnostic test of the power converter 2, a specified time Yareg is set to the duration of the constant voltage output for each of the target voltage modes γ1 to γ6. The specified time Yareg is set to be longer than the time from the start of the output until the current flowing through the motor 1 reaches saturation. However, the specified time Yareg is set to a short time to suppress the rise in junction temperature of the semiconductor element 5 caused by energization. As mentioned earlier, the current flowing through the motor 1 reaches saturation after a short energization period of approximately 0.1 seconds. Therefore, the specified time Yareg for the duration of the constant voltage output for each of the target voltage modes γ1 to γ6 can be set to a short time.

[0073] Furthermore, in the diagnostics of the power converter 2, the specified time Ybreg is set as the interval between the constant voltage outputs of the target voltage modes γ1 to γ6. Therefore, in the diagnostics of the power converter 2, after the specified time Ybreg elapses from the end of the constant voltage output of a certain target voltage mode, the constant voltage output of the next target voltage mode begins. Additionally, it is preferable that the specified time Ybreg is longer than the specified time Yareg for the duration of the constant voltage output. The degradation determination unit 23 and the correction unit 25 calculate the average value of the current detected by the current detection circuit 11 during the constant voltage outputs of each of the target voltage modes γ1 to γ6. Therefore, the degradation determination unit 23 and the correction unit 25 obtain the average value of the current (time average value) between the specified time Yareg for the constant voltage outputs of each of the target voltage modes γ1 to γ6 as the detection result of the current flowing through the motor 1.

[0074] Temperature sensor 17 detects the ambient temperature Ta of the aforementioned power converter 2 (semiconductor element 5), and temperature sensor 18 detects the temperature T of the aforementioned motor 1. The A / D converter 21 of the diagnostic device 15 converts the analog signal representing the detection results of the ambient temperature Ta and temperature T into a digital signal and inputs it to the correction unit 25. The storage unit 26 stores information related to the temperature characteristics of the semiconductor element 5, including information representing the relationship between the aforementioned saturation voltage of the semiconductor element 5 and the ambient temperature Ta of the power converter 2. Based on the detection results of the ambient temperature Ta of the power converter 2 and the information related to the temperature characteristics of the semiconductor element 5, the correction unit 25 corrects the detection results of the current flowing through the motor 1 in the constant voltage output of each of the target voltage modes γ1 to γ6. At this time, information regarding the current flowing through the motor 1 in the constant voltage output of each of the target voltage modes γ1 to γ6 is corrected (converted) to the case where the ambient temperature Ta of the power converter 2 is the reference temperature Taref.

[0075] Furthermore, the storage unit 26 stores information related to the temperature characteristics of the motor winding resistance. The correction unit 25, based on the detection results of the motor temperature T and the information related to the temperature characteristics of the winding resistance, corrects the detection results of the current flowing through the motor 1 in the constant voltage output of each of the target voltage modes γ1 to γ6. At this time, the current flowing through the motor 1 in the constant voltage output of each of the target voltage modes γ1 to γ6 is corrected (converted) to the case where the temperature T of the motor 1 is the reference temperature Tref, based on the detection results. As described above, the correction unit 25 corrects the detection results of the current detection circuit 11 for the current flowing through the motor 1 in the constant voltage output to any one of the following: information where the ambient temperature Ta of the power converter 2 is the reference temperature Taref; information where the temperature T of the motor 1 is the reference temperature Tref; and information where the ambient temperature Ta of the power converter 2 is the reference temperature Taref and the temperature T of the motor 1 is the reference temperature Tref. The degradation determination unit 23 and the correction unit 25, for the current flowing through the motor 1 in the constant voltage output of each of the target voltage modes γ1 to γ6, will store one of the detection results, including the average value between Yaregs over a specified time, and the information after the detection results are corrected by the correction unit 25 as described above, in the storage unit 26.

[0076] Furthermore, the diagnostics of the power converter 2 are performed periodically after the power converter 2 is put into use. The degradation determination unit 23 compares the information from the real-time diagnostics with the information from any previously performed diagnostics for the current flowing through the motor 1 in the constant voltage output of each of the target voltage modes γ1 to γ6. Based on the comparison result between the information from any previously performed diagnostics and the information from the real-time diagnostics regarding the aforementioned current, the degradation determination unit 23 determines the degradation state of the corresponding semiconductor element 5.

[0077] Furthermore, in comparing the current flowing through the motor 1 in the constant voltage output of each of the target voltage modes γ1 to γ6, the detection results of the current detection circuit 11 can be compared, as well as the information corrected by the correction unit 25 as described above. However, in the aforementioned current comparison, it is preferable to compare the information when the ambient temperature Ta of the power converter 2 is the reference temperature Taref and the temperature T of the motor 1 is the reference temperature Tref. Here, a first period and a second period later than the first period are defined. Furthermore, it is assumed that any of the previous diagnoses were performed in the first period, and real-time diagnoses are performed in the second period. In this embodiment, in each of the first and second periods, a constant voltage output is performed to keep the output voltage of the motor 1 constant in each of the target voltage modes γ1 to γ6.

[0078] exist Figure 7 , Figures 9 to 11 In one example, for the current IUp flowing through the semiconductor element 5Up in the constant voltage output of the target voltage mode γ1, information from a first period (previous diagnosis) is compared with information from a second period (real-time diagnosis). In this case, based on the comparison result of the current IUp, the degradation state of the semiconductor element 5Up on the positive side of the U phase is determined. The degradation determination unit 23 reads the current IUp information from the storage unit 26 for the first period. Furthermore, for the current flowing through the semiconductor element 5Up in the constant voltage output of the target voltage mode γ1, the degradation determination unit 23 determines whether the current represented as information for the second period decreases relative to the current represented as information for the first period by exceeding a reference level. If the current in the second period decreases relative to the current in the first period by exceeding the reference level, the degradation determination unit 23 determines that the degree of degradation of the semiconductor element 5Up exceeds the reference level and determines that the lifespan of the semiconductor element 5Up is nearing its end.

[0079] For the current flowing through the corresponding semiconductor element 5 in the constant voltage output of each of the target voltage modes γ2 to γ6, the information from the first period (previous diagnosis) is compared with the information from the second period (real-time diagnosis). Therefore, for each of the target voltage modes γ2 to γ6, the degree of degradation of the corresponding semiconductor element 5 is determined to be whether it exceeds a reference level. That is, for the current IWm flowing through semiconductor element 5Wm in the constant voltage output of target voltage mode γ2, the current IVp flowing through semiconductor element 5Vp in the constant voltage output of target voltage mode γ3, the current IUm flowing through semiconductor element 5Um in the constant voltage output of target voltage mode γ4, the current IWp flowing through semiconductor element 5Wp in the constant voltage output of target voltage mode γ5, and the current IVm flowing through semiconductor element 5Vm in the constant voltage output of target voltage mode γ6, the information from the first period is compared with the information from the second period. Furthermore, for each of semiconductor elements 5Um, 5Vp, 5Vm, 5Wp, and 5Wm, the degree of degradation and lifespan are determined in the same manner as for semiconductor element 5Up.

[0080] If the degradation level of any one of the semiconductor elements 5 in the power converter 2 exceeds a reference level, the degradation determination unit 23 issues a warning. The warning is issued using a user interface (not shown) separate from the diagnostic device 15 or from the diagnostic device 15, for example, via screen display or sound transmission. Furthermore, when issuing a warning, the degradation determination unit 23 can also indicate which of the multiple semiconductor elements 5 has a higher degree of degradation. In another example, if the degradation level of any one of the semiconductor elements 5 exceeds a reference level, the degradation determination unit 23 may, instead of issuing a warning, send a command to the drive control device 8 to reduce the AC power output of the power converter 2 to the motor 1 when the motor 1 is being driven. In this case, while the motor 1 is being driven, the drive control device 8 controls the operation of the power converter 2 based on the command from the diagnostic device 15, thereby reducing the AC power output to the motor 1 compared to before the diagnostic test.

[0081] Furthermore, in this embodiment, the diagnostics of the power converter 2 are performed while the motor 1 has not been driven for an extended period, i.e., while each of the semiconductor elements 5 has been de-energized for a long time. Moreover, the diagnostics of the power converter 2 are performed immediately before the start of driving the motor 1. Figure 7 In one example, the diagnostic device 15 can communicate with the drive control device 8 to obtain whether a drive command to drive the motor 1 has been input. Furthermore, if a drive command has been input, before driving the motor 1 under control based on the drive control device 8, as described above, the output control unit 22 outputs power from the power converter 2 to the motor 1 at a constant voltage in each target voltage mode. Thus, before driving the motor 1 under control based on the drive control device 8, the degradation state of each semiconductor element 5 is determined, and a diagnosis of the power converter 2 is performed.

[0082] Furthermore, the determination of whether to perform a diagnostic test on power converter 2 can be based not only on the presence or absence of a drive command input for motor 1, but also on either the elapsed time Xa since the last diagnostic test or the elapsed time Xb since the end of the last drive of motor 1. In one example, even if a drive command to drive motor 1 is input, if the elapsed time Xa since the last diagnostic test is shorter than the reference time Xaref, the aforementioned constant voltage output to motor 1 will not be performed, and the diagnostic test on power converter 2 will not be performed. In another example, even if a drive command to drive motor 1 is input, if the elapsed time Xb since the end of the last drive of motor 1 is shorter than the reference time Xbref, the aforementioned constant voltage output to motor 1 will not be performed, and the diagnostic test on power converter 2 will not be performed.

[0083] Figure 12 An example of processing via the processor of the diagnostic device 15 is shown. Figure 12 The process begins when no AC power is supplied to motor 1 and motor 1 is not driven. When Figure 12 When the processing begins, the diagnostic device 15 determines, based on information from the drive control device 8, whether a drive command to drive the motor 1 has been input (S51). If no drive command has been input (S51-No), the device remains in standby mode in S51. Furthermore, when a drive command is input (S51-Yes), the diagnostic device 15 determines, based on information stored in the storage unit 26, whether the elapsed time Xa since the last diagnosis is greater than or equal to the reference time Xaref (S52).

[0084] If the elapsed time Xa is greater than or equal to the reference time Xaref (S52-Yes), the diagnostic device 15 determines, based on information from the drive control device 8, whether the elapsed time Xb since the end of the last drive of the motor 1 is greater than or equal to the reference time Xbref (S53). If the elapsed time Xb is greater than or equal to the reference time Xbref (S53-Yes), the diagnostic device 15 performs diagnostic processing for the power converter 2 (S54). Furthermore, when the diagnostic processing is complete, the diagnostic device 15 sends a message to the drive control device 8 indicating that the diagnostic process is complete, and the drive control device 8 drives the motor 1. The drive control device 8 then controls the drive of the motor 1 as described above (S55). On the other hand, in cases where the elapsed time Xa is shorter than the reference time Xaref (S52-No) and the elapsed time Xb is shorter than the reference time Xbref (S53-No), no diagnostic processing is performed, and the drive of the motor 1 is controlled by the drive control device 8 (S55).

[0085] Figure 13 An example of the diagnostic process (S54) for power converter 2 is shown. Figure 13 In the processing, a count value N is specified, which can be set to a natural number greater than or equal to 1 and less than or equal to a reference value Nref. In one example, during diagnostic processing, constant voltage output is performed in each of the aforementioned six target voltage modes γ1 to γ6, with a reference value Nref of 6. Furthermore, the count value N can be set to a natural number greater than or equal to 1 and less than or equal to 6. When starting... Figure 13During diagnostic processing, the output control unit 22 sets the counter value N to 1 (S61). Furthermore, the output control unit 22 outputs a constant voltage to the motor 1 from the power converter 2 based on the target voltage mode corresponding to the set counter value N among multiple target voltage modes (S62). In one example, when the counter value N is set to 1, a constant voltage output is performed using the aforementioned target voltage mode γ1. The degradation determination unit 23, etc., obtains the detection result of the current flowing through the motor 1 during the constant voltage output of the target voltage mode corresponding to the counter value N (S63). At this time, the degradation determination unit 23, etc., calculates the average value (time average) of the current flowing through the motor 1.

[0086] Furthermore, the output control unit 22 determines whether the duration Ya of the constant voltage output is greater than or equal to a predetermined time Yareg (S64). If the duration Ya is shorter than the predetermined time Yareg (S64-No), the processing returns to S63, and the processing after S63 is performed sequentially. Therefore, the constant voltage output of the target voltage mode corresponding to the counter value N continues. On the other hand, if the duration Ya is greater than or equal to the predetermined time Yareg (S64-Yes), the output from the power converter 2 to the motor 1 is stopped (S65), and the constant voltage output ends. In addition, during the constant voltage output, by calculating the average value of the current flowing through the motor 1, the degradation determination unit 23 and others obtain the average value of the current flowing through the motor 1 over the predetermined time Yareg for the constant voltage output of the target voltage mode corresponding to the counter value N as the detection result of the current flowing through the motor 1.

[0087] Furthermore, the correction unit 25, based on the detection results of the ambient temperature Ta of the power converter 2 and the temperature T of the motor 1, corrects the detection results of the current flowing through the motor 1 in the constant voltage output of the target voltage mode corresponding to the counter value N (S66). The correction based on the detection results of the current at ambient temperature Ta and temperature T is performed as described above. Furthermore, the correction unit 25 and others save the information of the corrected detection results of the current flowing through the motor 1 in the constant voltage output of the target voltage mode corresponding to the counter value N to the storage unit 26 (S67). Furthermore, the output control unit 22 determines whether the elapsed time Yb since the end of the last constant voltage output is more than or equal to the predetermined time Ybreg (S68). If the elapsed time Yb is shorter than the predetermined time Ybreg (S68-No), standby is initiated at S68. On the other hand, if the elapsed time Yb is more than or equal to the predetermined time Ybreg (S68-Yes), the output control unit 22 and others determine whether the counter value N is more than or equal to the reference value Nref (S69).

[0088] If the count value N is smaller than the reference value Nref (S69-No), the output control unit 22 increments the count value N by 1 (S70) and updates the count value N. Then, the processing returns to S62, and the processing after S62 is performed sequentially. Therefore, based on the target voltage mode corresponding to the updated count value N, a constant voltage output is provided to the motor 1 from the power converter 2. If the count value N is greater than or equal to the reference value Nref in S69 (S69-Yes), the degradation determination unit 23 compares the information flowing through the motor 1 in the constant voltage output of each of the multiple target voltage modes (the same number as the reference value Nref) with the information in the first period (any previous diagnosis) (S71). Figure 13 In one example, for the current flowing through motor 1 in the constant voltage output of each target voltage mode, information is compared between the ambient temperature Ta of power converter 2 and the reference temperature Taref, and the temperature T of motor 1 and the reference temperature Tref. The comparison of current between the first and second periods is performed as described above.

[0089] Furthermore, based on the comparison results in S71, the degradation determination unit 23 determines whether one of the semiconductor elements 5 of the power converter 2 has deteriorated beyond a reference level (S72). The determination of the degradation state of each semiconductor element 5 based on the comparison results of the current between the first period and the second period is performed as described above. If the degree of degradation of any semiconductor element 5 exceeds the reference level (S72-Yes), the degradation determination unit 23, etc., issues a warning (S73). On the other hand, if the degree of degradation of any semiconductor element 5 does not exceed the reference level (S72-No), no warning is issued and the diagnostic process ends.

[0090] As described above, in this embodiment, during the diagnosis of the power converter 2, the output control unit 22 of the diagnostic device 15 controls the operation of the semiconductor element 5 to maintain a constant voltage output to the motor 1 in a target voltage mode, thereby enabling the power converter 2 to output power to the motor 1. Furthermore, the degradation determination unit 23 determines the degradation state of one or more semiconductor elements 5 based on the current flowing through the motor 1 in the aforementioned constant voltage output. Therefore, the degradation state of the semiconductor element 5 provided in the power converter 2 is determined without causing a short-circuit current in the power converter 2. Moreover, as described above, the current flowing through the motor 1 in the constant voltage output changes corresponding to a change in the saturation voltage of its corresponding semiconductor element 5. Therefore, by detecting the change in the current flowing through the motor 1 in the constant voltage output, the change (rise) in the saturation voltage of the corresponding semiconductor element 5 is appropriately detected, and the degradation state of the corresponding semiconductor element 5 is appropriately determined.

[0091] Furthermore, in this embodiment, under multiple target voltage modes (e.g., γ1 to γ6) with different applied states of the motor 1 from the output voltage of the power converter 2, a constant voltage output is sequentially performed to keep the output voltage of the motor 1 constant under the target voltage modes. Furthermore, the degradation state of the corresponding semiconductor element 5 is determined based on the current flowing through the motor 1 in the constant voltage output of each of the multiple target voltage modes. By performing a constant voltage output from the power converter 2 under multiple target voltage modes with different applied voltage states of the motor 1, the degradation state of the multiple semiconductor elements 5 mounted on the power converter 2 can be appropriately determined. For example, based on the current flowing through the motor 1 in the constant voltage output of target voltage mode γ1, the degradation state of semiconductor element 5Up is appropriately determined as described above; and based on the current flowing through the motor 1 in the constant voltage output of target voltage mode γ2, the degradation state of semiconductor element 5Wm is appropriately determined as described above.

[0092] In addition, Figure 7 as well as Figures 9 to 11 In one example, during the diagnostics of power converter 2, the number of target voltage modes for constant voltage output exceeds the number of semiconductor elements 5 in power converter 2. Therefore, for all semiconductor elements 5 mounted in power converter 2, their degradation state can be appropriately determined. Consequently, it is possible to appropriately determine which of the semiconductor elements 5 mounted in power converter 2 has a higher degree of degradation. Thus, the accuracy of the diagnostics for power converter 2 is improved.

[0093] Furthermore, in this embodiment, the correction unit 25 corrects the detection results of the current flowing through the motor 1 in constant voltage output based on the detection results of the temperature T of the motor 1 and the temperature characteristics of the winding resistance of the motor 1. The degradation determination unit 23 determines the degradation state of the semiconductor element 5 based on information about the aforementioned current detection results corrected for the temperature T of the motor 1. Therefore, by appropriately considering the influence of the winding resistance of the motor 1 on the current flowing through the motor 1 in constant voltage output, i.e., the influence of the winding resistance of the motor 1 on the saturation voltage of the corresponding semiconductor element 5, the degradation state of the semiconductor element 5 is determined.

[0094] Furthermore, in this embodiment, the correction unit 25 corrects the detection results of the current flowing through the motor 1 in constant voltage output based on the detection results of the ambient temperature Ta of the power converter 2 (semiconductor element 5) and the temperature characteristics of the semiconductor element 5. The degradation determination unit 23 determines the degradation state of the semiconductor element 5 based on information about the aforementioned current detection results corrected for the ambient temperature Ta of the power converter 2. Therefore, by appropriately considering the influence of the temperature of the semiconductor element 5 on the current flowing through the motor 1 in constant voltage output, i.e., the temperature characteristics of the saturation voltage of the semiconductor element 5, the degradation state of the semiconductor element 5 is determined.

[0095] Furthermore, in this embodiment, diagnostic processing of the power converter 2 is performed before starting the drive of the motor 1 with AC power. Moreover, the diagnostics of the power converter 2 are only performed if the elapsed time Xb since the end of the last drive of the motor 1 is greater than or equal to the reference time Xbref. Therefore, the diagnostics of the power converter 2 are appropriately performed even when each semiconductor element 5 has been unpowered for an extended period. Furthermore, in the aforementioned embodiment, the duration of the constant voltage output during diagnostics is short, and the energization time of each semiconductor element 5 during the constant voltage output is short. Therefore, the rise in junction temperature of the semiconductor element 5 caused by the energization of the constant voltage output can be appropriately suppressed. Thus, even if the ambient temperature of the semiconductor element 5 (power converter 2) is considered to be the same as the junction temperature of each semiconductor element 5, as described above, the degradation state of the semiconductor element 5 can be appropriately determined.

[0096] Furthermore, in determining the degradation state of each of the semiconductor elements 5, since the determination is based on the assumption that the ambient temperature and junction temperature are the same, it is unnecessary to install sensors or similar devices to detect the junction temperature of each of the semiconductor elements 5 in the power converter 2. This appropriately reduces the complexity of the power converter 2's configuration. In addition, in this embodiment, whenever a diagnostic test is performed on the power converter 2, information about the current flowing through the motor 1 in the constant voltage output of each target voltage mode is stored in the storage unit 26 as a diagnostic result. Therefore, the information from the previous diagnostic test (first period) and the information from the current diagnostic test (second period) can be compared for the current flowing through the motor 1 in the constant voltage output. This allows for a more appropriate determination of the degradation state of the semiconductor elements 5.

[0097] Furthermore, in this embodiment, the diagnostic device 15 obtains the detection result of the current flowing through the motor 1 in the aforementioned constant voltage output with higher resolution, compared to the detection result of the current flowing through the motor 1 when the motor 1 is in a driving state. Here, for the current flowing through the motor 1 in the constant voltage output, the amount of change between the corresponding undegraded state of the semiconductor element 5 and the corresponding state with a higher degree of deterioration is small, as described above. In this embodiment, since the detection result of the current flowing in the constant voltage output is obtained with higher resolution, it is possible to appropriately detect the small change in the current caused by the deterioration of the corresponding semiconductor element 5. Therefore, the deterioration state of the semiconductor element 5 can be determined more appropriately.

[0098] In addition, Figure 7 In one example, the diagnostic device 15 and the drive control device 8 are provided separately, but this is not a limitation. In another example, the diagnostic device 15 may diagnose the power converter 2 in the same way as in the aforementioned embodiments, and the processing may be performed by the drive control device 8 in the aforementioned embodiments. In this case, when the motor 1 is driven by the supply of AC power, the diagnostic device 15 controls the output of multiphase AC power from the power converter 2 to the motor 1 by controlling the operation of the semiconductor element 5 of the power converter 2.

[0099] Furthermore, in one example, a voltage detection circuit is provided to detect the output voltage from the DC power supply 3 to the power converter 2. In this case, the output control unit 22 of the diagnostic device 15 obtains the detection result of the output voltage from the DC power supply 3. The output control unit 22 controls the operation of multiple semiconductor elements 5 of the power converter 2 based on the output voltage from the DC power supply 3, thereby achieving a constant voltage output to the motor 1 in the target voltage mode, as described above, so that power is output from the power converter 2 to the motor 1. Therefore, even if the output voltage from the DC power supply 3 changes, by controlling the output from the power converter 2 in accordance with the change in the output voltage from the DC power supply 3, a constant voltage output to the motor 1 is achieved in the target voltage mode, so that power is output from the power converter 2 to the motor 1.

[0100] (Implementation methods and related verification)

[0101] Furthermore, as a verification related to the aforementioned embodiments, the following first verification was performed. In the first verification, a power cycle test was conducted, in which a power converter identical to power converter 2 was operated under specified power cycle conditions. Furthermore, during the power cycle test, diagnostics of the power converter were performed periodically. In this verification, the power converter was diagnosed in multiple states, including a state with 30 power cycles (30 cycles) and a state with 15360 power cycles. In each of the multiple diagnostics performed, the results were consistent with those of the aforementioned embodiments. Figure 7 , Figures 9 to 11 Similarly, in one example, constant voltage outputs are performed sequentially in target voltage modes γ1, γ2, γ3, γ4, γ5, and γ6 to maintain a constant output voltage to the motor. The duration of the constant voltage output of each of the target voltage modes γ1 to γ6 is such that it suppresses the rise in junction temperature of the semiconductor components. An interval is set between the constant voltage outputs of one target voltage mode and the constant voltage output of the next. In each diagnostic performed during the power cycling test, the current flowing through the U phase of the motor during the constant voltage outputs of each of the target voltage modes γ1 to γ6 is detected.

[0102] Figure 14 This represents the time-dependent change in the current flowing through the U-phase of the motor under constant voltage output conditions in six target voltage modes γ1 to γ6, for two different diagnostic times. Figure 14 In the diagram, the horizontal axis represents the time referenced to the start of the diagnostic test, and the vertical axis represents the current in phase U. Furthermore, in... Figure 14 In this context, the current IUp flowing from the positive-side semiconductor element (e.g., 5Up) towards the motor is represented by a positive value, and the current IUm flowing from the motor towards the negative-side semiconductor element (e.g., 5Um) is represented by a negative value. Furthermore, in... Figure 14 The diagram shows the changes in the U-phase current over time during diagnostics for the states after 30 power cycles (solid line) and 15360 power cycles (dashed line) following the start of the power cycling test. Figure 14 As shown, in this verification, the current IUp flowing through the U phase of the motor in the constant voltage output of the target voltage mode γ1 decreased by 170mA after 15360 power cycles compared to after 30 power cycles. Furthermore, in the power cycle test of this verification, after 15360 power cycles, a semiconductor element (e.g., 5Up) on the positive side of the U phase failed.

[0103] Figure 15 As a verification result, the relationship between the number of power cycles and the current IUp flowing through the U phase of the motor in the constant voltage output of the corresponding target voltage mode γ1 is expressed. Figure 15 In the diagram, the horizontal axis represents the number of power cycles (cycle count), and the vertical axis represents the current IUp flowing from the positive semiconductor element to the U-phase of the motor. For example... Figure 15 As shown in the figure, this verification confirms that as the number of power cycles increases, the current IUp flowing through the U phase of the motor in the constant voltage output of the target voltage mode γ1 will decrease.

[0104] Furthermore, in this verification, the temperature T of the motor was detected. And, in multiple diagnostic tests of each power converter, based on the detected motor temperature T and the temperature characteristics of the motor winding resistance, similar to the aforementioned implementation methods, the detection results of the current IUp flowing through the U-phase of the motor in the constant voltage output of the target voltage mode γ1 were corrected. In this verification, the reference temperature Tref of the motor temperature T was set to 20°C, and the detection results of the current IUp flowing through the U-phase of the motor in the constant voltage output of the target voltage mode γ1 were corrected. Information regarding the case where the temperature T is 20°C was used as the correction value (correction information) for the current IUp flowing through the U-phase of the motor in the constant voltage output of the target voltage mode γ1.

[0105] Figure 16 Indicates according to Figure 15 The relationship shown is the result of correcting the detected current IUp of phase U to the corrected value when the motor temperature T is 20℃. Figure 16 In the diagram, the horizontal axis represents the number of power cycles (cycle count), and the vertical axis shows the correction value for the U-phase current IUp at a temperature T of 20°C. For example... Figure 16 As shown, for the current IUp flowing through the U phase of the motor in the constant voltage output of the target voltage mode γ1, by correcting the detection result to the correction value when the motor temperature T is 20°C, the decrease of the current IUp in the constant voltage output of the target voltage mode γ1 with the increase of the number of power cycles is more clearly shown.

[0106] Furthermore, in this verification, during each diagnostic test performed in the power cycling test, the aforementioned analog signal, representing the time-dependent change in the current of phase U under the target voltage modes γ1 to γ6 sequentially, was amplified using an amplifier. The amplified analog signal was then converted to an analog signal using an A / D converter, and the digital signal representing the time-dependent change in the current of phase U was converted to a voltage signal, which became an analog signal, using a D / A converter.

[0107] Figure 17 Indicates to Figure 14 The voltage signal is generated by amplifying and performing A / D conversion on the time-varying current changes of each U-phase shown, followed by D / A conversion. Figure 17In the diagram, the horizontal axis represents the time referenced to the start of the diagnosis, and the vertical axis represents the voltage signal corresponding to the current in phase U. Furthermore, in this verification, the analog signal is inverted and amplified during the current amplification of phase U. Therefore, in... Figure 17 In the voltage signal shown, relative to Figure 14 The current in phase U shown is reversed in both positive and negative directions. That is, in Figure 17 In this context, the voltage corresponding to the current IUp flowing from the positive semiconductor element (e.g., 5Up) toward the motor is represented by a negative value, while the voltage corresponding to the current IUm flowing from the motor toward the negative semiconductor element (e.g., 5Um) is represented by a positive value.

[0108] like Figure 17 As shown, in this verification, the voltage corresponding to the current IUp flowing through the U-phase of the motor in the constant voltage output of the target voltage mode γ1 decreased by 50mV after 15360 power cycles compared to after 30 power cycles. This 50mV change in the voltage signal corresponds to a 130mA change in the U-phase current. In this verification, the decrease in current IUp in the constant voltage output of the target voltage mode γ1 was appropriately detected with increasing power cycle count. Therefore, it was confirmed that the degradation state of the semiconductor element (e.g., 5Up) on the positive side of the U-phase can be appropriately determined based on the decrease in current IUp in the constant voltage output of the target voltage mode γ1.

[0109] Furthermore, as a verification different from the first verification, a second verification was performed. In the second verification, a cyclic test was conducted where the same power converter as power converter 2 was operated under specified conditions different from those in the first verification. Furthermore, during the power cyclic test, diagnostics of the power converter were performed periodically. In each of the multiple diagnostics performed, the methods described in the aforementioned embodiment were... Figure 7 , Figures 9 to 11 Similarly, in one example, constant voltage output is performed sequentially in target voltage modes γ1 to γ6 to maintain a constant output voltage to the motor in the target voltage mode. The duration of the constant voltage output in each of the target voltage modes γ1 to γ6, as well as the interval between the constant voltage output of one target voltage mode and the constant voltage output of the next target voltage mode, are set in the same way as in the first verification.

[0110] Furthermore, in each diagnostic performed in this verification, the current flowing through the motor in the constant voltage output was detected, similar to the aforementioned implementation methods. At this time, the following currents were detected: IUp from the positive semiconductor element (e.g., 5Up) to the U phase of the motor in the constant voltage output of target voltage mode γ1; IWm from the motor to the negative semiconductor element (e.g., 5Wm) in the constant voltage output of target voltage mode γ2; IVp from the positive semiconductor element (e.g., 5Vp) to the V phase of the motor in the constant voltage output of target voltage mode γ3; IUm from the motor to the negative semiconductor element (e.g., 5Um) in the constant voltage output of target voltage mode γ4; IWp from the positive semiconductor element (e.g., 5Wp) to the W phase of the motor in the constant voltage output of target voltage mode γ5; and IVm from the motor to the negative semiconductor element (e.g., 5Vm) in the constant voltage output of target voltage mode γ6.

[0111] Furthermore, the motor temperature T was also measured in this verification. In various diagnostic tests of the power converter, based on the measured motor temperature T and the temperature characteristics of the motor winding resistance, the measured results for currents IUp, IUm, IVp, IVm, IWp, and IWm were corrected in the same manner as in the aforementioned implementation. In this verification, the reference temperature Tref for the motor temperature T was set to 20°C. The measured results for currents IUp, IUm, IVp, IVm, IWp, and IWm were corrected. For the current flowing through the motor in the constant voltage output of each of the target voltage modes γ1 to γ6, information with a temperature T of 20°C was used as correction values ​​(correction information) for calculation.

[0112] Figure 18 The verification results are presented as follows: the correction values ​​of the current detected in the constant voltage output of each of the six target voltage modes γ1 to γ6 are expressed as a function of the number of power cycles. That is, in Figure 18 The diagram shows the relationship between the correction values ​​of the detected currents IUp, IUm, IVp, IVm, IWp, and IWm, relative to the number of power cycles, at a temperature T of 20°C. Figure 18 In the diagram, the horizontal axis represents the number of power cycles (cycle count), and the vertical axis shows the correction value for the current at a temperature T of 20°C. For example... Figure 18 As shown in the figure, this verification confirms that the current flowing through the motor in the constant voltage output of each of the target voltage modes γ1 to γ6 decreases with the increase of the number of power cycles. That is, it confirms that the currents IUp, IUm, IVp, IVm, IWp, and IWm each decrease with the increase of the number of power cycles.

[0113] In addition, such as Figure 18 As shown, after the start of the power cycling test, the decrease in the correction values ​​of currents IUp, IUm, IVp, IVm, IWp, and IWm is relatively small with the increase of the number of power cycles. On the other hand, after a certain number of power cycles, the decrease in the correction values ​​of currents IUp, IUm, IVp, IVm, IWp, and IWm is relatively large with the increase of the number of power cycles. Therefore, it is confirmed that by comparing the changes in the real-time diagnostic information of currents IUp, IUm, IVp, IVm, IWp, and IWm with the information from the previous diagnostic test, the degradation state of the corresponding semiconductor device can be appropriately determined.

[0114] Furthermore, in this verification, after a final diagnostic of the power converter, a fault occurred in the semiconductor element (e.g., 5Vp) on the positive side of phase V. Here, the degradation of the semiconductor element on the positive side of phase V significantly impacts the current flowing through the motor, i.e., the current IVp, in the constant voltage output of the target voltage mode γ3. Figure 18 As shown, in this verification, regarding the current IVp, the correction value of the final diagnosis decreased by approximately 4% compared to the initial diagnosis correction value at the beginning of the power cycle test. Therefore, it is confirmed that, regarding the current flowing through the motor in constant voltage output, by comparing the information from the initial diagnosis with the real-time diagnosis information, the degradation state of the corresponding semiconductor element can be appropriately determined.

[0115] According to at least one of these embodiments or examples, by controlling the operation of multiple semiconductor elements of a power converter, a constant voltage output to the motor is achieved, ensuring a constant output voltage to the motor within a target voltage mode, thereby enabling power output from the power converter to the motor. Furthermore, based on the current flowing through the motor in the constant voltage output from the power converter to the motor, a degradation state is determined for one or more semiconductor elements. Thus, a diagnostic apparatus, diagnostic system, diagnostic method, and diagnostic procedure for a power converter can be provided that appropriately determines the degradation state of semiconductor elements without causing a short-circuit current in the power converter.

[0116] Several embodiments of the present invention have been described, but these embodiments are merely illustrative and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, and are also included in the scope of the invention as set forth in the claims and its equivalents.

Claims

1. A diagnostic device for diagnosing a power converter that drives a motor by outputting converted AC power. Its features are, have: The output control unit controls the operation of multiple semiconductor elements of the power converter to maintain a constant voltage output to the motor in a target voltage mode, thereby enabling power to be output from the power converter to the motor. as well as The degradation determination unit determines the degradation state of one or more semiconductor elements based on the current flowing through the motor in the constant voltage output from the power converter to the motor.

2. The diagnostic device according to claim 1, characterized in that, The output control unit sequentially executes a constant voltage output under multiple target voltage modes, where the applied state to the motor differs from the output voltage from the power converter, to maintain a constant output voltage to the motor under each target voltage mode. The degradation determination unit determines the degradation state of one or more semiconductor elements based on the current flowing through the motor in the constant voltage output of each of the multiple target voltage modes.

3. The diagnostic device according to claim 2, characterized in that, The output control unit sequentially executes the constant voltage output that keeps the output voltage of the motor constant under the target voltage mode in which the external states of the motor and the output voltage from the power converter are different and the number of modes is greater than or equal to the number of semiconductor elements of the power converter.

4. The diagnostic device according to claim 1, characterized in that, The output control unit performs constant voltage output in the target voltage mode during the first period and in each of the second period later than the first period, ensuring that the output voltage to the motor remains constant. The degradation determination unit determines the degradation state of one or more semiconductor elements by comparing the current flowing through the motor in the constant voltage output during the first period with the current flowing through the motor in the constant voltage output during the second period.

5. The diagnostic device according to claim 1, characterized in that, It also has: The calibration unit performs at least one of two calibrations, namely, calibration based on the detection results of the temperature of the motor and information related to the temperature characteristics of the motor winding resistance, for the detection results of the current flowing through the motor in the constant voltage output; and calibration based on the detection results of the ambient temperature of the power converter and information related to the temperature characteristics of the semiconductor element, for the detection results of the current flowing through the motor in the constant voltage output. The degradation determination unit determines the degradation state of one or more semiconductor elements based on the corrected information, which is information corrected according to the detection result regarding the current flowing through the motor in the constant voltage output.

6. The diagnostic device according to claim 1, characterized in that, The degradation determination unit obtains the detection result of the current flowing through the motor in the constant voltage output with a higher resolution than the detection result of the current flowing through the motor in the state where the motor is driven by the AC power from the power converter.

7. The diagnostic device according to claim 1, characterized in that, Before the motor is driven by the AC power from the power converter, the output control unit performs a constant voltage output to keep the output voltage to the motor constant under the target voltage mode. Before the motor is driven by the AC power from the power converter, the degradation determination unit determines the degradation state of one or more semiconductor elements based on the current flowing through the motor in the constant voltage output.

8. A diagnostic system for a power converter, characterized in that, have: The diagnostic device according to any one of claims 1 to 7; The power converter includes a plurality of semiconductor elements, and the operation of each semiconductor element is controlled by the output control unit of the diagnostic device; and The electric motor is driven by the AC power converted by the power converter, which is output from the power converter. The power converter outputs power to the motor by controlling the operation of each of the semiconductor elements by the output control unit to achieve a constant voltage output that keeps the output voltage of the motor constant under the target voltage mode.

9. A diagnostic method for diagnosing a power converter that drives a motor by outputting converted AC power to the motor. Its features are, have: By controlling the operation of multiple semiconductor elements of the power converter, a constant voltage output is achieved to the motor in a target voltage mode, thereby enabling power to be output from the power converter to the motor. The degradation state of one or more semiconductor elements is determined based on the current flowing through the motor in the constant voltage output from the power converter to the motor.

10. A storage medium storing a diagnostic program for diagnosing a power converter that drives a motor by outputting converted AC power. Its features are, The diagnostic procedure enables the computer By controlling the operation of multiple semiconductor elements of the power converter, a constant voltage output is achieved to the motor in a target voltage mode, thereby enabling power to be output from the power converter to the motor. The degradation state of one or more semiconductor elements is determined based on the current flowing through the motor in the constant voltage output from the power converter to the motor.

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