JP2003009541A - Inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately judge the life of a power semiconductor device. SOLUTION: An inverter 1 is mounted on a hybrid car wherein power from a direct-current power supply 4 is supplied to a motor 2 by the inverter 1 and further the engine 3 is driven. In the inverter 1, a power transistor Tr is driven so as to supply a current of a specified value to the motor 2 only for a specified period before the car is driven. When the current of the specified value is supplied to the motor 2 only for the specified period, the value of thermal resistance of the power transistor Tr is computed through an inverter control portion 16. Based on the computed value of thermal resistance, the life of the power transistor Tr is judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device that drives a power semiconductor element to supply power to a load such as a motor.

[0002]

2. Description of the Related Art Conventionally, an inverter for converting a DC power into an AC power and supplying the AC power has been used as a device for driving a motor mounted on a vehicle. This inverter is
On / off control of a power transistor, which is a power semiconductor element, is used to convert DC power from a DC power supply into AC power and supply AC power to, for example, a three-phase AC motor.

The power transistor used in such an inverter generates heat when it is turned on, but is designed so that the heat is not radiated by a heat sink provided in the vicinity and is not destroyed by heat.

However, in this inverter, the heat generated by turning on the power transistor causes thermal stress to be applied to the power transistor, and this thermal stress causes cracks in the solder portion connecting the power transistor and the substrate. When cracks occur in this way, the thermal resistance increases and the amount of heat dissipation decreases, making it impossible to obtain the desired heat dissipation effect. If cracks proceed further, the heat resistance limit of the power transistor will eventually be exceeded. .

In such an inverter, Japanese Unexamined Patent Publication No. Hei 8 (1998)
In Japanese Patent Laid-Open No. 126337, the temperature value of the power transistor is estimated from the current value detected by the current sensor that detects the current supplied to the motor and the temperature of the heat sink provided in the vicinity of the power transistor, and this temperature value change The life of the power transistor was determined by calculating and integrating the thermal stress of the power transistor.

[0006]

However, in the determination of the life by the above-mentioned inverter, the thermal stress is calculated from the estimated temperature of the power transistor, and the thermal stress is added to each power transistor by integrating the thermal stress. Since the life of the power transistor is determined by detecting whether the power has accumulated, it is possible to accurately determine the life by the error due to the integration of thermal stress when there is a large change in the load, such as in electric vehicles that use electric power. There wasn't.

Therefore, the present invention has been proposed in view of the above situation, and an object thereof is to provide an inverter device capable of accurately determining the life of a power semiconductor element.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 converts a DC voltage from a DC power supply into an AC voltage by driving a power semiconductor element on and off, In an inverter device for driving the load by supplying this AC voltage to the load, temperature detecting means for detecting the temperature of the substrate to which the power semiconductor element is bonded, and power for driving the power semiconductor element on / off. A semiconductor element drive means and a thermal resistance of the power semiconductor element when the power semiconductor element is on / off controlled by the power semiconductor drive means so that a current having a predetermined value is supplied to the load for a predetermined period. Based on the thermal resistance calculating means for calculating and the thermal resistance of the power semiconductor element calculated by the thermal resistance calculating means, the life of the power semiconductor element is determined. And a determination unit.

According to a second aspect of the present invention, in the inverter device according to the first aspect, the power semiconductor element driving means has a thermal resistance of the power semiconductor element calculated by the thermal resistance calculating means of a predetermined value or more. In the case of, the current supplied to the load is limited.

According to a third aspect of the invention, the inverter device according to the second aspect further includes an engine for driving the vehicle, and when the current supplied to the load is limited, it corresponds to the limited current. Torque is generated by the engine.

[0011]

According to the invention of claim 1, the temperature detecting means detects the temperature of the substrate to which the power semiconductor element is joined, and the thermal resistance calculating means applies the load to the load for a predetermined period.
The thermal resistance of the power semiconductor element is calculated when the power semiconductor element is controlled to be turned on and off so that a current of a predetermined value is supplied, and the life determining unit calculates the thermal resistance of the power semiconductor element based on the thermal resistance of the power semiconductor element. Since the life of the semiconductor element is determined, the life of the power semiconductor element can be directly determined from the thermal resistance of the semiconductor element, and the life of the power semiconductor element can be accurately determined. Have.

According to the second aspect of the present invention, when the thermal resistance of the power semiconductor element is not less than a predetermined value, the current supplied to the load is limited, so that the life of the power semiconductor element is deteriorated. There is no such thing.

According to the third aspect of the invention, when the current supplied to the load is limited, the engine generates a torque corresponding to the limited current. The vehicle can be stably driven regardless of the life.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

The present invention is applied to an inverter device 1 constructed as shown in FIG. 1, for example. This inverter device 1 is mounted on a hybrid vehicle that uses a motor 2 and an engine 3 as a drive source, and is configured to convert DC power from a DC power supply 4 into AC power to drive the motor 2. An engine control unit 5 and a hybrid system control unit 6 for driving and controlling the engine 3 are connected to the inverter device 1.

In the inverter device 1, for example, when the accelerator operation amount is input to the hybrid system control unit 6, the required motor torque value from the hybrid system control unit 6 based on the accelerator operation amount and the running state of the vehicle is input. A current according to the required motor torque value is supplied to the motor 2 to generate a driving force. The torque request from the hybrid system control unit 6 is also output to the engine control unit 5, and the engine control unit 5 operates the engine 3 according to the torque request to generate a driving force. In addition,
Detailed processing contents of the hybrid system control unit 6 and the engine control unit 5 will be described later.

[Construction of Inverter Device 1] This inverter device 1 includes a smoothing capacitor 11 connected in parallel with a DC power source 4, power transistors Tr1 to Tr6 connected in parallel with a motor 2 and a smoothing capacitor 11, and a power transistor Tr1. To temperature detection diodes D1 to D6 and current feedback diode D11 arranged in the vicinity of Tr6
To D16, the transistor driver 12 connected to the power transistors Tr1 to Tr6, and the power transistor Tr
Current supply line L1 connecting 1 to Tr6 and the motor 2
~ Inverter control unit 1 connected to current detection units 13, 14, 15 and transistor drive unit 12 provided on L3
6 is provided.

The transistor drive unit 12 is connected to the power transistors Tr1 to Tr6 (hereinafter, simply referred to as "power transistors Tr" when collectively referred to), and is also connected to the inverter control unit 16. The transistor drive unit 12 is supplied with a control signal from the inverter control unit 16 and generates and outputs a drive signal for driving the power transistor on / off to control the on / off state of the power transistor Tr.

More specifically, the transistor drive section 12 includes a power transistor Tr1 and a power transistor Tr2.
To control the current supply to the motor 2 via the current supply line L1 by controlling the driving state of the power transistor Tr3 and the power transistor Tr4 to control the driving state of the power transistor Tr4 to the motor 2 via the current supply line L2. The current supply to the motor 2 via the current supply line L3 is controlled by controlling the current supply to the power transistor Tr5 and the drive state of the power transistor Tr6.

Temperature detecting diodes D1 to D6 (hereinafter,
When collectively referred to, they are simply referred to as “temperature detection diode D”. ) Is provided in the vicinity of the power transistor Tr, so that the temperature becomes substantially the same as the temperature at which heat is generated when the current is supplied to the power transistor Tr. The resistance value of the temperature detecting diode D changes according to the temperature thereof, and the current value supplied from the transistor driving unit 12 and supplied to the transistor driving unit 12 is changed. That is, due to the structure of the power transistor Tr, the temperature detection diode D supplies the transistor drive unit 12 with a current according to the transistor junction temperature that is the temperature of the solder layer that joins the power transistor Tr and the pattern.

As a result, the transistor driver 12 is
Based on the current value from the temperature detection diode D, temperature detection information indicating the temperature of the solder joint portion of each power transistor Tr is supplied to the inverter control unit 16.

The inverter control unit 16 includes the current detection unit 1
Current detection information indicating a current value flowing through the current supply lines L1 to L3 is input from 3, 14, and 15, a position detection signal is input from a position detection unit 21 that detects a magnetic pole position of the motor 2, and a transistor drive unit is input. The temperature detection information is input from 12. The inverter control unit 16 outputs a control signal for controlling the drive timing of each power transistor Tr according to each input detection information.
2, the driving force of the motor 2 is controlled. The detailed processing contents of the inverter control unit 16 will be described later.

In this inverter device 1, as shown in a top view of FIG. 2 and a side view of FIG. 3, a solder layer 32, a pattern 33, an insulating plate 34, a pattern 35, and a solder layer are formed on the base plate 31. 36, a power transistor Tr is formed, and a temperature detecting diode D is embedded in the upper end portion of the power transistor Tr. Further, in the inverter device 1, the current feedback diode D is provided on the pattern 35 and in the vicinity of the power transistor Tr.

[Detailed Processing Procedure of Inverter Control Section 16] FIG. 4 shows a processing procedure when the inverter control section 16 controls the inverter to drive the motor 2.

When the driver starts the vehicle and starts the traveling operation, the inverter control section 16 starts the processing from step S1. In step S1, a position detection signal indicating the magnetic pole position is input from the position detection unit 21 that detects the magnetic pole position of the motor 2, so that a current is caused to flow in the motor d axis (magnetic pole direction) without generating torque in the motor 2. The power transistor Tr to be driven is determined, and step S
The process proceeds to 2.

In step S2, the power transistor Tr determined in step S1 is driven as shown in FIG. That is, the power transistor Tr determined in step S1 is driven in a pulsed manner for a predetermined period from time T1 to time T2 to drive the motor 2 to supply a current having a predetermined current value I.

In the next step S3, step S2
Then, the transistor loss P of the power transistor Tr is calculated from the predetermined current value I supplied to the motor 2 via the power transistor Tr, and the process proceeds to step S4.

At this time, the transistor loss P is calculated by the following equation (1) P = Psw + Pf equation (1) Psw: switching loss Pf: steady loss. Here, in this example, in order to obtain the transistor loss P due to one pulse drive, the switching loss P
Since sw is so small that it can be ignored, transistor loss P
Is equivalent to the steady loss Pf, and the transistor loss P is calculated by the following formula (2) P≈Pf = Vce (sat) × I [W] formula (2). Vce in formula (2)
(Sat) is a saturation voltage (voltage when turned on) between the collector and the emitter of the power transistor Tr, and is a value determined to be a constant value by the transistor characteristics when the current is a constant current (predetermined voltage value I).

In step S4, temperature detection information based on the current value from the temperature detection diode D when the power transistor Tr is pulse-driven from time T1 to time T2 in step S3 is input from the transistor drive section 12. , The transistor junction temperature Tj as shown in FIG.
The temperature change width ΔTj, which is the change amount of
The process proceeds to 5.

In step S5, using the transistor loss P calculated in step S3 and the temperature change width ΔTj calculated in step S4, the transient thermal resistance θth (which is the current thermal resistance value of the power transistor Tr determined in step S1 is determined. jw) is calculated and the process proceeds to step S6.
At this time, the transient thermal resistance θth (jw) is calculated by the following equation (3) θth (jw) = ΔTj / P [K / W] equation (3).

In step S6, referring to the table which describes the relationship between the transient thermal resistance θth (jw) and the solder crack area ratio as shown in FIG. 6, from the transient thermal resistance θth (jw) obtained in step S5. The solder crack area ratio is obtained, and it is determined whether or not the solder crack area ratio is equivalent to a predetermined solder crack area ratio and exceeds the life judgment value indicating the life of the power transistor Tr. When it is determined that the transient thermal resistance θth (jw) exceeds the life judgment value, the process proceeds to step S7. When it is determined that the transient thermal resistance θth (jw) does not exceed the life judgment value, the process proceeds to step S13. Proceed.

In step S7, referring to the table that describes the relationship between the transient thermal resistance θth (jw) and the motor torque limit value Tlim as shown in FIG. 7, from the transient thermal resistance θth (jw) obtained in step S5. Then, the motor torque limit value Tlim indicating the limit value of the torque that can be generated by the inverter device 1 is obtained, and the process proceeds to step S8.

In step S8, the motor torque limit value Tlim obtained in step S7 is stored in an internal memory (not shown) and is output to the hybrid system control unit 6 and the process proceeds to step S9.

In step S9, the above-mentioned step S
The control process for determining the life of the power transistor Tr up to 8 is ended, the process proceeds to the travel control process for causing the motor 2 to generate torque to drive the vehicle, and the process proceeds to step S10.

At step S10, the motor torque limit value T is sent to the hybrid system control unit 6 at step S8.
When the motor torque request value Tm, which is a response to the output of lim, is input, the process proceeds to step S11.

In step S11, step S10
By comparing the motor torque request value Tm input in step S8 with the motor torque limit value Tlim stored in step S8, it is determined whether the motor torque limit value Tlim is smaller than the motor torque request value Tm. When it is determined that the motor torque limit value Tlim is smaller than the motor torque request value Tm, the process proceeds to step S12, and when it is determined that the motor torque limit value Tlim is not smaller than the motor motor torque request value Tm, the process proceeds to step S13. Proceed.

In step S12, step S10
According to the motor torque request value Tm input in
When generating the maximum value of the torque that can be generated as the motor torque command value Tm ^* , the motor torque command value Tm ^* is changed to the motor torque limit value Tlim and the process proceeds to step S14.

In step S13, the motor torque command value Tm ^* is set to the motor torque request value Tm input in step S10, and the process proceeds to step S14.

In step S14, step S12
Alternatively, the motor torque command value Tm generated in step S13
^* Is output to the hybrid system control unit 6 and the process proceeds to step S15.

In step S15, step S12
Alternatively, the motor torque command value Tm determined in step S13
^The inverter control is performed by driving the power transistor Tr with ^* to supply current to the motor 2.

Inverter control unit 1 for performing such processing
According to 6, in step S1 before driving the motor 2, by supplying a current of a magnitude that does not generate torque to the motor 2, the transient thermal resistance θth (j-
Since w) can be calculated and the crack progress state of the solder joint can be estimated, the life of the power transistor Tr can be estimated without depending on the integration of thermal stress. Therefore, according to the inverter device 1, the current thermal resistance of the power transistor Tr can be directly calculated, so that the current life of the power transistor Tr can be accurately determined.

Further, according to the inverter control unit 16, the motor torque limit value Tlim supplied to the motor 2 is determined from the transient thermal resistance θth (jw), so that the current supplied to the motor 2 according to the life of the motor 2 is determined. You can adjust the value.

Therefore, according to the inverter control unit 16, even if the life of the power transistor Tr is short, the motor 2 can be stably driven while supplying a current of a magnitude that does not damage the power transistor Tr. It is possible to prevent the power transistor Tr from being unable to be driven while the motor 2 is being driven.

[Detailed Processing Procedure of Hybrid System Control Unit 6] FIG. 8 shows the inverter control unit 1 as described above.
6 shows a processing procedure of the hybrid system control unit 6 when the processing is performed by the control unit 6.

The inverter control unit 16 starts the process of step S21 in response to the inverter control unit 16 performing the process of step S8.
The motor torque limit value Tlim from is input, and the process proceeds to step S22.

In step S22, step S21
The motor torque limit value Tlim input in step S23 is stored in an internal memory (not shown), and the process proceeds to step S23.

In step S23, the control process for determining the life of the power transistor Tr is ended, the process proceeds to the traveling control process for driving the motor 2 and the engine 3 to drive the vehicle, and the process proceeds to step S24.

In step S24, information indicating the running state of the vehicle is input from the outside, and the motor torque request value Tm and the engine torque request value Te indicating the torque amount requested to the engine 3 are calculated according to the running state. , And advances the processing to step S25. The information indicating the running state of the vehicle includes the speed of the vehicle, the number of revolutions of the engine, the accelerator operation amount, and the like.

In step S25, the motor torque request value Tm calculated in step S24 is set to the inverter control unit 1
6 and outputs the engine torque request value Te calculated in step S24 in step S26 to the engine control unit 5
, And the process proceeds to step S27.

In step S27, the motor torque command value Tm ^* calculated in step S12 or step S13 is input and the process proceeds to step S28.

In step S28, step S22
And the motor torque limit value Tlim stored in step S27.
The motor torque command value Tm ^* input in is compared to determine whether the motor torque limit value Tlim is larger than the motor torque command value Tm ^* . Motor torque limit value T
When it is determined that lim is greater than the motor torque command value Tm ^* , the process proceeds to step S29, and when it is determined that the motor torque limit value Tlim is not greater than the motor torque command value Tm ^* , the process proceeds to step S30.

In step S29, in response to the fact that the motor 2 can realize the motor torque request value Tm calculated in step S24, the engine torque request value Te calculated in step S24 is directly used as the engine torque command value Te ^*. The process proceeds to step S34. Then, in step S34, the engine torque command value Te ^* set in step S29 is transmitted to the engine control unit 5, and in step S35, the motor 2 is driven with the torque according to the motor torque command value Tm ^* , and the engine torque command value Te Control is performed to drive the vehicle by driving the engine 3 with a torque according to Te ^* .

On the other hand, in step S30, the motor 2
Is the motor torque command value Tm ^* calculated in step S24 ^.
If it is impossible to realize the above, the engine output possible torque Tep, which is the limit value of the torque that can be generated by the engine 3, is input, and the process proceeds to step S31.

In step S31, step S30
It is determined whether or not the engine output possible torque Tep input in is larger than a value obtained by adding a value obtained by subtracting the motor torque limit value Tlim from the motor torque request value Tm to the engine torque request value Te, and it is determined to be large. If so, the process proceeds to step S32. If it is determined not to be large, the process proceeds to step S33. As a result, it is determined whether or not the engine 3 can generate a shortage of the engine torque command value Te ^* and the required motor torque value Tm.

In step S32, the engine outputtable torque Tep is larger than the value obtained by subtracting the motor torque limit value Tlim from the motor torque request value Tm and adding it to the engine torque request value Te, and the engine 2 can generate the torque. The engine torque command value Te ^* is determined so as to generate an unusable torque in the engine 3, and the process proceeds to step S34. That is, the engine torque command value Te ^* is a value obtained by subtracting the motor torque limit value Tlim from the motor torque request value Tm, and the engine torque request value T
The value added to e is output to the engine control unit 5 in step S34, and the vehicle is controlled to travel in step S35.

In step S33, the torque amount that cannot be generated by the motor 2 cannot be generated by the engine 3. Therefore, the engine torque command value Te ^* is set to the engine output possible torque Tep, and the step S33 is performed.
In step S34, the output is output to the engine control unit 5, and step S
At 35, the vehicle is controlled to run.

[Detailed Processing Procedure of Engine Control Unit 5] FIG. 9 shows a processing procedure of the engine control unit 5 when the hybrid system control unit 6 performs processing as described above.

The engine control unit 5 starts the process of step S41 in response to the hybrid system control unit 6 performing the process of step S26 described above, inputs the engine torque request value Te, and advances the process to step S42. .

In step S42, step S41
The engine torque request value Te input in step 3, information indicating the traveling state from the hybrid system control unit 6, the engine 3
Based on the state, the engine output possible torque Tep is calculated and the process proceeds to step S43.

In step S43, step S42
The engine outputtable torque Tep calculated in step S21 is output to the hybrid system control unit 6, and the process proceeds to step S44.

In step S44, the engine torque command value Te ^* set in the above-described step S29, step S32 or step S33 is input, and the process proceeds to step S45.

In step S45, step S44
The engine control for controlling the torque of the engine 3 is performed on the basis of the engine torque command value Te ^* input in step S4, and the process ends.

[Description of Overall Operation Contents] When the present invention is applied to a hybrid vehicle, the overall processing contents will be described.

First, the control starts when the driver of the vehicle starts the vehicle, and the inverter control unit 16
Thus, the process of determining the life of the power transistor Tr is started. As a result, it is determined whether or not the thermal stress of the power transistor Tr is accumulated and the inverter device 1 has reached the end of its life. When it is determined that the end of the life is reached, the motor torque limit is set so that the power transistor Tr is not damaged even if it is supplied to the motor 2. The value Tlim is calculated and output to the hybrid system control unit 6, and the life determination process is ended.

Next, the hybrid system control section 6 determines the motor torque request value Tm based on the running state of the vehicle.
And an engine torque request value Te are calculated and transmitted to the inverter control unit 16 and the engine control unit 5.

On the other hand, in the inverter controller 16,
The input motor torque request value Tm is compared with the motor torque limit value Tlim. If the motor torque limit value Tlim exceeds the motor torque request value Tm, the motor torque command value Tm ^{* is set} to the motor torque limit value Tlim. Output to the hybrid system control unit 6.

On the other hand, the engine control section 5 calculates the engine output possible torque Tep from the input engine torque request value Te, the running state of the vehicle and the operating state of the engine 3 and outputs it to the hybrid system control section 6.

On the other hand, the hybrid system control unit
6, the motor torque limit value Tlim and the motor torque command
Value Tm^*And the motor torque limit value Tlim is
Data torque command value Tm^*Motor 2 is exceeded
Torque shortage that cannot be generated by the engine
The value obtained by adding the required torque value Te to the engine torque command value T
e^*And output to the engine control unit 5. Where en
Jin torque command value Te ^*Before setting
Consider the value of acquired engine outputtable torque Tep
I shall.

In order to generate a torque for traveling the vehicle, the inverter control unit 16 drives the motor 2 according to the motor torque command value Tm ^* , and the engine control unit 5 drives the engine 2 according to the engine torque command value Te ^*. Drive 3

As a result, even when the life of the power transistor Tr of the inverter device 1 is shortened, the motor 2 is driven by setting the motor torque limit value Tlim based on the life of the power transistor Tr. It is possible to prevent the power transistor Tr from becoming unusable due to the accumulation of the thermal resistance of the power transistor Tr when the torque is generated in 2.

The above-described embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and other than this embodiment, as long as it does not deviate from the technical idea of the present invention, various types according to the design etc. Of course, it is possible to change.

That is, in the above-mentioned example, the example in which the present invention is applied to the hybrid type vehicle in which the vehicle is driven by generating the torque in the motor 2 and the engine 3 has been described, but the torque is generated only in the motor 2. It is needless to say that the present invention can be applied even when driving a vehicle by driving.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a hybrid vehicle including an inverter device to which the present invention is applied.

FIG. 2 is a top view showing a structure near a power transistor.

FIG. 3 is a side view showing a structure near a power transistor.

FIG. 4 is a flowchart showing processing contents by an inverter control unit of an inverter device to which the present invention is applied.

FIG. 5 is a diagram showing a relationship between a current value supplied to a power transistor, a transistor junction temperature, and time.

FIG. 6 Solder crack area ratio and transient thermal resistance θth (jw)
FIG. 6 is a diagram for explaining a life judgment value of a power transistor in the relationship with FIG.

FIG. 7: Transient thermal resistance θth (jw) and motor torque limit value Tl
It is a figure which shows the relationship with im.

FIG. 8 is a flowchart showing the processing contents of a hybrid system control unit.

FIG. 9 is a flowchart showing the processing contents of an engine control unit.

[Explanation of symbols]

1 Inverter device 2 motor 3 engine 4 DC power supply 5 Engine control section 6 Hybrid system controller 11 Smoothing capacitor 12 Transistor driver 13, 14, 15 Current detector 21 Position detector 31 base plate 32,36 Solder layer 33 patterns 34 Insulation plate 35 patterns

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5H007 AA17 BB06 CA01 CB02 CB05                       CC07 DB02 DB03 DC02 DC08                       FA03 FA13 FA18 HA03                 5H115 PA08 PG04 PI16 PU11 PU21                       PV09 PV23 SE10 TO05 TO12                       TR02 TU11

Claims (3)

[Claims] 1. An inverter device for converting a DC voltage from a DC power supply into an AC voltage by driving a power semiconductor element on and off and supplying this AC voltage to a load to drive the load, Temperature detecting means for detecting the temperature of the substrate to which the power semiconductor element is joined, power semiconductor element driving means for driving the power semiconductor element on and off, and a current of a predetermined value is supplied to the load for a predetermined period. And a thermal resistance calculating means for calculating a thermal resistance of the power semiconductor element when the power semiconductor element is on / off controlled by the power semiconductor driving means, and the power semiconductor calculated by the thermal resistance calculating means. An inverter device comprising: a life determining unit that determines the life of the power semiconductor element based on the thermal resistance of the element. 2. The inverter device according to claim 1, wherein the power semiconductor element driving means is configured to: when the thermal resistance of the power semiconductor element calculated by the thermal resistance calculating means is equal to or more than a predetermined value. An inverter device characterized by limiting a current supplied to a load. 3. The inverter device according to claim 2, further comprising an engine that drives a vehicle, and when the current supplied to the load is limited, a torque corresponding to the limited current is generated by the engine. An inverter device characterized by being generated.