阅读说明：本技术 电动机驱动装置 (Motor driving device ) 是由 黑木渉 于 2019-08-09 设计创作，主要内容包括：电动机驱动装置(1)具备：交流稳定化电源装置(11)，其将商用交流电源(2)的交流电压变换为与接收到的电压指令值相应的输入电源电压后输出；转换器(12)，其将输入电源电压变换为直流电压后输出到直流环节；逆变器(13)，其将直流环节中的直流电压变换为用于驱动电动机的交流电压后输出；以及输入电源电压控制部(15)，其对交流稳定化电源装置(11)输出的输入电源电压进行控制。(A motor drive device (1) is provided with: an AC stabilization power supply device (11) which converts the AC voltage of the commercial AC power supply (2) into an input power supply voltage corresponding to the received voltage command value and outputs the converted voltage; a converter (12) for converting an input power supply voltage into a DC voltage and outputting the DC voltage to a DC link; an inverter (13) for converting the DC voltage in the DC link into an AC voltage for driving the motor and outputting the AC voltage; and an input power supply voltage control unit (15) that controls the input power supply voltage output by the AC stabilized power supply device (11).)

1. A motor drive device is provided with:

an ac stabilizing power supply device that converts an ac voltage of a commercial ac power supply into an input power supply voltage and outputs the converted input power supply voltage;

a converter which converts the input power supply voltage into a direct current voltage and outputs the direct current voltage to a direct current link;

an inverter for converting the dc voltage in the dc link into an ac voltage for driving the motor and outputting the ac voltage; and

and an input power supply voltage control unit that controls the input power supply voltage output by the ac stabilized power supply device.

2. The motor drive device according to claim 1,

further comprising a temperature acquisition unit for acquiring a temperature of at least one of the converter and the inverter,

the input power supply voltage control unit controls the input power supply voltage output by the ac stabilized power supply device according to the temperature acquired by the temperature acquisition unit.

3. The motor drive device according to claim 2,

the input power supply voltage control unit generates a voltage command value for controlling the input power supply voltage output by the ac stabilized power supply device based on the temperature acquired by the temperature acquisition unit, and transmits the voltage command value to the ac stabilized power supply device,

the ac stabilization power supply device converts an ac voltage of the commercial ac power supply into an input power supply voltage corresponding to the voltage command value received from the input power supply voltage control unit and outputs the converted voltage.

4. The motor drive device according to claim 3,

the input power supply voltage control unit generates the voltage command value for causing the ac stabilization power supply device to output an input power supply voltage higher than an input power supply voltage to be originally output, in place of the input power supply voltage to be originally output, when the temperature of the inverter acquired by the temperature acquisition unit is lower than a preset inverter lower limit temperature threshold value,

the input power supply voltage control unit generates the voltage command value for causing the ac stabilization power supply device to output an input power supply voltage lower than an input power supply voltage to be originally output, instead of the input power supply voltage to be originally output, when the temperature of the inverter exceeds an inverter upper limit temperature threshold value which is set in advance to a value larger than the inverter lower limit temperature threshold value,

the input power supply voltage control unit generates the voltage command value for maintaining the input power supply voltage that the ac stabilized power supply device is outputting, when the temperature of the inverter is between the inverter lower limit temperature threshold and the inverter upper limit temperature threshold.

5. The motor drive device according to claim 3,

the input power supply voltage control unit generates the voltage command value for causing the ac stabilized power supply device to output an input power supply voltage lower than an input power supply voltage to be originally output, in place of the input power supply voltage to be originally output, when the temperature of the converter acquired by the temperature acquisition unit is lower than a preset converter lower limit temperature threshold,

the input power supply voltage control unit generates the voltage command value for causing the ac stabilized power supply device to output an input power supply voltage higher than an input power supply voltage to be originally output, in place of the input power supply voltage to be originally output, when the temperature of the converter exceeds a converter upper limit temperature threshold value which is set in advance to a value larger than the converter lower limit temperature threshold value,

the input power supply voltage control unit generates the voltage command value for maintaining the input power supply voltage that the ac stabilized power supply device is outputting, when the temperature of the converter is between the converter lower limit temperature threshold and the converter upper limit temperature threshold.

6. The motor drive device according to claim 3,

the input power supply voltage control unit generates the voltage command value for causing the ac stabilization power supply device to output an input power supply voltage lower than an input power supply voltage to be originally output, in place of the input power supply voltage to be originally output, when the difference between the temperature of the inverter and the temperature of the converter acquired by the temperature acquisition unit is outside a preset temperature difference range and the temperature of the inverter is higher than the temperature of the converter,

the input power supply voltage control unit generates the voltage command value for causing the ac stabilized power supply device to output an input power supply voltage higher than an input power supply voltage to be originally output, in place of the input power supply voltage to be originally output, when the difference between the temperature of the inverter and the temperature of the converter acquired by the temperature acquisition unit is outside the temperature difference range and the temperature of the inverter is lower than the temperature of the converter.

7. The motor drive device according to claim 6,

the input power supply voltage control unit generates the voltage command value for maintaining the input power supply voltage that the ac stabilized power supply device is outputting, when a difference between the temperature of the inverter and the temperature of the converter is within the temperature difference range.

8. The motor drive device according to claim 6,

in the case where the difference between the temperature of the inverter and the temperature of the converter is within the temperature difference range and the temperature of the inverter is between a preset inverter lower limit temperature threshold value and an inverter upper limit temperature threshold value that is preset to a value greater than the inverter lower limit temperature threshold value,

alternatively, when the difference between the temperature of the inverter and the temperature of the converter is within the temperature difference range and the temperature of the converter is between a preset converter lower limit temperature threshold and a converter upper limit temperature threshold preset to a value greater than the converter lower limit temperature threshold,

the input power supply voltage control unit generates the voltage command value for maintaining the input power supply voltage that the ac stabilized power supply device is outputting.

9. The motor drive device according to claim 8,

further comprising an inverter load control unit that, when a difference between the temperature of the inverter and the temperature of the converter is within the temperature difference range, the temperature of the inverter is lower than the inverter lower limit temperature threshold, and the temperature of the converter is lower than the converter lower limit temperature threshold, the inverter load control unit further increases the load borne by the inverter, when the difference between the temperature of the inverter and the temperature of the converter is within the temperature difference range and the temperature of the inverter exceeds the inverter upper limit temperature threshold value, or when the difference between the temperature of the inverter and the temperature of the converter is within the temperature difference range and the temperature of the converter exceeds the converter upper limit temperature threshold value, the inverter load control unit further reduces the load on the inverter.

10. The motor drive device according to claim 9,

the inverter load control unit increases the load on the inverter by changing the PWM frequency used for PWM switching control of the power elements in the inverter to a higher PWM frequency, and decreases the load on the inverter by changing the PWM frequency to a lower PWM frequency.

11. The motor drive device according to claim 9,

the inverter load control unit increases the load on the inverter by controlling the ac voltage output from the inverter so that the output of the electric motor becomes a larger output, and decreases the load on the inverter by controlling the ac voltage output from the inverter so that the output of the electric motor becomes a smaller output.

Technical Field

The present invention relates to a motor drive device having an input power supply voltage adjustment function.

Background

In a motor driving device for driving a motor in a machine tool, a forging press machine, an injection molding machine, an industrial machine, or various robots, ac power supplied from an ac power supply is converted into dc power by a converter (rectifier) and output to a dc link, the dc power in the dc link is converted into ac power by an inverter, and the ac power is supplied as driving power to a motor provided for each drive shaft.

An inverter for supplying driving power to a motor in a motor driving device includes a bridge circuit including a power element (semiconductor switching element) and a diode connected in anti-parallel with the power element. The inverter converts an input dc voltage (i.e., a dc voltage in the dc link) into an ac voltage for driving the motor by turning on and off a power element in the inverter based on a switching command received from the motor control unit. In addition, a diode rectifier is widely used as a converter for converting (rectifying) an input power supply voltage into a dc voltage and outputting the dc voltage to a dc link in a motor drive device, but in recent years, a PWM control type converter capable of returning regenerative power generated at the time of motor deceleration to an ac power supply side has been used. A converter of the PWM control type includes a bridge circuit of a power element and a diode connected in inverse parallel thereto.

When the motor is driven by the motor driving device, the converter, the inverter, and the motor generate heat due to currents flowing through the converter, the inverter, and the motor. In addition, in the inverter and the converter of the PWM control method, heat generation due to the switching operation of the power element is also generated. The heat generation of the converter, the inverter, and the motor causes a reduction in the power factor of the motor drive device and a malfunction, which leads to a damage and a reduction in the life of the motor drive device and various peripheral devices. Therefore, various measures against heat generation are taken when the motor drive device is operated.

For example, as described in japanese patent application laid-open No. 2015-167436, a numerical controller provided with a cooling function and provided with a motor drive device that drives at least 1 motor is known, the numerical controller including: a temperature acquisition unit that acquires, from a temperature detector provided in the motor drive device, a temperature of a component located in a motor unit of the motor drive device; an ambient temperature acquisition unit that acquires an ambient temperature of a motor unit of the motor drive device from a temperature detector provided in the motor drive device; an input energy acquisition unit that acquires input energy input to the component; an output energy acquisition unit that acquires output energy output from the component; a heat dissipation characteristic estimation unit that estimates a heat dissipation characteristic of the component based on a temperature of the component, the ambient temperature, the input energy, and the output energy; and a heat radiation characteristic output unit that outputs the estimated heat radiation characteristic of the component as a normality/abnormality determination signal of the cooling function.

For example, as described in japanese patent application laid-open No. 2009-261078, there is known a motor control device including: a converter that converts an alternating-current voltage into a direct-current voltage; an inverter that converts the dc voltage into an ac voltage to drive a motor; a speed control unit that generates a torque command based on the speed command and the motor speed; a torque control unit that generates a PWM signal based on the torque command and a motor current to drive an inverter; a current detection unit that detects the motor current; an inverter temperature detection unit that detects a temperature of the inverter and generates an inverter temperature signal; and an overload protection unit that generates a torque limit signal based on a motor temperature signal, the inverter temperature signal, the motor current, and the motor speed, wherein the overload protection unit includes: a power element loss estimation unit that generates a power element estimation loss of the inverter from the motor current; a junction temperature estimating unit that estimates a junction temperature based on the power element estimated loss and the inverter temperature; a motor loss estimation unit that estimates a motor loss from the motor current and the motor speed; a coil temperature estimating unit that estimates a coil temperature from the motor estimated loss and the motor temperature signal; and an overload processing unit that generates a torque limit signal or an alarm signal based on the estimated junction temperature and the estimated coil temperature.

For example, as described in japanese patent application laid-open No. 02-138084, there is known an elevator emergency operation method at the time of power failure, which is suitable for improving riding comfort during emergency rescue operation.

Disclosure of Invention

The heat generation of the converter, the inverter, and the motor in the motor drive device causes a decrease in the power factor of the motor drive device and a malfunction, and causes damage to the motor drive device and various peripheral devices and a reduction in the life. For example, the larger the voltage at the dc link between the converter and the inverter in the motor drive device (hereinafter simply referred to as "dc link voltage"), the larger the output of the motor can be made, but the switching loss of the inverter increases, and therefore the heat generation of the inverter becomes large. For example, when the motor is driven while maintaining a fixed motor output, the higher the dc link voltage in the motor driving device, the less the current flowing through the converter and the motor, and therefore the heat generation can be suppressed. On the other hand, when the motor is driven while maintaining a fixed motor output, the lower the dc link voltage in the motor driving device, the smaller the heat generation of the inverter, and the higher the actual resolution of the voltage command to the inverter, so that the motor can be controlled with high accuracy. Therefore, in the motor driving device, a technique capable of efficiently controlling the motor while suppressing heat generation of each part is desired.

According to one aspect of the present disclosure, a motor drive device includes: an ac-stabilized power supply device that converts an ac voltage of a commercial ac power supply into an input power supply voltage corresponding to a received voltage command value and outputs the converted voltage; a converter which converts an input power voltage into a direct current voltage and outputs the direct current voltage to a direct current link; an inverter for converting the dc voltage in the dc link into an ac voltage for driving the motor and outputting the ac voltage; a temperature acquisition unit that acquires a temperature of at least one of the converter and the inverter; and an input power supply voltage control unit that controls the input power supply voltage output by the ac stabilized power supply device according to the temperature acquired by the temperature acquisition unit.

Drawings

The present invention will be more clearly understood by reference to the following drawings.

Fig. 1 is a diagram showing a motor drive device according to a first embodiment of the present disclosure.

Fig. 2 is a diagram illustrating a relationship among an input power supply voltage of the converter, a temperature of the inverter, and a temperature of the motor.

Fig. 3 is a flowchart showing a first mode of input power supply voltage control in the motor drive device according to the first embodiment of the present disclosure.

Fig. 4 is a flowchart showing a second mode of input power supply voltage control in the motor drive device of the first embodiment of the present disclosure.

Fig. 5 is a flowchart showing a third mode of input power supply voltage control in the motor drive device according to the first embodiment of the present disclosure.

Fig. 6 is a diagram showing a motor drive device according to a second embodiment of the present disclosure.

Fig. 7 is a flowchart showing input power supply voltage control in the motor drive device of the second embodiment of the present disclosure.

Detailed Description

A motor drive device having an input power supply voltage adjustment function will be described below with reference to the drawings. The drawings are appropriately modified in scale for easy understanding. The embodiment shown in the drawings is an example for implementation and is not limited to the illustrated embodiment.

Fig. 1 is a diagram showing a motor drive device according to a first embodiment of the present disclosure.

As an example, the following will be explained: 1 ac motor (hereinafter, simply referred to as "motor") 3 is controlled by a motor drive device 1 connected to a commercial ac power supply 2. The number of the motors 3 is not particularly limited to the present embodiment, and may be other numbers. The number of phases of the commercial ac power supply 2 and the motor 3 is not particularly limited to this embodiment, and may be, for example, three phases or a single phase. Examples of the commercial ac power supply 2 include a three-phase ac 400V power supply, a three-phase ac 200V power supply, a three-phase ac 600V power supply, and a single-phase ac 100V power supply. The type of the motor 3 is not particularly limited to the present embodiment, and may be, for example, an induction motor or a synchronous motor. Here, the machine provided with the motor 3 includes, for example, a machine tool, a robot, a forging machine, an injection molding machine, an industrial machine, various electric appliances, an electric car, an automobile, an airplane, and the like.

As shown in fig. 1, the motor drive device 1 of the present embodiment includes an ac stabilization power supply device 11, a converter 12, an inverter 13, a temperature acquisition unit 14, an input power supply voltage control unit 15, and a motor control unit 20. In the illustrated example, the input power supply voltage control unit 15 and the motor control unit 20 are provided in the control device 100. The control device 100 may be, for example, a numerical controller of a machine tool.

Further, the motor control unit 20 in the motor drive device 1 controls the inverter 13 in the same manner as in a general motor drive device, and the inverter 13 performs power conversion between the dc power in the dc link and the ac power which is the drive power or the regenerative power of the motor 3. That is, the motor control unit 20 generates a switching command for controlling the speed and torque of the motor 3 or the position of the rotor based on the speed of the motor 3 (speed feedback), the current flowing through the winding of the motor 3 (current feedback), a predetermined torque command, an operation program of the motor 3, and the like. The power conversion operation of the inverter 13 is controlled based on the switching command generated by the motor control unit 20. The motor control unit 20 controls the opening and closing operations of the electromagnetic contactor 25.

The ac stabilizing power supply device 11 converts the ac voltage of the commercial ac power supply 2 into an input power supply voltage corresponding to the received voltage command value and outputs the converted voltage. Generally, the value and waveform of the ac voltage obtained from the commercial ac power supply 2 are affected by various loads connected to the power supply line, the impedance of the power supply line itself, and the like. In contrast, even if the value or waveform of the input ac voltage varies, the ac stabilizing power supply device 11 can output a stable ac voltage conforming to the voltage command value while eliminating the influence of the variation. In the present embodiment, the ac stabilizing power supply device 11 is provided between the commercial ac power supply 2 and the converter 12, and the ac voltage output from the ac stabilizing power supply device 11 is used as the input power supply voltage to be input to the converter 12. The ac voltage output from the ac stabilizing power supply device 11 (i.e., the input power supply voltage input to the converter 12) is controlled by an input power supply voltage control unit 15 described later. That is, the ac stabilizing power supply device 11 converts the ac voltage input from the commercial ac power supply 2 into an ac voltage corresponding to the voltage command value received from the input power supply voltage control unit 15 based on the voltage command value received from the input power supply voltage control unit 15 and the input power supply voltage detected by the input power supply voltage detection unit 24, and outputs the ac voltage as the input power supply voltage input to the converter 12. Therefore, the converter 12 receives a supply of a stable input power supply voltage corresponding to the voltage command value from the ac stabilizing power supply device 11. Specific examples of the AC-stabilized power supply device 11 include an AC stabilizer (AVR) and a frequency converter (CVCF). As the AC stabilizer, there are an AC stabilizer of a tap switching method including a multi-tap transformer and a semiconductor switch, an AC stabilizer of a sliding transformer method including a sliding transformer (japanese: スライダック) and a servo motor, an AC stabilizer of a phase control method including a semiconductor switch and a resonant circuit, and an AC stabilizer of a linear amplifier method. As the frequency converter, there are an inverter type frequency converter, a linear amplifier type frequency converter, and the like. Examples of the range of the ac voltage that can be generated by the ac stabilization power supply device 11 include a range of 200V to 240V and a range of 380V to 480V.

The converter 12 converts an input power supply voltage supplied from the ac stabilized power supply device 11 into a dc voltage and outputs the dc voltage to the dc link. Converter 12 includes ac/dc conversion unit 21, input power supply voltage detection unit 24, and temperature acquisition unit 14. Although input power supply voltage detection unit 24 is provided in converter 12 in fig. 1 as an example, it may be provided outside converter 12.

The ac/dc converter 21 in the converter 12 may be any converter capable of converting ac power into dc power, and examples thereof include a diode rectifier circuit, a 120-degree conduction rectifier circuit, and a PWM switching control type rectifier circuit including a switching element therein. When the input power supply voltage is a three-phase voltage, the ac/dc converter 21 is configured as a three-phase bridge circuit, and when the input power supply voltage is a single-phase voltage, the ac/dc converter 21 is configured as a single-phase bridge circuit. When the ac/dc converter 21 is a rectifier circuit of a PWM switching control system, it includes a bridge circuit including a power element and a diode connected in inverse parallel thereto. In this case, the power elements include IGBTs, thyristors, GTOs (gate turn-OFF thyristors), SiC (silicon carbide), transistors, and the like, but the kind of the power element itself is not limited to this embodiment, and other power elements may be used.

The input power supply voltage detection unit 24 detects the value of the input power supply voltage (i.e., the ac voltage output from the ac stabilization power supply device 11) input to the converter 12. The value of the input power supply voltage detected by the input power supply voltage detection unit 24 is transmitted to the input power supply voltage control unit 15 to be used for control of the ac stabilization power supply device 11, and is also transmitted to the motor control unit 20 to be used for power conversion control of the ac/dc conversion unit 21 in the converter 12 and power conversion control of the dc/ac conversion unit 22 in the inverter 13.

An electromagnetic contactor 25 and an ac reactor 26 are connected to the ac input side of the converter 12. The electromagnetic contactor 25 opens and closes an electric circuit connecting the ac stabilization power supply device 11 and the converter 12 in accordance with a command received from the motor control unit 20. That is, the closing operation for electrically connecting the ac stabilization power supply device 11 and the converter 12 is performed by closing the contacts of the electromagnetic contactor 25, and the opening operation for electrically disconnecting the ac stabilization power supply device 11 and the converter 12 is performed by separating the contacts of the electromagnetic contactor 25. Note that, for example, a relay, a power semiconductor switching element, or the like may be used instead of the electromagnetic contactor 25 as long as the flow of ac power from the ac stabilization power supply device 11 to the converter 12 can be cut off when the close command is received from the motor control unit 20.

The dc output side of the converter 12 and the dc input side of the inverter 13 are connected in parallel via a dc link. A dc link capacitor 23 is provided in the dc link. The dc-link capacitor 23 has a function of suppressing a ripple component of the dc voltage output from the converter 12 and a function of accumulating the dc power in the dc link. Examples of the dc link capacitor 23 include an electrolytic capacitor and a film capacitor. The dc link voltage is used for controlling the inverter 13 by the motor control unit 20, and a detection unit for detecting the dc link voltage is not shown in fig. 1.

The inverter 13 converts the dc voltage in the dc link into an ac voltage for driving the motor and outputs the ac voltage. The inverter 13 includes a dc/ac conversion unit 22 and a temperature acquisition unit 14.

The dc/ac conversion unit 22 in the inverter 13 may be any one as long as it can convert dc power into ac power, and for example, there is a PWM inverter circuit having switching elements therein. When the motor 3 is a three-phase ac motor, the dc/ac conversion unit 22 is configured as a three-phase bridge circuit, and when the motor 3 is a single-phase motor, the dc/ac conversion unit 22 is configured as a single-phase bridge circuit. The dc/ac conversion unit 22 receives a command from the motor control unit 20, converts the dc voltage in the dc link into an ac voltage for driving the motor, and outputs the ac voltage to the motor 3, and converts the ac voltage regenerated by the motor 3 into a dc voltage at the time of motor regeneration, and returns the dc voltage to the dc link side. When the dc/ac converter 22 is formed of a PWM inverter circuit, it includes a bridge circuit including a power element and a diode connected in anti-parallel with the power element. In this case, the power element may be an IGBT, a thyristor, a GTO (Gate Turn-off thyristor), SiC (silicon carbide), a transistor, or the like, but the type of the power element itself is not limited to this embodiment, and other power elements may be used.

The temperature acquisition unit 14 acquires the temperature of at least one of the converter 12 and the inverter 13. In the example shown in fig. 1, the temperature acquisition unit 14 is provided in both the converter 12 and the inverter 13, and the temperature acquisition unit 14 acquires both the temperature of the converter 12 and the temperature of the inverter 13, but either one of the temperature acquisition units 14 may be omitted in accordance with a control example of the input power supply voltage to be described later.

The temperature acquisition unit 14 is constituted by a temperature sensor, for example. The temperature sensor as the temperature acquisition unit 14 is provided, for example, in the vicinity of the power element or the radiator in the ac/dc conversion unit 21 in the converter 12, and detects the temperature of the converter 12. The detected temperature of converter 12 is sent to input power supply voltage control unit 15. Similarly, the temperature sensor as the temperature acquisition unit 14 is provided in the vicinity of the power element or the radiator in the dc/ac conversion unit 22 in the inverter 13, for example, and detects the temperature of the inverter 13. The detected temperature of converter 12 is sent to input power supply voltage control unit 15. As the temperature sensors provided in the converter 12 and the temperature acquisition unit 14 in the inverter 13, a plurality of temperature sensors may be provided in the vicinity of the power element or the vicinity of the radiator, or only 1 temperature sensor may be provided. For example, when a plurality of temperature sensors are provided in the converter 12, a plurality of temperatures are detected, but the highest temperature of the plurality of detected temperatures may be the temperature of the converter 12 acquired by the temperature acquisition unit 14. Similarly, for example, in the case where a plurality of temperature sensors are provided in the inverter 13, a plurality of temperatures are detected, but the highest temperature among the plurality of detected temperatures may be the temperature of the inverter 13 acquired by the temperature acquisition unit 14.

Alternatively, instead of acquiring the temperature of the converter 12 and/or the inverter 13 through actual measurement by the temperature sensor, the temperature of the converter 12 and/or the inverter 13 may be acquired through estimation by software simulation. In this case, the function of the temperature acquisition unit 14 is realized by causing an arithmetic processing device such as an MPU or a DSP to execute a temperature estimation program. The temperature acquisition unit 14 based on the temperature estimation program is provided in, for example, an arithmetic processing device in the control device 100 or an arithmetic processing device in an external computer (not shown). For example, the correspondence relationship or the calculation formula between the content of the switching operation of each power element in the converter 12 and/or the inverter 13 and the temperature (or the temperature increase rate) is predetermined in the temperature estimation program, the operation processing device as the temperature acquisition unit 14 acquires the switching command actually output from the motor control unit 20, and the temperature of the converter 12 and/or the inverter 13 is estimated based on the temperature estimation program.

The input power supply voltage control unit 15 controls "the input power supply voltage to the converter 12" output from the ac stabilized power supply device 11 based on the temperature acquired by the temperature acquisition unit 14. Therefore, the input power supply voltage control unit 15 generates a voltage command value for controlling the input power supply voltage output from the ac stabilizing power supply device 11 based on the temperature acquired by the temperature acquisition unit 14, and transmits the voltage command value to the ac stabilizing power supply device 11. In the illustrated example, the input power supply voltage control unit 15 is provided in the control device 100, but may be provided in an arithmetic processing device outside the control device 100.

Here, a relationship among the input power supply voltage of the converter 12, the temperature of the inverter 13, and the motor 3 will be described.

Fig. 2 is a diagram illustrating a relationship among an input power supply voltage of the converter, a temperature of the inverter, and a temperature of the motor.

When the motor 3 is driven with a fixed output by the motor driving device 1, if the input power supply voltage of the converter 12 is increased, the dc link voltage (i.e., the input/output voltage peak value × √ 2 in the case where the ac/dc conversion unit 21 in the converter 12 is a full-wave rectifier circuit) increases, and the current flowing through the converter 12 and the current flowing through the motor 3 decrease. As a result, the temperature of the converter 12 and the temperature of the motor 3 decrease. On the other hand, the switching loss of the inverter 13 increases due to the increase of the dc link voltage, and the temperature of the inverter 13 increases. In addition, although the motor 3 is driven with a fixed output, when the input power supply voltage of the converter 12 is raised to drive the motor 3, the inverter 13 converts the high dc-link voltage into an ac voltage for driving the motor 3, and therefore the ac voltage becomes higher and the output of the motor 3 becomes large.

In the case where the motor 3 is driven with a fixed output by the motor driving device 1, when the input power supply voltage of the converter 12 is lowered, the dc link voltage becomes low, and the current flowing through the converter 12 and the current flowing through the motor 3 increase. As a result, the temperature of the converter 12 and the temperature of the motor 3 increase. On the other hand, the dc link voltage decreases, which reduces the switching loss of the inverter 13 and lowers the temperature of the inverter 13. Further, since the inverter 13 converts such a low dc link voltage into an ac voltage for driving the motor 3 so as to maintain the output of the motor 3 constant, the actual resolution of the voltage command to the inverter 13 is improved, and therefore the motor 3 can be controlled with high accuracy.

As described above, the respective temperatures of the converter 12, the inverter 13, and the motor 3 fluctuate in accordance with an increase and a decrease in the input power supply voltage of the converter 12, and the magnitude of the output of the motor 3 and the accuracy of control of the motor 3 fluctuate. Therefore, in the present embodiment, the input power supply voltage of the converter 12 is supplied from the ac stabilization power supply device 11 that can output an ac voltage in accordance with a command, and the temperature of the converter 12, the inverter 13, and/or the motor 3 is controlled by controlling the input power supply voltage. That is, the input power supply voltage control unit 15 in the present embodiment controls the input power supply voltage, which is output from the ac stabilizing power supply device 11 and is input to the converter 12, in accordance with the temperature of the converter 12 and/or the inverter 13 acquired by the temperature acquisition unit 14.

How to raise and lower the input power supply voltage of the converter 12 may be set as appropriate according to the use of the motor drive device 1, the surrounding environment, and the like. For example, the control content of the input power supply voltage of the converter 12 is determined according to how to control the respective temperatures of the converter 12 and the inverter 13, whether the motor 3 is required to perform a large output, whether high-precision motor control is required, and the like. Next, an example of controlling the input power supply voltage of converter 12 will be described.

First, a first mode of control of the input power supply voltage of the converter 12 will be described. In the first aspect, the input power supply voltage of the converter 12 is controlled so that the temperature of the inverter 13 can be increased as much as possible. According to the first aspect, the output of the motor 3 can be increased while preventing excessive heat generation of the inverter 13. Fig. 3 is a flowchart showing a first mode of input power supply voltage control in the motor drive device according to the first embodiment of the present disclosure.

In the motor drive device 1 of the present embodiment, when the electromagnetic contactor 25 is closed to electrically connect the ac stabilization power supply device 11 and the converter 12, and the motor control unit 20 controls the power conversion operation of the converter 12 and the inverter 13 to drive the motor 3, the temperature acquisition unit 14 acquires the temperature of the inverter 13 in step S101. The acquired temperature of inverter 13 is notified to input power supply voltage control unit 15.

In step S102, the input power supply voltage control unit 15 determines whether or not the temperature of the inverter 13 acquired by the temperature acquisition unit 14 is lower than a preset inverter lower limit temperature threshold. The process proceeds to step S103 when it is determined that the temperature of the inverter 13 is lower than the inverter lower limit temperature threshold, and proceeds to step S105 when it is not determined that the temperature of the inverter 13 is lower than the inverter lower limit temperature threshold. The inverter lower limit temperature threshold may be set to a value smaller than an inverter upper limit temperature threshold described later. The difference between the inverter upper limit temperature threshold and the inverter lower limit temperature threshold is the hysteresis width of the temperature of the inverter 13.

When it is determined in step S102 that the temperature of the inverter 13 is lower than the inverter lower limit temperature threshold, the input power supply voltage control unit 15 controls the ac stabilizing power supply device 11 to output an input power supply voltage higher than the current input power supply voltage in step S103. That is, the input power supply voltage control unit 15 generates a voltage command value for causing the ac stabilizing power supply device 11 to output a higher input power supply voltage instead of the input power supply voltage output by the ac stabilizing power supply device 11 before, and outputs the voltage command value to the ac stabilizing power supply device 11. Thus, the ac stabilization power supply device 11 supplies the converter 12 with an input power supply voltage higher than the input power supply voltage outputted immediately before. As described with reference to fig. 2, the input power supply voltage of the converter 12 increases, so that the dc link voltage increases, and the output of the motor 3 increases. However, the switching loss of the inverter 13 increases due to the increase of the dc link voltage, and the temperature of the inverter 13 increases (step S104). On the other hand, the current flowing through the converter 12 and the current flowing through the motor 3 decrease, and the temperature of the converter 12 and the temperature of the motor 3 decrease. After step S104, the process returns to step S101 again.

If it is not determined in step S102 that the temperature of the inverter 13 is lower than the inverter lower limit temperature threshold value, the process proceeds to step S105.

In step S105, the input power supply voltage control unit 15 determines whether or not the temperature of the inverter 13 acquired by the temperature acquisition unit 14 exceeds a preset inverter upper limit temperature threshold. If it is determined that the temperature of the inverter 13 exceeds the inverter upper limit temperature threshold value, the process proceeds to step S106, and if it is not determined that the temperature of the inverter 13 exceeds the inverter upper limit temperature threshold value, the process returns to step S101. The inverter upper limit temperature threshold value may be set to a temperature at which damage to the inverter 13 or a reduction in the life of the inverter 13 due to heat generation is not caused, a temperature at which malfunction (thermal runaway) of the inverter 13 is not caused, or the like.

If it is not determined in step S105 that the temperature of the inverter 13 exceeds the inverter upper limit temperature threshold, the input power supply voltage control unit 15 generates a voltage command value for maintaining the input power supply voltage currently being output by the ac stabilization power supply device 11, and outputs the voltage command value to the ac stabilization power supply device 11. Thereafter, the process returns to step S101.

On the other hand, when it is determined in step S105 that the temperature of the inverter 13 exceeds the inverter upper limit temperature threshold, the input power supply voltage control unit 15 controls the ac stabilizing power supply device 11 to output an input power supply voltage lower than the current input power supply voltage in step S106. That is, the input power supply voltage control unit 15 generates a voltage command value for causing the ac stabilizing power supply device 11 to output a lower input power supply voltage instead of the input power supply voltage output by the ac stabilizing power supply device 11 before, and outputs the voltage command value to the ac stabilizing power supply device 11. Thus, the ac stabilization power supply device 11 supplies the converter 12 with an input power supply voltage lower than the input power supply voltage outputted immediately before. As described with reference to fig. 2, the input power supply voltage of the converter 12 decreases, so that the dc link voltage decreases, and the switching loss of the inverter 13 decreases due to the decrease in the dc link voltage, thereby decreasing the temperature of the inverter 13 (step S107). Thereby, the temperature of the inverter 13 no longer exceeds the inverter upper limit temperature threshold. Therefore, damage to the inverter 13 and reduction in the life due to heat generation can be avoided. In addition, the inverter 13 does not malfunction (thermal runaway). On the other hand, the current flowing through the converter 12 and the current flowing through the motor 3 increase, and the temperature of the converter 12 and the temperature of the motor 3 increase. After step S107, the process returns to step S101 again.

As described above, according to the first aspect, the output of the motor 3 can be increased while preventing excessive heat generation of the inverter 13. In addition, excessive heat generation can be prevented also with respect to the temperature of the converter 12 and the temperature of the motor 3. In the case of the first embodiment, the temperature of converter 12 is not used for the input power supply voltage control of converter 12, and therefore temperature acquisition unit 14 provided in converter 12 may be omitted.

Next, a second mode of control of the input power supply voltage of the converter 12 will be described. In the second mode, the input power supply voltage of converter 12 is controlled so that the temperature of converter 12 can be raised as much as possible. According to the second aspect, it is possible to control the motor 3 with higher accuracy while preventing excessive heat generation of the converter 12 and the motor 3. Fig. 4 is a flowchart showing a second mode of input power supply voltage control in the motor drive device of the first embodiment of the present disclosure.

In the motor drive device 1 of the present embodiment, when the electromagnetic contactor 25 is closed to electrically connect the ac stabilization power supply device 11 and the converter 12, and the motor control unit 20 controls the power conversion operation of the converter 12 and the inverter 13 to drive the motor 3, the temperature acquisition unit 14 acquires the temperature of the converter 12 in step S201. The acquired temperature of converter 12 is notified to input power supply voltage control unit 15.

In step S202, input power supply voltage control unit 15 determines whether or not the temperature of converter 12 acquired by temperature acquisition unit 14 is lower than a preset converter lower limit temperature threshold. If it is determined that the temperature of converter 12 is lower than the converter lower limit temperature threshold value, the process proceeds to step S203, and if it is not determined that the temperature of converter 12 is lower than the converter lower limit temperature threshold value, the process proceeds to step S205. The converter lower limit temperature threshold may be set to a value smaller than a converter upper limit temperature threshold described later. The difference between the upper and lower temperature thresholds is the hysteresis width of the temperature of the converter 12.

If it is determined in step S202 that the temperature of the converter 12 is lower than the converter lower limit temperature threshold, the input power supply voltage control unit 15 controls the ac stabilizing power supply device 11 to output an input power supply voltage lower than the current input power supply voltage in step S203. That is, the input power supply voltage control unit 15 generates a voltage command value for causing the ac stabilizing power supply device 11 to output a lower input power supply voltage instead of the input power supply voltage output by the ac stabilizing power supply device 11 before, and outputs the voltage command value to the ac stabilizing power supply device 11. Thus, the ac stabilization power supply device 11 supplies the converter 12 with an input power supply voltage lower than the input power supply voltage outputted immediately before. As described with reference to fig. 2, when the input power supply voltage of the converter 12 decreases, the dc link voltage decreases, and the current flowing through the converter 12 and the current flowing through the motor 3 increase. As a result, the temperature of the inverter 12 and the temperature of the motor 3 increase (step S204). On the other hand, the dc link voltage decreases, which reduces the switching loss of the inverter 13 and lowers the temperature of the inverter 13. Further, since the inverter 13 converts such a low dc link voltage into an ac voltage for driving the motor 3 so as to maintain the output of the motor 3 constant, the actual resolution of the voltage command to the inverter 13 is improved, and therefore the motor 3 can be controlled with high accuracy. After step S204, the process returns to step S201 again.

If it is not determined in step S202 that the temperature of converter 12 is lower than the converter lower limit temperature threshold, the process proceeds to step S205.

In step S205, input power supply voltage control unit 15 determines whether or not the temperature of converter 12 acquired by temperature acquisition unit 14 exceeds a preset converter upper limit temperature threshold. If it is determined that the temperature of converter 12 exceeds the converter upper limit temperature threshold value, the process proceeds to step S206, and if it is not determined that the temperature of converter 12 exceeds the converter upper limit temperature threshold value, the process returns to step S201. The converter upper limit temperature threshold value may be set to a temperature at which damage to the converter 12 or a reduction in the life of the converter due to heat generation does not occur, a temperature at which malfunction (thermal runaway) of the converter 12 does not occur, or the like.

If it is not determined in step S205 that the temperature of the converter 12 exceeds the converter upper limit temperature threshold, the input power supply voltage control unit 15 generates a voltage command value for maintaining the input power supply voltage currently being output by the ac stabilization power supply device 11, and outputs the voltage command value to the ac stabilization power supply device 11. After that, the process returns to step S201.

On the other hand, when it is determined in step S205 that the temperature of the converter 12 exceeds the converter upper limit temperature threshold, the input power supply voltage control unit 15 controls the ac stabilizing power supply device 11 to output an input power supply voltage higher than the current input power supply voltage in step S206. That is, the input power supply voltage control unit 15 generates a voltage command value for causing the ac stabilizing power supply device 11 to output a higher input power supply voltage instead of the input power supply voltage output by the ac stabilizing power supply device 11 before, and outputs the voltage command value to the ac stabilizing power supply device 11. Thus, the ac stabilization power supply device 11 supplies the converter 12 with an input power supply voltage higher than the input power supply voltage outputted immediately before. As described with reference to fig. 2, when the input power supply voltage of converter 12 is increased, the dc link voltage is increased, and the current flowing through converter 12 and the current flowing through motor 3 are decreased. As a result, the temperature of the inverter 12 and the temperature of the motor 3 decrease (step S207). On the other hand, the switching loss of the inverter 13 increases due to the increase of the dc link voltage, and the temperature of the inverter 13 increases. After step S207, the process returns to step S201 again.

As described above, according to the second aspect, it is possible to control the motor 3 with higher accuracy while preventing excessive heat generation of the converter 12 and the motor 3. In addition, excessive heat generation can be prevented also with respect to the temperature of the inverter 13. In the case of the second embodiment, the temperature of the inverter 13 is not used for the input power supply voltage control of the converter 12, and therefore the temperature acquisition unit 14 provided in the inverter 13 may be omitted.

Next, a third mode of control of the input power supply voltage of the converter 12 will be described. In the third aspect, the input power supply voltage of converter 12 is controlled so as to equalize heat generation of converter 12 and heat generation of inverter 13. According to the third aspect, since the heat generation of the converter 12 and the inverter 13 is equalized, for example, the lives of the converter 12 and the inverter 13 can be made substantially the same, and the burden of maintenance and replacement work can be reduced. Fig. 5 is a flowchart showing a third mode of input power supply voltage control in the motor drive device according to the first embodiment of the present disclosure.

In the motor drive device 1 of the present embodiment, when the electromagnetic contactor 25 is closed to electrically connect the ac stabilization power supply device 11 and the converter 12, and the motor control unit 20 controls the power conversion operation of the converter 12 and the inverter 13 to drive the motor 3, the temperature acquisition unit 14 acquires the temperature of the converter 12 and the temperature of the inverter 13 in step S301. The acquired temperature of converter 12 and the acquired temperature of inverter 13 are notified to input power supply voltage control unit 15.

In step S302, input power supply voltage control unit 15 determines whether or not the difference between the temperature of inverter 13 and the temperature of converter 12 acquired by temperature acquisition unit 14 is outside a preset temperature difference range. If it is determined that the difference between the temperature of inverter 13 and the temperature of converter 12 is outside the predetermined temperature difference range, the process proceeds to step S303, and if it is not determined that the difference between the temperature of inverter 13 and the temperature of converter 12 is outside the predetermined temperature difference range (that is, if it is determined that the difference is within the predetermined temperature difference range), the process returns to step S301. The more the "temperature difference range" is set to a value close to 0, the more the heat generation of converter 12 and the heat generation of inverter 13 can be equalized.

If it is not determined in step S302 that the difference between the temperature of the inverter 13 and the temperature of the converter 12 is outside the predetermined temperature difference range (that is, if it is determined that the difference is within the predetermined temperature difference range), the input power supply voltage control unit 15 generates a voltage command value for maintaining the input power supply voltage currently being output by the ac stabilization power supply device 11, and outputs the voltage command value to the ac stabilization power supply device 11. After that, the process returns to step S301.

When it is determined in step S302 that the difference between the temperature of inverter 13 and the temperature of converter 12 is outside the predetermined temperature difference range, input power supply voltage control unit 15 determines in step S303 whether or not the temperature of inverter 13 is higher than the temperature of converter 12. If it is determined that the temperature of inverter 13 is higher than the temperature of converter 12, the process proceeds to step S304, and if it is not determined that the temperature of inverter 13 is higher than the temperature of converter 12 (that is, if the temperature of inverter 13 is lower than the temperature of converter 12), the process proceeds to step S306.

When it is determined in step S303 that the temperature of the inverter 13 is higher than the temperature of the converter 12, the input power supply voltage control unit 15 controls the ac stabilizing power supply device 11 to output an input power supply voltage lower than the current input power supply voltage in step S304. That is, the input power supply voltage control unit 15 generates a voltage command value for causing the ac stabilizing power supply device 11 to output a lower input power supply voltage instead of the input power supply voltage output by the ac stabilizing power supply device 11 before, and outputs the voltage command value to the ac stabilizing power supply device 11. Thus, the ac stabilization power supply device 11 supplies the converter 12 with an input power supply voltage lower than the input power supply voltage outputted immediately before. As described with reference to fig. 2, the input power supply voltage of the converter 12 decreases, so that the dc link voltage decreases, and the switching loss of the inverter 13 decreases due to the decrease in the dc link voltage, thereby decreasing the temperature of the inverter 13 (step S305). On the other hand, the current flowing through the converter 12 and the current flowing through the motor 3 increase, and the temperature of the converter 12 and the temperature of the motor 3 increase (step S305). After step S305, the process returns to step S301 again.

If it is not determined in step S303 that the temperature of inverter 13 is higher than the temperature of converter 12 (that is, if the temperature of inverter 13 is lower than the temperature of converter 12), input power supply voltage control unit 15 controls ac stabilizing power supply device 11 to output an input power supply voltage higher than the current value in step S306. That is, the input power supply voltage control unit 15 generates a voltage command value for causing the ac stabilizing power supply device 11 to output a higher input power supply voltage instead of the input power supply voltage output by the ac stabilizing power supply device 11 before, and outputs the voltage command value to the ac stabilizing power supply device 11. Thus, the ac stabilization power supply device 11 supplies the converter 12 with an input power supply voltage higher than the input power supply voltage outputted immediately before. As described with reference to fig. 2, when the input power supply voltage of converter 12 is increased, the dc link voltage is increased, the current flowing through converter 12 and the current flowing through motor 3 are decreased, and the temperature of converter 12 and the temperature of motor 3 are decreased (step S307). On the other hand, the switching loss of the inverter 13 increases due to the dc link voltage becoming high, and the temperature of the inverter 13 rises (step S307). On the other hand, after step S307, the process returns to step S301 again.

As described above, according to the third aspect, since the heat generation of the converter 12 and the inverter 13 is equalized, for example, the lives of the converter 12 and the inverter 13 can be made substantially the same, and the burden of maintenance and replacement work can be reduced. For example, when the electrolytic capacitors and the cooling fans in the converter 12 and the inverter 13 are made of the same type of component, deterioration of the components due to heat generation progresses at substantially the same rate, so that the life of the converter 12 and the inverter 13 can be substantially the same, and efficient maintenance and replacement work can be performed.

Next, a motor drive device according to a second embodiment of the present disclosure will be described.

Fig. 6 is a diagram showing a motor drive device according to a second embodiment of the present disclosure. The motor drive device 1 of the second embodiment is a third embodiment in which the control of the input power supply voltage of the converter 12 in the first embodiment is further developed. In the third aspect of the control of the input power supply voltage to the converter 12 in the first embodiment, if it is not determined in step S302 of fig. 5 that the difference between the temperature of the inverter 13 and the temperature of the converter 12 is outside the predetermined temperature difference range (that is, if it is determined that the difference is within the predetermined temperature difference range), the current state is maintained without changing the input power supply voltage, and the process returns to step S301. In contrast, in the second embodiment, when it is not determined that the difference between the temperature of the inverter 13 and the temperature of the converter 12 is outside the predetermined temperature difference range, the load on the inverter 13 is changed to control the temperature of the converter 12 and the temperature of the inverter 13 when a predetermined condition is satisfied. Therefore, the motor drive device 1 according to the second embodiment further includes an inverter load control unit 16 with respect to the motor drive device 1 according to the first embodiment shown in fig. 1, and the inverter load control unit 16 performs the following control: when a predetermined condition is satisfied, the load on the inverter 13 is changed. That is, in the motor drive device 1 of the second embodiment, the control of the respective temperatures of the converter 12 and the inverter 13 (further, the motor 3) is performed by any one of the following controls: the input power supply voltage control unit 15 controls the ac stabilized power supply device 11; and a control in which the inverter load control unit 16 changes the load to be borne by the inverter 13. The inverter load control unit 16 is provided in the motor control unit 20.

The inverter load control unit 16 performs control as follows: when the difference between the temperature of the inverter 13 and the temperature of the converter 12 acquired by the temperature acquisition unit 14 is within the predetermined temperature difference range, the temperature of the inverter 13 is lower than the inverter lower limit temperature threshold, and the temperature of the converter 12 is lower than the converter lower limit temperature threshold, the inverter 13 is caused to bear a further increased load instead of the load that the inverter 13 previously bears. Further, the inverter load control unit 16 performs control as follows: when the difference between the temperature of the inverter 13 and the temperature of the converter 12 is within the temperature difference range and the temperature of the inverter 13 exceeds the inverter upper limit temperature threshold value, or when the difference between the temperature of the inverter 13 and the temperature of the converter 12 is within the predetermined temperature difference range and the temperature of the converter 12 exceeds the converter upper limit temperature threshold value, the inverter 13 is caused to bear a further reduced load instead of the load that the inverter 13 has previously been subjected to.

For example, the load on the inverter 13 can be changed by changing the PWM frequency used for PWM switching control of the power elements in the inverter 13. The higher the PWM frequency, the more the switching loss of the power elements in the inverter 13 increases, and therefore the more the load on the inverter 13 increases. That is, inverter load control unit 16 increases the load on inverter 13 by changing the PWM frequency used for PWM switching control on the power devices to a higher PWM frequency, and decreases the load on inverter 13 by changing the PWM frequency used for PWM switching control on the power devices to a lower PWM frequency. By changing the PWM frequency used for PWM switching control of the power elements to a higher PWM frequency by the inverter load control unit 16, the load borne by the inverter 13 increases, but the responsiveness of the inverter 13 increases. In addition, the heat generation of the motor 3 also decreases.

Further, for example, by changing the ac voltage output from the inverter 13 and changing the output of the motor 3, the load on the inverter 13 can be changed. That is, the inverter load control unit 16 controls the ac voltage output from the inverter 13 so that the output of the motor 3 becomes a larger output, thereby increasing the load borne by the inverter 13, and controls the ac voltage output from the inverter 13 so that the output of the motor 3 becomes a smaller output, thereby decreasing the load borne by the inverter 13.

Fig. 7 is a flowchart showing input power supply voltage control in the motor drive device of the second embodiment of the present disclosure.

In the motor drive device 1 of the present embodiment, when the electromagnetic contactor 25 is closed to electrically connect the ac stabilization power supply device 11 and the converter 12, and the motor control unit 20 controls the power conversion operation of the converter 12 and the inverter 13 to drive the motor 3, the temperature acquisition unit 14 acquires the temperature of the converter 12 and the temperature of the inverter 13 in step S401. The acquired temperature of converter 12 and the acquired temperature of inverter 13 are notified to input power supply voltage control unit 15.

In step S402, input power supply voltage control unit 15 determines whether or not the difference between the temperature of inverter 13 and the temperature of converter 12 acquired by temperature acquisition unit 14 is outside a preset temperature difference range. If it is determined that the difference between the temperature of inverter 13 and the temperature of converter 12 is outside the predetermined temperature difference range, the process proceeds to step S403, and if it is not determined that the difference between the temperature of inverter 13 and the temperature of converter 12 is outside the predetermined temperature difference range (that is, if it is determined that the difference is within the predetermined temperature difference range), the process proceeds to step S408. In particular, when the rated temperatures of the converter 12 and the inverter 13 are the same, the heat generation of the converter 12 and the heat generation of the inverter 13 can be equalized as the "temperature difference range" is set to a value close to 0.

When it is determined in step S402 that the difference between the temperature of inverter 13 and the temperature of converter 12 is outside the predetermined temperature difference range, input power supply voltage control unit 15 determines in step S403 whether or not the temperature of inverter 13 is higher than the temperature of converter 12. If it is determined that the temperature of inverter 13 is higher than the temperature of converter 12, the process proceeds to step S404, and if it is not determined that the temperature of inverter 13 is higher than the temperature of converter 12 (that is, if the temperature of inverter 13 is lower than the temperature of converter 12), the process proceeds to step S406.

If it is determined in step S403 that the temperature of the inverter 13 is higher than the temperature of the converter 12, the input power supply voltage control unit 15 controls the ac stabilizing power supply device 11 to output an input power supply voltage lower than the current input power supply voltage in step S404. That is, the input power supply voltage control unit 15 generates a voltage command value for causing the ac stabilizing power supply device 11 to output a lower input power supply voltage instead of the input power supply voltage output by the ac stabilizing power supply device 11 before, and outputs the voltage command value to the ac stabilizing power supply device 11. Thus, the ac stabilization power supply device 11 supplies the converter 12 with an input power supply voltage lower than the input power supply voltage outputted immediately before. As described with reference to fig. 2, the input power supply voltage of the converter 12 decreases, so that the dc link voltage decreases, and the switching loss of the inverter 13 decreases due to the decrease in the dc link voltage, thereby decreasing the temperature of the inverter 13 (step S405). On the other hand, the current flowing through the converter 12 and the current flowing through the motor 3 increase, and the temperature of the converter 12 and the temperature of the motor 3 increase (step S405). After step S405, the process returns to step S401 again.

If it is not determined in step S403 that the temperature of inverter 13 is higher than the temperature of converter 12 (that is, if the temperature of inverter 13 is lower than the temperature of converter 12), input power supply voltage control unit 15 controls ac stabilizing power supply device 11 to output an input power supply voltage higher than the current value in step S406. That is, the input power supply voltage control unit 15 generates a voltage command value for causing the ac stabilizing power supply device 11 to output a higher input power supply voltage instead of the input power supply voltage output by the ac stabilizing power supply device 11 before, and outputs the voltage command value to the ac stabilizing power supply device 11. Thus, the ac stabilization power supply device 11 supplies the converter 12 with an input power supply voltage higher than the input power supply voltage outputted immediately before. As described with reference to fig. 2, when the input power supply voltage of converter 12 is increased, the dc link voltage is increased, the current flowing through converter 12 and the current flowing through motor 3 are decreased, and the temperature of converter 12 and the temperature of motor 3 are decreased (step S407). On the other hand, the switching loss of the inverter 13 increases due to the increase of the dc link voltage, and the temperature of the inverter 13 rises (step S407). On the other hand, after step S407, the process returns to step S401 again.

When it is determined in step S402 that the difference between the temperature of the inverter 13 and the temperature of the converter 12 is within the predetermined temperature difference range, the inverter load control unit 16 determines in step S408 whether the temperature of the inverter 13 is lower than the inverter lower limit temperature threshold and the temperature of the converter 12 is lower than the converter lower limit temperature threshold. If it is determined in step S408 that the temperature of the inverter 13 is lower than the inverter lower limit temperature threshold and the temperature of the converter 12 is lower than the converter lower limit temperature threshold, the process proceeds to step S409, otherwise, the process proceeds to step S411. The inverter lower limit temperature threshold may be set to a value smaller than the inverter upper limit temperature threshold. The difference between the inverter upper limit temperature threshold and the inverter lower limit temperature threshold is the hysteresis width of the temperature of the inverter 13. The converter lower limit temperature threshold may be set to a value smaller than the converter upper limit temperature threshold. The difference between the upper and lower temperature thresholds is the hysteresis width of the temperature of the converter 12.

If it is determined in step S408 that the temperature of inverter 13 is lower than the inverter lower limit temperature threshold and the temperature of converter 12 is lower than the converter lower limit temperature threshold, inverter load control unit 16 controls in step S409 as follows: the inverter 13 is caused to bear a further increased load instead of the load that the inverter 13 had previously borne. Thereby, the temperature of inverter 13 and the temperature of converter 12 increase (step S410). After step S407, the process returns to step S401 again.

If it is not determined in step S408 that the temperature of inverter 13 is lower than the inverter lower limit temperature threshold and the temperature of converter 12 is lower than the converter lower limit temperature threshold, inverter load control unit 16 determines whether any of the following conditions is satisfied in step S411: the temperature of the inverter 13 exceeds an inverter upper temperature threshold; the temperature of the converter 12 exceeds the converter upper temperature threshold. If it is determined that the temperature of the inverter 13 exceeds the inverter upper limit temperature threshold value, the process proceeds to step S412. If it is determined that the temperature of converter 12 exceeds the converter upper limit temperature threshold value, the process proceeds to step S412.

In step S412, the inverter load control unit 16 controls the following: the inverter 13 is caused to bear a further reduced load instead of the load that the inverter 13 had previously been bearing. Thereby, the temperature of inverter 13 and the temperature of converter 12 decrease (step S413). After step S413, the process returns to step S401 again.

If it is determined in step S411 that the temperature of the inverter 13 does not exceed the inverter upper limit temperature threshold, the temperature of the inverter 13 is determined in the previous step S408 to be not lower than the inverter lower limit temperature threshold, and therefore the temperature of the inverter 13 is between the inverter lower limit temperature threshold and the inverter upper limit temperature threshold. In this case, the process returns to step S401. The inverter load control unit 16 maintains the load of the inverter 13 at the present state, and the input power supply voltage control unit 15 generates a voltage command value for maintaining the input power supply voltage being output by the ac stabilizing power supply device 11, and outputs the generated voltage command value to the ac stabilizing power supply device 11.

If it is determined in step S411 that the temperature of converter 12 does not exceed the converter upper limit temperature threshold, since it is determined in step S408 that the temperature of converter 12 is not lower than the converter lower limit temperature threshold, the temperature of converter 12 is between the converter lower limit temperature threshold and the converter upper limit temperature threshold. In this case, the process also returns to step S401. The inverter load control unit 16 maintains the load of the inverter 13 at the present state, and the input power supply voltage control unit 15 generates a voltage command value for maintaining the input power supply voltage being output by the ac stabilizing power supply device 11, and outputs the generated voltage command value to the ac stabilizing power supply device 11.

As described above, according to the second embodiment, the heat generation of the converter 12 and the inverter 13 is equalized by the control of the ac stabilizing power supply device 11 by the input power supply voltage control unit 15, so that, for example, the lives of the converter 12 and the inverter 13 can be made substantially the same, and the burden of maintenance and replacement work can be reduced. Further, according to the second embodiment, the inverter load control unit 16 controls the load to be applied to the inverter 13 so as to change, thereby preventing excessive heat generation of the inverter 13 and increasing the output of the motor 3, thereby enabling precise control of the motor.

The input power supply voltage control unit 15, the inverter load control unit 16, the motor control unit 20, and the input power supply voltage detection unit 24 may be implemented in the form of a software program, or may be implemented as a combination of various electronic circuits and software programs. For example, when they are constructed in the form of a software program, the functions of the above-described respective sections can be realized by causing an arithmetic processing device such as an MPU or a DSP in the control device 100 to operate in accordance with the software program. Alternatively, the input power supply voltage control unit 15, the inverter load control unit 16, and the motor control unit 20 may be implemented as a semiconductor integrated circuit in which a software program for realizing the functions of each unit is written. In the case where the temperature of the converter 12 and/or the inverter 13 is acquired by estimation using software simulation instead of actual measurement by a temperature sensor, the function of the temperature acquisition unit 14 is realized by causing an arithmetic processing device such as an MPU or a DSP to execute a temperature estimation program. In this case, the temperature acquisition unit 14 based on the temperature estimation program is provided in an arithmetic processing unit in the control device 100 or an arithmetic processing unit in an external computer (not shown).

If the motor drive device 1 described above is used as a drive source for a machine tool, a robot, a forging press, an injection molding machine, or an industrial machine, for example, heat generation of the converter 12, the inverter 13, and the motor 3 can be controlled, and therefore, it is possible to improve machining accuracy by reducing thermal displacement and to extend the life of the bearing of the motor 3.

According to one embodiment of the present disclosure, a motor drive device capable of suppressing heat generation of each part and efficiently controlling a motor can be realized.