JP2005218226A - Method and apparatus for controlling motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor driving method wherein the performance of a motor can be taken out to its thermal performance limit and the life time of the motor can be prolonged. <P>SOLUTION: A motor controller comprises a control circuit and a power conversion circuit. A temperature detector for detecting the temperature of a fin on which the power conversion circuit is mounted, and a plurality of coolers are added to the motor controller. The value of the loss of the power conversion circuit is computed from the value of the loss of the control circuit and a torque command at each control sampling time. The value of the loss of the power conversion circuit is inputted to a thermal equivalent circuit and to estimate the value of an internal temperature rise in the power conversion circuit. The fin temperature and the value of temperature rise are added, to estimate the internal temperature of the power conversion circuit. A plurality of coolers are selected and operated according to the estimated internal temperature and a plurality of preset temperature specification ranges. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a motor control method and apparatus for protecting a motor control device from overheating.

A conventional overheat protection method for a motor control device is disclosed in Patent Document 1, for example.
Patent Document 1 tries to further reduce the size of a driving device composed of a transistor and a thermistor attached to a radiating fin. The thermistor detects the temperature of the transistor without time lag by attaching the transistor and the thermistor to the closest positions on the front and back of the fin. It is what I tried. Furthermore, the fan consumes a large amount of power and tries to operate when the temperature of the fin exceeds a specified value in order to reduce the drive time as much as possible. In FIG. 12, reference numeral 102 denotes a radiation fin, 110 denotes a transistor, 109 denotes a thermistor, and 108 denotes a cooling fan.
JP 2000-294706 A

However, in the prior art, only the operation when the temperature of the fin exceeds a specified value drives the fan or lowers the operating frequency of the circuit is described. The rules for starting and stopping the fan are important for extending the life of the fan. However, if the fan is started and stopped with only one standard value as in the prior art, not only will the frequency of start and stop increase, the life of the fan will be significantly reduced, but the power supplied to the fan will also increase. .
FIG. 13 shows a time chart when the fan is started and stopped with only one standard value, and the number of times the fan is started and stopped is considerably increased. FIG. 13 shows the result of simulation using the thermal equivalent circuit of FIG. 11 and is not actually measured. The simulation conditions are as follows: junction-die thermal resistance is 0.1 ° C / W, die-case (fin) thermal resistance is 0.2 ° C / W, and fin-ambient thermal resistance is when the fan is not operating. 3 ° C / W, 1 ° C / W when the fan is operating, heat capacity of the die is 1 Joule / ° C, heat capacity of the fin is 100,000 Joule / ° C, delay time from temperature detection to fan operation is 0.5 sec, control circuit Loss is 20 W, and the loss during operation of the power conversion circuit is 40 W. In this example, the fan repeats operation / non-operation 7 to 8 times per minute, which is a problem in terms of life.
The present invention has been made in view of such problems, and provides a motor control method and apparatus that draws out the performance of a motor drive device to the thermal performance limit and has a long life.

According to a first aspect of the present invention, there is provided a control method for a motor control device including a control circuit and a power conversion circuit, wherein a temperature detector for detecting a fin temperature on which the power conversion circuit is mounted and a plurality of coolers are added and controlled. The power converter circuit loss value is calculated from the control circuit loss value and torque command at each sampling time, the power converter circuit loss value is input to the thermal equivalent circuit, the internal temperature rise value of the power converter circuit is estimated, and the fin temperature And the temperature rise value are added to estimate the internal temperature of the power conversion circuit, and the plurality of coolers are selected and operated according to the estimated internal temperature.
According to a second aspect of the present invention, in the motor control method according to the first aspect, the cooler is a fan and includes a first fan and a second fan, and first temperature <second temperature <third temperature. <4th temperature is set, and when the estimated internal temperature is lower than the first temperature, both the first fan and the second fan are turned off, and the estimated internal temperature is higher than the first temperature and higher than the second temperature. When the temperature is low, the first fan is kept in the state determined at the previous sampling time, the second fan is turned off, and when the estimated internal temperature is higher than the second temperature and lower than the third temperature, the first fan Is turned on and the second fan maintains the state determined at the previous sampling time. When the estimated internal temperature is higher than the third temperature and lower than the fourth temperature, both the first fan and the second fan are turned on. When the estimated internal temperature is higher than the fourth temperature It is to shut down all the switching elements of the power conversion circuit off, and to output an alarm signal overheating outside.
According to a third aspect of the present invention, in the motor control method according to the first or second aspect, the cooler is n fans, and the temperature range is classified from the first temperature to the (n + 2) th temperature. The same fan setting was made.
According to a fourth aspect of the present invention, in the motor control method according to the first aspect, the temperature detector is a thermistor, and the output signal of the thermistor is converted into a digital quantity by an AD converter and taken into the CPU.
According to a fifth aspect of the present invention, in the motor control method according to the first aspect, the temperature detector is attached to the printed circuit board of the control circuit, the inside air temperature of the motor control device is detected, and the transient heat obtained by measuring in advance is obtained. An equivalent circuit was used to estimate the temperature rise value inside the power conversion circuit, and the internal temperature was estimated by adding to the inside air temperature to drive the cooler.
According to a sixth aspect of the present invention, a motor control device including a control circuit and a power conversion circuit includes a temperature detector for detecting a fin temperature on which the power conversion circuit is mounted and a plurality of coolers, and controls each control sampling time. Loss value calculation means for calculating the loss value of the power conversion circuit from the circuit loss value and the torque command, and the internal temperature rise for estimating the internal temperature rise value of the power conversion circuit by inputting the loss value of the power conversion circuit to the thermal equivalent circuit The value estimation means, the fin temperature and the temperature rise value are added to estimate the internal temperature of the power conversion circuit, and the estimated internal temperature is selected according to a plurality of temperature standard ranges set in advance, and a plurality of coolers are selected, And means for operating.
According to a seventh aspect of the present invention, in the motor control device according to the sixth aspect, the first fan and the second fan are provided using the cooler as a fan, and first temperature <second temperature <third temperature <fourth. When the estimated internal temperature is lower than the first temperature, both the first fan and the second fan are turned off. When the estimated internal temperature is higher than the first temperature and lower than the second temperature, The first fan is kept in the state determined at the previous sampling time, the second fan is turned off, and when the estimated internal temperature is higher than the second temperature and lower than the third temperature, the first fan is turned on. The second fan maintains the state determined at the previous sampling time, and when the estimated internal temperature is higher than the third temperature and lower than the fourth temperature, both the first fan and the second fan are turned on and estimated. When the internal temperature is higher than the 4th temperature, And shuts down all the switching elements of the power conversion circuit off, and so that the means for outputting an alarm signal overheating outside.
The present invention according to claim 8 is the motor control device according to claim 6 or claim 7, wherein the cooler is n fans, and the temperature range is classified from the first temperature to the n + 2th temperature. It is made up of means for performing similar fan settings.

According to the motor control method and apparatus of the present invention, the internal temperature of the power conversion circuit can be accurately estimated, and cooling is performed using a plurality of coolers, so that the performance of the motor control apparatus can be brought out to the thermal limit, In addition, the lifetime can be extended.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a motor control apparatus provided with a motor control method according to a first embodiment of the present invention.
In FIG. 1, 1 is a power conversion circuit, 2 is a control circuit, 3 is an inverter circuit, 4 is a rectifier, 5 is a temperature detector, 6 is an AD converter, 7 is a CPU, 8 is a fan control circuit, and 9 is a first fan. Reference numeral 10 denotes a second fan, and 11 denotes a control power source. When a speed command or a position command is given from an external host system, the interface circuit IF converts the command data into data that can be decoded by the CPU. A position detector coupled to the motor outputs position data to a position detector input circuit of the control circuit, which converts the data readable by the CPU. Although not shown in the figure, the CPU fetches position command data and position data at each control sampling time, generates a torque command by performing a position control calculation and a speed control calculation, and outputs a d-axis current command and a q-axis current command. Generate and output to the current controller. The current detector detects the three-phase current of the motor and passes it to the control circuit. The three-phase-dq converter of the control circuit performs coordinate conversion of the three-phase current into a d-axis current and a q-axis current, and outputs them to the current controller. The current control unit performs dq-axis current control, performs dq-3 phase coordinate conversion to generate a three-phase voltage command, generates a three-phase pulse width modulation signal from the three-phase voltage command, and outputs it to the gate drive circuit . The gate drive circuit insulates and amplifies the gate signal and drives the gate of the IGBT of the inverter circuit. The inverter applies a pulse-width modulated voltage to the motor, and generates a current that matches the speed and motor constant. When current flows through the motor, torque is generated and the motor rotates at a speed corresponding to the load and moment of inertia.
The temperature detector is attached to the fin that cools the power conversion circuit, and detects the temperature of the fin. The detected temperature signal is converted into a form readable by the CPU by an AD converter. The CPU reads the fin temperature and generates a loss of the power conversion circuit by referring to the table from the torque command. Since the loss of the power conversion circuit is a value related to the torque command, the relationship between the torque command and the loss (FIG. 2) is acquired in advance through experiments or the like and stored in the memory table of the CPU (FIG. 6). When the CPU knows the loss of the power conversion circuit, the CPU estimates the junction temperature rise value of the IGBT in the power conversion circuit with reference to the heat equivalent circuit of FIG. 3 acquired in advance. The cooler is selected and operated depending on where the junction temperature falls in the preset temperature range.
FIG. 3 shows a heat equivalent circuit of the motor control device, where 30 is a total loss value, 31 is a junction, 32 is a die, and 33 is a portion indicating the temperature of the case or fin. 34 is a junction-die thermal resistance R1 (° C / W), 35 is a die-case (fin) thermal resistance R2 (° C / W), and 36 is a fin-ambient thermal resistance R3 (° C / W). It is. The cooler has the effect of reducing R3.

FIG. 4 is a block diagram showing a second embodiment of the present invention, in which a plurality of coolers are constituted by a first fan and a second fan, and a temperature detector is constituted by a thermistor. FIG. 5 is a flowchart of overheat protection.
In FIG. 4, 1 is a power conversion circuit, 2 is a printed wiring board on which a control circuit is mounted, 5 is a temperature detector attached to the fin, 7 is a CPU mounted on the printed wiring board, and 9 is a cooler. The first fan, 10 is a second fan which is a cooler, and 22 is a heat generating part of the control circuit unit.
Step ST1 is a scheduled interruption by control sampling.
In step ST2, the temperature signal detected by the thermistor is read from the AD converter.
Next, in step ST3, the torque command used for the motor control calculation is read.
In step ST4, the loss value of the power conversion circuit is generated from the torque command with reference to the table of FIG.
In step ST5, the loss of the power conversion circuit is input to the thermal equivalent circuit to estimate the knowledge of the junction temperature of the IGBT of the power conversion circuit, and is added to the temperature of the fin to estimate the junction temperature.
Also, four levels of specified temperatures of the first temperature, the second temperature, the third temperature, and the fourth temperature are prepared in advance and compared with the estimated junction temperature value of the power conversion circuit.
If the estimated temperature is lower than the first temperature in step ST6, both the first fan and the second fan are turned off and the process ends.
In step ST7, it is determined whether the estimated temperature is higher than the first temperature and lower than the second temperature, the first fan maintains the value determined in the previous sampling time, and the second fan is turned off.
In step ST8, it is determined whether the estimated temperature is higher than the second temperature and lower than the third temperature, and the state in which the first fan is turned on and the second fan is determined at the previous sampling time is maintained.
In step ST10, it is determined whether the estimated temperature is higher than the third temperature and lower than the fourth temperature, and both the first fan and the second fan are turned on.
In step ST12, it is determined whether the estimated temperature is higher than the fourth temperature, the first fan and the second fan are turned on, an overheat signal is generated, and an alarm signal is output to the outside.
FIG. 7 summarizes the conditions used for these determinations in a table.
FIG. 8 is a time chart when the control circuit loss is 20 W and the power conversion circuit loss is 100 W. The first temperature is set to 90 ° C., the second temperature is set to 100 ° C., the third temperature is set to 110 ° C., and the fourth temperature is set to 120 ° C. The conditions of the transient heat equivalent circuit are the same as those in the simulation of the conventional example. That is, the junction-die thermal resistance is 0.1 ° C./W, the die-case (fin) thermal resistance is 0.2 ° C./W, and the fin-ambient thermal resistance is 3 ° C./when the fan is not operating. W, when the fan is operating, 1 ° C / W, die heat capacity is 1 Joule / ° C, fin heat capacity is 100,000 Joule / ° C, delay time from temperature detection to fan operation is 0.5sec, control circuit loss is 20W. The difference is that the loss during operation of the power conversion circuit is increased from 40 W to 100 W. While the first fan is operating, the second fan is repeatedly turned on and off. The repetition frequency of on / off is about once every two minutes, which is reduced to 1/20 compared to the conventional example. Further, the junction temperature ΔTj by driving the fan is 10 ° C. or less, which is a level that hardly affects the life of the power cycle.
FIG. 9 shows a third embodiment of the present invention, in which the number of fans is increased to n and the temperature range is also increased to n + 2. Basically, it is the same as the second embodiment.
FIG. 10 shows a fourth embodiment of the present invention. A temperature detector is attached to the printed circuit board of the control circuit, the inside air temperature of the motor control device is detected, and measured in advance. A transient heat equivalent circuit is used to estimate the temperature rise value inside the power conversion circuit, and the internal temperature is estimated by adding to the inside air temperature to control the cooler.
The transient heat equivalent circuit of FIG. 11 is obtained by adding a heat capacity to the heat equivalent circuit of FIG. 3, wherein 37 is the heat capacity of the die and 38 is the heat capacity of the fin.
The junction temperature rise of the power conversion circuit during the sampling time is as follows: junction-die thermal resistance is R1, die-case (fin) thermal resistance is R2, case-ambient thermal resistance is R3, die thermal capacity is C1, fin thermal capacity If C2 is the loss P (W) to be generated, it can be approximately expressed by the equation (1), and can be stopped by simply substituting it into the calculation formula without using an equivalent circuit.
θ = PR ₁ + θ ₁ + θ ₂ (1)
Here, θ is a temperature rise value. t1, t2, θ1, and θ2 can be expressed by the following equations.
t ₁ = 2C ₁ C ₂ R ₂ R ₃
/ (C ₁ (R ₂ + R ₃ ) + C ₂ R ₂ + √ (C ₁ ² (R ₂ + R ₃ ) ² ) -4C ₁ C ₂ R ₂ R ₃ )
(2)
t ₂ = 2C ₁ C ₂ R ₂ R ₃
/ (C ₁ (R ₂ + R ₃ ) + C ₂ R ₂ −√ (C ₁ ² (R ₂ + R ₃ ) ² ) −4C ₁ C ₂ R ₂ R ₃ )
(3)
θ ₁ = θ ₁₀ * exp (−t _s / t ₁ ) +
_{P (1-exp (-t s} / t 1)) (C 2 R 2 R 3 - (R 2 + R 3) t 1) / (t 2 -t 1)
(4)
θ ₂ = θ ₂₀ exp (−t _s / t ₂ ) +
_{P (1-exp (-t s} / t 2)) (C 2 R 2 R 3 - (R 2 + R 3) t 2) / (t 1 -t 2)
(5)
Here, θ ₁₀ and θ ₂₀ are temperature rise values before one sampling.

  Since it can be used safely and continuously by preventing destruction due to temperature overheating or stopping of the apparatus, it can also be applied to motor control applications such as robots, machine tools, and industrial machines.

The block diagram which shows 1st Example of this invention Temperature time chart in an embodiment of the present invention Thermal equivalent circuit The block diagram which shows 2nd Example of this invention Flowchart for preventing overheating according to the second embodiment of the present invention. Memory table that subtracts power conversion circuit loss from torque command Table to control the cooler state Time chart of the second embodiment Configuration diagram of the third embodiment Configuration diagram of the fourth embodiment Transient thermal equivalent circuit Configuration diagram of conventional example Conventional time chart

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power conversion circuit 2 Control circuit 3 Inverter circuit 4 Rectifier circuit 5 Temperature detector 6 AD converter 7 CPU
8 Fan Control Circuit 9 First Fan 10 Second Fan 11 Control Power Supply 21 Fin 30 Heat Source 31 Junction Temperature 32 Die Temperature 33 Fin Temperature 34 Junction-Die Thermal Resistance 35 Die-Case (Fin) Thermal Resistance 36 Case (Fin) -Ambient thermal resistance 37 Die heat capacity 38 Fin heat capacity

Claims (8)

In a control method of a motor control device including a control circuit and a power conversion circuit,
Adding a temperature detector and a plurality of coolers for detecting the fin temperature on which the power conversion circuit is mounted;
Calculate the loss value of the power conversion circuit from the control circuit loss value and torque command at each control sampling time,
The loss value of the power conversion circuit is input to a heat equivalent circuit to estimate the internal temperature rise value of the power conversion circuit,
Estimating the internal temperature of the power conversion circuit by adding the fin temperature and the temperature rise value,
A motor control method comprising: selecting and operating the plurality of coolers according to a plurality of temperature standard ranges in which the estimated internal temperature is set in advance. The cooler is a fan, and includes a first fan and a second fan,
First, set the temperature of 1st temperature <2nd temperature <3rd temperature <4th temperature,
When the estimated internal temperature is lower than the first temperature, both the first fan and the second fan are turned off,
When the estimated internal temperature is higher than the first temperature and lower than the second temperature, the first fan is maintained at the state determined at the previous sampling time, the second fan is turned off,
When the estimated internal temperature is higher than the second temperature and lower than the third temperature, the first fan is turned on and the second fan remains in the state determined in the previous sampling time;
When the estimated internal temperature is higher than the third temperature and lower than the fourth temperature, both the first fan and the second fan are turned on,
2. The motor control method according to claim 1, wherein when the estimated internal temperature is higher than the fourth temperature, all the switching elements of the power conversion circuit are turned off to shut down, and an overheat alarm signal is output to the outside. .   3. The motor control method according to claim 1, wherein the cooler includes n fans, and the temperature range is classified from the first temperature to the n + 2th temperature, and the fan setting similar to that of claim 2 is performed.   2. The motor control method according to claim 1, wherein the temperature detector is a thermistor, and an output signal of the thermistor is converted into a digital quantity by an AD converter and is taken into a CPU.   The temperature detector is attached to the printed circuit board of the control circuit, the internal temperature of the motor control device is detected, and the temperature inside the power conversion circuit is calculated using a formula using a transient heat equivalent circuit obtained by measurement in advance. The motor control method according to claim 1, wherein an increase value is estimated, added to the inside air temperature to estimate an internal temperature, and the cooler is driven. In a motor control device composed of a control circuit and a power conversion circuit,
A temperature detector for detecting a fin temperature on which the power conversion circuit is mounted and a plurality of coolers;
A loss value calculating means for calculating the loss value of the power conversion circuit from the control circuit loss value and the torque command at each control sampling time;
An internal temperature rise value estimating means for inputting a loss value of the power conversion circuit to a heat equivalent circuit and estimating an internal temperature rise value of the power conversion circuit;
The internal temperature of the power conversion circuit is estimated by adding the fin temperature and the temperature increase value, and the plurality of coolers are selected according to a plurality of temperature standard ranges in which the estimated internal temperature is set in advance. And a motor control device. A first fan and a second fan with the cooler as a fan;
First, a temperature of first temperature <second temperature <third temperature <fourth temperature is set, and when the estimated internal temperature is lower than the first temperature, both the first fan and the second fan are turned off, and the estimated When the internal temperature is higher than the first temperature and lower than the second temperature, the first fan is maintained at the state determined at the previous sampling time, the second fan is turned off, and the estimated internal temperature is When the temperature is higher than 2 temperature and lower than the third temperature, the first fan is turned on, the second fan maintains the state determined in the previous sampling time, and the estimated internal temperature is higher than the third temperature, When the temperature is lower than the fourth temperature, both the first fan and the second fan are turned on. When the estimated internal temperature is higher than the fourth temperature, all the switching elements of the power conversion circuit are turned off and shut down. Overheating The motor control apparatus according to claim 6, characterized in that it consists of means for outputting over beam signal.   8. The motor according to claim 6, wherein the cooler includes n fans, and the temperature range is classified from the first temperature to the n + 2th temperature and the fan setting similar to that of the seventh aspect is performed. Control device.

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