JP2007014075A - Motor driving unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the breakage caused by the excessive rise of temperature of a power factor improving circuit while securing the load range of a brushless motor to its maximum. <P>SOLUTION: In case that the temperature of the power factor improving circuit 4 goes higher than a certain value, it operates a switch 10, whereby the resistance value of an external circuit connected to an oscillator 4e fluctuates, which drops oscillating frequency. Hereby, the number of times of switching of an IGBT4a used for a power factor improving circuit can be dropped, and the effect of temperature rise suppression of the power factor improving circuit thanks to the drop of the number of times of switching can be obtained. It becomes possible to continue the operation of a motor, also in a load range where it must be stopped for protection against temperature in conventional system. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric motor drive device that controls the operation of an electric motor used in an air conditioner or the like, and particularly to an electric motor drive device that uses a DC voltage variable function of a power factor correction circuit.

  The motor drive device is boosted by a rectifier circuit that converts AC voltage input from an AC power source into DC, a power factor correction circuit that boosts the DC voltage from the rectifier circuit to improve the power factor, and a power factor correction circuit. A smoothing capacitor for smoothing the DC voltage, an inverter circuit for converting the DC voltage smoothed by the smoothing capacitor into an AC voltage, a drive circuit for driving the power factor correction circuit, an inverter drive circuit for driving the inverter circuit, It consists of a control unit that controls each circuit. The output voltage from the motor drive device is supplied to the motor, and the operation of the motor is controlled based on the magnitude, frequency, etc. of the output voltage. The power factor correction circuit has two roles: a power factor improvement function by shaping the waveform of the output current into a waveform similar to that of the AC power supply and a boost function that holds the DC voltage in a boosted state. The larger the is, the greater the load on the power factor correction circuit. The power factor correction circuit normally uses a heat sink to suppress the temperature rise, but if the airflow to the heat sink is disturbed or if an abnormal increase in the ambient temperature is multiplied, the temperature of the power factor improvement circuit May overheat, causing overheating destruction of elements used in the circuit.

  Conventionally, as a means for preventing overheat destruction of the power factor correction circuit, a temperature sensor is provided on the heat sink surface to detect the temperature of the power factor correction circuit and stop the protection when an overheated state occurs. Has been used (see, for example, Patent Document 1).

FIG. 3 shows a conventional electric motor drive device described in Patent Document 1. In FIG. As shown in FIG. 3, the motor drive device converts the AC voltage from the AC power source 1 into a DC voltage by the rectifier circuit 2, and the ripple component of the DC voltage is eliminated by the smoothing capacitor 7. The smoothed DC voltage is input to the inverter circuit 8, and the electric motor 9 is driven. Further, a power factor correction circuit 4 including an IGBT 4a, a diode 4b, a control unit 4c, and a heat sink 4d is provided between the rectifier circuit 2 and the smoothing capacitor 7. The heat sink 4d is provided with a temperature sensor 5, the output of the temperature sensor 5 is input to the microcomputer 6, and the power factor correction circuit 4 is operated or stopped by an ON / OFF input signal from the microcomputer 6 to the control unit 4c. To do. When the power factor improving circuit 4 is overheated during operation and the output of the temperature sensor 5 detected by the microcomputer 6 exceeds a threshold value, the output of the control unit 4c is switched from the microcomputer 6 to the OFF state. This prevents overheating destruction of the rate improvement circuit.
JP 2001-355895 A

  However, in the conventional configuration, when the temperature of the power factor correction circuit exceeds the threshold value, the power factor improvement circuit is stopped by stopping the power factor correction circuit, and the performance deterioration due to the DC voltage drop occurs. Had a problem.

  The present invention solves the above-mentioned conventional problems, avoids destruction due to overheating of the power factor correction circuit, and operates the motor while minimizing the power factor and performance deterioration of the motor driving device due to temperature protection. It is an object of the present invention to provide a drive device that is realized by continuing the above-described operation and that improves the load range in which the electric motor can operate.

  In order to solve the conventional problem, an electric motor drive device according to the present invention includes a rectifier that rectifies a voltage input from an AC power supply, boosts the DC voltage according to a command value, and an input voltage waveform of the AC power supply. Power factor improving means for matching the input current waveform, inverter means for converting a DC voltage by the power factor improving means into an AC voltage of a desired magnitude and supplying it to the motor, and the power factor improving means and the inverter means Control means for controlling the output; temperature detection means for detecting the outer temperature of the power factor improvement means; switch element that can be opened and closed according to the temperature of the temperature detection means; and An oscillation frequency changing means capable of changing the oscillation frequency of the power factor improving means is provided.

  When the output of the power factor improving means becomes higher than a certain value, the switch element operates to reduce the oscillation frequency of the power factor improving means and suppress the temperature rise of the power factor improving means. Can do.

  The electric motor drive device of the present invention continues the operation while suppressing the temperature rise when the power factor improving means becomes overheated, so that the power factor can be reduced even in a load region that must be stopped by the conventional temperature protection. It becomes possible to continue the operation of the electric motor while maintaining the improvement function. Therefore, it is possible to expand the load range in which the electric motor can be used.

According to a first aspect of the present invention, there is provided a rectifying means for rectifying a voltage inputted from an AC power supply, and a power factor improving means for boosting the DC voltage according to a command value so as to make the input voltage waveform and the input current waveform of the AC power supply coincide with each other. An electric motor drive comprising: inverter means for converting a DC voltage by the power factor improving means into an AC voltage of a desired magnitude and supplying the same to the motor; and control means for controlling the output of the power factor improving means and the inverter means In the apparatus, a temperature detecting means for detecting an outer temperature of the power factor improving means, a switch element that can be opened / closed according to a temperature of the temperature detecting means, and a power element improving means according to opening / closing of the switch element. Equipped with oscillation frequency changing means that can change the oscillation frequency,
When the output of the power factor improvement means becomes higher than a certain value, the switching element operates, and the switching frequency of the switch element used for the power factor improvement means is reduced by reducing the oscillation frequency of the power factor improvement means. Can be reduced. The increase in temperature of the power factor improving means is suppressed by the decrease in the number of times of switching, and it becomes possible to continue the operation of the motor even in a load region that conventionally has to be stopped by temperature protection.

  According to a second aspect of the present invention, when the electric motor driving device is for an outdoor unit of an air conditioner, the temperature detecting unit is replaced with a suction temperature detecting unit of an outdoor unit heat exchanger to control the oscillation frequency changing unit. Thus, it is possible to reduce the cost required for mounting the sensor used for the temperature detecting means.

According to a third aspect of the present invention, when the electric motor driving device is for an outdoor unit of an air conditioner, the temperature detection unit is replaced with a suction temperature detection unit of an outdoor unit heat exchanger, and includes an outdoor unit current detection unit, The opening and closing of the switch element by the temperature detection means is determined by adding the correction based on the magnitude of the electric current of the motor in addition to the output of the suction temperature detection means of the outdoor heat exchanger, thereby determining the power factor estimated by the ambient temperature and the load. It becomes possible to increase the temperature detection accuracy of the improvement means.
In a fourth aspect of the present invention, the oscillation frequency changing means is provided with a plurality of switching elements, so that three or more oscillation frequencies can be set with respect to the output of the temperature detecting means. As a result, the controllability of temperature suppression of the power factor improving means can be improved, and the load range in which the operation of the electric motor can be continued can be increased.

  According to a fifth aspect of the present invention, the oscillation frequency changing unit includes a switching element having a linear characteristic that follows the output of the temperature detecting unit, and thus oscillates with a linear characteristic with respect to the output of the temperature detecting unit. The frequency can be set, the controllability of temperature suppression of the power factor improving means can be further improved, and the load range in which the operation of the electric motor can be continued can be expanded.

  According to a sixth aspect of the present invention, the power factor improving means includes means for making the target DC voltage variable with respect to the output of the temperature detecting means, and when the output of the temperature detecting means becomes higher than a certain value, the target DC voltage As a result of the decrease, the ON time of the switch element used for the power factor improvement means is reduced, and it becomes possible to suppress the temperature rise as a means different from the reduction of the oscillation frequency.

  According to a seventh aspect of the present invention, when the output of the temperature detecting means is higher than a certain value, the power factor improving means simultaneously lowers the target DC voltage and the oscillation frequency to increase the temperature of the power factor improving means. Therefore, it is possible to improve the controllability of the load and to expand the load range in which the operation of the electric motor can be continued.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows an outdoor compressor driving device for an air conditioner according to an embodiment of the present invention. In FIG. 1, the compressor driving device converts an AC voltage from an AC power source 1 into a DC voltage by a rectifier circuit 2, and a ripple component of the DC voltage is deleted by a smoothing capacitor 7. The smoothed DC voltage is input to the inverter circuit 8, and the compressor 16 is driven. A current sensor 14 is connected in series to the AC power source 1. Further, a power factor correction circuit 4 including an IGBT 4a, a diode 4b, a control unit 4c, a heat sink 4d, and an oscillator 4e is provided between the rectifier circuit 2 and the smoothing capacitor 7.

  The suction port of the outdoor unit is provided with a suction temperature sensor 5 for measuring the ambient temperature of the outdoor unit, and the output of the suction temperature sensor 15 is input to the microcomputer 6. The oscillation frequency of the oscillator 4e is determined by the resistor 11 and the capacitor 12 of the external circuit. A switch 10 and a resistor 13 are connected to the external circuit. About the outdoor compressor drive device of the air conditioner comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  The driving of the compressor 16 is achieved by supplying a current from the AC power source 1, but the output of the current sensor 14 of the AC power source is proportional to the load of the compressor. In the power factor correction circuit 4, the load increases according to the load of the compressor. Therefore, the temperature of the power factor correction circuit rises according to the output of the current sensor 14. It is also proportional to the ambient temperature of the outdoor unit. Therefore, the temperature of the power factor correction circuit 4 is proportional to the ambient temperature and the current as shown in FIG. 2, and can be estimated in the microcomputer 6 from the outputs of the suction temperature sensor 15 and the current sensor 14. Become.

  When the temperature of the power factor correction circuit 4 estimated by the microcomputer 6 becomes higher than a certain value, the switch 10 is operated to change the resistance value of the external circuit connected to the oscillator 4e, thereby lowering the oscillation frequency. Let Thereby, the switching frequency of IGBT4a used for a power factor improvement means can be reduced, and the effect of temperature rise suppression of the power factor correction circuit by the reduction of switching frequency is acquired. Conventionally, the operation of the electric motor can be continued even in a load region that must be stopped by temperature protection.

As described above, the electric motor drive device according to the present invention can expand the load range that can be operated when the ambient temperature is high or in a high load state. It can also be applied to a brushless motor drive application in an electric vehicle or the like that is supposed to be.

The block diagram of the outdoor compressor drive device of the air conditioner in the embodiment of the present invention Relationship diagram between power factor correction circuit temperature, ambient temperature, and current load Block diagram of a conventional motor drive device described in Patent Document 1

Explanation of symbols

1 AC power supply 2 Rectifier circuit 3 Reactor 4 Power factor correction circuit 4a IGBT
4b Diode 4c Controller 4d Heat sink 4e Oscillator 5 Temperature sensor 6 Microcomputer 7 Smoothing capacitor 8 Inverter circuit 9 Motor 10 Switch 11 Oscillation frequency setting resistor 12 Oscillation frequency setting capacitor 13 Temperature rise suppression resistor 14 Current sensor 15 Outdoor unit suction Temperature sensor 16 Compressor

Claims (7)

Rectifying means for rectifying a voltage input from an AC power supply, power factor improving means for boosting the DC voltage according to a command value, and matching an input voltage waveform and an input current waveform of the AC power supply, and the power factor An electric motor drive device comprising: inverter means for converting a DC voltage by an improvement means into an AC voltage of a desired magnitude and supplying the same to an electric motor; and a control means for controlling the output of the power factor improvement means and the inverter means. A temperature detecting means for detecting the outer temperature of the rate improving means, a switch element that can be opened and closed according to the temperature of the temperature detecting means, and the oscillation frequency of the power factor improving means can be changed according to the opening and closing of the switch element An oscillation frequency changing means, and when the output of the power factor improvement means becomes higher than a certain value, the switching element operates to cause the oscillation frequency of the power factor improvement means. Motor driving apparatus characterized by lowering. 2. The electric motor drive device according to claim 1, wherein when the electric motor drive device is for an outdoor unit of an air conditioner, the temperature detection means is substituted by a suction temperature detection means of an outdoor unit heat exchanger. The outdoor unit of the air conditioner has a current detection means, and the switching of the switch element by the temperature detection means is performed by adding a correction according to the magnitude of the outdoor unit current in addition to the output of the suction temperature detection means of the outdoor heat exchanger. The electric motor drive device according to claim 2, wherein the electric motor drive device is determined. The motor drive device according to claim 1, wherein the oscillation frequency changing unit includes a plurality of switch elements. 5. The electric motor drive device according to claim 1, wherein the oscillation frequency changing unit includes a switching element having a characteristic of linear output following the output of the temperature detection unit. The power factor improving means includes means for making the target DC voltage variable with respect to the output of the temperature detecting means, and reduces the target DC voltage when the output of the temperature detecting means becomes higher than a certain value. The electric motor drive device according to claim 1, wherein: 7. The electric motor according to claim 1, wherein the power factor improvement means simultaneously reduces the target DC voltage and the oscillation frequency when the output of the temperature detection means becomes higher than a certain value. Drive device.

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