JP2000116171A - Motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor controller which can monitor the rotational speed of a hysteresis motor without generating any self-excited phenomenon as a filter circuit remains in the controller. SOLUTION: A motor controller for driving and controlling a hysteresis motor 3 has a variable-voltage and variable-frequency power supply unit 2 for converting the power fed from a commercial power supply 1 into the power having a desired voltage and frequency to output the converted power, a filter circuit having a capacitor 5 and provided in the output portion of the variable- voltage and variable-frequency power supply unit 2 to smooth its output, switching means 6, 7 for switching on or off the filter circuit, and a control circuit 9 for controlling the switching means 6, 7. The capacitance of the capacitor 5 of the foregoing filter circuit is so selected that the counter electromotive force of the hysteresis motor 3 which exceeds its rated voltage never occurs due to its self-excited phenomenon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a hysteresis motor, and more particularly to a motor control device for stably driving a hysteresis motor while monitoring an operation state of the motor.

[0002]

2. Description of the Related Art A hysteresis motor is used as a drive motor for a high-speed rotating body such as a centrifugal separator because its rotation is made of a hysteresis material and its structure is simple and robust. As a method of detecting the number of rotations of the hysteresis motor, as shown in Japanese Patent Publication No. 56-10879, a switch is provided between the power supply and the motor, and the back electromotive voltage of the motor is used when the power supply is temporarily disconnected from the power supply. There has been proposed a method of monitoring the number of rotations. However, in the case of this publication, there is a drawback that a switch for disconnecting the electric motor from the power supply is required.

According to Japanese Patent Application Laid-Open No. 57-6590, when one hysteresis motor is driven by a power source such as an inverter, the inverter is temporarily stopped without providing the above-described switch, and during this time, A method of detecting the back electromotive voltage of a hysteresis motor and monitoring the rotation speed has been proposed.

A hysteresis motor can operate by generating torque regardless of the presence or absence of slip due to its characteristics. However, the disadvantage is that the operating power factor is very bad, for example, 0.1 to 0.2. . When driven by a power supply such as an inverter, the output voltage waveform contains harmonics, and therefore a filter circuit is often provided to improve the power factor and the waveform.

[0005]

When one of the above-described hysteresis motors is operated by providing a filter circuit with a power supply such as an inverter, a method of detecting the back electromotive voltage of the hysteresis motor and monitoring the rotation speed is adopted. 56-1
As disclosed in Japanese Patent No. 0879, a method of providing a mechanical switch between a power supply and an electric motor and opening and closing the switch has a problem of mechanical life. Japanese Patent Application Laid-Open No. 57-6590 discloses a method of temporarily stopping an inverter. In a device provided with a filter circuit, if the capacitor of the filter circuit is large, the back electromotive voltage of the hysteresis motor increases due to a self-excitation phenomenon. A voltage higher than the rated voltage, for example, a motor rated at 200 V generates a back electromotive voltage of about 50 to 100 V, but it has been confirmed by experiments that a voltage of 400 V or more is generated by a self-excited phenomenon. May be invited.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has an object to provide a motor control device capable of monitoring the number of revolutions of a hysteresis motor without generating a self-exciting phenomenon while a filter circuit is provided. The purpose is to provide.

[0007]

According to a first aspect of the present invention, there is provided an electric motor control device for driving and controlling a hysteresis electric motor, wherein electric power from a commercial power supply has a desired voltage and frequency. A variable voltage variable frequency power supply device for converting the output into a variable voltage variable frequency power supply device, a filter circuit having a capacitor and provided at an output section of the variable voltage variable frequency power supply device for smoothing an output from the variable voltage variable frequency power supply device, and the filter circuit Opening and closing means for turning on and off the
A control circuit for controlling the opening / closing means, wherein a capacitor of the filter circuit is selected so that a back electromotive voltage of the hysteresis motor does not rise to a rated voltage or more due to a self-excitation phenomenon. Therefore, according to the present invention, it is possible to monitor the rotation speed of the hysteresis motor without causing a self-excitation phenomenon while the filter circuit is provided.

Further, in the invention according to claim 2, when the output frequency of the variable voltage variable frequency power supply is equal to or lower than a predetermined value, the filter circuit is turned off to drive the hysteresis motor, and the variable circuit is driven at a predetermined time period. The output of the voltage variable frequency power supply is stopped for a predetermined time, and the frequency of the back electromotive voltage of the hysteresis motor is monitored. Therefore, according to the present invention, it is possible to monitor the rotation speed of the hysteresis motor without causing a self-excitation phenomenon while the filter circuit is provided.

Further, according to the present invention, when the output frequency of the variable voltage variable frequency power supply is accelerating or decelerating, the filter circuit is turned off and the hysteresis motor is driven, and the filter circuit is turned off at a predetermined time period. The output of the variable voltage variable frequency power supply is stopped for a predetermined time, and the frequency of the back electromotive voltage of the hysteresis motor is monitored. Therefore, according to the present invention, it is possible to monitor the rotation speed of the hysteresis motor without causing a self-excitation phenomenon while the filter circuit is provided.

Further, according to the present invention, the output of the variable voltage / variable frequency power supply is stopped for a predetermined time while the filter circuit remains on, and the back electromotive voltage of the hysteresis motor is reduced during the stop. It is characterized in that, based on the detected back electromotive voltage, the variable voltage variable frequency power supply is operated again to continue operating the hysteresis motor. Therefore, according to the present invention, it is possible to monitor the rotation speed of the hysteresis motor without causing a self-excitation phenomenon while the filter circuit is provided.

According to a fifth aspect of the present invention, the capacitor of the filter circuit is provided such that a current flowing by the back electromotive force of the hysteresis motor becomes equal to or less than a rated current while the variable voltage variable frequency power supply is stopped for a predetermined time. It is characterized by selecting the capacity. Thus, according to the present invention,
It is possible to monitor the number of rotations of the hysteresis motor without causing a self-exciting phenomenon with the filter circuit provided.

Further, the invention according to claim 6 is characterized in that the output of the variable voltage variable frequency power supply is stopped for a predetermined time at a predetermined time period. Therefore, according to the present invention, it is possible to monitor the rotation speed of the hysteresis motor without causing a self-excitation phenomenon while the filter circuit is provided.

Further, according to the present invention, the output of the variable voltage variable frequency power supply is stopped for a predetermined time and the detection result of the back electromotive force of the hysteresis motor is determined before the stop of the variable voltage variable frequency power supply. If a difference equal to or more than the predetermined value has occurred, the output frequency of the variable voltage variable frequency power supply device is changed to a difference within the predetermined value, and the operation is performed again. Therefore, according to the present invention, by performing the hysteresis motor monitoring operation, it becomes possible to drive the hysteresis motor at a slip frequency within a specified value.

According to an eighth aspect of the present invention, there is provided a variable voltage / variable frequency power supply device comprising: a converter for converting commercial power to DC; a DC filter circuit for smoothing DC; and an inverter for converting DC to AC. It is characterized by comprising a control circuit for controlling the converter and the inverse converter.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the commercial power supply 1 is converted into a desired voltage and frequency by a VVVF 2;
The hysteresis motor 3 as a load is driven by the electric power. Between the output side of the VVVF 2 and the hysteresis motor 3, a filter circuit composed of a reactor 4 and a capacitor 5 and switches 6, 7 are provided, and a switch 8 for inputting a load is provided at the output.

Next, the normal operation will be described. When the hysteresis motor 3 is driven by VVVF2, the filter circuit is in an off state (switch 6 is on and switch 7 is off) in order to avoid resonance of the filter circuit at an intermediate frequency during startup and acceleration operation. The device 8 is turned on and driven.

When VVVF2 reaches the rated frequency, a filter input command is output from the filter control circuit 9, whereby the switch 6 connected in parallel to the reactor 4
Is turned off, and the switch 7 provided in the preceding stage of the capacitor 5 is turned on, whereby the reactor 4 and the capacitor 5 constituting the filter circuit are turned on.

The VVVF 2 uses a monitoring operation method for detecting slippage of the hysteresis motor 3 in order to prevent the rotor from generating heat due to loss of synchronism due to loss of synchronism when the overload occurs during the synchronous operation. It is carried out.

The start / stop control circuit 10 sets the set time of the hysteresis motor monitoring cycle to, for example, VV every 30 seconds.
The output of the VF 2 is stopped for a predetermined time (for example, 1 second), the hysteresis motor back electromotive voltage V hysteresis motor is detected by the rotation detector 11 during that time, and the rotation speed is displayed on the display 14. The hysteresis motor rotation speed f hysteresis motor obtained by the rotation detector 11 is based on the inverter output frequency fINV detected by the frequency detector 12 and the frequency comparator 13.
, The slip is detected, and the state of the hysteresis motor is monitored (hysteresis motor monitoring). Note that VVVF
2, after stopping for a predetermined time (for example, Is), restart the operation at the frequency before the stop and continue the hysteresis motor operation. In this hysteresis motor monitoring operation, when the hysteresis motor is monitored when the filter circuit is not in operation, the hysteresis motor back electromotive voltage during the hysteresis motor monitoring is usually 1/2 to 1/3 of the power supply voltage. When the hysteresis motor is monitored in a state where the power is on, if the capacity of the filter capacitor 5 is large, the hysteresis motor back electromotive voltage V hysteresis motor rises due to a self-excitation phenomenon, and a voltage exceeding the power supply voltage may be generated. For this reason, the capacity of the filter capacitor 5 should be selected so that it does not rise above the rated voltage of the power supply due to the self-excited phenomenon, so as to be below the exciting current of the hysteresis motor and below the rated current of VVVF2. I do. FIG. 2 shows the relationship between the measurement results of the back electromotive voltage VHM when the hysteresis motor is connected to the capacitor and the capacitor capacity is varied in a state where the hysteresis motor is operated at the rated frequency to select the amount of the filter capacitor. From FIG. 2, the amount of the capacitor at which the back electromotive voltage VHM does not increase is set.

Further, in the present embodiment, the filter control circuit 9 is controlled according to a filter input condition as shown in FIG. That is, when the power supply is rated (acceleration → highest frequency (for example, 1 k
Hz) → automatic transition to constant speed operation), the output frequency of VVVF2 is followed (decelerated or accelerated) by the operation / stop control circuit 10 according to the slip frequency obtained in the hysteresis motor monitoring operation, Thereafter, the operation is returned to the power supply rated operation and the operation is continued. At this time, if the output frequency is equal to or more than a predetermined value (for example, 95% or more), the follow-up operation is performed while the filter circuit is on, and if the output frequency is equal to or less than the predetermined value (for example, less than 95%), the filter circuit is turned off.

According to the present embodiment, it is possible to monitor the rotation speed of the hysteresis motor without causing a self-excitation phenomenon while the filter circuit is provided, and to generate a slip when the power supply is in a rated state. Even under the condition that the output frequency is equal to or higher than the predetermined value, the monitoring of the hysteresis motor is continued with the filter circuit provided, and the following operation becomes possible.

Next, a second embodiment will be described. In the present embodiment, the output of VVVF2 is set for a predetermined time (for example, 1
Second), when the back electromotive voltage of the hysteresis motor 3 is measured and the difference between the frequency before the stop of VVVF and the frequency before the stop is more than a specified value (for example, 3 Hz), the output frequency of the power supply device is set to a predetermined value. The operation is changed again within the difference (for example, 2 Hz).

At this time, VVVF2 is set to VV
While the output of the VF 2 is stopped for a predetermined time, control of a converter (for example, a thyristor rectifier) that converts commercial power into DC may be temporarily stopped.

According to the present embodiment, by performing the hysteresis motor monitoring operation, the hysteresis motor can be driven at a slip frequency within a specified value.
Next, a third embodiment will be described.

As shown in FIG. 4, the present embodiment is different from FIG.
In the configuration of VVVF, a converter 21 for converting the commercial power supply 1 to DC, a DC filter circuit 22, an inverse converter 23 for converting DC to AC, and a converter for converting a desired output voltage and frequency It comprises a control circuit 24 for controlling.

In this embodiment, as shown in FIG. 5, the converter is constituted by a thyristor rectifier 25 and has a phase control circuit 26 for controlling the thyristor rectifier 25 so as to obtain a desired output voltage. ing. Although FIG. 5 shows a three-phase configuration, a one-phase configuration may be used. As shown in FIG. 6, the converter of the present embodiment is replaced with a diode rectifier 27.
And the chopper circuit 28, a voltage control circuit 29 for controlling the chopper circuit 28 may be used.

As shown in FIG. 7, the inverter 30 comprises a semiconductor element (for example, a transistor) with a gate control pole, and a control circuit 31 for performing PAM or PWM control on these inverter circuits. As shown in FIG. 8, the inverter 32 is an insulating semiconductor device (for example, IGB) as a semiconductor device with a gate control pole.
T), and these inverter circuits may be constituted by a control circuit 33 that performs PAM or PWM control.

FIG. 9 shows an example of an output voltage waveform at the time of PAM or PWM control. Next, a fourth embodiment will be described. As shown in FIG. 10, in the present embodiment, VVV
To temporarily stop the output of F, the control circuit stops the gate signal of the semiconductor device with gate control that constitutes the inverter circuit. Therefore, the stop of the gate signal of the semiconductor device is controlled by the hysteresis motor monitoring signal.

Next, the operation will be described. As shown in FIG. 10, the main circuit of VVVF is constituted by the commercial power supply 1, the diode rectifier 34, the chopper circuit 35, the DC filter circuit 36, and the inverter circuit 37. Inverter circuit 37
Is composed of a semiconductor device with a gate control (for example, IGBT), and has a gate control of an inverter circuit 37 through a control circuit 39 and a gate drive circuit 40 by a hysteresis motor monitoring signal from a hysteresis motor monitoring control circuit 38. The semiconductor element is controlled on / off, and VV
The VF output is temporarily stopped.

[0030]

As described above, according to the present invention, the number of rotations of the hysteresis motor can be monitored without generating a self-exciting phenomenon by providing an optimum filter circuit in the output section as the motor control device. Can be. In addition, when slippage occurs in the hysteresis motor, the inverter output frequency is controlled to eliminate the slippage, and the hysteresis motor can be safely operated without increasing the voltage of the hysteresis motor.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a graph showing a back electromotive voltage-capacitor amount characteristic at a rated frequency in the first embodiment.

FIG. 3 is a block diagram of a filter input interlock block.

FIG. 4 shows VVV in the third embodiment of the present invention.
The schematic block diagram which shows F.

FIG. 5 is a schematic configuration diagram showing a VVVF converter according to the present invention.

FIG. 6 is a schematic configuration diagram showing another converter of VVVF of the present invention.

FIG. 7 is a schematic configuration diagram showing a VVVF inverter according to the present invention.

FIG. 8 is a schematic configuration diagram showing another inverter for VVVF according to the present invention.

FIG. 9 shows a PAM according to the third embodiment of the present invention.
FIG. 4 is an output voltage waveform diagram during / PWM control.

FIG. 10 is a schematic configuration diagram showing a fourth embodiment of the present invention.

[Explanation of symbols]

1 ... commercial power supply, 2 ... VVVF, 3 ... hysteresis motor 4 ... reactor, 5 ... condenser, 6,7,8 ...
Switch 9: Filter control circuit, 10: Start / stop control circuit 11: Rotation detector, 12: Frequency detector, 13 ...
Frequency comparator

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (8)

[Claims] 1. A motor control device for driving and controlling a hysteresis motor, comprising: a variable voltage variable frequency power supply device for converting electric power from a commercial power supply into electric power having a desired voltage and frequency and outputting the electric power; A filter circuit provided at an output unit of the variable frequency power supply device, for smoothing an output from the variable voltage variable frequency power supply device, opening and closing means for turning on and off the filter circuit, and a control circuit for controlling the opening and closing means, The motor control device is characterized in that a capacitor of the filter circuit is selected so that a back electromotive voltage of the hysteresis motor does not increase to a rated voltage or more due to a self-excitation phenomenon. 2. When the output frequency of the variable voltage variable frequency power supply is equal to or lower than a predetermined value, the filter circuit is turned off to drive the hysteresis motor, and the variable voltage variable frequency power supply at a predetermined time period. 2. The motor control device according to claim 1, wherein the output of the motor is stopped for a predetermined time to monitor the frequency of the back electromotive voltage of the hysteresis motor. 3. When the output frequency of the variable voltage variable frequency power supply is accelerating or decelerating, the filter circuit is turned off to drive the hysteresis motor, and the variable voltage variable frequency power supply is driven at a predetermined time period. 2. The motor control device according to claim 1, wherein the output of the device is stopped for a predetermined time to monitor the frequency of the back electromotive voltage of the hysteresis motor. 4. The output of the variable voltage / variable frequency power supply is stopped for a predetermined time while the filter circuit remains on, and the back electromotive voltage of the hysteresis motor is detected while the output is stopped. 2. The variable voltage variable frequency power supply is operated again based on the back electromotive force to continue operating the hysteresis motor.
An electric motor control device as described in the above. 5. The capacitor of the filter circuit is selected such that a current flowing by a back electromotive force of the hysteresis motor is equal to or less than a rated current while the variable voltage variable frequency power supply is stopped for a predetermined time. The motor control device according to claim 3, wherein: 6. The motor control device according to claim 4, wherein the output of the variable voltage / variable frequency power supply is stopped for a predetermined time at a predetermined time period. 7. The output of the variable voltage variable frequency power supply is stopped for a predetermined time, and the detection result of the back electromotive voltage of the hysteresis motor is a difference of a predetermined value or more from the value before the stop of the variable voltage variable frequency power supply. The motor control device according to any one of claims 2 to 4, wherein when the occurrence of the error occurs, the output frequency of the variable voltage variable frequency power supply device is changed to a difference within a predetermined value and the operation is performed again. . 8. The variable voltage / variable frequency power supply,
It comprises a converter for converting the commercial power to DC, a DC filter circuit for smoothing DC, an inverter for converting DC to AC, and a control circuit for controlling the converter and the inverter. The motor control device according to claim 1, wherein: