KR200141191Y1 - A speed control circuit for an induction motor - Google Patents

Abstract

The speed control circuit of the induction motor of the present invention includes an image detection unit for detecting an input unit phase loss of a converter for converting an AC power source to a DC power source, and providing a compensation value accordingly, a speed command unit for applying a speed command value; And a compensation circuit unit for compensating the speed command value as much as the compensation value of the open phase detection unit during the open phase or single phase through the open phase detection unit, and by further connecting the open phase detection unit as described above, the speed command value suitable for the single phase or phase open phase By compensating for, the torque reduction of the motor is prevented, and accordingly, the speed of the motor can be accurately controlled.

Description

Speed control circuit of induction motor

1 is a block diagram of a speed control circuit of an induction motor according to the prior art.

2 is a block diagram of a speed control circuit of an induction motor according to the present invention.

3 is a detailed circuit diagram of an image detection unit in the speed control circuit of FIG.

* Explanation of symbols for main parts of the drawings

11 power supply unit 12 electric motor

13: converter 14: inverter

15: phase detection part 16: speed command part

17: compensation circuit section 18: triangle wave generator

19: reference signal generator 20: pulse width modulator

21: base drive unit

The present invention relates to a speed control circuit of an induction motor, and more particularly, to a speed control circuit of an induction motor for preventing a torque drop of the motor during phase open or single phase operation.

As shown in FIG. 1, the speed control circuit of the conventional induction motor includes a power supply unit 1 for applying AC power, a converter 3 for converting AC power to DC, and a smoothing capacitor. (C1), an inverter 4 for converting the DC voltage smoothed through the smoothing capacitor C1 into an AC voltage and supplying it to the motor 2, and a speed command unit 5 for applying a speed command value. And pulse width modulation by inputting the reference signal generator 6 and the triangle wave generator 7 for generating the reference signal and the triangle wave, and the outputs of the reference signal generator 6 and the triangle wave generator 7. A pulse width modulator 8 for generating a signal, and a base driver 9 for driving the base of the inverter 4 according to the output of the pulse width modulator 8; Is supplied to the electric motor 2 by switching the transistor of the inverter 4 through Controlling the AC voltage and frequency to control the rotational speed of the motor.

However, the prior art has a problem that it is difficult to control the exact speed by reducing the torque of the motor during single phase or phase open operation.

Therefore, in order to solve the above problems, the present invention connects the phase detection unit to detect a single phase or phase loss and compensates the voltage and frequency command signal values so that the speed of the induction motor can be precisely controlled. The purpose is to provide.

Speed control circuit of the induction motor of the present invention for achieving the above object, the phase detection unit for detecting the phase loss of the input terminal of the converter for converting the AC power source to the DC power source and providing the compensation value accordingly, and applying the speed command value And a compensation circuit unit for compensating for the speed command value by the compensation value of the phase detection unit during phase open or single phase through the phase detection unit.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 2, the speed control circuit of the induction motor of the present invention includes a power supply unit 11, a converter 13 and a smoothing capacitor C1, an inverter 14, a triangular wave generator 18, The pulse width modulator 20 and the base driver 21 are connected in the same manner as in the related art, and an image detection unit for detecting an image at an input terminal of the converter 13 and providing a compensation value in the case of an image or single phase ( 15) is further connected to compensate for the speed command value of the speed command unit 16 as much as the compensation value of the phase detection unit at the time of open phase or single phase.

At this time, the phase detection unit 15 is connected to an input terminal of the converter 13, as shown in FIG. 3, and resistors R1 to R6 for detecting respective phase voltages, and a voltage detected from the resistors is DC. NAND gates for inputting diodes D1 to D3 for rectifying the capacitors, capacitors C2 to C4 for smoothing the voltage rectified by the diodes D1 to D3, and voltages across the capacitors C2 to C4. And a variable resistor VR1 for determining a DC voltage value to be compensated by receiving the output of the NAND gate, wherein a compensation value for single phase or phase loss is determined, and the compensation of the actual speed command value is performed by a compensation circuit unit ( 17) to make the connection.

That is, in the three-phase operation, the output of the phase detection unit 15 becomes 0, and the voltage / frequency command signal is supplied to the reference signal generator 19 only by the speed command unit 16, thereby generating the reference signal. The reference signal of the unit 19 and the triangular wave of the triangular wave generator 18 are input to the pulse width modulator 20 and supplied to the transistor base terminal of the inverter 14 through the base driver 21 to switch transistors. The rotational speed of the motor rotates at the specified speed by adjusting the AC voltage and frequency applied to (12).

On the other hand, when the single phase or one phase is missing, the output from the phase detection unit 15 has an arbitrary compensation value, and the compensation circuit unit 17 compensates the speed command value with an arbitrary compensation value and then the reference signal generator 19 ) To compensate for the reduction of the DC voltage value across the smooth capacitor C1 and the resulting torque reduction of the motor 12.

As described above, according to the present invention, by connecting the phase detection unit and compensating for the speed command value suitable for single phase or phase loss, torque reduction of the motor is prevented, and thus, the speed of the motor can be accurately controlled.

Claims (1)

The phase detection unit for detecting the phase loss of the input terminal of the converter for converting AC power to the DC power source and providing a compensation value, the speed command unit for applying the speed command value, and the phase detection or phase loss through the phase detection unit In an induction motor configured to include a compensation circuit unit for compensating a speed command value by a compensation value of an image detection unit, the image detection unit is connected to an input terminal input to the converter by pairing two resistors to detect each phase voltage. A diode and capacitor for rectifying and smoothing the voltage detected through each pair of resistors, a NAND gate for inputting the voltage across the capacitor, and an output of the NAND gate. Characterized by comprising a variable resistor for determining the DC voltage value to be compensated for Speed control circuit for induction motors.