KR830001119Y1 - Motor driving device using pulse width modulated inverter - Google Patents

Abstract

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Description

Motor driving device using pulse width modulated inverter

1A and 1B are schematic diagrams of an electric motor driving circuit used in an electric motor driving device as one embodiment according to the present invention.

2 is a detailed view of the signal generation circuit shown in FIG.

3 is a view for explaining the inverter output waveform shown in FIG.

4 is a diagram showing motor driving characteristics in two regions.

5 shows waveforms relating to the operation of a comparator.

6 (a) is a waveform diagram of the analog voltage S (1) corresponding to the command speed of the motor supplied to the voltage-to-frequency converter.

6 (b) is a waveform diagram of a pulse signal S (2) generated from a frequency converter and proportional to the analog voltage S (1).

6 (c) is a waveform diagram of pulse signal S (2) counted by a counter.

Figures 6 (d) and 6 (e) are waveform diagrams of signals and resulting analog voltages generated from digital to analog converters.

FIG. 7 shows analog value signal S (4) which is an output of a function generator corresponding to command speed signal S (1) and shows a change according to the characteristics of a motor.

The present invention relates to a motor drive device for driving an AC motor using a pulse width modulation inverter (PWM inverter).

It is known that the AC motor is operated in each of the A and B areas by dividing it into the area below the base speed (area A) and the area above the base speed (area B) with the basic speed as its boundary. The driving characteristics in each of the B regions are not necessarily satisfied.

Accordingly, an object of the present invention is to obtain a good AC motor driving characteristic based on the idea that a pulse width modulated inverter as a driving power source of an AC motor can drive a sine wave in the A region and a square wave in the B region. .

In the present invention, the AC motor is variably driven by a pulse width modulated inverter connected to a current source. In the area below the basic speed (area A), the torque of the motor is limited to a constant value, and the area above the basic speed is not limited to (B). In the region), the output power is limited to a constant value. In the region A, the motor is driven by a pseudo sine wave using PWM, and in the region B, the motor is driven by a square wave using PWM.

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

1A and 1B show an electric motor driving circuit used in an electric motor driving apparatus as an embodiment according to the present invention. The AC motor 33 includes switching elements 21, 22, 23, 24, 24, 26 and rectifiers 27, 28, such as transistors connected to a DC source 34. It is driven by the inverter circuit consisting of (29), (30), (31) and (32). The bases (b21), (b22), (b23), (b24), (b25) and (b26) of the transistors 21, 22, 23, 24, 25, and 26 are provided. The output of the signal generating circuit shown in FIG. 1A is applied, which includes a wave-wave generating circuit 35, sawtooth wave generating circuit 8, comparator 9, and 10 having a variable frequency and amplitude. (11), inverters (12), (13), and (14).

The sawtooth output Vc at the frequency f 'from the sawtooth wave generating circuit 8 of the sinusoidal wave output ei, which is the frequency f from the sinusoidal wave generating circuit 35, is compared in the comparators 9, 10, and 11, Vc. In the case of <ei, the output of the comparator is at a high level, and in the case of Vc> ei, the output of the comparator is at a low level. Therefore, during the period in which the output of the comparator is at the high level, the transistor that receives the high level signal as the base signal is in a conductive state.

In a PWM inverter, the voltage applied to the motor as a load is in a period in which the upper transistor (connected to the positive terminal side of the DC power supply) and the lower transistor (connected to the negative terminal side of the DC power supply) are in the conduction state at the same time. Determined by That is, when the ratio t / T of the time t in which the transistor is in the conduction state and the chopper period T is changed, the voltage applied to the motor changes linearly in response. The present invention takes advantage of this feature.

2 is a detailed view of the signal generation circuit shown in FIG. 1A. The sinusoidal wave generation circuit consists of a voltage-to-frequency converter (2), a counter (3), a function generator (4), and a digital-to-analog (D / A) converter (5) (6) and (7). The converter 2 is supplied with the analog voltage S 1 corresponding to the command signal of the motor as shown in FIG. 6 (a), and the analog voltage S (1) is supplied from the voltage-to-frequency converter 2. Pulse signal S (2) shown in FIG. This pulse signal S (2) is counted by the counter 3 as shown in FIG. 6 (c). The coefficients of the counter 3 are used as address signals for the digital-to-analog converters 5, 6, and 7, and data corresponding to the address signals is used for the digital-to-analog converters 5, 6, Stored in (7). As such, the data stored in the digital-to-analog converters 5, 6, and 7 are selected and sinusoidal signals S (5), S (6), and S (7) as shown in FIG. And the resulting analog voltages S '(5), S' (6) and S '(7) are generated in the digital to analog converters 5, 6 and 7. On the other hand, the command speed signal S (1) is applied to the function generator 4 as shown in FIG. 6 (a) and the function generator 4 receives the command speed signal S as shown by the solid line in FIG. The signal S (4) of the analog value corresponding to (1) is generated. This analog value signal S (4) may be replaced by the signal of S '(4) or S "(4) shown by dashed lines, depending on the characteristics of the motor. The analog value signal S (4) may be digital. To analog converters (5), (6) and (7), and analog to analog converters (5), (6) and (7), analog voltages S '(5) and S' (6). Is multiplied by S '(7) with the analog value of signal S (4), and therefore from digital to analog converters 5, 6, and 7, as shown in FIG. A sinusoidal signal ei is generated, thus the amplitude of the sinusoidal signal ei is determined by the analog value of the signal S4 from the function function generator 4. The comparators 9, 10 and 11 are digital versus ana The output ei from the log converters 5, 6, and 7 is received as the first input signal, and the output Vc from the sawtooth wave generating circuit 8 is received as the second input signal. , (10), (11) outputs via transistors (15), (17), (19) Supplied to the bases b21, b23, and b25 of (21) (23) and (25), and also the inverters (12), (13), (14) and drivers (16) and (18). , 20 is supplied to the bases b22, b24, and b26 of the transistors 22, 24, and 26.

In FIG. 2, the sinusoidal signal ei of frequency f and the sawtooth signal Vc of frequency f are compared by comparators 9, 10 and 11 and pulsed as shown in FIG. The transistor is selectively conducted in response to the waveform. In this case, the comparison value of the sinusoidal signal ei changes in response to the frequency f in the function generator 4.

FIG. 3 shows the waveform of the sinusoidal wave ei and the corresponding output waveform of the PWM inverter when the PWM inverter of FIG. 1B is operated using the circuit of FIG. ei (1) and ei (2) are input sinusoidal waveforms in the area A, the amplitude of which is small, and the motor is driven by the corresponding inverter output waveforms PWM (1) and PWM (2). On the other hand, ei (3) and ei (4) are input sinusoidal waveforms in the region B and have a large amplitude, and the motor is driven by the corresponding inverter output waveforms PWM (3) and PWM (4).

As described above, according to the embodiment of the present invention, since the pseudo sine wave using the PWM is applied to the motor in the area A, smooth motor rotation at low speed is achieved, and the square wave using the PWM is applied to the motor in the B area, The driving method of the electric motor which does not reduce the power utilization rate in the motor is achieved. In addition, the switching between the A and B areas can be performed smoothly, and the continuous control can be ensured over the entire A and B areas.

Claims (1)

The motor driving apparatus using the pulse width modulation inverter responds to a circuit for generating a sinusoidal signal ei, a circuit for generating a sawtooth wave signal Vc, a comparator for receiving and comparing a sinusoidal signal ei and a sawtooth wave signal Vc, and a signal from the comparator. A pulse width modulation inverter for driving an electric motor is provided so that the motor is driven by a pulse width modulated waveform corresponding to a pseudo sine wave voltage in the region below the basic speed of the motor, and the motor is driven by a square wave in the region above the basic speed. The sinusoidal signal generating circuit includes a voltage-to-frequency converter 12 for receiving a signal corresponding to the command speed of the motor, a counter 3 for counting pulse signals from the voltage-to-frequency converter, and a speed command signal. Sine in response to the function generator 4 receiving and the signals from the counter 3 and the function generator 4 Issued by the comparator (9, 10, 11) for a digital analogue converter motor drive system using a pulse width modulation inverter consisting of (5, 6, 7) to be applied to the signal.