JPS6028782A - Controller of induction motor - Google Patents

Abstract

PURPOSE:To improve the controlling performance by varying the chopper frequency of a chopper for shortcircuiting the secondary rectified output in response to the slip frequency of a motor. CONSTITUTION:A speed control amplifier 34 outputs a current reference I* in response to the difference between a speed reference NP and a speed feedback signal N, and a current control amplifier 38 outputs the difference V1 between a current reference I* and a current feedback signal I. On the other hand, an operational amplifier 53 outputs the difference between a synchronizing speed N0 and a speed signal N, i.e., a slip corresponding signal VS, which is converted to a triangular wave V2 proportional to the slip. A chopper controller 44 controls a chopper 3 by the pulse signal of the pulse width proportional to the magnitude of the voltage V1. Thus, sufficient secondary current can be flowed in all range of the speed.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an induction motor control device (-) that adjusts the secondary current of a wound induction motor using a chopper and thereby controls the speed of the motor. It is something.

[Technical background of the invention and its problems]

There is a stationary Servius device as a speed control device using secondary current control for a wound induction motor, but the device is large, so it is difficult to apply it to a small motor. In addition, attempts have been made to use a secondary rectifier and chopper for small electric motors, but conventionally the secondary rectifier output is intermittently short-circuited using a chopper with a constant frequency, so impedance increases in the high-speed region. However, there were two limitations in terms of performance (there were two limitations).

[Purpose of the invention]

The present invention changes the chopper frequency of the chopper that short-circuits the secondary rectified output in accordance with the overall frequency of the electric motor, thereby controlling the frequency of the chopper so that sufficient secondary direct current can flow over the entire rotational speed range. The purpose of this invention is to provide a control device for a secondary rectifier chopper short-circuit induction motor that improves performance.

[Summary of the invention]

The present invention rectifies the secondary output of a wound induction motor with a rectifier, and uses a chopper to periodically short-circuit the rectified output to adjust the secondary current, thereby controlling the speed of the motor. In a control device for an induction motor, a chopper frequency adjustment circuit is provided that automatically adjusts the operating frequency of the chopper according to the speed of the motor.
This makes it possible to flow a sufficient secondary current over the entire range of control, and increases the torque sufficiently to improve speed control performance.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG.

In Figure 1 (2), the primary side of the wound induction motor 1 is connected to an AC power supply, and the secondary side is connected to a chopper 3 through a rectifier 2.
, the chopper 3 is energized to short-circuit the output of the rectifier 2 (secondary direct current is thereby controlled).

The speed N of the induction motor is detected via a tachometer 11 and a speed signal generator 21, and the secondary DC current I is detected via a current detector 12 and a current signal generator 22.

4 is a secondary parallel resistor, and 44 is a chopper controller.

Next (the operation of the two-side one-output circuit) will be explained in detail.

Speed control amplifier 3 from speed setter 31 via resistor 32
4 (= A speed reference N is input, and a speed feedback signal N is input from the speed signal generator 21 through a resistor.

The difference N-N is amplified by the input impedance and the impedance ratio, and the output becomes the current reference voltage 8.

This current reference voltage is input to the current control amplifier A via the resistor I, and simultaneously (=from the current signal generator n to the operational amplifier 3
8 (A current feedback signal is input via two resistors 37.

The difference I*-I is amplified by the input impedance and an impedance ratio of 39, and the output v1 becomes the chopper energization signal circuit 420 input.

On the other hand, the operational amplifier 53 (= is the negative input N corresponding to the synchronous speed
o is input via the resistor 52, and a two-speed signal N is also input.

The difference N - No is amplified by an impedance ratio of 54 to the input impedance, and the output becomes a subev equivalent signal v3.

Further, the positive or negative constant voltage of the output of the Zener diode 61 T: voltage limited operational amplifier 60 is multiplied by the slip signal V in the multiplier 55, and the output is
A positive or negative voltage proportional to

The positive or negative voltage of the output of the multiplier 55 is input to the operational amplifier 57 via the resistor 56, and by the action of the capacitor 58, the positive or negative voltage of the input (2, therefore, becomes a constant increase or constant decrease integral output v2, which is used as a triangular wave signal. It is also input to the operational amplifier 60 via the resistor 59.

Since the input and output of the operational amplifier 60 are short-circuited with Zener diodes with opposite directions connected in series with Shimono 61, the amplification factor is almost infinite, but since positive feedback is applied, there is a hysteresis characteristic. When the voltage exceeds a certain level, the output is reversed and becomes a positive or negative output with a constant voltage determined by the Zener voltage.

When this voltage is inverted by operational amplifier B and applied to multiplier 55, the input to operational amplifier 57 is inverted, and the slope of its output is reversed.

The frequency of the triangular wave output from the operational amplifier 57 is proportional to the magnitude of the input voltage from the multiplier 55, and its magnitude is
Since s+=proportional, the frequency of the triangular wave, that is, the chopper frequency, is also proportional to υS (2).

The output v1 of the operational amplifier 38 is input to the operational amplifier 42 via the resistor 40, and simultaneously (-the output v2 of the operational amplifier 57)
is also input via the resistor 41.

Operational amplifier 420 input/output time is Zener diode 43
Since it is short-circuited, its output v3 has a waveform as shown in FIG.

(As shown in Figure 2, the pulse width of the output V varies linearly (2) depending on the magnitude of the output voltage vI of the operational amplifier 38, so if this is used as the chopper energization signal, the average value of the chopper DC can be changed approximately linearly (-) depending on the magnitude of the operational amplifier's output voltage Vl.

In a normal Servius device where the secondary current is a square wave, if the power frequency is f and the slip is S, then the secondary (2 anti-phase 5 +
Currents with harmonic frequencies such as sf and positive phase 7sf are generated, and the negative side (second is (1-6s)f and (1+6s)f
appears as a current. This state is shown in FIG. 3(A) (-).

On the other hand, in the conventional secondary rectifier chopper short-circuit method, the chopper frequency must be constant, for example, if it is a frequency of 2Of, since this is an intermittent frequency, equal amounts of positive phase and negative phase occur, and (1-20-a)f and (1+
20s) appears as a current of f. This state is shown in Figure 3 (B
) (1 shown.

Next, in the secondary rectifier chopper short-circuit method of the present invention, the chopper frequency is made proportional to 2, so for example, 20sf
If it is controlled at the frequency of - next side (- is (1-21
, s ) f and (1+19a) f . This state is shown in FIG. 3(C) (1).

Next, the present invention will be described in detail based on the following (two electric bases, etc.).

The ratio of the chopper frequency (2 to the impedance source frequency) seen from the negative side with respect to the rotational speed N is as shown in FIG.

In the present invention, as shown by ZA + ZB, when the synchronous speed approaches 1 (approximately 2) (2), in the conventional method, ZC * ZD (
= As shown, it is clear that the value is always high.

If the leakage reactance of the electric motor is 0.2P, U, then
The current that can be passed at the chopper frequency is as shown in 1 in FIG.

The device of the present invention normally has a square torque load as shown in Fig. 4 T(N).
Although the present invention can flow a sufficient magnetic current (0.25 to 5P, U,) over the entire speed range, the conventional method has a limit. It's obvious.

That is, in order to obtain sufficient torque with the conventional method, it is necessary to use a special electric motor with low leakage reactance, but this is not necessary with the present invention.

〔Effect of the invention〕

As explained above, according to the present invention. In an induction motor control device that is equipped with a chopper that short-circuits a rectifier and its output, and controls the speed of the induction motor by opening and closing the chopper (2), the switching frequency of the chopper is set as a function of all 9 functions of the induction motor. Since the impedance in the high speed region is lowered by changing the impedance, it is possible to flow sufficient secondary current throughout the entire speed range, thereby obtaining sufficient torque and improving speed control performance. can do.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing one embodiment of the present invention, and Fig. 2 is a system diagram showing an embodiment of the present invention.
Figure 3 is a time chart showing the waveform of the chopper control signal vI I V2 +V in the figure.
FIG. 4 is a diagram showing the impedance of the chopper frequency as seen from the side next to the magnetic motor. 1 Wound type conductive motor 2 Current generator 3 Chopper 4 Parallel resistor 11 Tachometer generator 12 Current detector 31 Speed setting device 38, 42.57.62.64 Operational amplifier 44
Chopper controller 55 Norishinki (8733) Agent Patent attorney Yoshiaki Inomata (1 person) ill Figure 2 Figure ll3al Figure 4

Claims (1)

[Claims] The secondary output of the wound induction motor is rectified by a rectifier, and the rectified output is periodically shorted by a chopper (2) to adjust the secondary current, and this (2) is used to control the speed of the motor. !A control device for an induction chamber 1iJJ Iso, characterized in that a chopper frequency adjustment circuit is provided for automatically adjusting the operating frequency of the chopper according to the frequency of the electric motor.