JPS58201594A - Drive system for induction motor - Google Patents

Abstract

PURPOSE:To smoothly decelerate a rotor by controlling the phase shifting angle of the positive and negative waveform in an AC power source on the basis of a phase shifting angle control data which is stored in a memory. CONSTITUTION:A memory 4 stores a high speed rotary zone data of a motor 1, a phase shifting angle control data corresponding to the high speed rotating zone, low speed rotating zone data, phase shifting control data corresponding to the low speed rotating zone, and a speed indicating data, and the like. A control circuit 6 counts by a counter 6a the digital signal which is inputted through a position detector 3 of the motor 1 and a converter 5, compares the counted number with various data from the memory 4, and controls to drive the motor 1 through a drive circuit 7. The drive circuit 7 controls to open or close a bidirectional element on the basis of the phase shifting angle control data which is inputted from the control circuit 6 in response to the various operation modes of the motor 1, and supplies the voltage of an AC power source AC which is controlled by stationary coils L1, L2.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a capacitor running type induction motor drive system, and more particularly to an induction motor drive system that allows an induction motor to rotate smoothly in a low speed rotation range.

Conventional technology Conventionally, in the above-mentioned type of induction motor drive system, AC power with a controlled phase shift angle is applied to the main coil in the low-speed rotation region to accelerate the rotor, and then the positive direction voltage of the AC power is applied to the main coil. In this method, the rotor is driven to rotate at a low speed by applying voltage to the coil to constrain the rotor, decelerating it by braking, accelerating it, and repeatedly braking it. It had the disadvantage that movement was not smooth.

OBJECTS OF THE INVENTION An object of the present invention is to provide an induction motor drive system that can smoothly decelerate the rotational drive of the rotor 9 in a low speed rotation region in view of the above-mentioned conventional drawbacks.

Composition of the invention The system of the present invention will be explained below according to examples.

FIG. 1 is an electrical block diagram schematically showing an induction motor drive system according to the present invention. In the figure, an induction motor (hereinafter referred to as a motor) 1 is of a capacitor running type, and fixed windings L1, One end of L2 is connected in common and connected to one side of the AC power supply AC, and one fixed winding L2 to which the phase advance capacitor C is connected in series is connected in common, and is connected to a trihook, for example, which will be described later. It is commonly connected to the anodes of bidirectional elements 2 such as. Further, a position detector 3 such as an alternating current generator (tacho generator) is connected to one end of the rotor of the motor 1, and outputs a predetermined number of analog signals per revolution according to the rotation of the motor 1. There is.

The memory 4 stores high-speed rotation area data of the motor 1, phase shift angle control data corresponding to the high-speed rotation area, low-speed rotation area data, phase shift angle control data corresponding to the low-speed rotation area,
It also includes a read-only memory in which various data such as speed instruction data are written in advance.

The conversion circuit 5 converts the detection signal ss consisting of six analog signals inputted from the position detector 3 into a digital signal DGS, and outputs the digital signal DGS to the control circuit 6.

The control circuit 6 counts the digital signal DGS inputted from the conversion circuit 5 using a counter circuit 6a, and also calculates the count number of the counter circuit 6a and various data transferred from the memory 4 in 1rII via the data bus. are compared sequentially, and the motor is controlled as described below. Incidentally, the memory 4 and the control circuit 6 are constituted by a one-chip microcomputer.

The drive circuit 7 applies a gate voltage to the gate of the bidirectional element 2 based on the respective phase shift angle control data inputted from the control circuit 6 in accordance with various operation modes of the motor, thereby controlling the bidirectional element 2. 2 to open and close the fixed windings L1 and L2 to supply an alternating current power supply AC whose phase shift angle is controlled.

Next, the operation of this embodiment will be explained with reference to FIGS. 2 to 4.

First, the rotation speed N of a capacitor running type motor is determined by 120・f N= □ (P is the number of poles, f is the AC power frequency.) If the number of poles P is constant, the rotation speed N is It can be varied by changing the AC power frequency f.

A running object (not shown) connected to the motor 1 is the origin P
1, the control circuit 6 outputs the acceleration data accessed from the memory 4 to the drive circuit 7, opens and closes the bidirectional element, and supplies AC power supply AC whose phase shift angle is controlled to enable acceleration. and accelerate the drive.

Due to the above operation, the traveling object moves a predetermined distance #Q1 from the origin P1,
When the object is moved or after the object is accelerated for a predetermined time tl [indicated by point P2 in FIG. 2]. ],
The control circuit 6 calculates the number of digital signals DGS that are output from the position detection signal 3 and input from the conversion circuit 5 based on a signal from a limit switch LS that is turned on when it comes into contact with a traveling object, for example, and a counter circuit 6 @ At the same time, the rotation speed of the motor 1 calculated by the reference clock signal output from the oscillator 6b and the manually input digital DGS is compared with the rotation speed data stored in the memory 4, and the rotation speed data of the motor 1 is counted. When the rotation speed is less than the predetermined rotation speed a, an acceleration signal is output to the drive circuit 7 to accelerate the motor 1, and when the rotation speed of the motor 1 is more than the predetermined rotation speed 8, a deceleration signal is output to the drive circuit 7. It outputs a direct current constraint to the rotor of the motor 1, and maintains the rotational speed of the motor 1 at a predetermined rotational speed a.

After the constant speed driving, the count number of the counter circuit 6a is set to a preset count number (indicated by P3 in the figure).

), the control circuit 6 applies DC constraint to the rotor based on the deceleration data accessed from the memory 4, and the motor 1
After decelerating the rotation speed to a predetermined rotation speed, a plurality of positive direction voltages at the frequency of the AC power supply AC supplied to the motor l based on the phase shift angle control data in the low speed rotation region accessed from the memory 4. At the same time as sequentially controlling the phase shift angle of #1 negative direction voltage, for example, a pulsating current (where one cycle is 10 cycles of AC power supply AC)
It is shown by the broken line in Figure 4. ) and controls the rotational speed of the motor 1 to reduce its speed.

Therefore, compared to the conventional motor drive method shown in FIGS. 3(A) and 3(B), this embodiment uses a simpler method to apparently change the AC frequency of the AC power source to smoothly rotate the rotor in the low speed rotation region. It is possible to drive it.

In this embodiment, a low-cost alternating current generator is used as the position detector 3, but the method of the present invention can of course be implemented with a rotary encoder type position detector.

Further, the present invention includes two bidirectional elements 2 as shown in FIG.
Of course, it is also possible to implement a method of controlling the drive of the motor using methods a and 2b.

As described in detail of the invention, the phase shift angle of a plurality of positive waveforms at the AC power frequency is controlled to half a cycle based on the phase shift angle control data stored in the memory in advance, and A plurality of negative direction waveforms are controlled in phase shift angle to form a pulsating current of 1 cycle as a half cycle, and an AC power source consisting of the pulsating current is used to rotationally drive an induction motor to rotationally drive a rotor in a low speed rotation region. This is an induction motor drive system that provides smooth deceleration drive.

[Brief explanation of the drawing]

Fig. 1 is an electrical block diagram showing the outline of the interaction motor drive system according to the present invention, Fig. 2 is a diagram showing the motor operation mode, and Fig. 3 (A) is the acceleration at low speed rotation in the conventional drive system. (B) is a waveform diagram showing the braking waveform during low speed rotation; Figure 4 is a waveform diagram of AC power supplied to the motor; Figure 5 is an electric block showing a modified embodiment of the present invention. In the figure, 1 is the motor, 4 is the memory, f is the AC power frequency, and A
C is an AC power source.

Claims (1)

[Claims] 1. When driving and controlling the induction motor, the phase shift angle of a plurality of positive waveforms at the AC power frequency is controlled to half a cycle based on the phase shift angle control data stored in the memory in advance, and the AC power frequency 1. An induction motor drive system characterized by controlling the phase shift angle of a plurality of negative direction waveforms to form one cycle of pulsating current as a half cycle, and rotationally driving an induction motor by an AC power source made up of the pulsating flow.