JPS5854889A - Controller for speed of revolution of induction motor - Google Patents

Abstract

PURPOSE:To simplify constitution by forming the AC circuit side only by elements controlling power, such as a semiconductor control rectifying device, a phase synchronous signal generating section, etc. CONSTITUTION:An arithmetic section 12 conducts PID arithmetical operation using signals E4 as measuring value and signals EO as set value, and outputs control signals E5. The control signals E5 are digitally converted into signals E6 by means of a V/F converter 14, and transmitted to a counter 17. A zero-cross detecting circuit 16 detects the zero-cross point of the voltage wave-form ESO of a power supply 2, and outputs signals E7. Photo thyristors PS1, PS2 are ON- OFF controlled by the output of the counter 17. The firing angle of a voltage wave-form ES1 applied to the motor 1 is controlled through the operation of the photo thyristors PS1, PS2.

Description

[Detailed description of the invention] The present invention relates to a rotational speed control device for an induction motor.

Conventionally, there has been a rotational speed control device for an induction motor as shown in FIG. In Fig. 1, 1 is an induction motor, 2
3 is an AC power supply, 3 is a tachometer that outputs a voltage signal E□ proportional to the rotational speed of the motor 1, and 4 is a signal E1 and a setting signal E.
. a rotational speed setting section consisting of a differential amplifier inputting 5;
is a photoconductive element whose output is controlled by the output of the rotation speed setting unit 4; 6 is an AC voltage control unit consisting of diodes D□ to D4 and thyristor SCR; 7 is a double base diode (unijunction transistor).
, a thyristor phase control section consisting of the passive element RT of the photocoupler 5, resistors R□, R2, and a capacitor C, and 8 is a drive power supply section of the phase control section 7 consisting of a diode D5, a T resistor R3, and a zener diode z0. .

In such a conventional device, the firing angle of the power supply voltage of the motor 1 is controlled by a thyristor SCH to control the average voltage of the voltage applied to the motor 1, thereby obtaining a predetermined rotation speed.

However, in the conventional device, the power supply circuit side of the electric motor 1 includes an AC voltage control section 6. It is complicated because it is composed of a phase control section 7 centered on a double base diode, a UJT, etc. In addition, since the control signal is given by the comparison operation in the rotation speed setting section 4, the rotation speed control range is only 1 to 178 degrees, and it is difficult to smoothly control the rotation speed. It was difficult.

On the other hand, recent advances in technology in the electronics field have been remarkable, and inexpensive, high-performance devices, especially a wide variety of digital circuit elements, have become available.
, it has become highly desirable to apply such elements to the above-mentioned devices.

The present invention has been made in view of the above points, and has the purpose of simplifying the configuration of an AC circuit and facilitating the configuration using digital circuit elements and widening the rotational speed range to perform smooth control. , an object of the present invention is to provide a device having a PID calculation control section.

The present invention will be described below with reference to the drawings.

FIG. 2 is an explanatory diagram of the configuration of an apparatus according to an embodiment of the present invention. In Fig. 2, 1 is an induction motor, 2 is an AC power supply,
9 is a tachometer that outputs a sine wave voltage signal E2 with a frequency proportional to the rotational speed of the motor 1; 10 is a sine wave voltage signal E2;
11 is an F/V converter that converts the frequency signal E3 into an analog signal E4. 12 is a rotation speed setting signal E. set value, signal E4
PID is calculated using the measured value and outputs the signal E5.
The ID calculation unit 14 is a V/F converter that converts the signal E5 into a frequency signal E6.

15 is triac T photothyristor pS□ and I
AC voltage control section consisting of I pS2, 16 a photothyristor coupler PC, zero cross detection circuit consisting of pC2 and NAND circuit NAND, 17 a counter, 18 CP
It is U.

Next, the operation of the apparatus having the above configuration will be explained with reference to FIGS. 3 and 4.

The calculation unit 12 converts the signal E4 into a measured value and a signal E. Set value (
5) Perform the PID calculation as follows and output the control signal E5.

Now, the control signal E5 is digitally converted by the v/F converter 14, becomes a signal E6, and is sent to the counter 17.
Therefore, if the signal E6 is used as the output signal of the calculation unit 12, and the relationship between the person and the output is shown, Figure 3 (C) and (2)
As in, when the measured value (signal E4)>the set value (signal Eo), the signal E6 becomes a low frequency; conversely, when the measured value <the set value, the signal E6 becomes a high frequency. Note that the signal E4 is a sine wave signal E2 with a frequency proportional to the rotational speed, which is sent to the comparator 1.
0 into a square wave signal E3, and an F/v converter 11 performs analog conversion.

On the other hand, the zero-cross detection circuit 16 is configured as shown in FIGS.
As shown in b), the Xerox point of the voltage waveform ESO of the power source 2 is detected, and a signal E7 periodic to the voltage waveform Eso is output. The counter 17 is reset at the falling edge of the signal E7, and starts at the rising edge of the signal E7. Further, the set value of the counter 17 is given from the CPU 18. Then, the counter 17 outputs a signal E8 of 1'1 when II Q II1 counts up with the reset signal (Fig. 3 (E)).
On/off control of photothyristors PS□ and PS2 (
4) Do. The firing angle of the voltage waveform E81 applied to the motor 1 is controlled by the operation of the photothyristors pS and pS2, and a current I is applied to the power supply line of the motor 1.
s flows (Figure 5 (c) and (g)).

The above firing angle control will be explained in more detail.

When the rotation speed of electric motor 1 is υ slower than the set value (E4〈Eo)
, the signal E6 has a high frequency, so the count-up time T□ of the counter 7 is short. Conversely, when the rotation speed is faster than the set value (E4 > E□), the signal E
6 has a low frequency, so the count-up time -T2 of the counter 7 is long (FIG. 3 (e)).

Therefore, the photothyristors PS□ and PS2 are turned off when the current Is is zero (as they are inductance loads, so there is a phase lag in the current Is), and are turned on at firing angles corresponding to the count-up times T□, T2, etc. The average voltage of the applied power source can be controlled and the rotation speed can be maintained at a set value.

The above device is used in various fields, and is particularly suitable for application to a rotation speed control device for a blood pump in an artificial kidney device.

As shown in FIG. 4, the main parts of the blood pump 20 include a tube 22 installed in a cylindrical wall 21;
p-shira 23, which rotates while pressing against the wall surface and squeezing;
It has an induction motor (not shown) that rotates the roller 23, and the rotation of the roller 23 transfers blood within the tube 22 and circulates it between the artery and the dialyzer vein.

In such a blood pump 21, the roller 23 operates to squeeze out the tube 22 at point A in FIG. is likely to occur.

In addition, since the tube 22 is sandwiched between the inner wall 21 and the roller 23 to transfer blood, if the tube 22 gets caught and continues to be rotated at the maximum torque of the motor, it will not be damaged. be.

According to the control device of the present invention, the calculation unit 1.2 performs differential calculation,
(o$*) fi=*t7+Of, □1ilF! *
'/f di y 7'. 6-Ra rotational unevenness can be suppressed. Also, since the electric motor 1 has torque characteristics as shown in FIG. 5 (characteristic (a): thick firing angle, characteristic (b): small firing angle), By setting it to a predetermined value, the maximum torque of the electric motor 1 can be controlled. Therefore, if the blood pump does not rotate even after the rotational speed is set, the torque can be limited or the drive of the electric motor can be stopped to prevent damage to the tube 22.

As explained above, according to the rotational speed control device for an induction motor of the present invention, the AC circuit side is equipped with a semiconductor-controlled rectifying element,
The configuration is simple because it consists only of elements that control power, such as a phase synchronization signal generator (zero-cross detection circuit). Furthermore, since there is no need to use high-voltage components on the AC circuit side, reliability is improved. Furthermore, since the calculation section performs PID calculation, rotational speed control becomes smooth and the speed control range can be expanded to 1-1140.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the configuration of a conventional rotational speed control device;
3 is an explanatory diagram of the configuration of the rotation speed control device according to the present invention, FIG. 3 is an explanatory diagram of the operation of the device of the present invention (7), FIG.
The figure is a torque characteristic diagram of an induction motor. 1...Induction motor, 2...Power supply, 9...Tachometer,
1o...Comparator, :I-1,=F/V :I
y bar p, 12-0. Performance n part, 14...V/
F converter, 15... AC voltage control section, 1G...
Zero cross detection circuit, 17... Counter, 18...
CPU 0 (8)

Claims (1)

[Scope of Claims] A device for controlling the rotational speed of the induction motor by controlling the firing angle of a power supply voltage waveform applied to the induction motor using a semiconductor-controlled rectifier, comprising: a frequency corresponding to the rotational speed of the induction motor; A tachometer that outputs a signal, a phase synchronization signal generator that outputs a signal synchronized with the phase of the power supply voltage, and a predetermined control calculation using the rotational speed signal as a measured value to output a digitized control signal. a counter that counts the control signal and controls the semiconductor-controlled rectifying element with a count-up signal, the counter whose reset and start are controlled by the signal of the phase synchronization signal generator; 1. A rotation speed control device for an induction motor, comprising: a setting section that provides a set value to a counter.