CN102111096A

CN102111096A - Method for preventing asynchronous motor from shocking during soft start

Info

Publication number: CN102111096A
Application number: CN 201110047287
Authority: CN
Inventors: 黄声华; 邓衍贵; 苏洪昌; 杨青; 曾昭国
Original assignee: YICHANG QINGJIANG ELECTRIC CO Ltd
Current assignee: YICHANG QINGJIANG ELECTRIC CO Ltd
Priority date: 2011-02-28
Filing date: 2011-02-28
Publication date: 2011-06-29
Anticipated expiration: 2031-02-28
Also published as: CN102111096B

Abstract

The invention relates to a method for preventing an asynchronous motor from shocking during soft start. An effective phase shift angle gamma of a thyristor can be determined only by detecting voltages at both ends of a bidirectional thyristor instead of detecting a power factor angle phi in the soft start operation of the asynchronous motor. Through the dynamic regulation of thyristor phase shift angle alpha according to the effective phase shift angle gamma of the thyristor, the stability of the effective phase shift angle gamma of the thyristor is kept and the vibration in the process of the soft start of the asynchronous motor is reduced or eliminated. When the method provided by the invention is used, secondary impact currents cannot be generated in the motor, so that the requirements of the soft start of the asynchronous motor are better met, and the functions of light load voltage regulation and energy conservation of the asynchronous motor can be fulfilled.

Description

A kind of method that prevents asynchronous motor soft start concussion

Technical field

The invention belongs to Motor Control and single chip microcomputer applied technical field, be specifically related to a kind of method that prevents asynchronous motor soft start concussion.

Background technology

Adopting the Soft Starter of Induction Motor of thyristor phase-shift voltage regulating to have advantages such as volume is little, in light weight, originate mode is many, control is flexible, is one of scheme of present asynchronous motor soft start first-selection.But the harmonic voltage electric current that the thyristor phase-shift voltage regulating produces, can influence the starting operation performance of asynchronous motor, be embodied in, the starting torque of asynchronous motor reduces and generation pulsation moment, its pulsation moment can cause the fluctuation of asynchronous motor speed, and the fluctuation of asynchronous motor speed can cause the fluctuation of asynchronous motor power-factor angle Φ again.

The present thyristor phase-shift voltage regulating system that adopts, control to as if with respect to the phase shifting angle α of supply voltage zero crossing, and in the asynchronous motor starting process, when relative speed variation is big, the power-factor angle Φ fluctuation of motor is bigger, cause effective phase shifting angle γ fluctuation of thyristor phase-shift voltage regulating bigger, and then cause the asynchronous electric set end voltage to change greatly, motor produces more significantly concussion.In order to reduce the motor concussion, the technical measures that soft start is at present adopted are, when motor speed begins fast rise, when starting current obviously descends, immediately asynchronous motor is added full voltage, promptly avoided the fluctuation of asynchronous electric set end voltage, prevented the concussion of asynchronous motor.But when existing the impact total head, this method can produce bigger secondary pulse electric current, and all unfavorable to motor and electrical network.

Summary of the invention

The present invention seeks to a kind of method that prevents asynchronous motor soft start concussion, can directly detect the effective phase shifting angle γ of thyristor, and, reach to prevent to produce in the asynchronous motor Soft Start-up Process and shake by dynamic adjustments thyristor phase shifting angle α.

The present invention is achieved in that a kind of method that prevents asynchronous motor soft start concussion, need not detect the power-factor angle Φ in the asynchronous motor soft start runner, only by detecting the bidirectional thyristor both end voltage, just can judge effective phase shifting angle γ of thyristor, effective phase shifting angle γ according to thyristor, dynamic adjustments thyristor phase shifting angle α reaches the stable of the effective phase shifting angle γ of maintenance thyristor, reduces or eliminates the reforming phenomena in the asynchronous motor Soft Start-up Process.

The resistance and the photoelectrical coupler that are connected in parallel on the bidirectional thyristor two ends can detect thyristor turn-on and turn-off interval, are exactly effective phase shifting angle γ of thyristor and turn-off interval corresponding electrical degree.

The effective phase shifting angle γ of the detected thyristor of photoelectrical coupler delivers in DSP or the single-chip microcomputer, according to effective phase shifting angle γ of detected thyristor and the deviation of setting the effective phase shifting angle of thyristor, adopt the dynamic thyristor phase shifting angle of closed-loop control strategy α, and then keep the effective phase shifting angle γ of thyristor stable, reach the stable purpose of maintenance asynchronous motor.

Described bidirectional thyristor can also adopt the reverse parallel connection of two unidirectional thyristors to constitute.

A kind of method that prevents asynchronous motor soft start concussion of the present invention, by detecting the voltage at bidirectional thyristor two ends, can judge effective phase shifting angle γ of thyristor, and then dynamic adjustments thyristor phase shifting angle α, keep effective phase shifting angle γ of thyristor stable, reach and reduce or eliminate the purpose of shaking in the asynchronous motor starting process, the stable operation that also can guarantee asynchronous motor in service of asynchronous motor pressure regulating energy-saving.

Adopt the inventive method, can not produce the secondary pulse electric current, therefore more meet the requirement of asynchronous motor soft start, can also realize the function of asynchronous motor underloading pressure regulating energy-saving motor.

Description of drawings

The invention will be further described below in conjunction with drawings and Examples:

Fig. 1 is a three-phase main circuit theory diagram of the present invention;

Fig. 2 is that the single-phase main circuit of the present invention detects the interval schematic diagram of thyristor break-make;

Fig. 3 is that the present invention detects the effective phase shifting angle γ of thyristor oscillogram.

Embodiment

The invention provides a kind of method that can directly detect the effective phase shifting angle γ of thyristor, as shown in Figure 1, three-phase main circuit A, B, C are every by being connected in parallel on bidirectional thyristor after resistance and the series connection of a pair of photoelectrical coupler, also can be with two unidirectional thyristor inverse parallels formations.With A is example mutually, bidirectional thyristor or two unidirectional thyristor inverse parallels, its two ends are A1, A2 end, when the bidirectional thyristor conducting, the former side's light-emitting diode of photoelectrical coupler no current passes through, photoelectrical coupler pair side output high level, when bidirectional thyristor ended, a light-emitting diode in the photoelectrical coupler had electric current to pass through, corresponding photoelectrical coupler pair side output low level, the width of photoelectrical coupler pair side output low level, the effective phase shifting angle γ of promptly corresponding thyristor, as shown in Figure 2.

The effective phase shifting angle γ of thyristor that detects is sent into DSP, and effective phase shifting angle γ compares with the given thyristor in the asynchronous motor Soft Start-up Process, removes to control the output voltage of thyristor soft starter after PI regulates as the working control phase shifting angle α of soft initiator.Because the effective phase shifting angle γ of given thyristor is stable, and power-factor angle Φ fluctuates in the asynchronous motor starting process, so the working control phase shifting angle α of soft initiator is a dynamic adjustments, thereby reach the purpose of stablizing thyristor soft starter output voltage, reduced or eliminated the reforming phenomena of asynchronous motor starting process.

This method expands in the asynchronous motor underloading voltage-regulating and energy-saving controller and uses, because asynchronous motor underloading voltage-regulating and energy-saving controller is operated in the non-full conducting operating mode of thyristor when the asynchronous motor underloading, the variation of motor load can cause the fluctuation of motor power factor angle Φ, adopt present thyristor phase-shifting control method, may cause the concussion of motor.And adopt new method provided by the invention, and can stablize the triac controller output voltage, reduce or eliminate the operating reforming phenomena of asynchronous motor underloading pressure regulating energy-saving.

Embodiment:

The present invention is applied to a cover 50KW Soft Starter of Induction Motor, and main circuit as shown in Figure 1.Main circuit is made of the three-phase anti-parallel thyristor, and every phase anti-parallel thyristor two ends are parallel with a resistance and two testing circuits that the photoelectrical coupler series connection constitutes, and this testing circuit can detect the on off operating mode of every phase thyristor.The concrete parameter of testing circuit is illustrated in fig. 2 shown below: first resistance R 1=100K Ω/2W connects, minimum power factor angle Φ in the asynchronous motor starting process=30 degree, the minimum current of first resistance R 1 of therefore flowing through is (380V*sin30 °)/100 K Ω=1.9mA, the maximum current of first resistance R 1 of flowing through is 380V/100 K Ω=3.8mA, the maximum power P=380V*3.8mA=1.44W that first resistance R 1 is born, the resistance of choosing can satisfy the demand that detects electric current.Photoelectrical coupler G1, G2 adopt PC817, and its current transfer ratio minimum is 0.5, so the output sampling second resistance R 2=R3=5V/0.9mA=5.5K Ω gets the 2nd R2=R3=5.6 K Ω in fact.Usc1 and Usc2 output is square wave voltage signal among Fig. 2, as shown in Figure 3, this square-wave signal is through filter shape, after eliminating the influence of disturbing pulse, give the mouth of catching of digital signal processor DSP, DSP is converted to the high level width of output voltage U sc1, the Usc2 of filter shape the effective phase shifting angle γ of thyristor of digital quantity.According to different soft start patterns, as: voltage ramp, current ramp, decide electric current etc., calculate the effective phase shifting angle set-point of thyristor γ, the difference of the effective phase shifting angle set-point of thyristor γ g and the effective phase shifting angle measured value of thyristor γ is carried out PI regulates, its output is as the working control phase shifting angle α of thyristor soft starter, the output voltage that obtains can not fluctuate with the fluctuation of motor power factor angle Φ, can reduce or eliminate the concussion in the asynchronous motor starting process.

Claims

1. method that prevents asynchronous motor soft start concussion, it is characterized in that: need not detect the power-factor angle Φ in the asynchronous motor soft start runner, only by detecting the bidirectional thyristor both end voltage, just can judge effective phase shifting angle γ of thyristor, effective phase shifting angle γ according to thyristor, dynamic adjustments thyristor phase shifting angle α reaches the stable of the effective phase shifting angle γ of maintenance thyristor, reduces or eliminates the reforming phenomena in the asynchronous motor Soft Start-up Process.

2. according to the described a kind of method that prevents asynchronous motor soft start concussion of claim 1, it is characterized in that: the resistance and the photoelectrical coupler that are connected in parallel on the bidirectional thyristor two ends can detect thyristor turn-on and turn-off interval, are exactly effective phase shifting angle γ of thyristor and turn-off interval corresponding electrical degree.

3. according to the described a kind of method that prevents asynchronous motor soft start concussion of claim 1, it is characterized in that: the effective phase shifting angle γ of the detected thyristor of photoelectrical coupler delivers in DSP or the single-chip microcomputer, according to effective phase shifting angle γ of detected thyristor and the deviation of setting the effective phase shifting angle of thyristor, adopt the dynamic thyristor phase shifting angle of closed-loop control strategy α, and then keep the effective phase shifting angle γ of thyristor stable, reach the stable purpose of maintenance asynchronous motor.

4. according to the described a kind of method that prevents asynchronous motor soft start concussion of claim 1, it is characterized in that: bidirectional thyristor can also adopt the reverse parallel connection of two unidirectional thyristors to constitute.