CN101425677A - Anti-fraud induction motor protector - Google Patents

Abstract

The invention relates to an anti-false action induction motor protector, in particular to a motor measurement and controlling device for solving the problem that the motors as the terminal load are mutually disturbed when being out of service. The device can calculate the reverse power and the number of the zero-crossing points of the phase current to judge whether the device self is failed or not through the computational analysis to the current-voltage sampled data, only the faulted motor is eliminated for the entire towage system by the judgment, and the normal running of other non-fault motors is not affected. Therefore, the concrete faulted motor not only can be found, but also the overall production is not affected, and the production efficiency is greatly improved.

Description

Anti-fraud induction motor protector

Technical field: the present invention is that a kind of assurance motor is got rid of external disturbance, and can correctly in time find the motor protector of faults itself, is applied to the three phase induction motor measurement and control area.

Background technology: motor occupies critical role as the important component part in the dragging system in national economy, its use almost has been penetrated into all trades and professions, be the important assurance that industry, agricultural and national defense construction and people's lives are normally carried out, thereby guarantee that the normal operation of motor just seems very important.

Motor during normal use uses as the electric power system terminal; because power of electric motor is big; use longer duration; and motor is the synthetic load of an energy storage; characteristic is unusual after the fault, tend to make adjacent motor mistrip, and self also very easily is subjected to the influence of other problems motor; in this case, realize that the monitoring and controlling protector of anti-error jumping is of crucial importance.

Present motor measure and control device concentrates on major function in the protection for motor; for example: long protection start-up time; overcurrent protection; thermal overload protection; zero-sequence current protection; the negative-sequence current protection; rotation-clogging protection; low-voltage variation; decompression is restarted etc., and present protector can effectively protect motor to burn really, but in service in actual field; because present most of industrial enterprise drop into a motor; when system failure decompression, as the motor of terminal synthetic load the characteristic of current feedback is arranged, this has just influenced the accuracy of motor observing and controlling greatly; present protector has fatal defective in this field; after an induction machine or electric power system went wrong, the situation that whole process of production is interrupted appearred in motor protecter group move often; and can not rapidly find out that guilty culprit also be problem of puzzlement production one of because the protector action is more this moment.

Summary of the invention: in some industrial enterprise inside, often use a large amount of induction motors, when breaking down, these motor tend to occur the tripping operation of non-selectivity, in order to make induction machine have optionally tripping operation, the present invention has used a kind of characteristics of utilizing induction machine as the energy storage load, the feedback of normal induction current of electric when coming detection system or motor fault, thus realize the selectively method of tripping operation of TT﹠C system.By judgement, can realize selectable open failure element for this feedback power.

The hardware system host CPU of this invention adopts dsp system, and data sampling adopts outside AD converter, and the data that can the assurance system need are for accurately, and its main block diagram is referring to accompanying drawing.

The main basis of this invention is to calculate the power flow direction that motor is found instant of failure, when self goes wrong, rated output is from system's flow direction motor, and when non-fault own, power is for to flow to external system from motor body, because realization that should theory needs higher sample rate and art of programming, though some theory has been designed into inverse probability and has calculated, but all can not realize in practice, if another theoretical foundation of this invention is that load is heavier when motor is found fault, in the time that inverse probability can not being calculated, carry out the zero crossing of failure judgement phase current, if not fault own, then the electric current of surveying passes the numerical value at zero point and is no more than four.

This method comprises:

1, judge that by electrical fault judgement system motor fault has taken place, the data acquisition when carrying out fault.

2, by current value and the magnitude of voltage gathered are calculated inverse probability numerical value:

P＝U*I*cos?α

Wherein cos α is a power factor, if voltage phase angle leading current, then negate.

If the numerical value that calculates, is then thought external fault greater than threshold value.

3, in inverse probability hour, the zero crossing of fault phase current is counted.

4, after being judged as external fault, recover and motor power-off time when restarting the time less than maximum decompression at voltage, motor resets automatically, and resumes production.

It is very important in producing that motor has the automatic recovery of differentiation to be enabled in reality, one, what can guarantee to greatest extent to produce carries out smoothly, its two, can in the shortest time, guarantee to find out the guilty culprit place.

By the enforcement of such scheme, can guarantee that induction motor can move reliably when own fault, externally differentiation that can be correct during fault can the fastest resuming production after the correct excision fault.

Embodiment:

1, the collection foreign current voltage value that system does not stop through the AD module, and be transferred to CPU through data/address bus, whether fault of system is judged in the calculating that does not stop in CPU.See Fig. 1.

2, if fault has taken place in the judgement system, then carry out inverse probability calculating gathering the data of coming, the voltage value that adopt this moment is the memory numerical value of all wavefront,

P＝U*I*cos?α

Wherein cos α is a power factor, if voltage phase angle leading current, then negate

If the numerical value that calculates, is then thought external fault greater than threshold value.

The inverse probability feature is seen Fig. 2.

3, in inverse probability hour, the zero crossing of fault phase current is counted, if the zero crossing number smaller or equal to four, then is judged to external fault.See Fig. 3.

4, judge laggard behaviour so handle in the fault zone, even external area error also needs exit relay under the situation of big inverse probability,, be convenient to restart to reduce energy loss.

5, restart after the fault, after being judged as external fault, recover and motor power-off time when restarting the time less than maximum decompression at voltage, motor resets automatically, and resumes production.

Description of drawings:

Fig. 1 is that whole device hardware is formed general flowchart.

Fig. 2 is the phase diagram of electric current and voltage during fault externally.

Fig. 3 is induction-motor load current attenuation figure during external fault when big.

Claims (2)

1 one kinds of power when drawing the system failure, the motor protector of the anti-error jumping of current characteristic is characterized in that:

Its implementation comprises:

(1) the motor inverse probability during the computing system fault;

(2) calculate the voltage data that inverse probability adopts a last cycle;

(3) the phase current zero crossing after the system failure is counted.

The motor protector of the anti-error jumping in 2 claims 1 is characterized in that:

(1) adopt fault current, fault wave voltage the last week carries out the calculating of single-phase power, compares calculating good each phase inverse probability and threshold value, if greater than threshold value, then thinks non-fault own.

Computing formula is: P=U*I*cos α, wherein cos α is the power factor of system.If voltage phase angle leading current, then negate.

(2) carry out the zero crossing counting for each phase current after the fault, if the zero crossing numerical value that a phase current is arranged is then thought external fault smaller or equal to four.

(3) after thinking external fault, if being no more than the motor decompression, system's decompression time restarts the time restriction definite value, then restart motor.

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