CN2134737Y

CN2134737Y - Protector for 3-phase asynchronous motor

Info

Publication number: CN2134737Y
Application number: CN92206970U
Authority: CN
Inventors: 陈春平
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-03-31
Filing date: 1992-03-31
Publication date: 1993-05-26
Anticipated expiration: 2002-03-31

Abstract

The utility model relates to a protector for a three-phase asynchronous motor, which comprises a three-phase four-column type current transducer as a signal source, an R-C time delay link, the switch circuit of a semi-conductor device, an electric relay, etc. Compared with an electrothermal relay with an open-phase protector, the utility model has the advantages of convenient adoption and adjustment, low cost, simple and reliable structure, energy saving for more than 50%, etc. The mounting dimension thereof is the same as that of the electrothermal relay. The utility model can replace the electrothermal relay and can be used as the open-phase protector of the three-phase asynchronous motor or a three-phase current relay.

Description

Protector for 3-phase asynchronous motor

The utility model belongs to the phase asynchronous protector in the electric product, especially to the protection of motor owing to the overload and the phase failure.

The insulation of three-phase asynchronous motor is brought up to present E class F insulation by the A class F insulation in past.Therefore, International Electrotechnical Commission (IEC) has revised the standard of electric motor protecting electrical equipment: 1, the overload protection characteristic that allows requires to reduce; 2, increased the open phase protection requirement.The heat utensil that continues of band open phase protection has following shortcoming in the prior art: 1, its actuating signal is not directly taken from the electric current of motor, but changes electric energy into heat energy earlier; 2, thermal relay is installed in the control cabinet (cabinet) away from motor, and is also far different in its hot state and the motor; 3, the protective feature of the thermal relay of band open phase protection is dispersed big, therefore selects for use and adjusts very difficult.

The utility model is improved at above-mentioned shortcoming, proposes a kind of new protective device, it is characterized in that signal source adopts a three-phase and four-pole formula power pack that had not only reflected overload current but also can reflect phase failure overcurrent.Whole device not only has 1, can make the motor normal starting; 2, can give full play to the functions such as overload capacity of motor, and with the thermal relay following outstanding advantage of having compared of band open phase protection: 1, simple and reliable for structure; 2, select for use with easy to adjust; 3, cost is low; 4, every three extremely specified power consumption of thermal relay is about 9 watts, adopts the utility model whenever to economize on electricity more than 50% only; 5, installation dimension can be identical with thermal relay, is the renewal product of thermal relay.

It in accompanying drawing 1 frame of broken lines a kind of electrical schematic diagram of this protective device.Signal source is a three-phase and four-pole formula power pack.Elementary winding string in motor main circuit, secondary winding A-X, B-y, C-Z full-wave rectification Hou And connection add C ₁After the filtering as the DC power supply of switching circuit.The iron core of three-phase current converter adopts the three-phase and four-pole formula, and two stems and two return yokes are arranged.Return yoke and upper and lower yoke core sectional area be heart column section long-pending 1/2.On two return yokes winding is arranged, the number of turn equates with umber of turn on the stem.Winding on two return yokes is in series the back as the phase in three phase windings.

By following measured data as can be known, no matter be motor three-phase symmetrical operation or a phase phase failure is arranged, as long as the motor stator electric current is substantially the same, the direct voltage of power pack output also is substantially the same.Stator current 3 ampere-hours for example, no matter the three symmetrical or phases failure, the converter output dc voltage is about 36 volts.

I wherein _A, I _B, I _CBe motor threephase stator electric current;

U ₂A, U ₂B, U ₂C is a converter secondary winding output AC voltage;

U ₀Be output C ₁The end direct voltage.

Utilize the above-mentioned characteristic of converter, we can adjust and reach setting value (120%I for example when motor stator side electric current _N) time, the relay J action shields to motor.

Concrete working condition is as follows:

1, just often, the input voltage U of switching circuit ₀Be no more than setting value, voltage-stabiliser tube CW does not puncture, and triode BG does not have base current and ends, and relay J is failure to actuate.

2, under overload or the phase failure situation electric current as surpassing setting value, the input voltage U of switching circuit ₀Surpass setting value, voltage-stabiliser tube CW punctures, triode BG saturation conduction, relay J action.

Capacitor C ₂The effect of charging delay time mainly is to make electronic function normal starting.

Current potential W ₁Main effect be to adjust the operating current setting value, to fill part overload capacity of performance motor.

The utility model can also is characterized in that signal source is a three-phase and four-pole formula power pack separately as the phase failure protector or the three-phase current relay of three-phase asynchronous motor.

Claims

1, a kind of phase asynchronous protector is characterized in that signal source system adopts a three-phase and four-pole formula power pack, has both reflected the open phase fault signal, reflects the overload signal again.

2, according to the described phase asynchronous protector of claim 1, it is characterized in that by (1) signal source; (2) switching circuit of compositions such as R-C time delay process, semiconductor device; (3) the execution link of being made up of relay etc. is formed by combining.

3, according to claim 1,2 described phase asynchronous protectors; as required can be separately as the phase failure protector or the three-phase current relay of three-phase asynchronous motor, what it is characterized in that reflecting open phase fault signal or current signal is a three-phase and four-pole formula power pack.