CN2206509Y - Phase failure protector for three-phase motor - Google Patents

Abstract

The utility model relates to a three-phase motor open-phase protector signal acquisition circuit 1 that comprises signal acquisition circuit 1, switch circuit 2, starting circuit 3 and execution circuit 4 sends the three-phase current signal who gathers into switch circuit 2, remove the operating condition of controlling this circuit, switch circuit 2 connects starting circuit 3 and execution circuit 4, execution circuit 4 carries out switch circuit 2's output signal, execution circuit 4 controls starting circuit 3, switch circuit 2's originated operating condition is controlled by starting circuit 3. The utility model has the advantages of simple circuit, small volume, light weight, low cost, convenient installation and use, etc. It is suitable for all three-phase motors using AC power supply as power.

Description

Open-phase protector for three-phase motor

The utility model belongs to a kind of phase failure protector of electric motor that is used for the threephase motor open phase protection.

In a single day phase failure phenomenon appears in threephase motor, then in seconds burns motor.People are devoted to the research of open phase protection in decades, various phase failure protectors occur.But their ubiquities poor reliability, wiring complexity, the shortcoming that volume is big, cost is high: present existing undercurrent type phase failure protector, performance is more reliable, but still has complex circuit, the higher defective of cost.

The purpose of this utility model is to design the open-phase protector for three phase motor that a kind of circuit is simple, volume is little, cost is low.

The utility model is realized by following approach: three current transformers are set, and they are together in series, form signal acquisition circuit 1 with elements such as coupling, rectification, dividing potential drop, voltage stabilizings, gather the phase failure signal of motor, this signal is sent in the switching circuit 2, sending in the executive circuit 4 after differentiating (normal is " 0 " for " 1 ", the phase failure), still is shutdown so that determine start.Since the hysteresis of current signal, an ad hoc start-up circuit 3, and in the moment of electric motor starting, start-up circuit 3 is sent into enabling signal in the switching circuit 2.For " 1 " signal that prevents signal acquisition circuit 1 is scurried into start-up circuit 3 and executive circuit 4 causes misoperation, diode of forward serial connection between the switch element control end of the output of start-up circuit 3 and switching circuit 2.So just guaranteed that the level"1" that starts back signal acquisition circuit 1 collection just is unlikely to enter in start-up circuit 3 and the executive circuit 4.

When motor start-up, this enabling signal moment is sent in the start-up circuit 3 by executive circuit 4, and the signal of start-up circuit 3 outputs makes switching circuit 2 enter opening, and control executive circuit 4 is carried out boot actions.Start-up circuit 3 utilizes a dropping resistor, makes the signal of start-up circuit 3 outputs be lower than the signal voltage that signal acquisition circuit 1 provides.After the start, by the work of signal acquisition circuit 1 replacement start-up circuit 3, the signal control switch circuit 2 of output is kept opening.When phase failure phenomenon takes place, level "0" of signal acquisition circuit 1 output, switching circuit 2 is in off state, and control executive circuit 4 is carried out the shutdown action, thereby reaches the purpose of protection motor.

The utlity model has the simple advantage of circuit, owing to do not set up power circuit, thereby have also that volume is little, in light weight, cost is low and the advantage of reliable operation.

Accompanying drawing and drawing explanation:

Fig. 1---electric functional-block diagram of the present utility model.

Fig. 2---circuit theory diagrams of the present utility model.

In the drawings: 1-signal acquisition circuit, 2-switching circuit, 3-start-up circuit, 4-executive circuit.

Below in conjunction with accompanying drawing the utility model is described further.

With reference to Fig. 1, Fig. 2: current transformer TA ₁-TA ₃, diode D ₁-D ₂, capacitor C ₁-C ₂, resistance R ₁, voltage-stabiliser tube D ₃Form signal acquisition circuit 1.TA ₁-TA ₃Series connection back one end ground connection, the other end passes through C ₁Meet D respectively ₁Negative pole and the positive pole of D2, D ₁Plus earth; D ₂Negative pole meet R respectively ₁And C ₂An end, C ₂Other end ground connection; R ₁The other end meet D respectively ₃Negative pole and be D as the input of the output termination switching circuit 2 of signal acquisition circuit 1 ₄Positive pole, D ₃Plus earth.TA ₁-TA ₃Be on magnet ring, to make D around 200 circles by the enamelled wire of diameter 0.02mm ₁-D ₂Be 1N4148 type diode, D ₃Be 7V voltage stabilizing didoe, C ₁And C ₂Capacity be respectively 10uF and 4.7uF, R ₁Resistance is 10K Ω.Field effect transistor BG ₁, diode D ₄-D ₅, resistance R ₂, capacitor C ₃Form switching circuit 2.D ₄Positive pole meet R respectively as signal input part ₁An end and D ₃Negative pole, its negative pole meets D respectively ₅Negative pole and BG ₁Grid and R ₂, C ₃A common port, R ₂, C ₃Another common end grounding; D ₅Positive pole meet R in the start-up circuit 3 ₃, C ₄A common port; BG ₁Source ground, its drain electrode meets R in the start-up circuit 3 respectively ₅, R ₇An end and one of the bridge rectifier in the executive circuit 4 output brachium pontis.Adjust R ₂, C ₃Numerical value can adjust open phase protection time of delay, BG ₁Be IRF520 type field effect transistor, D ₄-D ₅Be 1N4148 type diode, R ₂Resistance is 100K Ω, C ₃Capacity is 4.7uF.Resistance R ₃-R ₇, capacitor C ₄, diode D ₇, voltage stabilizing didoe D ₆Form start-up circuit 3.R ₃, C ₄Termination D after the parallel connection ₅Positive pole, the other end meet R respectively ₄An end and D ₆Negative pole, D ₆Plus earth; R ₄Another termination D ₇Negative pole; R ₅, R ₆Series connection back one end ground connection, the BG in another termination switching circuit 2 ₁Drain electrode and one of the bridge rectifier in the executive circuit 4 output brachium pontis, its mid point meets D ₇Positive pole, R ₇Be connected across between two output brachium pontis of bridge rectifier.R ₃-R ₇Resistance be respectively 390K Ω, 10K Ω, 390K Ω, 68K Ω, 100K Ω, C ₄Capacity is 4.7uF, D ₆Be 7V voltage-stabiliser tube, D ₇Be 1N4148 type diode.Executive circuit 4 be one by D ₈-D ₁₁The bridge rectifier of forming.Ground connection of its output brachium pontis, another meets R respectively ₇, R ₅An end and BG ₁Drain electrode; Its input brachium pontis is received on the start stop switch of threephase motor.D ₈-D ₁₁Be 1N4007 type diode.

Operation principle of the present utility model is: when motor start-up, AC power is rectified into direct voltage through bridge rectifier, and one the tunnel directly sends into the BG in the switching circuit ₁Drain electrode, a route R ₅Dividing potential drop is after D ₇, R ₄, R ₃, D ₅Send into BG ₁Grid, make BG ₁Conducting rapidly, the bridge rectifier in the executive circuit 4 has electric current to flow through, and makes external A.C. contactor enter operating state.After starting, because D ₆Pressure stabilization function make R ₄, R ₃, C ₃The voltage clamping of common point at 7V, but because of R ₃The dividing potential drop effect make D ₅Cathode voltage is lower than 7V.The induced current of three current transformers lags behind 180 ° of voltages, and therefore behind motor start-up, this induced current is by D ₂Be rectified into semi-wave DC, through R ₁Convert to behind the direct voltage by D ₃Voltage stabilizing is with BG ₁Grid potential is limited to 7V, still is in conducting state, at this moment D ₅Cathode voltage be higher than positive pole, so D ₅Not conducting, BG ₁The high voltage signal of grid can't be scurried in the start-up circuit 3, and start-up circuit is not worked.When phase failure phenomenon takes place, TA ₁-TA ₃Middle no current, so BG ₁Grid voltage is low level, BG ₁Be in off state, make that no current flows through in the executive circuit 4, thereby make external A.C. contactor disconnect, motor does not turn round, and reaches the purpose of protection motor.

Claims (6)

1, the open-phase protector for three phase motor a kind of by signal acquisition circuit 1, that switching circuit 2, start-up circuit 3, executive circuit 4 are formed is characterized in that:

(1), in signal acquisition circuit 1, current transformer TA1-TA3 series connection back one end ground connection, the other end connects D1 negative pole and D2 positive pole respectively through C1, D1 plus earth, the D2 negative pole connects the end of C2, R1 respectively, C2 other end ground connection, the other end of R1 connect the D3 negative pole respectively and as signal output part, the plus earth of D3;

(2), in executive circuit 2, the positive pole of D4 is connected on the signal output part of signal acquisition circuit 1, its negative pole connects the control end of switch element respectively, the common port of the negative pole of D5 and R2 and C3, another common end grounding of R2 and C3, the positive pole of D5 connects the signal output part of start-up circuit 3, an end ground connection in the two ends in addition of switch element, the end of R5, R7 in the signal input part of another termination executive circuit 4 and the start-up circuit 3;

(3), in start-up circuit 3, the common port of R3 and C4 connects the D5 positive pole as signal output part, another common port connects D6 negative pole and R4 one end respectively, D6 plus earth, the negative pole of another termination D7 of R4, D7 positive pole connect the mid point of R5 and R6 series connection, and be in parallel with R7 again after R5 and the R6 series connection, a common end grounding in parallel, another the public signal input part of executive circuit 4 and end of the switch element in the switching circuit 2 of connecing respectively;

(4), in executive circuit 4, D8-D11 forms bridge rectifier, its output brachium pontis ground connection, another meets R7 respectively as signal input part, an end of R5 and switch element, its input brachium pontis is as the start stop switch of the external threephase motor of signal output part.

2, open-phase protector for three phase motor according to claim 1 is characterized in that: the TA1-TA3 in the signal acquisition circuit 1 is cascaded, and its turn ratio is 20-500.

3, threephase motor power-off protector according to claim 1 is characterized in that: the switch element in the switching circuit 2 is a trigistor.

4, open-phase protector for three phase motor according to claim 1, the voltage stabilizing value of its feature: D3, D6 is 2-20V.

5, according to the open-phase protector for three phase motor described in the claim 1, it is characterized in that: the resistance of R1, R2, R4 is respectively 1 Ω-1M Ω, 1K Ω-1M Ω, 1 Ω-1M Ω.

6, open-phase protector for three phase motor according to claim 1 is characterized in that: the capacity of O2, O4 is respectively 0.1-2200uF, 0.1-1000uF.

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