CN2318744Y - Open-phase protector for three-phase AC. machine - Google Patents

Abstract

The utility model relates to an open-phase protector for a three-phase AC motor. The utility model is characterized in that a DC voltage stabilizing circuit used as a working power supply is connected in parallel between two phase wires of a main loop of a motor, and a third phase wire of the main loop of a motor is connected with a voltage sampling circuit, a photoelectric coupler and an electronic switch which is composed of a triode and a relay coil connected with a triode collector loop, wherein, the input end and the output end of the photoelectric coupler are respectively connected with the voltage sampling circuit and the base of the triode, and the normally open contact of a relay is connected in series into a control loop of a motor. When any phase in the main loop of a motor is open, the triode is stopped, and the main loop of a motor is switched off.

Description

The three phase alternating current motor phase failure protector

The utility model relates to the phase failure protector of a kind of protective device of alternating current machine, particularly a kind of three phase alternating current motor.

The prior motor phase failure protector is the current sample mode mostly.Because the watt level difference of motor, its phase current are also different, even and same motor, starting different because of load during with operation, its electric current also is different.Therefore, the current calibration of this type of phase failure protector and adjustment be difficulty relatively, and its sensitivity and reliability are relatively poor.Chinese patent CN2087836 discloses a kind of motor phase failure protector; it is by step-down, rectification, the filtering DC circuit be made up of transformer, diode and electric capacity that is attempted by on two phase lines of motor main circuit; but this protector is a kind of high-current switch formula structure; the power consumption of itself is bigger; but also need itself relay coil and the original control relay coil of motor are interconnected again; make structure complicated, reliability reduces.

The purpose of this utility model provide a kind of simple in structure, reliability is high, and is not subjected to the three phase alternating current motor phase failure protector of Disturbance in Power Net.

The solution that realizes the utility model purpose is: the three phase alternating current motor phase failure protector that is provided; comprise the DC power supply of being made up of step-down transformer and rectification, filtering, voltage stabilizing circuit that is attempted by in the motor main circuit between two phase lines, this DC power supply is as the working power of phase failure protector.Of the present utility model this advance part be provided with one with motor main circuit in the voltage sample circuit that joins of third phase line, photoelectrical coupler and the electronic switch formed by triode and relay coil, wherein the input of photoelectrical coupler and voltage sample circuit join, the output of photoelectrical coupler and the base stage of aforementioned triode are joined, relay coil is connected between transistor collector and the above-mentioned DC power supply, and the normally open contact of relay is serially connected in the control loop of motor.Under normal circumstances, above-mentioned triode is conducting, the relay normally open contact closure, and the control loop of motor is switched on.After arbitrary disconnection mutually in the motor main circuit, will cause the voltage sample circuit open circuit (being the transistor base open circuit) of protector or the collector loop open circuit of triode; then not conducting of triode; the relay coil dead electricity; motor control loop is disconnected; thereby the three-phase of motor main circuit is disconnected, and the protection motor can not burnt out.

The utility model adopts the voltage sampling mode, control the break-make of the contactor coil in the electric motor loop by triode, so electric current is little, the power consumption of self is little, the quarantine measures of photoelectricity coupling have been adopted between voltage sample circuit and the triode in addition, thereby being subjected to extraneous interference little, working stability is reliable.In addition, the utility model adopts the voltage sampling mode, thus the watt level of protected motor there is not any restriction, thereby the scope of application is wider.

Below in conjunction with accompanying drawing content of the present utility model is illustrated.

Accompanying drawing is circuit theory diagrams of the present utility model.

As shown in the figure: the DC power supply part of this phase failure protector is made up of step-down transformer 1, bridge rectifier 2, filter capacitor C1 and three terminal regulator 3.Wherein transformer 1 elementary is attempted by on two phase line V, the W of motor 6 major loops.The voltage sample circuit of phase failure protector is connected on the 3rd the phase line U of motor 6 major loops; it is made up of resistance R 1 and rectifier diode D1 and the filter capacitor C2 of serial connection; change the 220V ac voltage signal into low-voltage dc signal after step-down, rectification, filtering, this low-voltage dc signal changes the base stage that dc control signal is delivered to triode 5 into through photoelectrical coupler 4.The main effect of photoelectrical coupler 4 is that sample circuit and the control circuit that will join with electrical network are isolated, and eliminates the interference of electrical network to control circuit.Triode 5 plays on-off action, is connected to the coil of a relay J between the output of its collector electrode and three terminal regulator 3, and the normally open contact of this relay J is connected on again in the self-holding circuit of the former control circuit of motor.At the two ends of relay J coil also and met a light-emitting diode D3, be used for the indication of normal condition.Resistance R 2 is base biasing resistors of triode 5 among the figure, and diode D2 shields to relay J, and resistance R 3 is current-limiting resistances of light-emitting diode D3.The control circuit of motor is made up of starting button QA, stop button TA and A.C. contactor JC.Under normal circumstances, press starting button QA, contactor JC coil electricity, its contact closure is connected the major loop of motor 6.In the case, the DC power supply circuit of phase failure protector is switched on, and gives photoelectrical coupler 4 and triode 5 power supplies.And be added on the base stage of triode 5 by photoelectrical coupler 4 from the voltage signal of voltage sample circuit, make triode 5 conductings, the coil electricity of relay J is connected on the contact closure of the relay J in the motor control loop, thereby motor 6 can normally be remained in operation.When the V in the motor main circuit mutually or W when mutually the phase failure taking place, then the elementary of transformer 1 opened a way, three terminal regulator 3 no-outputs, triode 5 ends, the relay J dead electricity disconnects motor control loop.If the U of motor main circuit disconnects mutually, sample circuit no-output then, the base stage of triode 5 do not have input and end.So no matter which disconnects mutually, triode 5 all will end, and the major loop of motor all be disconnected, thereby play phase failure protective effect.This protector can be connected on before the main contact of the contactor JC that controls motor, but preferably is connected on after the main contact of contactor JC, also can play a protective role when contactor JC main contact breaks down like this.

Claims (2)

1; a kind of phase failure protector of three phase alternating current motor; comprise be attempted by in motor (6) major loop between two phase lines by step-down transformer and rectification; filtering; the DC power supply that voltage stabilizing circuit is formed; this DC power supply is as the working power of phase failure protector; it is characterized in that being provided with one with motor (6) major loop in the voltage sample circuit that joins of third phase line; photoelectrical coupler (4) and the electronic switch of forming by triode (5) and relay (J) coil; wherein the input and the voltage sample circuit of photoelectrical coupler (4) join; the base stage of the output of photoelectrical coupler (4) and aforementioned triode (5) is joined; relay (J) coil is connected between triode (5) collector electrode and the above-mentioned DC power supply, and the normally open contact of relay (J) is serially connected in the control loop of motor (6).

2, phase failure protector as claimed in claim 1 is characterized in that described voltage sample circuit is made up of resistance (R1) and rectifier diode (D1) and the filter capacitor (C2) of serial connection.