CN2253069Y

CN2253069Y - Over-current protector for motor

Info

Publication number: CN2253069Y
Application number: CN 95242876
Authority: CN
Inventors: 苏良臣
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-03-16
Filing date: 1995-03-16
Publication date: 1997-04-23
Anticipated expiration: 2005-03-16

Abstract

The utility model discloses an over-current protector for a motor. In the utility model, a current transformer senses the current signals of the motor, the current signals are sampled by a resistor R1, rectified by a diode D1, filtered by a capacitor C1 and then transmitted to the base of a triode BG2 of a comparison circuit 2, and the collector of the triode BG2 is connected in parallel with an intermediate relay J2 branch circuit and a comparison relay J3 branch circuit so as to control an AC contactor CJ to work. The utility model has the advantages of small size, simple structure, flexible action, high precision, function of open-phase protection, etc.

Description

The motor overcurrent protection device

The utility model relates to a kind of motor protecting device, relates in particular to a kind of motor overcurrent protective device.

Two kinds of thermal relay and electronic protectors are adopted in the overcurrent protection of motor mostly at present.Thermal relay, low precision, be difficult to adjust, action is insensitive.And electronic protector such as Chinese patent CN872043870 disclosed " the motor phase failure, overcurrent protector " adopt integrated circuit and SCR structure, circuit complexity, debugging inconvenience, cost height.

But the purpose of this utility model just provides a kind of over-current adjusting value regulated at will, is active in one's movements, and the control precision height is simple in structure, the low novel motor overcurrent protector of holding concurrently of cost.

The purpose of this utility model is achieved in that in the motor overcurrent protection device that is made of current transformer, comparison circuit, A.C. contactor, startup delay circuit etc., the motor current signal that current transformer induces is sampled through sampling resistor, diode rectification, the signal of the sampling behind the capacitor filtering send comparison circuit relatively with the work of control A.C. contactor; In the comparison circuit, the base stage input sample signal of triode, collector electrode also connects two branch roads, and the normally-closed contact by auxiliary relay, comparator relay is formed, and another is made up of comparator relay, potentiometer; The base stage of the triode of startup delay circuit also is connected to the delay capacitor branch road and the branch road of the normally-closed contact of base resistance and auxiliary relay formation, the collector electrode of this triode and the normally opened contact of comparator relay, and time-delay relay links to each other; The normally-closed contact of time-delay relay seals in the comparator relay branch road in the comparison circuit.

Below in conjunction with the drawings and specific embodiments the utility model is described in further detail.

Fig. 1 is the low-pressure section electrical schematic diagram of the utility model one embodiment.

Fig. 2 is the utility model embodiment high-pressure section winding diagram.

Find out that from Fig. 1, Fig. 2 the structure of the utility model embodiment is:

In the motor overcurrent protection device that constitutes by current transformer, comparison circuit 2, A.C. contactor CJ startup delay circuit 1 etc.:

The motor current signal that current transformer L induces, through sampling resistor R1 sampling, diode D1 rectification, capacitor C 1 filtered sampled signal send comparison circuit 2 relatively with control A.C. contactor CJ work;

In the comparison circuit 2, the base stage input sample signal of triode BG2, collector electrode also connects two branch roads, and the normally-closed contact J3-2 by auxiliary relay J2, comparator relay J3 forms, and another is made up of comparator relay J3, potentiometer W;

The base stage of the triode BG1 of startup delay circuit 1 also is connected to delay capacitor C2 branch road and the branch road of the normally-closed contact J2-2 of base resistance R2 and auxiliary relay J2 formation; The collector electrode of this triode BG1 links to each other with the normally opened contact J3-4 of comparator relay, time-delay relay J1; The normally-closed contact J1-2 of time-delay relay J1 seals in the comparator relay J3 branch road in the comparison circuit.

The concrete course of work of the utility model embodiment is:

When electric motor starting, press start button TA, A.C. contactor CJ gets, the motor three-phase line is connected, current transformer L induces and the proportional current signal of motor D electric current, on sampling resistor R1, produce pressure drop, through diode D1 rectification, capacitor C 1 filtered sampled signal is sent into the base stage of the triode BG2 of comparison circuit 2 through base resistance R2, make the BG2 conducting, auxiliary relay J2 coil electricity on the BG2 collector electrode, be connected on the J2 normally opened contact J2-1 adhesive on the A.C. contactor CJ, keeping CJ gets, machine operation (TA unclamps the back), be connected on simultaneously and start the disconnection of the J2 normally-closed contact (J2-2) on the triode BG1 base resistance R3 in the delay circuit 1, because the charging time-lag action of the capacitor C 2 of another branch road of BG1 base stage, the BG1 base stage still has voltage, BG1 does not end temporarily, the coil of time-delay relay J1 on the collector electrode is still switched on, be connected on the maintenance of the J1 normally-closed contact J1-2 on comparator relay J3 branch road disconnection in the comparison circuit 2, comparator relay J3 no power, the utility model has just escaped the starting current of motor like this, and unlikely generation misoperation.

Time-delay finishes the back, the C2 charging finishes, BG1 base stage no-voltage, BG1 ends, the J1 outage on the collector electrode, its normally-closed contact J1-2 closure, and J1-2 and potentiometer W, comparator relay J3 are serially connected on the triode BG2 collector electrode in the comparison circuit 2, so the J3 coil electricity (BG2 when starting by the conducting of J2 branch road), adjust the value of W, when making motor current normal (less than the over-current adjusting value), the electric current of J3 coil of flowing through is lower than its attract current, and motor runs well.When current of electric is higher than the over-current adjusting value; sampled signal increases, and the BG2 collector current increases, and the J3 coil current meets or exceeds its pickup value; be connected on J1 respectively; J3 normally-closed contact J3-4, J3-2 on the J2 disconnects, J1, J2 coil blackout, and its normally opened contact J1-1, J2-1 all disconnect; and link to each other with A.C. contactor CJ behind the J1-1, J2-1 parallel connection; thereby the motor major loop is cut off in the CJ outage, realizes the overcurrent protection of motor.

When the utility model is used for three phase alternating current motor, then has the open-phase protection function, three ones of current transformer L serial connection are wound on respectively on the motor three-phase line, when arbitrary phase shortage appears in motor, it is zero that the voltage that all the other two-phases of L are partly responded to interacts, the BG2 base stage is zero, and BG2 ends, the J2 outage on the BG2 collector electrode; Start the J2 normally-closed contact J2-2 closure in the delay circuit 1, capacitor C ₂Time-delay discharge make BG ₁The J on, collector electrode still ₁Also outage, J at this moment ₁, J2 normally opened contact J1-1, J2-1 all disconnect, contactor CJ discharges, the motor circuit outage, thereby realized the open-phase protection of motor.

When the utility model also can increase the protection action easily in reality is implemented, functions such as indicator light demonstration, audible alarm.At J1-1, J2-2, on the CJ connection in series-parallel branch road, and connect HT pilot as directly, the high pressure acoustic alarm gets final product.

The utility model compared with prior art has: volume is little, simple in structure, the action spirit Quick, the over-current adjusting value can be regulated arbitrarily, and the control accuracy height (can exceed 2.5% in power output And the advantage such as default-phase protection function arranged Shi Jinhang protection).

Claims

1, a kind of motor overcurrent protection device is made of current transformer, comparison circuit, A.C. contactor, startup delay circuit etc., it is characterized in that:

The motor current signal that a, current transformer (L) induce, through sampling resistor (R1) sampling, diode (D1) rectification, the filtered sampled signal of electric capacity (C1) send comparison circuit (2) relatively with control A.C. contactor (CJ) work;

In b, the comparison circuit (2), the base stage input sample signal of triode (BG2), collector electrode also connects two branch roads, and the normally-closed contact (J3-2) by auxiliary relay (J2), comparator relay (J3) is formed, and another is made up of comparator relay (J3), potentiometer (W);

Triode (BG1) base stage of c, startup delay circuit (1) also is connected to delay capacitor (C2) branch road and the branch road of the normally-closed contact (J2-2) of base resistance (R3) and auxiliary relay (J2) formation; The collector electrode of this triode (BG1) links to each other with normally opened contact (J3-4), the time-delay relay (J1) of comparator relay; The normally-closed contact (J1-2) of time-delay relay (J1) seals in comparator relay (J3) branch road in the comparison circuit (2).