Overhead Crane AC Contactor and Relay

- Nov 07, 2017-

Failure Analysis and Elimination Method of Overhead Crane AC Contactor and Relay


AC Contactor

Alternating Current Contactor widely used as power breaking and control circuit.

From the use point of view, AC contactor can be divided into:

Industrial contactors, mostly general-purpose models, common models mainly for CJ series CJX2 series, CJ20 series, CJT1 series;

Construction and household contactors, ABBESB series, Hicker HBC1 series, Chint NCH8 series, Siemens 3TF series, Schneider ICT series.

AC contactor mainly consists of four parts:

(1) electromagnetic system, including a magnetic coil, moving iron core and static iron core;

(2) Contact system, including three sets of main contacts and one to two sets of normally open and normally closed auxiliary contacts, which are linked together with the moving iron core to each other;

(3) arc extinguishing device, the general capacity larger AC contactor is equipped with arc extinguishing device, in order to quickly cut off the arc, from burning the main contact;

(4) insulation shell and accessories, all kinds of springs, transmission, short-circuit ring, terminal and so on.


Relay is an electronic control device, it has a control system (also known as the input circuit) and the controlled system (also known as the output circuit), usually used in automatic control circuit, which is actually a smaller current to control the larger An "automatic switch" of current. Therefore, the circuit plays an automatic adjustment, safety protection, conversion circuit and so on. The relay coil is indicated by a box symbol in the circuit. If the relay has two coils, draw two juxtaposed boxes. At the same time in the rectangular box or long box marked next to the relay symbol "J". Relay contact there are two ways to express: one is to draw them directly on the side of the box, this representation is more intuitive.

Failure Analysis and Elimination Method of Crane AC Contactor and Relay:

Coil overheating: 

Reason for failure:

Coil overload,

The movable part of the conductor comes into contact with the stationary part;

The voltage of the coil used is lower than the coil voltage.

Ways to eliminate the problem:

Reduce the pressure of the movable contact spring;

Eliminate the cause of the abnormal movement of the movable part of the magnet (bending, jamming)

Change the coil