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AC Contactor Introduction

1 Introduction
A contactor is an automatically controlled electrical appliance used to make or break AC and DC main and control circuits. The KM symbol, whose main control object is the motor, can also be used for other electrical loads, such as electric heaters, welding machines, etc.

2. The difference between contactor and knife switch
The contactor acts like a knife switch. The contactor can not only turn on and off the circuit, but also has the advantages of under-voltage release protection, zero-voltage protection, large control capacity, suitable for frequent operation and remote control, reliable operation, and long service life. However, the knife switch has no undervoltage protection and can only be operated at a short distance.

3. Structure and principle
A contactor is generally composed of a contactor electromagnetic mechanism, a contact system, an arc extinguishing device, a spring mechanism, a bracket and a base. AC contactor contacts can be divided into main contacts and auxiliary contacts. The main contact is normally open and acts on the main circuit, and the auxiliary contact cooperates with the contactor coil to act on the control circuit, and the operation of the circuit is indirectly controlled by controlling the contactor coil.
A contactor is an electrical appliance that uses the attractive force of an electromagnet and the reaction force of a spring to open or close the contacts. Whether AC or DC is controlled by its contacts can be divided into AC contacts and DC contactors. The difference between the two is mainly due to the different arc extinguishing methods.

4. Wiring of the contactor
The main contacts L1-L2-L3 of the contactor enter the three-phase power supply. A friend asked if the main contact of the contactor can enter the single-phase power supply? The answer is yes, a single-phase power supply can only use two contacts. Then there are the contactor auxiliary contacts, NO – NC. It is emphasized here that NO means that the auxiliary contact of the contactor is normally open, and NC means that the auxiliary contact of the contactor is normally closed.

Post time: Oct-20-2022