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    Tag: contactor

    How to Select a Right AC Contactor?

    AC contactor is generally classified into class I, class II, class III and class IV according to the type of load, and they are respectively recorded as AC-1, AC-2, AC-3 and AC-4. AC-1 AC contactor corresponds to non inductive or micro inductive load as its control object, such as the filament lamp, resistor furnace. AC-2 AC contactor is used for starting and stopping of wound asynchronous motor. Typical application of AC-3 AC contactor is the operation of squirrel-cage asynchronous motor and the break in operation. AC-4 AC contactor is used for starting, reverse braking, reversing and jog of cage asynchronous motor. All ATO AC contactors with 24V/110V/220V coil operating at AC-3 380V or 660V.

    How to Select a Contactor?

    As equipment to disconnect load power, selection of contactor should meet requirements of controlled equipment. Except that the rated operational voltage is the same with the rated operational voltage of controlled equipment, load power, usage category, control mode, operation frequency, working life, installation method, installation dimension and economy of controlled equipment are the basis of selection. How to choose a right contactor? The principles are as follows:

    Contactor Troubleshooting Guide

    Short circuit of the contactor
    Possible causes of the fault:

    • The contactor works in the environment of damp, dust, steam, or corrosive gases.
    • The arc chute damages or falls, load short leads to the contact short of the contactor.
    • Incorrect operation of the positive and reverse contactor, as well as unreliable interlocking, make two contactors to pull in at a same time when reversing.

    Maintenance method:

    1. Improve the working environment and keep clean.
    2. Match an arc-extinguishing equipment again.
    3. Handle the load short failure.
    4. Recheck the contactor's interlocking circuit, change the operation mode.
    Basic Structure of AC Contactor

    Contactor is an automatic electromagnetic switch for long-distance frequently connected or disconnected AC and DC main circuit and high-capacity control circuit. The main control object of a contactor is the motor, it can be used to control other loads as well.
    According to the current types that through the main contacts, contactor is divided into AC contactor and DC contactor. The structure and working principle of both are basically the same, which mainly consists of three parts, electromagnetic mechanism, contact system and arc-extinguishing equipment. In the electrical control circuit of machine tool, AC contactor is mainly used. This article focuses on the basic structure of the AC contactor.

    Difference between Contactor and Relay

    A contactor is mainly used in a primary loop, which can go through a large current (several hundred to about one thousand Amps). While a relay is used in a secondary circuit to achieve various control functions, which can only go through a small current (several to decades Amps). Functions, contacts opening and closing situation of the two subject are different.