The classification and selection of ac contactor

Update date:2017-12-28 Source:MAXGE

Any kind of product, only understand its basic knowledge, understand the difference of different model of similar product and connect, can truly choose the product that oneself need.


First, the classification:

Control circuit types according to the main contact points: can be divided into two categories, ac and ac/dc this position according to the main contact points (when the excitation coil without electricity) : can be divided for normally open, normally closed, and part of normally open, another kind of normally closed the three categories

It can be divided into single pole, double pole, three pole, four pole and five pole


It can be divided into air type and vacuum type

Use ofac contactor


1. Determine the type of ac contactor

The type of contactor can be selected according to the controlled motor or load current type. Ac contactor should be used for ac load. Dc load should use dc contactor. If the whole control system is mainly ac load, and the capacity of dc load is less than an hour, the ac contactor can be all used, but the rated current of the contact head should be appropriately larger. The three-pole contactor is usually used in three-phase ac system.

2. Determination of main circuit parameters

Choose to determine the main circuit parameters of the main work for rated voltage (frequency), rated current (or the rated power), on-off capacity rating, tolerance ability of overload current and short circuit protection appliances for coordination. The contactor can operate at different rated working voltages and rated working hours. But in any event, the rated working voltage of the selected shall not be higher than that of the contactor rated insulation voltage, the rated working current of the selected (or the rated power) also shall not be higher than contactor in the corresponding working conditions stipulated by the rated current (or the rated power).


3. Determination of control circuit parameters and auxiliary circuit parameters

The coil voltage of the contactor shall be determined according to the selected control circuit voltage. The control circuit current of ac contactor is divided into two kinds of ac and dc.

4. Ac contactor coil voltage

Generally, the voltage of the contactor coil corresponds to the voltage level of the control circuit. If the control circuit is relatively simple, the number of contacts used is small, and the rated voltage of ac contactor coil is usually directly selected 380V or 220V. If the control circuit is more complicated, the use of the electrical appliances is more. For the sake of safety, the rated voltage of the coil can be lower, and a control transformer should be added.

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