Knowledge of selection of AC contactors

How to choose the AC contactor? Influence factors of AC CONTACTOR

time: 2015-06-22-08:28:10 EDIT: Electrician column: CONTACTOR

Guide: How to choose the AC contactor? In the selection of AC contactor, it will encounter the problem of series-parallel contactor, and need to consider the influence of power frequency, the influence of operating frequency and other factors.

How to choose the AC contactor?

1. Serial and parallel use of contactor

　　
There are many electrical devices that are single-phase loads, so several poles of a multi-pole contactor can be used in parallel. such as resistance furnace, welding transformers. When used in parallel with a few poles, a smaller capacity contactor can be chosen.

Note that the contracted heating current of a parallel contactor is not fully proportional to the number of Poles in parallel.

This is because the active, static contact circuit resistance values are not necessarily equal, so that the flow of positive currents is not evenly distributed.

Therefore, the two analysis shunt after the current can only increase to 1.8 times times, three poles in parallel, the current can only be increased to 2~2.4 times.
　
In addition, it is necessary to point out that the connection and breaking capacity cannot be improved because the connected contacts cannot be connected and disconnected at the same time.

Sometimes, several poles of the contactor can be used in series, because the increase of the contact fracture can divide the arc into many segments, improve the ability of arc-extinguishing, accelerate the quenching of the arc.

Therefore, a few poles in series can improve their operating voltage, but cannot exceed the rated insulation voltage of the contactor. The contracted heating current and rated operating current of the contactor after series are not changed.

2. Influence of Power frequency
　　
For the main circuit, the frequency changes affect the skin effect, the frequency is high multiset skin effect increases, for most products 50 khz and 60 khz on the conduction circuit temperature rise is not very large.

However, for the suction coil, it is important to note that the 50 khz design of the suction coil for 60 khz magnetic flux will be reduced, the suction will be reduced, whether it can be used to see the design margin.

In general, the user is best to use the value of their calibration, when ordering according to the operating power frequency used to order. (Electrician Technology House www.dgjs123.com)

3, the effect of operating frequency

The number of operating cycles per hour of contactor has a great influence on the burning loss of the contact, attention should be paid to the selection, and the applicable operating frequency is given in the technical parameters of the contactor.

When the actual operating frequency of the electrical equipment is higher than the given value, the contactor must be reduced to use.

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Knowledge of selection of AC contactors