# 3-pole or 4-pole contactor

Home Electrical Engineering Forum General Discussion 3-pole or 4-pole contactor

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• #10479
simone
Participant

Let's take the case that you have four one-phase circuits that you have to switch together. ¿Wich one of the following devices would you use?

1) A four-pole contactor, connecting each pole to one of the four circuits

2) A three-pole contactor, in order to switch the three phases, thus the four circuits downstream will be also switched

#12079
erickench
Participant

How can you have 4 single phase circuits? If it's a three phase circuit and your trying to setup an ATS you would need a four-pole contactor so that the neutral would also be switched. Otherwise the two power sources would not be separately derived.

#12189
Spir Georges GHALI
Participant

simone said:

Let's take the case that you have four one-phase circuits that you have to switch together. ¿Wich one of the following devices would you use?

1) A four-pole contactor, connecting each pole to one of the four circuits

2) A three-pole contactor, in order to switch the three phases, thus the four circuits downstream will be also switched

Dear Simone ;

As I understood, you have ” 4 Single Circuits ” and you want to switch ” On & Off ” together, if yes, you should define if these 4 circuits will be supplied by ” 3 phases + neutral ” or ” 1 pahse + neutral ” .

If the sypply is ” 1 phase + neutral “, you can choice a power contactor usning 2 of the main contacts to switch On & Off the supply, then the output of these 2 contacts will electrify the 4 circuits via ” 2 poles circuit breaker ” for each circuit. Noting the the nominal current of contactor should be equal or bigger than the total current value of these 4 circuits.

If the supply is ” 3 phase + neutral “, you can choice a 4P power contactor usning the main contacts to switch On & Off the ” 3 phase + neutral supply “, then the output of this contactor will electrify the 4 circuits via ” 2 poles circuit breakers ” for each circuit. Noting the nominal current for contactor should be the current value for 2 circuits, because you have 2 circuits on the same phase.

Regards.

#12191
simone
Participant

Thank you, Spir Georges GHALI,

That's exactly what I needed to know. Perfect answer with a very clear explanation.

Thanks and regards.

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