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Applications of Latched type VCs

Applications of Latched type VCs

(OP)
Where are the latched type VC's are used? Are latched type Vacuum Contactors with fuses are equivalent to VCB's? In reactor starter motor feeder, one manufacturer has used latched type VC's? Is there any disadvantage of latched type as opposed to the electrically holding type Vacuum contactor in the reactor starter?

RE: Applications of Latched type VCs

Wherever you want to have the standard motor starter you have to use the electrically holding type contactor. The beauty is that it gives a default under voltage protection.

Latched type contactors generally used in combination with the fuse, is a cheaper alternative to the fully equipped circuit breaker. It can be used for the lower current rating applications as generally available rating is 400A. Of late few manufactures started to supply up to 800A. But I personally prefer to go for a circuit breaker above 400A application.

RE: Applications of Latched type VCs

Latching type contactors are often used in motor starters where an unexpected brief drop in supply and thus control voltage might cause the contacts to "kiss" and/or chatter which in motors can be dangerous. There are other alternatives now in the way the coil is powered and controlled, but this is an older design concept.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

RE: Applications of Latched type VCs

Latched contactor is a cheaper alternative to a 5 kV class breaker, especially if there is a 5kV MCC feeding a few motors in the area and you need a 1 or 2 MVA 5kV-480V transformer.
A feed to a transformer does not create issues like a motor starter if it doesn't trip open during an outage.

RE: Applications of Latched type VCs

We regularly use them in transformer feeders. The main reason is to ensure the transformer comes back online after a power fail without a human having go go out and press the 'close' button. I don't recall ever using one in a motor starter.

There is at least one manufacturer that makes a magnetically latched contactor. It basically uses an electromagnet to create enough force to close it and then the electromagnet is reversed to force it back open. The force to hold the contactor closed comes from a permanent magnet vs a low energy electromagnet circuit like most large contactors use. You might have run into these, and since the contactor design means they always latch, it's the way they have to be.

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