MV Vacuum Contactors & Break Time 3

[RRaghunath]

I find some of the VCU makes have break times like 400 milliseconds (Siemens 3TL8).
I am used to seeing break times of the order of 50ms for the HV/MV switchgear. Any thoughts!!
Thanks in advance.

 

[rbulsara]

50ms could be for vacuum circuit breakers not contactors. Contactors are inherently slower than breakers.

 

[RRaghunath]

rbulsara,
Why is it so!
The contactors have less gap between the contacts and so I thought less opening time they should have. Is it because of the necessity to be compact!

Thanks for your response.

 

[Laplacian]

The contact separation springs on breakers are several orders of magnitude larger (and stronger) than the separation springs on contactors. Breakers have springs similar to those used automotive suspensions and contactors have very small low energy coil or leaf springs.

 

[rbulsara]

raghun:
Laplacian answered the question. Breakers have special mechanism and are "made" to interrupt fault currents, contactors are not. Contactors depend on upstream fuse or breaker for short circuit protection.

Get yourself familiarized with breaker and contractor construction.

 

[jraef]

Very common misconceptions. People use VCBs quite often as contactors, then assume that contactors are the same as VCBs. The bottles inside are often the same, but the difference is in the mechanism.

Nice responses Laplacian and rbulsara.


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[RRaghunath]

rbulsara and other experts,
I have come across no. of makes with break time in 30-50 ms in Vacuum contactors. 3TL6 model of Siemens is one example. Others include ABB, TAMCO.

Thanks for your responses.

 

[rbulsara]

raghun:

Firstly, we were only responding to what you posted (400ms). It may be possible to have fast vacuum contractor. However you may want to ask clarification from the manufacturer on the significance of "100ms minimum closing command for the solenoid".

Regardless, not sure what is your objective or issue but a contactor is no substitute for a breaker.