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Non synchronous power sources

Non synchronous power sources

(OP)
I am testing a transfer switch that is supposed to be able to handle two single phase sources that are asynchronous, and switch seamlessly from the first source to the second when the first one fails.

In our office we have a three phase supply. So if I took one single phase supply off red to use as the first source, and one single phase supply from the white phase as the second source, would these two count as asynchronous sources? Would their sine waves be in phase or not necessarily so?

RE: Non synchronous power sources

They will be precisely synchronized but always 120º out of phase. This will only show that your transfer switch can handle exactly one specific case. Using yet another phase will show that your switch can precisely handle exactly two cases. Not a very thorough test.

I hope your three phase is not delta...

Much better testing would be to use one of your building phases and then use a generator that is not synched to provide all other phase angle possibilities.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Non synchronous power sources

A lot of equipment doesn't like an abrupt phase shift. Depending on the point on the wave that the phase shift occurs, you may trigger excessive transformer inrush and mechanical stress on motors, including broken shafts and high transient currents. Testing may not be trivial.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Non synchronous power sources

Sounds like a fairly stock standard static switch. It will have programmable parameters that let you adjust the amount of phase shift allowed for a seamless transfer, normally about 15 degrees is the maximum. Outside of that range, if there is a failure of the primary source the load will transfer, but with a break, again set by programmable parameters.

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