45kVA transfromer controlled by a contactor

[bozzah]

Are there any effects on a 45kVA transformer if the primary is switched on-off few times throughout a day?

In order to siplify wiring, owner wants to control lighting panel by turing on-off the whole lighting panel via contactor on MCC; i.e. having primary side of the transformer is swiched on-off at least 2 times a day. Would this reduce the life of the transformer by this frequent magnetization of the transformer; is it necessary to specify specific transformer?

 

[alehman]

I don't see any problem with that for the transformer. The inrush will cause a brief voltage dip when the transformer is energized. You might ask the contactor manufacturer if they see any problem for their contactor.

Alan
----
"It’s always fun to do the impossible." - Walt Disney

 

[ScottyUK]

It will be tough on the contactor - transformer inrush is usually more severe than that found in motor duty. If you're intending to do this strictly by the book then you need to check the current rating for AC-6a duty, although in practice a contactor rated for AC-4 duty with appropriate current rating will likely be adequate.


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If we learn from our mistakes I'm getting a great education!

 

[bozzah]

thanks all.

 

[VladimirM]

IMHO that is not very good solution since the transformer will be subjected to frequent inrush currents and hence frequent mechanical stresses. I think it's lifetime will be reduced.

Why not to switch the secondary side of the transformer?

 

[racobb]

Our municipal clients typically use primary switching for athletic field lighting on a regular basis. Granted the cycle is done only once per day, if at all on many days, so I have never considered the stresses on the transformers.

It is a good question though! Don't know if the standards speak to this or not.

If it does shorten the life of the transformer, then by how much. I guess you would need to make an effort to quantify that cost and balance that cost against the cost of secondary switching of the load.

Alan

Democracy is two wolves and a sheep deciding what to have for dinner. Liberty is a well armed sheep!
Ben Franklin

 

[bozzah]

After the conversations with a number of transformer manufacturers, there is no issue with switching it 2-3 times a day, which is the situation in my case.
Having a switching contactor at secondary, would introduce additional cost since 45kVA (600V-208/120V)is a bit far from the source, 600V MCC.

 

[racobb]

Then I would switch the primary with an appropriate device.

Alan

Democracy is two wolves and a sheep deciding what to have for dinner. Liberty is a well armed sheep!
Ben Franklin