Help sizing buck/boost transformer?

Jan 27, 2007 2 Replies

Load is 130A FLA at 220V = 28.6KVA. Supply is 3-phase, "Y", 208V.



Using a 120-240/12-24 buck-boost transformer, what KVA should I look for? One source says that this transformer increases voltage by 10 percent, so KVS should be rated at 10 percent also. This means I should look for 3KVA transformer?



Also, if my understanding is correct, because of the nature of buck boosts, under light loading the output voltage will be higher than under heavy load. The equipment should be OK with this voltage swing, and if not, a full isolation transformer should be used. What might this swing be? (Note my use of "might"...)



Is my thinking sound?



Thanks, Sparky



130 * 12 = 1560 130 * 24 = 3120

That's the VA you need for each case, buck or boost. I assume the transformer is NOT a three phase model - you will use three of them? The VA will be for each, not the total.

Slightly but no more than if you had the correct voltage.

. . . . . . . .

BTW, I'm considering single-phase b-b transformers. Two of them apparently will be needed for three-phase voltage conversion.

Thanks, Sparky

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