Help sizing buck/boost transformer?

[SparkyGuy]

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

 

[Homer J Simpson]

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?

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.

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.

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


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[SparkyGuy]

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

Thanks,
Sparky