Xantrex versus Sunny Boy [RE-wrenches]

[Kent Sheldon]

Bill, utility companies do charge on Amps used. It doesn't matter if it is real or reactive. So indirectly, they do charge for VAR, which in a transformer is a larger portion of the zero load losses than the watts. I'm glad to see that Jeff's real world numbers are the identical to my theoretical calculations.

Here are some real world transformer numbers:

112.5kVA, 80C rise, CU, 208:480 isolation transformer (this is considered a high-efficiency model BTW). No load losses are 1065W, 2050VAR, resulting in 2280VA loss. This is more than twice the Watts loss. Most people don't consider the VAR losses, as the transformer companies don't publish this information. But you can get it if you call.

Granted, this example is a fairly large transformer (it happens to be the one I'm doing some research on right now), but keep in mind, that the smaller transformers are usually more lossy than the large ones.

Kent

>>> Bill Brooks<billb at endecon.com> 8/1/2003 3:46:44 PM >>>
Jeff,

How are you measuring this 6% loss? I think that is excessive if the proper
efficient transformer is used. If you are measuring volt-amps, that is not
an accurate assessment of energy lost. Certainly there is heating of
conductors because of the current flow, but this the main real power loss.
Contrary to Kent's post, most customers do not pay for VARS unless they have
a really bad power factor that the utility is penalizing them for. I think
you either have the wrong transformer, or you are not calculating your
energy loss properly.

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