wrote in message
oups.com...
Someone asked me a question the other day and gave me these specs about
a transformer and I did not know the answer.

They gave me the scenario of a 1000VA transformer with losses of 5%
core losses and 3% copper losses. I told them that the losses in the
core are due to voltage and frequency and that the losses in the copper
are due to amperage. I also told them that eddy currents cause core
losses, but that these are minimized by the the laminations of the
transformer.

Core losses are a function of core material, core design, and frequency.
With certain exceptions, core loss tends to be fairly constant regardless of the
load on the transformer. That is why an energized but unloaded transformer
still gets quite warm. Copper loss is simply a function of Ohm's law (I squared
R). Copper loss would be near zero on an unloaded transformer and at its
maximum with a fully loaded transformer.

A transformer designed for step-down will typically have heavier copper in
the secondary to efficiently accommodate the larger current, while a step-up
transformer would normally have the reverse design.

Vaughn