On 18 Mar 2006 22:57:51 -0800, "
wrote:

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.

Since these losses are related to the VA of the transformer I just took
8% of 1000 and assumed the total losses to be 80VA. I assume that this
is correct.

He then asked about what if the transformer was loaded to its maximum.
This is the part I was unsure of, but going back to my memories of AC
circuit analysis I told him that I thought that the VA losses remained
the same for the core and copper losses since the input to the primary
does not change. However, the voltages change depending on whether the
transformer is a step up or down and that has to do with the number of
turns. I also told him that the amperage will be different in each side
of the transformer depending on if it is a step up or down but that
this did not effect the core and copper losses.

Was I completely incorrect in this assumption?

Thanks, Steve

Core loss will remain constant (for given excitation voltage and
frequency) regardless of load.

Copper loss will increase as the square of load current.