GUIDE FOR THE EVALUATION OF LARGE POWER TRANSFORMER LOSSES
a. Load losses (sometimes called copper or coil losses);
b. No-load losses (sometimes called core or iron losses); and
c. Auxiliary losses (electric fan losses, other such equipment losses).
This guide is from United States Department of Agriculture Rural Utilities Service RUS Bulletin 1724-301. Stated in this guide is that Losses and Purchase price should be considered when deciding which transformer to purchase. The purpose of this bulletin is to present a uniform approach that can be used to determine the dollar value of these losses over the life of the transformer.
The three different types of transformer losses that should be evaluated separately are:
a. Load losses (sometimes called copper or coil losses);
b. No-load losses (sometimes called core or iron losses); and
c. Auxiliary losses (electric fan losses, other such equipment losses).
Load losses are primarily from the IsquaredR losses in the transformer windings and eddy current losses. If a value of load losses is not directly given, load losses can be determined by subtracting no-load losses from total losses. No-load losses consist of the hysteresis and the eddy current losses in the iron core of the transformer and the IsquaredR losses in the windings due to the excitation current. Auxiliary losses consist of the power necessary to drive the auxiliary cooling pumps and fans.
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