Chapter 2, Problem 2.1P

A 100-kVA, 8000/277-V distribution transformer has the following resistances and reactances: $\begin{array}{l}{R}_P=5\Omega R_S=0.005\Omega \\ X_P=6\Omega X_S=0.006\Omega \\ R_C=50\text{kΩ}{X}_M=10\text{kΩ}\end{array}$

The excitation branch impedances are given referred to the high-voltage side of the transformer.

1. Find the equivalent circuit of this transformer referred to the low-voltage side.
2. Find the per-unit equivalent circuit of this transformer.
3. Assume that this transformer is supplying rated load at 277 V and 0.85 PF lagging. What is this transformer’s input voltage? What is its voltage regulation?
4. What are the copper losses and core losses in this transformer under the conditions of part (c)?
5. What is the transformer’s efficiency under the conditions of part (c)?