# Calculate the Per-Unit Source Voltages

Three zones of a single-phase circuit are identified in the attached figure 3.10(a) {see attachment}. The zones are connected by two transformers, T1 and T1, whose ratings are also shown in the same figure. Using the base values 20 kVa and 115 volts in zone 3, calculate the per-unit source voltage. Neglect the transformer winding resistances and the shunt admittance breaches.

**Please see the attachment for the figure and multiple choice answers.

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#### Solution Preview

Solution:

VBase = 115 Volts, VABase = 20,000 VA

ZBase = (VBase)2/ VABase = (115)2/20,000 = 0.66 Ohms

ZLoad = (0.9 + j0.2)/0.66 = ...

#### Solution Summary

The answer is calculated by looking at the base values of the three zones that are connected by two transformers. By inputting the base values into the equations for each zone's loads and voltage equations, the per unit source voltage is determined.