# Calculate the Per-Unit Current and Load Current in Amperes

Three zones of a single-phase circuit are identified in figure 3.10(a) {see the 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 current and load current in amperes. 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 = 1.36 + j 0.3 p.u.

IBase = VBase/ZBase =115/0.66 = ...

#### Solution Summary

The solution looks at three zones of a single-phase circuit that are connected by two transformers, with the per-unit load current and load current in amperes still to be determined. This solution is found by calculating the total voltage of the two transformers and inputting that value within the equation of the load current.