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Determination of Transformer equivalent circuit from Open Circuit and Short Circuit Test
Theory

Introduction

The basic theory of transformer operation is adequately explained in Reference 1. For our purposes here we will concentrate on the test methods and the experimental set-up
Figure 1 shows the traditionally accepted electrical equivalent circuit for a power transformer in steady-state. This particular equivalent circuit’s parameters are referred to side 1. All relevant impedances, voltages, and currents are shown in the figure.

It is important to note that for a typical power transformer the ratio of the parallel combination of the common leg impedances to the total impedance of either winding will exceed 200. Algebraically, this can be described as