The performance of an transformer are often calculated on the idea of its equivalent circuit that contains four main parameters, the equivalent resistance R01 as brought up primary (or secondary R02), the equivalent leakage reactance X01 as referred primary (or secondary X02), the core-loss conductance G0 (or resistance R0 ) and also the magnetizing susceptance Bo (or reactance X0).
These constants or parameters are often simply determined by two steps.
- Open-circuit test and
- Short-circuit test.
The figure shows an equivalent circuit on the transformer with its parameter.
These tests are terribly cost-effective and convenient, because they furnished the essential data while not truly loading the transformer. In fact, the testing of terribly large A.C. machinery consists of running two tests just like the open and short-circuit tests of transformer.