Some practical equivalent circuits for multi-circuit transformers

The exact practical theory of the transformer that has been previously described is extended to transformers with more than two windings. An exact equivalent circuit results which is simpler than that usually used. The equivalent circuit, and the performance of the transformer, are expressed in terms of parameters that can be measured by test. An approximate equivalent circuit is derived in such a way that the influence of the approximation can be expressed in an explicit manner. Some calculations are made of the reactances of three-circuit and four-circuit transformers, in order to indicate how the disposition of the windings affects the performance.