Sumpner's Test Or Back-To-Back Test On Transformer
Procedure Sumpner's Test on Transformers :As shown in Fig, primaries of the two transformers are connected in parallel across the same a.c. supply. With switch S open, the wattmeter W1 reads the core loss for the two transformers.
Finding Losses With Sumpner's Test On Transformer
i.e. copper loss per transformer PCu = W2/2.
i.e. iron loss per transformer Pi = W1/2.
From results of sumpner's test, the full load efficiency of each transformer can be given as