ON-LOAD TAP CHANGING TRANSFORMER

PURPOSE:To omit a quartic tap winding and to obtain a small-sized on-load tap changing transformer by a construction wherein a tap is provided in the shunt winding of a autotransformer, and the serial transformer is excited by the tap voltage. CONSTITUTION:A shunt tap winding 2A for changing the tertiary voltage is provided in a shunt winding 2. The winding 2A forms an excitation circuit for a serial transformer 5 together with a tap selector 7, a changing switch 8 and a porality changer 9. It is arranged in the order of a tertiary winding 4, the winding 2A, 2, 3 and 1 from the inner side. By so doing, it becomes possible to omit a quartic tap winding and to solve the problem attendant on anomalous voltage caused by an idle tap of the quartic tap winding. Further, reduction in both size and loss can be effected.