PURPOSE: To ensure the positions of the leads of helical winding easily by dividing wire arrangement in the helical winding into two groups and dividing and disposing the position of the lead of the winding on both sides in the direction of lamination of a core.

CONSTITUTION: A helical winding 51 is wound on a core 50, and a high-voltage winding 52 is wound on the outside of the winding 51. The winding 51 is partitioned into wires of two groups in the axial direction, and both upper and lower wires of a first group are drawn out of the high voltage side A, and each function as the leads 53, 54. On the other hand, both upper and lower wires of a second group are drawn out of the low voltage side B, and each function as the leads 55, 56. The winding 51 is started from the lower section of the core 50 and ended to the upper section of the core. According to such constitution, the leads 53, 54 and 55, 56 of the winding can be separated in the direction of lamination of the core 50 without increasing circulating currents in the winding 51 because the wires of these groups make magnetic flux interlinking in the winding approximately the same, and the positions of leads of the winding 51 can be ensured easily.