PURPOSE: To enahnce the mechanical strength as well as the dielectric strength of the titled coil by a method wherein a solution, which is the mixture of silicon resin, mica powder of 44μm or below in average scale diameter and inorganic fibers of 0.5mm or above in length which was diluted with an organic solvent, is impregnated and hardened on a coil whereon an insulated wire was wound around.

CONSTITUTION: The solution of mixture of silicon resin of 50W30wt%, mica powder of 44μm or below in average scale diameter of 40W30wt%, and inorganic fibers of 30W20wt%, containing fibers of 0.5mm or above in length of 50wt% or avove, which was diluted with an organic solvent, is impregnated and hardened on the coil 1, whereon an insulated wire was wound around. As a result, the dielectric strength and the mechanical strength of the coil can be improved.