The effect of the heat applied during removal of the burned windings in electric motors to structure of material and magnetic characteristic of (stator) armature

Summary form only given. As is known, electric motors and generators are varnished for insulation after winding. These varnished coils are formed in stiff construction in the slot. Because of heavy-duty conditions, whole or a part of coils could become burned out or broken. There are two main methods to remove the defective coils. These are thermal method and chemical method. In this study, the burning method of varnish in flame burning room is studied. In the thermal method, either a voltage is applied to defective coils by using a high-power autotransformer (variac) and a short-circuit current flows until all varnish is burned, or, if all of the coils are out of order, varnish is burned by putting the stator or armature in a burning room. The effect of the heat applied in this stage to structure of material and magnetic characteristics of the armature have been investigated. The relations between magnetic characteristics and metallurgical structure of material and their solutions have been emphasized under laboratory and service conditions.