Motor insulation, heat, and moisture

THE subject of nondestructive tests on insulation has received much attention. Since a function of insulation in a given application is to provide a certain minimum dielectric strength, tests at their greatest usefulness would give a measure of dielectric strength without requiring a dielectric breakdown. Additional indications like proneness to loss of dielectric strength if subjected to certain hazards of service are valuable, and information on the deterioration or aging of insulation with service may follow from periodic tests.