Characteristic of magnet wire based on the effect of electrical and thermal ageing

Polyimide film, a new-style insulation material developed by Dupont Company, has been widely used in the stator winding of PWM frequency control and adjustable speed electromotor. The stator winding insulation is exposed to a combination of electrical, thermal and other stresses, which causes insulation ageing and even failure of the electromotor. Therefore the investigation on aging law of polyimide film of stator winding subjected to multifactor is of great significance for the assessment of insulation and reliability evaluation. In this article, the breakdown voltage with different rising rate is present. The aged material was not only assessed by the dielectric measurements, but also examined by scanning electron microscopy. The dielectric loss factor of polyimide film insulation is investigated at various aging factors with aging time and testing voltage. Ageing mechanism is discussed according to the change of dielectric loss factor through ageing.