The insulation system of inverter-fed motors is subjected to repetitive impulse voltages, which are generated by pulse width modulation (PWM) converters, and is expected to withstand partial discharge (PD) activity during service. PD-induced dielectric breakdown becomes one of the most important reasons for premature failures of motor insulation. Therefore, the dielectric properties of insulation material used in inverter-fed motors need to be improved to meet the requirement for rapid development of applications. Many approaches have been proposed to improve dielectric properties of insulation material used in inverter-fed motors. In this chapter, we will discuss the failure mechanism, modification approaches, and their effects on dielectric properties of insulation material of inverter-fed motors.
Part of the book: Modern Applications of Electrostatics and Dielectrics
Polyimide (PI) is a commonly used insulating material to resist surface discharge, for instance, as turn-to-turn insulating material in inverter-fed motors driven by pulse width modulation (PWM) converters. Under the effect of repetitive impulse voltages, PI is expected to withstand surface partial discharge (PD) during service. However, lifetime under repetitive impulse voltages is much shorter than that under AC voltages due to storage effect of charges. Many approaches have been proposed to improve lifetime of polyimide under repetitive impulse voltages, such as using nanocomposites, surface modification, and structure design. In this chapter, we will discuss the lifetime of polyimide under repetitive impulse voltages and corresponding theoretical mechanism, together with modification approaches and their effects on lifetime improvement.
Part of the book: Polyimide for Electronic and Electrical Engineering Applications