With the development of power electronic technology, the frequency conversion speed regulation technology of motors has been rapidly promoted, and the corona-resistant enameled wire for frequency conversion motors has also become a hot spot. The pulse wave generated by the frequency conversion IGBT and PWM speed control device has a towering peak, and the wave peak has a steep rising voltage, and the extremely high frequency (sometimes up to 20kHz) damages the insulating paint film of the enameled wire, making the motor very easy Inter-turn breakdown occurs, how to improve the life of variable frequency motor has become a hot topic of research in recent years.
 
The corona-resistant polyamide-imide topcoat has a great contribution to the corona resistance life of the enameled wire. With the increase of the coating ratio of the topcoat, the corona resistance life increases. This is because the corona aging process of the enameled wire is a process of discharge erosion on the surface of the material. In addition to the degradation of charged particles and ultraviolet radiation, there is also a high-temperature ablation process. The continuously injected electrons generate a lot of heat in the process of colliding with polymer molecules, which increases the local temperature of the polymer surface and is prone to thermal breakdown. The topcoat polyamide-imide has good heat resistance, and the coating amount of the topcoat increases, which can improve the thermal stability of the corona resistance enameled wire, thereby improving the corona resistance enameled wire's corona resistance time.  

Appropriate curing degree is very important to the life of corona resistance enameled wire. When the curing is excessive, the flexibility of the enameled wire paint film will decrease, which will shorten the corona resistance life; when the curing is insufficient, the enameled wire paint film has insufficient heat resistance and is easily damaged Thermal damage caused by partial discharge, resulting in a dramatic drop in corona resistance   The corona resistance life of Corona resistance enameled wire increases as the proportion of the corona resistance topcoat polyamideimide increases. The curing degree of the corona resistant enameled wire should be moderate. Over-curing and insufficient curing will lead to a decrease in the corona-resistant life.