Comparison of Voltage Endurance Performance of Different Industry-Grade Polyimide and Nano-Coated Films Under Square Waveforms

Conventional insulation systems were designed for sinusoidal excitations at power frequency. With the advent of inverter-fed applications, especially with wide bandgap semiconductors, large voltage transients and fast switching speeds have led to a steep rise in premature insulation failures within inverter-fed machines. To understand the impact of high-voltage and high-frequency emerging power electronic inverters on insulation lifetime, a medium-voltage H-bridge inverter test-bed was built to stress industrially available Kapton (Polyimide) - Kapton HN, Kapton CR, and Kapton MT and their breakdown time has been compared. Additionally, a novel polymer-based coating with self-assembling, inorganic 2D nano-filler montmorillonite (MMT) on was applied on polyimide (Kapton HN film) using a versatile spray coating process. Results of breakdown time of our nano-coated samples show a 50% increase in the lifetime when compared to the industrially available insulation materials. This material can improve the insulator lifetime under harsh conditions, and find numerous applications, such as electrification of transportation ships.