Power electronic converters used in aircraft have previously been used at reasonably low voltages which have not been associated with a significant risk of electrical discharge. Items such as circuit boards are designed in accordance with standards such as IPC2221A but this is often seen as conservative. Given the drive to the more electric aircraft and the need to increase power density of the electrical sub-systems, power electronic converters are now at increased risk of electrical discharge given the increase in voltage and are under increased pressure to remain as compact and light weight as possible. This project identified a coating that could be applied to power electronic converter components to reduce the risk of electrical discharge and also identified suitable techniques for integrating the application of this coating within a manufacturing environment.

Coatings applied to high voltage equipment can reduce the risk of electrical discharges. Conformal coatings based on polymer films have been applied commercially onto electronic circuit boards. However, they might not be suitable to be used in low pressure operation of high voltage power electronics reliably given the relatively poor performance of such coatings when exposed to tracking / partial discharge.

We examined the options for the deployment of novel and cost-effective coatings to be placed onto the printed circuit boards and power electronic components that may require protection in open box power electronics. Our focus developed:

• A coating type that can withstand the aerospace environment;
• A coating that when applied to open box power electronics will inherently reduce the risk of electrical discharge;
• A coating that is straightforward to apply (ideally using techniques identical to those in present manufacturing);
• A coating that can withstand damage from electrical discharges should a localised defect occur which allows these to take place.