Nomex® Electrical Insulation: Voltage Endurance

The Voltage Endurance test determines the ability of an insulating material to withstand the damaging effects of partial discharge. Ideally, a piece of equipment would be manufactured such that there is never partial discharge, but physical limitations such as size often make that impossible. Voltage Endurance is tested by putting a voltage stress on the insulation high enough to create partial discharges within the sample or on the surface. The test can be run at various frequencies and temperatures and can be run on sheet insulation, shaped magnet wire, motor stator bars, and even small microwave and lighting-ballast transformers. Looking closely at the base of the electrode, you can see the faint blue glow of corona discharge. This sheet shows the rings left behind from the partial discharge around the electrodes. This testing is vital to new product development for medium and high voltage applications.