Effect of low temperature on tracking failure process of Epoxy/BN composite

Epoxy resin as an insulating material is widely used in superconducting motors because of its excellent insulation properties under low temperature. However, epoxy has a relatively low thermal conductivity so it may be damaged by thermal breakdown. Tracking failure is a kind of thermal breakdown happened on polymer surface. In this paper, the tracking failure behaviors of Epoxy/BN (boron nitride) composites under low temperature were studied to clarify the effects of low temperature and BN particles on tracking performance. Tracking failure process under different pulse frequency was measured with a digital camera and an infrared thermal imager. The CCD camera was used to observe the failure process while the infrared imager was used to measure the thermal accumulation and decay process. Obtained results showed that the addition of BN fillers and low temperature had a significant inhibitory effect on tracking failure process. In liquid nitrogen environment, the time to tracking failure increased obviously. It is concluded that the ability to inhibit tracking is improved by reducing the temperature at the concentrated discharge region and increasing the heat dissipation region.