Enhanced thermal conductivity and insulation properties of mica tape with BN coating via electrostatic spraying technology

The bottleneck problem of the development of high-voltage motors to a larger capacity can be solved if the thermal conductivity is improved without sacrificing the insulation characteristics of the main insulation material. In this paper, a spraying technology based on electrospinning is proposed that can evenly spray boron nitride (BN) with high thermal conductivity onto the surface of mica tape. With the increase in BN content, the insulation and thermal conductivity of mica tape are optimized to varying degrees. When the BN content reaches 2.25 wt%, the in-plane conductivity increases from 1.6 to 2.7 w/(m K), while the out-of-plane conductivity increases from 0.17 to 0.26 w/(m K). Additionally, the direct-current (DC) breakdown strength has increased from 90.6 to 96.9 kV/mm and the dielectric constant and dielectric loss are almost unchanged. Finally, through simulation verification, if the modified mica tape is applied to the main insulation of a synchronous motor, the operating temperature of the motor insulation will be reduced from 73.5 to 66.1 degrees C. This study provides a new research idea for the preparation of high thermal conductivity insulating materials.