Research On Thermal Conductivity And Insulation Properties Of Boron Nitride Coated Mica Tape Based On Electrostatic Spraying

With the development of science and technology and the progress of manufacturing technology,large-scale,high-voltage generators are developing toward large capacities.The thermal conductivity of the main insulation of the stator winding has become a bottleneck problem,restricting its development to higher capacity.In order to solve the problems of generator heating and main insulation deterioration caused by poor thermal conductivity of the main insulation of the generator stator winding.Mica tape was electrostatically sprayed with high-thermal conductivity boron nitride(BN),with nano-and micron-sized BN acting as the thermally conductive coating in this study.Firstly,the micro morphology and structure of the prepared mica tape were characterized,and then the thermal conductivity,breakdown strength,and dielectric properties of the mica tape were studied.Then,the simplified winding model of main insulation is established by ANSYS simulation software to study the temperature rise of main insulation when mica tape with different thermal conductivity is used as insulation material.Finally,the stability of the mica tape was proven by the stability test at working temperature.The results show that the thermal conductivity of BN coated mica tape with 200 nm particle size increased by 24% at 25°C,while the increase was more obvious when the BN particle size was 2 μm.When the mass fraction is 2.25 wt.% and the particle size of BN is 2 μm,the thermal conductivity of mica tape coated with BN can be increased from 0.17 W/(m·K)to 0.257 W/(m·K)at 25℃,an increase of 51%.The DC breakdown and AC breakdown at 25℃ are 96.4 k V/mm and 9.49 k V/mm,respectively,which are 6% and 7% higher than the original mica tape.The introduction of BN coating makes the relative dielectric constant of mica tape increase slightly,and the dielectric loss factor has no obvious increasing trend.The simulation results show that the increase in thermal conductivity of the mica tape can effectively reduce the temperature rise of the main insulation of the generator.In addition,the mica tape prepared in this paper has stable thermal conductivity and insulation performance under long-term working temperatures.The high thermal conductivity mica tape designed in this paper has good thermal conductivity and insulation properties,which provides a new research idea for the preparation and production of high thermal conductivity mica tape.