Coupled simulation of eddy-current thermal field in medium voltage switchgear

The temperature rise is very critical for the normal operation of switchgear, in which eddy current and contact resistance are the two important influence factors. In this paper, firstly, the main conductive circuit model of one kind of 12kV medium voltage switchgear is established using commercial software Solidworks. Secondly, the effect of the eddy current and contact resistance on the temperature rise of switchgear is simulated with consideration of heat conduction, convection and radiation, and also reasonable boundary conditions. Simulation results show that the loss of eddy current accounts for 20% of the total loss, which indicates the eddy current is so significant that it can´t be neglected. Then, the effect of the different position of the contact resistance on temperature rise is also studied. Simulation results show that when the contact resistance is close to the edge, the heat loss of the contact increases significantly due to the longer conductive path. The temperature of the contact near the edge grows significantly due to the skewed-slots coil structure of the axial magnetic field contact, which is unfavorable for the energy transfer through heat conduction. And because of the higher temperature at the edge, the temperature of other positions can also be increased.