Study on the Influence of Excitation Structure of Cup-Type AMF Contact on Thermal Performance of Vacuum Circuit Breaker

For high voltage vacuum circuit breaker (VCB), the thermal performance under the rating current has become a key parameter. The objective of this paper is to study the influence of the excitation structure of the cup-type AMF contact on the thermal performance of the VCB. A three-dimensional electro-thermal coupling model of the VCB was built, and the power loss was calculated by the electromagnetic field analysis. The heat transfer coefficients on the boundaries were numerically calculated by the commercial software. The electrical contact resistance was taken into account in the electro-thermal coupling model. Under various excitation structures of cup-type AMF contact, the thermal performance of VCB has been determined. The power loss of the contact accounts for a large proportion of the total power loss, and the highest temperature of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$245^{\circ}\mathrm{C}$</tex> occurs on the contact plate. As the thickness of the contact cup increases, the loss of the contact cups decreases and the loss of the moving contact plate increases. The total power loss increases, but the increase is only 2%. As the height of the contact cup increases, the power loss of the contact cup increases, and the power loss of the contact plates also increases. The total power loss can reach 9.1% with the change in height.