An Equivalent Heat Source Calculation Model for HSER Under Overload Conditions

The temperature of hermetically sealed electromagnetic relay (HSER) continues to rise during opening and closing process of contacts under overload condition. Contact is one of the important components of small sealed electromagnetic relays, and its contact characteristics and heating characteristics are closely related to the reliability of the whole relay. During the operation of the relay, there is physical wear between the contacts, after the load is applied, there is also the problem of arc erosion, in the working conditions of overload, the problem of electrical ablation is more serious, which will lead to the deterioration of the contact surface, the contact resistance between the contacts increases, the contact heat increases, affecting the life and reliability of the relay. The DC relay overload test rig was built, the scanned topography of contact surfaces under different load levels was photographed, and the effects of overload on the physical and electrical properties of the contacts were analyzed. By studying the microscopic contact process between the contacts and the effect of surface roughness on the contact resistance, the probability density function of the surface roughness of the contacts is introduced into the mathematical formulation of the contact resistance, and the mathematical model of the contact resistance between the contacts related to the surface roughness is obtained. The contact depth and contact temperature rise of contacts with different surface roughness were simulated by finite element method. The contact system thermal characteristic test system was designed and constructed, and the relay overload temperature rise test was carried out to verify the validity of the calculation model by comparing with the measured results.