Numerical Simulation Of Transient Temperature Field Of Relays And Experiments

It is important to analyze heat generation in electrical apparatus during the design, and thermal analysis is becoming more and more important with the development of large capacity and miniaturization of apparatus. Heat generation and dissipation of electrical apparatus is complex. There are many factors that have effects on them. It is difficult to build an analytic expression that includes all the factors to describe the heat flow in electrical apparatus. With the development of the numerical method, comparatively precise results can be obtained by using computers, and it can cut the costs for experimental investigations and shorten the development cycles.In this paper, the transient temperature field of commercial automotive relay working under 3 different input power when the environment temperature was 25℃was calculated by FEM software ANSYS. Several typical points inside relay were selected and their temperature changes with time were calculated and compared. The simulation results showed that the temperature distribution of relay was uniform when the input power was small and the temperature rises of metal components are almost equal. The temperature distribution is no longer uniform when the input power is larger. The temperatures of contacts and the stranded copper wire which connected to the dynamic contact were the highest when contacts close. The temperatures of the stationary contact and the terminal connected to it become the highest when contacts break.In this paper, different forms of heat dissipation and the change of environment temperature on the effect of temperature rise of relay were also considered. The results show that the effect of heat dissipation by convection and radiation became more and more important with the time and the heat dissipation by convection and radiation become more obviously with the increase of input power. It could be also known that the temperature distribution of relay had nothing to do with the environment temperature, however, the maximum temperature of relay increased with the increment of outside temperature.At the end of this paper, the temperature rise of relay was practically measured and it was compared with the simulation values. The results showed that the measured and calculated values of relay temperature rise were in good agreement.