A Multi-Physics Finite Element Analysis of Round Pin, High Power Connectors

Abstract

In the past decade, the general public’s means of transportation has begun to undergo a radical transformation, moving away from only using gasoline and moving toward using a combination of gasoline and electricity. This switch will depend on a number of parameters, including the cost, the availability, and the possible health and environmental effects of gasoline. However, these are not the only mechanisms driving the debate. The cost and feasibility of mass producing a reliable electric vehicle will also help to determine its popularity on the market. The paradigm by which the motor vehicle is viewed may need to change radically before the electric vehicle can totally take over the transportation needs of a country like the United States. One parameter that shouldn’t stand in the way is the overall reliability of the electric vehicle, which is dependent upon the electric connections between the power source and the motor. Contact degradation in the electric connector, caused by fretting, occurs as a result of relative motion between two surfaces, which can be caused by vibration, thermal cycling, electric cycling, etc. This degradation, which decreases the performance of the contact by adding resistance, needs to be minimized and then controlled in order to increase the operating lifetime of the connector. By understanding the fundamental multi-physics mechanisms that cause fretting, better connectors can be designed, built, and implemented in any number of applications, including automotive, manufacturing, and microelectronic industries. Using a commercial multi-physics finite element software package, a model, incorporating multiscale properties, such as electrical contact resistance and thermal contact resistance, was constructed to predict the behavior of the round pin, high power connector under normal operating conditions. As a way to test the validity of the model, an experiment was devised to measure connector resistance and temperature along the surface of the connector. The theoretical results were correlated with the experimental results and showed the same trends. The multiscale contact resistance was artificially increased by several factors as a way to show how the connector may perform under fretting conditions. The model predicts an increase in connector resistance and temperature for both increasing current and increasing electrical contact resistance. The model also shows, for increasing current and increasing electrical contact resistance, that current becomes more concentrated along the path it travels in and out of the connector. This constriction of current, most likely due to the connector geometry, could lead to much higher surface temperatures than the model currently predicts, resulting in thermally induced softening or distortion in the connector.