3D Analysis of the behaviour of a foreign object in electromagnetic relays
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Electromagnetic relays are electrically operated switches that can open or close a contact by means of an electromagnet. They have been used in a wide variety of applications throughout industry, such as in automobiles, household appliances and automation systems. Although there is a considerable amount of descriptive data regarding the electromagnetic relays, many questions remain unanswered regarding the behaviour of charged foreign objects in the electromagnetic relays. Electromagnetic relays are covered with a plastic case. The damage of the cover may result in the occurrence of foreign objects. In case that the foreign object is sandwiched between the movable and fixed contacts, conduction failures occur. Iida et al. investigated the motion of a charged foreign object in an electrical relay. Since they particularly focused on the 2-dimensional behaviour of the foreign object, the effect the shape of the relay on the motion of the charged foreign object was not examined. In this work, we investigated the 3-dimensional behaviour of a foreign object in the electromagnetic relays. The motions of the movable and fixed contacts were solved by the mode-superposition method. The colliding force between the foreign object and the fixed contact was calculated by the theory of elasticity. The electric field in the electric relay was solved by the finite difference method with the coordinate transformation. The motion of the charged object was calculated by the Runge Kutta method. It was shown that the motion of the charged object depends on the shape of the relay and the charge quantity of the object.
