Abstract:

This paper discusses contact discontinuity of electromechanical switches and presents a model that considers the effect of vibration-induced inertial force on operational reliability. Using this model, the operational reliability of a switch with a specific contact assembly can be assessed for given vibration conditions. Under the vibration conditions, a minimum contact spring force is necessary for proper functioning of the switch, while the magnitude of contact uncertainty determines the need of an additional force to ensure operational reliability. With reduced contact uncertainty, operational reliability of switches approaches either 0 or 1 solely depending upon design and operational conditions. In this model, the parameters of c, b in (2.5) and / in (2.6) need to be determined either empirically or experimentally before the model can be used for reliability assessment. To theoretically determine the contact behavior and contact uncertainty of a contact assembly with defined contact geometry, contact material, and contact surface conditions, Hertz contact with randomly distributed surface asperities could be considered. Finally, although this model starts from a log-normal distribution of electrical contact, the approach can be applied to other distributions, such as inverse Gaussian and Weibull distributions.

Key words: Electrical contact, electromechanical switch, contact discontinuity, loss of contact normal force, contact resistance, operational reliability

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