Cox-Proportional Hazards Modeling in Reliability Analysis—A Study of Electromagnetic Relays Data

Ambient temperature is an important factor influencing the reliability of electromagnetic relays. The effect of different environmental temperatures on relay lifetime can be examined through the Cox-proportional hazards model (PHM). In this paper, relay life tests were carried out at -20 °C, 20 °C, and 55 °C. Relay lifetime data were collected at various temperature conditions and were integrated to establish a Weibull PHM of electromagnetic relays. A comparative analysis of the experimental data indicates that an ambient temperature has a significant influence on contact resistance. The characteristic life, the mean life, and the probability density function of failure under temperature conditions not tested in the conducted experiment were estimated through the implementation of Cox PHM. Both the characteristic life and mean life decrease significantly with increasing ambient temperature. The perspectives and the methodology of the implementation of the Weibull PHM presented in this paper are generic and could be adopted for other systems/products directly.