Baldwin, M., "Capacitive Load Switching: Extending Relay Switching Life and Reliability in Military and Aerospace Power Systems," SAE Technical Paper 2014-01-2208, 2014, doi:10.4271/2014-01-2208.
This paper will illustrate how the increasing electrical power demands of military and aerospace applications can continue to successfully be met by high performance electromechanical relays. To meet these higher demands engineering compatibility must be properly understood between the intended application demands and relay switching performance parameters. With high performance electromechanical relays continuing to play a critical part in military and aerospace applications it is more important than ever that engineers capture all of the electrical power switching requirements.A critical area within powering military and aerospace systems is relay life when capacitive load switching. Capacitive loads generate high current levels that are transient in duration and often adversely affect the relay lifespan at the component level and the military or aerospace application reliability at the systems level. Often these transients, while brief in nature, can dramatically exceed the steady-state switching ratings for the contacts in a high performance electromechanical relay. In this paper practical examples of inrush current reduction of capacitive transient high current loads and corresponding increase of relay contact life rating will be reviewed and explored in detail.By adapting the relay circuit design with current inrush reduction components and techniques the user can ensure a properly rated relay will meet the capacitive load switching requirements of the end application. When capacitive loads are properly identified and contained within the relay capabilities a higher degree of application-relay compatibility can be achieved. There are many positive payoffs including increased switching lifespan, functionality, and reliability that enhance the customer experiences under demanding military and aerospace conditions.