Simulation of the heat transfer mechanism in relays to improve contact reliability at freezing temperatures

Computer simulations of thermodynamic processes optimally expand the alternatives available for experimental technology and thereby reveal problems at critical temperatures already at the developmental or design-in stage. In many cases, knowing the thermal efficiency within a relay can help to avoid switching problems. It is well known that at low temperatures, residual dampness in the relay or its materials can condense on the relay contacts. The speed of the cooling processes plays an important role in this respect. That condensation, at low temperatures, leads to ice formation and to an unstable or high-impedance contact resistance. Obviously this phenomenon depends on many parameters: besides load current and coil efficiency, the connection to the PCB plays a decisive role. In the following article, the thermal efficiency of a relay to be used at low temperatures and small load currents are calculated according to the finite element method. In several steps, the relevant influential variables are determined and the design thereby optimised. Comparative electrical and temperature measurements are also drawn upon to verify the simulation.