Effect of 42V on Automotive Relays and Switches

The proliferation of electrical power demands in today's vehicles and forecasted high power/high energy electrical loads in the near future have led the vehicle manufacturers and suppliers to the general consensus of 42V being the next generation automotive electrical system.

The electrical arc generated during the opening of a relay or switch, connected to an inductive or resistive load, has much greater energy at 42V than operating in the 14V system. Although the 42V system current is about one-third, the coil turns have to be proportionally increased in order to maintain the same flux for a similar torque/force characteristic as its 14V counterpart and, as a result, the inductive energy should be the same for both 42V and 14V loads. Therefore, the higher operating voltage is the main factor in creating a bigger arcing issue. The redesign of present switches or relays by increasing the contact gap alone for the 42V application is a marginal solution in some cases.