The Solid State Relay (SSR) are a series of single-pole, normally open, solid state switching devices with no moving parts, capable of tens of millions of cycles of operation. It is designed to control 120V, 240V or 480V (up to 660V) alternating current (VAC), and provides zero voltage switching and 2500VAC isolation between the load terminals and the control signal. A control signal causes the solid state relay (SSR) to switch the ac load ON or OFF just as a conventional mechanical contact switch does but with none of the problems associated with moving contact relays, such as corrosion, pitting, arcing, radio frequency interference (RFI) and bounce. The result: much longer life for the solid state relay (SSR).

Our solid state relay is designed around a pair of SCR’s mounted on a heat-spreading metal base to eliminate thermal fatigue failures. To dissipate the heat developed naturally in an Solid State Relay (SSR) due to a nominal voltage drop across the device, the Solid State Relay (SSR) must be mounted on a Finned Heat Sink (FHS), or on a metal plate of adequate size. It is advisable to install an solid state relay where the ambient temperature is relatively low because its current-switching rating is decreased as its temperature increases.

Control resistance heaters up to 40 kW use solid state relay in conjunction with lower-rated temperature controllers. Three-phase loads can be controlled using 2 or 3 SSR’s. Use 3 SSR’s for Y-phase loads using a neutral line. Three Solid State Relay are also used when there is no neutral load to provide redundancy and extra assurance of control. Two SSRs will control "delta" loads.