When the voltage peak of the SSR exceeds the maximum voltage peak capable of exceeding the SSR, the component in the solid state relay can cause SSR damage, selecting a suitable voltage grade and parallel sensitive resistance. Protect the SSR.  
A. When the AC load is a resistive load, the SSR is selected and the load rated voltage can be selected.  
B. When the AC load is an inductive load, it is recommended to select the SSR than the load rated voltage high.  
C. The nominal voltage of the DC SSR is the upper limit voltage of the load. When the sensing load, the SSR must be accepted to be protected, which can be taken in parallel metal oxide pressure resistance resistance (MOV) in the SSR output. Generally, the 220V series SSR can select a pressure sensitive resistance of 500V-600V, and 380V Series SSR can select a pressure sensitive resistance of 800V-900V, and 660V Series SSR can select a pressure sensitive resistance of 1100V-1200V.