I would like to switch a 10A AC load with a solid state relay (SSR) and I am wondering if a higher current SSR (e.g. 40A) would be more efficient and produce less heat than a lower current rated SSR (e.g. 25A).
Is the SSR's loss resistive (like a MOSFET) and improved with a higher rated SSR, or is it based on a forward voltage drop (like a transistor) meaning the wasted power would be unrelated to the SSR's current rating?
Best Answer
Most Solid State Relays use either a triac or inverse-paralell-connected SCRs as the switch element.
The forward voltage drop when the switch is turned ON is about 1 Volt (average). This voltage drop is relatively constant, no matter what the current rating of the switch element is.
So, no. I don't think that using a SSR that is much larger than is actually needed will give significantly lower losses.