Solid State Relay Problem

Hello there !

I am using a solid state relay to drive a 2KW water pump motor. See the attached image of circuit.
The solid state relay getting fried. I think due to inductive “Back EMF” pulse that is produced when the load is switched off.

What could be the solution to get rid of this problem ???



One solution would be to use suitable parts in the circuit.

Your picture tells, that you are using a MOC3031M triac driver for switching 230 VAC.

But the product description tells that this part is for 115 V AC only.

Peak Blocking Voltage
– 250 V, MOC303XM
– 400 V, MOC304XM

With AC the peak voltage is Vpeak = sqrt(2) * Veff

115 VAC: Vpeak = sqrt(2) * Veff = 1.414 * 115 = 163 V
230 VAC: Vpeak = sqrt(2) * Veff = 1.414 * 230 = 325 V

So a MOC3031M is NOT ABLE to block the peak voltage of 230 VAC.

I think the suitable part number for 230 V switching would be a MOC3041M (instead of MOC3031M)

And wow, the schematic is very hard to read. So I stopped spotting errors there. Maybe redraw it in a clear way? For example, keep the clearence between mains and Arduino in the drawing as well... And post it in like triple the resolution :/

And like jurs said, the triac driver is not suitable. And I doubt the triac itself is suitable.

For starters I hope you use a huge heatsink? @ 2kW you're burning 12W in the triac. And the inrush current might be to high for it as well. Or at least ir might take longer then the triac can handle.