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Three single-phase SSRs in place of one three-phase, with zero-cross

Three single-phase SSRs in place of one three-phase, with zero-cross

Three single-phase SSRs in place of one three-phase, with zero-cross

Hi Everyone,

We are having trouble getting three-phase sold-state relays. These are used to power a resistive heater load - in some instances a single heater is across two of the phases, and in others three heaters are distributed across the phases. I was able to find a single-phase SSR that otherwise has similar ratings to the normal 3Φ SSR we use (and for less than a third the cost!). Both SSRs have a zero-cross feature. Will there be any issue using three 1Φ SSRs? I am mainly worried that the zero-cross feature will not coordinate between phases, but I have trouble thinking that through.


RE: Three single-phase SSRs in place of one three-phase, with zero-cross

For simple on / off use, I don't understand there being an issue. You have 1 or 3 single phase objects that apparently have no sync required. That the SSRs are opto coupled, they are independent of their power source. I think it's irrelevant about phase sync and zero cross. Besides, the SSRs don't "know" or determine zero cross, they respond to it. Power control would work by using the thermal inertia of the heaters - X cycles on and Y cycles off.

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