Solid State Relays

[bsparky]

Question about what is meant by Zero Cross for a Solid State Relay such as this one.
http://oeiwcsnts1.omron.com/pdfcatal.ns ... MB0305.pdf

Thanks

[Chris Smith]

Phase control.

Zero crossing plays a part when using the solid state for more than just on and off control like DC.

To use the SSR output for phase control, select a model that does
not incorporate a zero-cross function.

[Robert Reed]

bsparky
The main advantage of "zero crossing" is that the load can only be switched on and off when the AC voltage swings thru the zero crossing point thereby switching it at presumably zero current(some inductive loads may still be drawing a small amount of current due to inherant phase shift of current at the voltage zero crossing). This enables load switching at zero voltage thereby greatly reducing switching transients. However phase control can never be accomplished by "zero crossing " devices by the fact that they can only be switched at zero voltage and not at any other firing angle.

[bsparky]

Thank you Robert very good explination.