Mohamed Ismail Bari wrote:
> Hi,
> 
> Thanks for all your suggestions..
> 
> The motor is single phase AC (240V) rated 1.5HP.
> 
> I can do the switching at zero crossing but I think the relay's response
> time might have an impact here. (coil energising time, mechanical
> delay..etc) This response time might vary for every relay and the problem
> might show up is some of the boards. (board to board variation)
> 
You could delay in software to allow for above and catch the next zero 
crossing exactly.

Even when its not exactly zero you will be switching at a low voltage.
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