Thanks for the Reply..
Your PCB layout is wrong, it does not have the spacings to work on 440VAC mains.
--> What should be the minimum spacing required to work with 440VAC. Can you help with any reference layout or documents.
Your relays, not enough clearance/creepage.
--> Can we get any reference design or application note to understand about it and follow the same.
The 440VAC line you run to your PCB terminal block will always have overvoltage transients and lightning etc. up to 6kV.
--> Please help with suggestions to avoid this transients and prevent the damage from this over voltage transients.
The motor contactor needs MOV across the coil
--> Please suggest recommended MOV spec to try it out.
Where is the fuse?
--> We dont have any fuse on board. Fused will be there for 3 phase supply as indicated in connection diagram.
Do we need fuse for relay contacts ?
Do you have long wire runs? A parallel lightning bolt can induce heavy current in long wire runs.
--> 3 phase supply line wires will be taken from transformer to starter input. These wires will be longer.
Also does DC or AC energize your relay coils? If it's DC then a freewheeling diode is typically necessary.
--> DC 5v is energizing relay. We have used free wheeling diode across coil.
Both relay and other components on the board are powered by single 5v DC supply.
Do we need separate supply for relay to isolate Relay part from rest of components and control relay through optocoupler?
Due to High voltage spike or lighting, if relay goes bad, other components should be safe.
Presently we are using sugar cube relay.
Do we need to go for rectangular or other type of relay to have more isolation between contact and coil ?