design a contactor based automatic power transfer switch

pls iam working on a contactor based auto power transfer switch. can i get the circuit diagram and more explanation on the interlocking mechanism.

their are two types of interlocking via contactors. One is Electrical and other one is Mechanical.

Mechanical interlocking is very good and their are no chance for short circuiting. However electrical interlocking is also very much good and required fool proof circuit.

For electrical interlocking you need one spare Normally closed contact on both contactors, Contactor-1 A1 supply must be connected to NC contact of Contactor-2 and than to supply, same will be for Contactor-2 via NC contact of Contactor-1.

thanks, but i need the schematic diagram for a single phase power system and more information on the electrical interlock

Will you please give some information for that? Do you want Generator to Main AC ATS? if yes than give brief description here

@masterleus

I need a similar setup but with the option of adding generator backup in addition to the two main lines. Can you please explain how can we achieve that? As this is for a typical home so power rating doesn't need to be more than 70amps for the 2 main lines