Two input (selectable) 3 phase breaker/switch for AC Induction Motor

Thread Starter


Joined Jun 15, 2011
Hi, i have a 50kW AC induction motor, which takes 150A at startup. I thought of using a 3Phase generator to start the motor, and after a little while, when the motor has gained the speed and current dropped to about 60A, change the power source to AC mains. When i change the power source, i can quickly turn off the motor start contactor and do the power source change using a mechanical switch, and then turn on the motor start contactor.

So, i would really appreciate if someone could let advise me on a suitable 3 phase mechanical switch which has two (selectable) 3phase inputs

Off position of the breaker/switch is the generator supply and the ON position will be the AC mains.

Thanks in Advance


Joined Jul 17, 2007
Why not start it from the mains to begin with?

I don't think you will be able to find a manual 3 pole double-throw switch designed for that kind of duty.

Have you contacted an electrical equipment manufacturer that has suppliers in your area? They have engineers on staff that will be happy to help you with your situation, and are intimately familiar with their product lines. You might contact a company like Square D/Schnieder Electric and ask them.

This Board is oriented primarily towards those who are in the beginning to intermediate level of expertise in electrical/electronic hobby projects. Your project really requires at least someone who is a licensed Journeyman Electrician, if not an Electrical Engineer.