Wiring DOL for 2 motors 3 phase..

[zai_jnr]

Hello members,

This is question from my friend regarding using 1 DOL motor starter for two motors.

He has 1 DOL starter that it output wiring to 2 motors. After power turn ON, motor A rotate to forward and motor B rotate to reverse.

His customer request him to rotate motor A to reverse. What he done is, he change the phase motor A cable from red to blue and blue to red terminal. Then, when power turn ON, motor A rotate reverse but motor B rotate to forward.

We wonder why this situation happen. He also try change motor B cable phase terminal. the condition will switch which is motor B reverse then motor A will forward back.

what we need to do if both motors need to reverse rotation?

1) maybe using separate DOL for two motor? ( existing right now using 1 DOL for two motor)...

Thank a lot for helping my friends....

 

[Viks]

Are both of your motors of the same size? I'm not sure if starting 2 motor on just one contactor and a thermal overload will give adequate protection to the motors in case of an overload. In the case of changing motor rotation,why dont you try to interchange two of the phases in the motor terminal box instead to minimise confusion of wires on the motor starter. If I were you, I would wire another starter (a contactor and overload) in parallel to the existing starter to get better protection. Just connect the contactor coils in parallel to the existing contactor and connect the second thermal overload contact in series with your existing control cct. Hope you got the point.......

 

[shooter]

change wires on the motor not on contactor

 

[Gil47]

What you have would be a breach of electrical codes where I live, and as our codes and your codes tend to follow the European codes then I believe your will also,
Your best course is to involve an electrician in what you are attempting to do so it is done correctly and safely.