Phase converter randomly switching rotation

[jjsparky]

We are were called because a trolley crane would run backwards randomly. Sometimes up would be up and sometimes up would be down. As though someone swapped phases for reverse rotation. The crane is 480 3 phase. They have a single phase 240 volt service, then through a transformer to create single phase 480 then through a phase converter to creat 3 phase 480.

 

[winnie]

If it is a rotary phase converter, then the phase rotation of the synthesized phase will be set by the actual rotation of the phase converter rotor.

The rotary phase converter is a 3 phase motor with two of its input leads connected to the single phase source. The motor itself doesn't have a natural sense of rotation when connected to the single phase source. Something has to get the motor spinning in the first place and set the direction of rotation.

If something is wrong with the phase converter starting mechanism, then it might be starting up going the wrong way.

-Jon

 

[LarryFine]

I bet there's a problem with one (or more) of the capacitors.

 

[winnie]

I bet there's a problem with one (or more) of the capacitors.

Agreed. The capacitors are what start (and sometimes maintain) the rotation. So the problem could be with the capacitors themselves or the switching mechanism if there are switched capacitors.

-Jon