3 phase pump

[Marvo]

I'd forget the motor for now, isolate it and focus on the YD starter or the drive that's supplying it.

 

[ChipFanDave]

Check across the phases at the incoming supply to the starter . If you have 400v across all three pairs there I would then I would check the fuses (sound obvious but these are normally the first thing to blow on jammed motors) isolate safely and mega the motor from the out going terminals in the starter panel this will also test the supply cables. If no fault is obvious on the motor windings or cables then look at the starter contactors.

 

[test electrical]

Look if you haven't done in 10 minutes what everyone has already said then listen to dark wood and get an electrician into look at it because it sounds like what it is. If you don't know what your doing you shouldn't be charging someone for it. That's why trade people get a bad name. Thank god its not the VT or the CT pumps in this weather lol. Am sure you'll check all the youtube clips just remember that pumps go off with a bang.

 

[Pat H]

Good link to starters and the theory.
Star-Delta Motor Starter | EEP - http://electrical-engineering-portal.com/star-delta-motor-starter