3 phase pump

[tommy.dale]

Hi All

i have 3 phase pump set on a primary chilled system for which i had a quick look at a few days ago ive given a quote to look at as its not running for love nor money, ive only spent 10 minutes fault finding but something doesn't add up, its 3 phases and earth no neutral, im getting 230v to earth on each phase but not 400v between phases, is this because no neutral is present (or needed) ?

im heading back with my megger but never meggered a pumpset before, im not to sure if its a BMS problem holding it off or the pump head is just nakered, can someone point me in the right direction what to look out for?

cheers

 

[sheephat]

What are you getting between phases?

 

[tommy.dale]

hi mate

nothing between phases at all 0v

 

[ruston]

Obvious, but have you checked the supply to the starter for supply?

 

[telectrix]

im getting 230v to earth on each phase but not 400v between phases,

sounds suspiciously like someone has removed the motor links ( star or delta). that's if you get 230V phase/earth at the motor. or am i barking.

 

[Pete999]

As Ruston say's check the supply first, where are you checking for phase to phase voltage? is the pump started DOL or Star Delta?

 

[tommy.dale]

hi guys

its star delta and i checked the supply at the pump itself while the casing was off

 

[Pete999]

hi guys

its star delta and i checked the supply at the pump itself while the casing was off

You need to check the starter is it operating correctly?

 

[Deleted member 26818]

Two phases out.

 

[Pat H]

That would be my guess as well. 2 phases down so only a single phase present. your reading the 230 to earth on each phase via the motor windings.
I'd disconnect the supply from the motor and measure each phase. Then do an impedance check of each motor winding.

 

[Rocboni]

Are you sure you are testing across phases and not testing L1 L1 ect? Don't mean to insult with this but it would explain 0v would it not?

 

[tommy.dale]

lol definately not testing that mate i can assure you like i said i was on site for only 10 minutes but as i dont really work on these pumps thoughts id get opinions, i have more than enough to go back and look now
thanks for everyone's help

 

[sheephat]

Either that or the source is linked out.

I have seen three phase "created" that way... they were not invited back to the job.

 

[Darkwood]

It appears as has been suggested that you have lost 2 ph at the motor, the 230v you see on all terminals is the 1ph feeding back across the very low impedance windings.

You have either blown 2 phases and if the star-delta starter has a independent control circuit then this could be the case as it still works, or you have lost 2 phase output of the star delta starter... if your control circuit was tapped of the 400v supply then this would also stop the operation of the star-delta starter if 2 ph were down.

If you know how motors work and their windings are configured then you should be able to see if the motor is the original problem/cause.

I would be cautious in taking on such work if your not familiar with it, some of the basics are quite simple but it can get very complex very quickly and experience and knowledge are essential to diagnose the causes and remedies, I have seen many hit with massive costs through basic errors because they didn't know what they were doing and in asking the question, I thought I best just give you a heads up, I have seen numerous sparkies fit rewound or new motors to many systems for them to burn out because they haven't identified the cause, its not just a matter of saying the motors gone fit a new one.

 

[ruston]

Good advice , also you may not have been first man there .

 

[Marvo]

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

 

[David Prosser]

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