Star delta motor help

[Romans99]

Right guys, apologies in advance for lack of detail etc but I've only had a very brief look at this one today and I'm expected to work miracles tomoro.

A three phase 13kw motor for an AHU extract fan was running very noisy and they sent it away to be refurbd
It has come back and been put back in.

It now runs for approx 20-30 seconds before blowing a 40amp fuse in the control panel.

Control is wired star delta and has not been altered, adjusted or messed around with.

Client is convinced it's wired wrong and want a quick fix.

I'm no expert on starters or indeed three phase motors,

Has anyone with more experience got any fault finding suggestions.

Why does it run for a while before blowing the fuse?

Again apologies for lack of detail but I'm back there tomoro and should now more then.

 

[UNG]

Is the starter switching to delta when the fuse blows

I assume by refurbed it has been rewound

If it is I would check that the motor connections are correct to the starter as motors do not normally come back rewound with the windings terminated onto the motor terminal block in the same order as they where taken out

 

[Sintra]

Right guys, apologies in advance for lack of detail etc but I've only had a very brief look at this one today and I'm expected to work miracles tomoro.

A three phase 13kw motor for an AHU extract fan was running very noisy and they sent it away to be refurbd
It has come back and been put back in.

It now runs for approx 20-30 seconds before blowing a 40amp fuse in the control panel.

Control is wired star delta and has not been altered, adjusted or messed around with.

Client is convinced it's wired wrong and want a quick fix.

I'm no expert on starters or indeed three phase motors,

Has anyone with more experience got any fault finding suggestions.

Why does it run for a while before blowing the fuse?

Again apologies for lack of detail but I'm back there tomoro and should now more then.

Check the connections at the motor to make sure there are no links in place (links might have been installed for testing after refurb)

 

[Darkwood]

although the timing sounds wrong, you need to watch the contactors change from star to delta if this is when the fuses blow then its a wiring issue, what fuses are blowing surely the overload should trip first unless their was a motor fault, that is if its connected up right.

 

[UNG]

I would expect more than one fuse to blow if links were fitted in the motor

 

[Sintra]

I would expect more than one fuse to blow if links were fitted in the motor

Agreed wasn't thinking properly.

Might be a cable not glanded back in to motor properly giving a fault to earth on the delta cycle.

 

[ryanryan]

I would firstly check that the connetiona are right at the motor... U1-V2, V1-W2, W1-U2..
If yo get your ones and twos crossed over, it creates mahem!

Also, drop all the connection outta the Starter (safely), AND start the Starter. If it run through the timed cycle then all the control circuits are ok, then back to the above

 

[thepurple1]

It could be that in STAR the motor is turning on way and when it changes to DELTA the motor is trying to go the opposite way. The motor needs to be belled out

 

[Romans99]

Thanks guys
I ended up on a different job and didn't get back to this one,

Slightly relieved I didn't have to figure it out but slightly disappointed I didn't get the chance to figure it out!

 

[jammyjim]

Thanks guys
I ended up on a different job and didn't get back to this one,

Slightly relieved I didn't have to figure it out but slightly disappointed I didn't get the chance to figure it out!

Its a simple case of the new winding not matching up to the original, in future ask the rewind company to check the phase progression of the windings while there detailing it and put it back as it was.


I work for a rewind company and we dont check phase progression on small machines.

 

[benji]

sounds like motors connected wrong,i would think 20s to 30s is too long for change over and could take the fuses out as youve no o/l protection in star

yours benji

 

[TF and the wire]

Almost certainly that the motro is reversing when it changes from star to delta. When motors are rewound, very often the direction of the windings aren't considered.

You need to drraw the circuits out in star and delta and work out which winding you need to reverse to give a change in delta but not in star.