3ph star delta starter motor drawing high amps

[Pete999]

Star delta starter / motor problem.
Starter starts runs as should on bench with no motor connected. Getting 230v to e on all 6 uvw 1s and uvw2. 415 u1 to v2 etc etc. But nothing 1 to 2s. As expected.
When motor connected up. (Single speed) it takes 3a in start on all . Drops into run fine but is taking 38a on all.
After 5 seconds it trips breaker.
When you say the Starter runs OK with no Motor connected, are you saying the Starter operates as it should? and what do you mean by single speed?
If the Motor is starting, and connecting the Motor's winding in a Star configuration, but trips when it changes into a delta mode, then it sounds like you have either a faulty Motor, of you have it wired up incorrectly.

Any ideas were to start. As both out of stores as spares and checking they work but now stumped

 

[Pete999]

Star delta starter / motor problem.
Starter starts runs as should on bench with no motor connected. Getting 230v to e on all 6 uvw 1s and uvw2. 415 u1 to v2 etc etc. But nothing 1 to 2s. As expected.
When motor connected up. (Single speed) it takes 3a in start on all . Drops into run fine but is taking 38a on all.
After 5 seconds it trips breaker.

Any ideas were to start. As both out of stores as spares and checking they work but now stumped

 

[Rocboni]

No not blown it out but it runs fine when connected to dol started with links in motor 3 wire.
It seems like losing a phase / low voltage high current???

Why do you need to start it via star delta if you are able to start it DOL, how big is the motor and are the windings rated 415/690 or there abouts?

How are you connecting the links when starting DOL I presume star as you say it starts fine when connected up to the star delta.

My bets on delta contactor in starter... although I can't understand from your original post if you've checked this?

 

[Pete999]

Why do you need to start it via star delta if you are able to start it DOL, how big is the motor and are the windings rated 415/690 or there abouts?

How are you connecting the links when starting DOL I presume star as you say it starts fine when connected up to the star delta.

My bets on delta contactor in starter... although I can't understand from your original post if you've checked this?

https://www.quora.com/Why-is-star-delta-starter-preferred-with-an-induction-motor

 

[Rocboni]

https://www.quora.com/Why-is-star-delta-starter-preferred-with-an-induction-motor

I understand this Pete but a motor that only draws 3A on start up doesn't need to be connected to a star delta starter to reduce starting current does it? without seeing the rating plate it's obviously small motor

 

[Pete999]

I understand this Pete but a motor that only draws 3A on start up doesn't need to be connected to a star delta starter to reduce starting current does it? without seeing the rating plate it's obviously small motor

What does the information relate to on the starting procedure? there must be some information regarding this. I f it's a small motor then we must ask the question why is star delta mentioned, what has happened to the rating plate?

 

[marconi]

 

[Pete999]

No not blown it out but it runs fine when connected to dol started with links in motor 3 wire.
It seems like losing a phase / low voltage high current???

If you were trying to start this motor via a star delta starter, there should be no links in at the motor terminal block, you would need 6 six wires from the starter to the motor.

 

[Rocboni]

What does the information relate to on the starting procedure? there must be some information regarding this. I f it's a small motor then we must ask the question why is star delta mentioned, what has happened to the rating plate?

This is my point, the OP has gathered components off a shelf and assembled to test either that the star delta starter is operational or that the motor is ok, but not every motor can be connected to a star delta motor as you know.

Never said was a star delta motor. It's just 2 items out of stores we were checking that are ok.

 

[Rocboni]

It really has to be the delta contactor if running fine in star, proves windings are ok, loosing a phase when delta contactor comes in.

 

[Pete999]

Never said was a star delta motor. It's just 2 items out of stores we were checking that are ok.

This is my point, the OP has gathered components off a shelf and assembled to test either that the star delta starter is operational or that the motor is ok, but not every motor can be connected to a star delta motor as you know.

h

It
I would like to see a photo of the OPs connections if running fine in star, proves windings are ok, loosing a phase when delta contactor comes in.

It really has to be the delta contactor if running fine in star, proves windings are ok, loosing a phase when delta contactor comes in.

Can the OP provide pictures of how he has connected the motor and the starter? this may help us to get to the answer, after all it may be just a simple mistake in the final connections.

 

[marconi]

Please ignore my post #22 which has a gross wiring error in the diagram - can you spot it?

 

[Rocboni]

Could a set of the windings be connected to the same phase e.g. U1 and U2

Edit, Andy 1960 already mentioned this.

 

[ipf]

I would double check the wiring as the motor could be single phasing when it goes into delta ( same phase across both end of the one winding)

It shouldn't take 5 seconds to trip. though.
Delta contactor problem.
....then again, if there are motor links, who knows? Someone playing about with something they shouldn't be springs to mind.

 

[marconi]

Star delta starter / motor problem.
Starter starts runs as should on bench with no motor connected. Getting 230v to e on all 6 uvw 1s and uvw2. 415 u1 to v2 etc etc. But nothing 1 to 2s. As expected.
When motor connected up. (Single speed) it takes 3a in start on all . Drops into run fine but is taking 38a on all.
After 5 seconds it trips breaker.

This statement is anomalous if you consider what you would measure with a voltmeter between the terminals of the Star and the Delta diagram in my post #15.

eg for STAR - One would measure 230V from each 1 to any 2 but between any 2s would measure zero Volts.

eg for DELTA - One would measure 415V between any pair of 1s or any pair of 2s.
Between U1 - W2, V1-U2 or W1-V2 one would measure zero Volts.