Troubleshooting on a star delta starter

[Thinus]

I've got a call about a pump that is not working. It was a 30 kw motor with a star delta starter. The motor start but before it changes to delta it trips. And it look like the motor is single phasing. So i disconnect both cables at the motor and start it again. As soon as the delta contactor came in it flashed on the delta contactor. The cables tested fine. Need some advice on what the problem can be please.

 

[David Prosser]

Check the fuses, check insulation resistance between phases on both sides delta contactor.
How did you leave the conductors when you disconnected them ? Have you insulation resistance tested the motor winding ?

 

[Thinus]

Check the fuses, check insulation resistance between phases on both sides delta contactor.
How did you leave the conductors when you disconnected them ? Have you insulation resistance tested the motor winding ?

The motor test fine. I've removed the conductors from the motor. The moment the delta contactor pulled in it flashed.

 

[westward10]

Is the motor attaining sufficient speed before the transition.

 

[David Prosser]

Did you test insulation resistance between phases on both sides of the delta contactor ?
It should be easy to find the culprit there are very few components in the circuit, just brake it down and test each individual part. Once these have been tested if there's still obvious candidate then put up the test results and maybe a drawing or picture.

 

[westward10]

I suspect the pump could be the culprit preventing the motor achieving sufficient speed before the transition. Maybe?

 

[David Prosser]

I suspect the pump could be the culprit preventing the motor achieving sufficient speed before the transition. Maybe?

If it's a waste water pump that's blocked, or a clean/potable water pump that is failing mechanically then could be but my experience with pumps is limited to water and food industry and 99.9% of the time will blow fuses or trip overload if it can't reach a decent speed before it's change over sometimes a loud whining from the controls or motor,especially at 30kW.

May just be a build up of carbon crud on the contacts ?

 

[snowhead]

Are the contacts on the Delta contactor all good?
Have you tried a clamp ammeter on the motor cables to see what the current is on Star and then on Delta as it changes over,, are all three phases equal?

 

[Pete999]

I've got a call about a pump that is not working. It was a 30 kw motor with a star delta starter. The motor start but before it changes to delta it trips. And it look like the motor is single phasing. So i disconnect both cables at the motor and start it again. As soon as the delta contactor came in it flashed on the delta contactor. The cables tested fine. Need some advice on what the problem can be please.

"Disconnect both cables at the Motor" there should be 6 not including the cpc.?
[automerge]1595738775[/automerge]

I've got a call about a pump that is not working. It was a 30 kw motor with a star delta starter. The motor start but before it changes to delta it trips. And it look like the motor is single phasing. So i disconnect both cables at the motor and start it again. As soon as the delta contactor came in it flashed on the delta contactor. The cables tested fine. Need some advice on what the problem can be please.

Has this pump just been re installed, or is it an existing install? did you check the connections at the Motr prior to switching it on? could have been a badly misconnected Motor.

 

[Thinus]

"Disconnect both cables at the Motor" there should be 6 not including the cpc.?
[automerge]1595738775[/automerge]

Has this pump just been re installed, or is it an existing install? did you check the connections at the Motr prior to switching it on? could have been a badly misconnected Motor.

I have disconnected them. Not sure if he re installed the pump. I'll find that out from him Thanx
[automerge]1595768987[/automerge]

Is the motor attaining sufficient speed before the transition.

The motor trips before the delta contactor pull in.
[automerge]1595769037[/automerge]

Did you test insulation resistance between phases on both sides of the delta contactor ?
It should be easy to find the culprit there are very few components in the circuit, just brake it down and test each individual part. Once these have been tested if there's still obvious candidate then put up the test results and maybe a drawing or picture.

Will do . I'll try that thanx
[automerge]1595769170[/automerge]

Are the contacts on the Delta contactor all good?
Have you tried a clamp ammeter on the motor cables to see what the current is on Star and then on Delta as it changes over,, are all three phases equal?

It trips before the delta contactor pull in

 

[Pete999]

I have disconnected them. Not sure if he re installed the pump. I'll find that out from him Thanx
[automerge]1595768987[/automerge]

The motor trips before the delta contactor pull in.
[automerge]1595769037[/automerge]

Will do . I'll try that thanx
[automerge]1595769170[/automerge]

It trips before the delta contactor pull in

Who is the he you ralk of, was / is he an electrician? 10 to 1 he has screwed up the connections if he did refit it

 

[Thinus]

Who is the he you ralk of, was / is he an electrician? 10 to 1 he has screwed up the connections if he did refit it

The farmer himself. Not sure if they did anything there. I'll find out tomorrow. Thanx for everything so far

 

[timbobelfast]

Check the winding connections. Could be trying to rotate in opposite direction after star contactor opens and delta closes. Seen this before. Check winding pairs with ohm meter.

 

[Pete999]

The farmer himself. Not sure if they did anything there. I'll find out tomorrow. Thanx for everything so far

you're welcome, good luck

 

[Pete999]

Check the winding connections. Could be trying to rotate in opposite direction after star contactor opens and delta closes. Seen this before. Check winding pairs with ohm meter.

Don't think that could cause the problem.