Star delta testing help needed

[ipf]

Fair enough it's still not the starter

Just an example.
One panel I installed over 30 years ago controlling 4 x 15kw motors via s/d starters. In all those years the motors have all been changed just once with the odd bearing change, whilst I would say that at least 25 contactors have needed changing with contact damage due to load.

 

[Kj14]

It's switching over and it will run for a while sometimes a few hours and then trip. It's running a vac pump. Just need to know how to test winding from the panel as the motor box is not easily accessible.

 

[Pete999]

Are you talking IR or resistance testing

It's switching over and it will run for a while sometimes a few hours and then trip. It's running a vac pump. Just need to know how to test winding from the panel as the motor box is not easily accessible.

Are you talking IR or winding resistance testing

 

[Deleted member 72666]

It could be a multitude of things, does the motor sound ok? rumbling or knocking noises could indicate bearings/ alignment problems, check the supply voltage at the panel (line to line and line to earth) then from there visually check for bad/burning connections ( does the panel smell of burning when first opened up?) then carry out all the dead testing checking contact resistance on all poles of the contactors not forgetting to check the resistance of the overloads themselves. Check that the resistance of the motor windings from the panel are balanced if not check at the motor terminals.

 

[Deleted member 72666]

I've just seen that it's a vac pump, when these start to fail they can become very noisey (sticking or broken blades) and at the same time take longer to reach the preset vacuum (this can checked by asking the operator if they have noticed any changes).

 

[David Prosser]

I'm going for mechanical fault (or lack of maintenance) on the vacuum pump. Oil and filter candles need changing. Just a complete guess but as I can't see it, hear it, or test it I'm just having fun guessing.

 

[Kj14]

Are you talking IR or resistance testing

Are you talking IR or winding resistance testing

Winding resistance from the panel

 

[Pete999]

Winding resistance from the panel

At which contactors? you will need to identify the 6 cables going to the motor

 

[Kj14]

That's what I need to know I can see the star contactor and the delta contactor

 

[Deleted member 72666]

Check at the main contactor and the delta contactor not forgetting the o/l unit. Identify the windings U1 start and finish U2, V1 & V2 and finally W1 & W2, these should have the same value, don't be surprised at the very low impedance readings. Also check for leakage to earth from U, V and W. Don't forget to check the input voltage.
If all above are present and correct including what was said in #24, then it's almost certain a mechanical problem.

 

[Deleted member 72666]

That's what I need to know I can see the star contactor and the delta contactor

What was the outcome?

 

[theguz]

make sure all the contacts in the contactors are making . you might be losing a phase

 

[Deleted member 72666]

The fault has probably been fixed by someone else as the op not been back with any info.