480v 25hp motor losing strength

[titan1021]

I've got a client that runs a small food processing facility. I connected this mixer for them approx two years ago and it has worked fine. However they have just informed me that the motor has become weak and the mixer can only handle about a 1/4 of the load it handled just a few months ago. They tell me that any more than about a 1/4 of the original load and the machine struggles to turn. The mixer is used to mix dry cereals in large quantities.
I have verified that it is getting the proper voltages and checked the windings for shorts as well as the ohms. I didn't discover any obvious issues, and it seems to me that it is just reached the end of its service life.
This machine was purchased used by my client with an unknown history. It is a 440v motor and It currently supplied with 480v which is actually about 495v on site. After talking with people here regarding this motor in the past, myself and the client decided to run the motor at this higher voltage knowing that it would shorten its overall life and replace it with a 480v motor whenever it finally died.
Just wanted to check in here to see if I might be missing something or if its time to replace this motor.

Thanks

 

[retirede]

I don’t think I’ve ever seen an induction motor”get weak.”
Are overloads tripping? Have you checked the current draw under load?

I suspect a mechanical problem.

 

[tom baker]

Do you have running amps from when first installed and recent readings?
Any way to measure RPMs?
Motors for a 480v system are rated 460 v.
Perhaps it a mechnical issue, if overloaded the overloads should trip if properly set.

 

[zbang]

Getting "weak" after a couple of years? Ask 'em when was the last time they did any maintenance on the machine...

Run the motor unloaded, what's the current?
Run the machine unloaded, what's the current?
If there's more than a little difference, check the mechanisms.

There is also the possibility that what they're mixing has changed and they're not telling you or they don't realize it.

 

[ptonsparky]

Check the fuses. They aren’t telling you something.

 

[MTW]

First guess from the photo is belt slippage on the motor sheave. Once they slip for a while, they become glazed and should be replaced, and the motor sheaves cleaned up.

 

[winnie]

I concur with a motor issue being unlikely.

It is possible that you could have turn to turn shots in the winding or cracked rotor bars, but as others have suggested I would check for mechanical faults first.

Jon

 

[ptonsparky]

And if it’s a fuse...that’s a dang good motor to have survived this long. A smell test is all you need.

 

[paulengr]

Capacitor is gone so power factor and torque is low.

 

[junkhound]

First guess from the photo is belt slippage on the motor sheave. Once they slip for a while, they become glazed and should be replaced, and the motor sheaves cleaned up.

+1, exactly my thought on seeing what is probably a 3 belt set of sheaves under that big cover that are worn and loose. Mght not evel nook like a rubber rope now vs. V-belts.
current measurement and PF will likely show lower power and current.
Another few days and will start to smell the belts big time.

Bad PFC cap an interesting possibility, but those nearly always fail short which would blow breaker.

 

[winnie]

Capacitor is gone so power factor and torque is low.

What sort of capacitor?

Jon

 

[Besoeker3]

Capacitor is gone so power factor and torque is low.

Very unlikely. I'm with the others - a mechanical problem.

 

[petersonra]

if the overloads and/or OCPD is not tripping it is likely something slipping like a belt. Could be the shaft is slipping too.

 

[Barbqranch]

How does it sound when it starts to be overloaded?

 

[Jraef]

If it's not a mechanical issue like belt slippage, then I would guess that the motor is getting low (or no) voltage on one phase, for example as a result of a blown fuse, loose connection or a contactor having burned contacts on one pole. If the load on the motor is well below the rating of it, the result will just be a loss of torque and may not show up in the Overload Relay yet. Or it did start tripping the OL relay and someone "cranked up the dial" to avoid having it trip.

 

[retirede]

If it's not a mechanical issue like belt slippage, then I would guess that the motor is getting low (or no) voltage on one phase, for example as a result of a blown fuse, loose connection or a contactor having burned contacts on one pole. If the load on the motor is well below the rating of it, the result will just be a loss of torque and may not show up in the Overload Relay yet. Or it did start tripping the OL relay and someone "cranked up the dial" to avoid having it trip.

I had thought about phase loss, but since it apparently starts without issue, it would have to be a really weird (or intermittent) condition that would allow starting but unable to load.

It would be nice to hear from the OP again!

 

[tom baker]

If it's not a mechanical issue like belt slippage, then I would guess that the motor is getting low (or no) voltage on one phase, for example as a result of a blown fuse, loose connection or a contactor having burned contacts on one pole. If the load on the motor is well below the rating of it, the result will just be a loss of torque and may not show up in the Overload Relay yet. Or it did start tripping the OL relay and someone "cranked up the dial" to avoid having it trip.

Ah yes the old cranked up the dial trick
I worked with a wise maintenance electrician, who worked on waste water lift stations. The pumps would "rag up" trip the overloads and then it was an electrical problem.
He told me "its always an electrical problem" IE what the mechanics says, but it almost never an electrical problem.

 

[titan1021]

I will have to check for the capacitor type, as well as have them put it under load while I am there. I will check on these and follow up on this post.
Thank you all for the input. The overload hasn't been tampered with and I've haven't detected any phase loss.