Two speed one winding motor troubleshooting advice

Status
Not open for further replies.
Might be more to the situation.

On a different note did anyone see the article about the picture of a cat made by entangled photons? Now that is something to argue about! The quantum world is weird :D
 
phineascage said:
Motor current was measured in the motor shop after rotor repair and bearing replacement. It was immediately measured on site after installation.

Per the repair report the voltage applied at the motor shop was an average of 452VAC. The current at the motor shop was an average of 159A

On site the voltage applied was an average of 476VAC with an average current of 195A.

Both tests were with motor uncoupled.
Click to expand...
All seems to point in one direction.
 
phineascage said:
It is a Marathon motor
Frame: 449T
Enclosure: TEFC
PH: 3
Design: IVT
Freq: 60
Duty: Cont
Insl: F
SF: 1.15
Amb: 40
Start Cycle: ACL

High Speed
HP: 250
Sync RPM: 1800
F.L. RPM: 1790
Volts: 460
Amps: 290
KVA Code: H

Low Speed
HP: 62
Sync RPM: 900
F.L. RPM: 890
Volts: 460
Amps: 100
KVA Code: H
Click to expand...

thanks
is there a stock number, pn, item number, etc?
 
Sahib said:
I thought motor predictive maintenance is of value to OP...........
Click to expand...
What is that?

That isn't my response, that it the response of most owners of the smaller organizations I typically have as clients.

They will cry about how many man hours are put into such a thing, but then will cry if they have a motor such as OP's that needs replaced or rewound. Only a 10 hp motor or smaller maybe will grumble a little when it fails but is quickly forgotten about.
 
kwired said:
What is that?

That isn't my response, that it the response of most owners of the smaller organizations I typically have as clients.

They will cry about how many man hours are put into such a thing, but then will cry if they have a motor such as OP's that needs replaced or rewound. Only a 10 hp motor or smaller maybe will grumble a little when it fails but is quickly forgotten about.
Click to expand...
Much of what we made was installed on continuous production process lines. By continuous I mean 24/7. Paper mills, steel mills, cement plants and such. The site electricians would take regular readings and print out trends of things like loads, speeds, thermal data etc. on a routine basis. That was a useful diagnostic procedure. Sometimes called "fingerprinting".

Once a year they typically had a two week annual shut at which routine maintenance was carried out. A good clean out, power connection tightness checked, any obvious damage, cooling fans checked.....
 
phineascage said:
Motor current was measured in the motor shop after rotor repair and bearing replacement. It was immediately measured on site after installation.

Per the repair report the voltage applied at the motor shop was an average of 452VAC. The current at the motor shop was an average of 159A

On site the voltage applied was an average of 476VAC with an average current of 195A.

Both tests were with motor uncoupled.
Click to expand...
Your motor rated voltage is 460V. The field voltage is 476V. Therefore the motor iron was saturated and drawing higher no load current of 195A than in the workshop. The non problem motor may not be of same make, model, size, or voltage rating as the problem motor and so may have more iron thereby drawing less no load current of 103A.
 
Last edited:
Sahib said:
Your motor rated voltage is 460V. The field voltage is 476V. Therefore the motor iron was saturated and drawing higher no load current of 195A than in the workshop. The non problem motor may not be of same make, model, size, or voltage rating as the problem motor and so may have more iron thereby drawing less no load current of 103A.
Click to expand...
From a nominally 480V source?
Get real.
 
Sahib said:
Your motor rated voltage is 460V. The field voltage is 476V. Therefore the motor iron was saturated and drawing higher no load current of 195A than in the workshop. The non problem motor may not be of same make, model, size, or voltage rating as the problem motor and so may have more iron thereby drawing less no load current of 103A.
Click to expand...

The iron was not saturated. Voltage ratings are nominal and can vary up to fifteen percent and still be in operating range.
 
See the paper below for no load performance of an induction motor. For induction motor with core of low iron content, saturation could occur even slightly above rated voltage on no load. www.easa.com>sites>files>NoloadCurrentBasics_0205.pdf
 
Last edited:
Sahib said:
See the paper below for no load performance of an induction motor. For induction motor with core of low iron content, saturation could occur even slightly above rated voltage on no load. www.easa.com>sites>files>NoloadCurrentBasics_0205.pdf
Click to expand...
Yes. Look at where it gets out of the linear region and approaches saturation.
 
Besoeker said:
Yes. Look at where it gets out of the linear region and approaches saturation.
Click to expand...

Per author of the paper, the linear region could end at rated voltage for induction motor with low iron content core and no load current could increase disproportionately on saturation.
 
OP did say the shop average voltage was 452. I'd expect some difference in current compared to supplying it with 476.

Not sure exactly what no load current would be like, loaded I'd expect more current when the lower voltage is supplied.

OP did have higher then expected current with and without mechanical load applied to the shaft.
 
Status
Not open for further replies.
Top