Two speed one winding motor troubleshooting advice

[phineascage]

I apologize for the delay. I have been out of the office and had no internet access during my sabbatical. I thought I would post my findings as of yet for the previous thread that everyone was so kind to post ideas, advice, and experience for.

As yet I finally received motor reports from our motor repair shop for our problem motor and another that was repaired some time back. They ran both motors in High at roughly 452VAC. Our problem motor in high drew current at roughly 160A. Our non problem motor drew current at roughly 103A. At this point we're looking to pull our problem motor and send for re-winding.

The lesson for me is, I should have had reports in front of me instead of relying on verbatim from the motor shop.

 

[Besoeker]

I apologize for the delay. I have been out of the office and had no internet access during my sabbatical. I thought I would post my findings as of yet for the previous thread that everyone was so kind to post ideas, advice, and experience for.

As yet I finally received motor reports from our motor repair shop for our problem motor and another that was repaired some time back. They ran both motors in High at roughly 452VAC. Our problem motor in high drew current at roughly 160A. Our non problem motor drew current at roughly 103A. At this point we're looking to pull our problem motor and send for re-winding.

The lesson for me is, I should have had reports in front of me instead of relying on verbatim from the motor shop.

Yes, I suppose so, but good that at least you seem to have narrowed the problem down to it being a motor issue. As I mentioned before, the 152A no-load current would/should have set off alarm bells with the motor shop.

 

[mivey]

Yes, I suppose so, but good that at least you seem to have narrowed the problem down to it being a motor issue. As I mentioned before, the 152A no-load current would/should have set off alarm bells with the motor shop.

So to put it in the words of a different member: you were r. you were rrr. you were rrrrrr.

I guess I'll have to stick to my own words: you were right!

 

[Besoeker]

So to put it in the words of a different member: you were r. you were rrr. you were rrrrrr.

I guess I'll have to stick to my own words: you were right!

Happens sometimes...........

 

[Sahib]

The lesson for me

Routine electrical maintenance of the motor and logging the results may also reveal any incipient fault in the motor.

 

[kwired]

I was mostly convinced the motor had a problem and not the premises wiring or the driven load.

 

[Russs57]

The rule of thumb is 33% of FLA for unloaded motor but as mentioned two speed motors can have terrible PF.

I would be having a lack of confidence in that motor shop.

Still not thrilled with the #2 wire.

 

[Besoeker]

The rule of thumb is 33% of FLA for unloaded motor but as mentioned two speed motors can have terrible PF.

Yes, can be. Jraef also mentioned that in the now closed thread. But I modeled the motor and came up with a 0.85 PF.

I would be having a lack of confidence in that motor shop.

I agree. As I mentioned in an earlier post

 

[Ingenieur]

the question still remains:
same motor
same v
+30% no load current shop vs field

the nla tells you nothing

be curious once the rewind is placed in service on the cooling tower
lo speed = ok, <20%
fla = >+15%
nla ???

can't that shop load test a motor?
if not, find another shop

if you can post a pc of the nameplate please

 

[Besoeker]

the question still remains:
same motor
same v
+30% no load current shop vs field

the nla tells you nothing

I respectfully disagree. As do others, it would seem.

This give the information you requested?

The motor nameplate information is below:

High: 460VAC / 250HP / 290FLA / 1.15SF / 1790RPM / 2 SPD 1 WDG Variable Torque
Low: 460VAC / 62HP / 100FLA / 1.15SF / 890RPM / 2 SPD 1 WDG Variable Torque

As given by the OP in the first post of the now closed thread.

 

[Ingenieur]

I respectfully disagree. As do others, it would seem.

This give the information you requested?


As given by the OP in the first post of the now closed thread.

explain: shop vs field +30%??

saw that data, used extensively in the thread

the nameplate will have mfg and PN
then the data sheet can be retrieved

 

[Besoeker]

explain: shop vs field +30%??

It's a problem motor - see post #1 of this thread

saw that data, used extensively in the thread

the nameplate will have mfg and PN
then the data sheet can be retrieved

And what you expect that to show you beyond what the OP presented?

 

[phineascage]

the question still remains:
same motor
same v
+30% no load current shop vs field

the nla tells you nothing

be curious once the rewind is placed in service on the cooling tower
lo speed = ok, <20%
fla = >+15%
nla ???

can't that shop load test a motor?
if not, find another shop

if you can post a pc of the nameplate please

Kinda hard to make out the data.

 

[phineascage]

explain: shop vs field +30%??

saw that data, used extensively in the thread

the nameplate will have mfg and PN
then the data sheet can be retrieved

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

 

[Sahib]

explain: shop vs field +30%?

The 30℅ increase would not have happened all of a sudden but gradual which OP might have failed to detect detect due to lack of maintenance.

 

[Besoeker]

The 30℅ increase would not have happened all of a sudden but gradual which OP might have failed to detect detect due to lack of maintenance.

How about failed bearing, rotor stator contact, damaged windings. Not a lot gradual about that.

 

[kwired]

I don't know if it was ever mentioned or if I missed it, including what was said in first thread, but when was motor current measured in the repair shop? And was the the on site comparison immediately after installed or had it been in use for some time then suspicion had risen and it was then measured on site? If not measured immediately, you can't say it wasn't damaged by potential conditions of use.

 

[mivey]

I respectfully disagree. As do others, it would seem.

I think one issue is the "r" word. A second issue is the "wr" word.

Apparently difficult to get beyond even in the face of what would be, at least at this point, overwhelming evidence that one should re-evaluate a position that says the motor is not the problem.

 

[Besoeker]

I think one issue is the "r" word. A second issue is the "wr" word.

Apparently difficult to get beyond even in the face of what would be, at least at this point, overwhelming evidence that one should re-evaluate a position that says the motor is not the problem.

He might get there eventually.

 

[phineascage]

I don't know if it was ever mentioned or if I missed it, including what was said in first thread, but when was motor current measured in the repair shop? And was the the on site comparison immediately after installed or had it been in use for some time then suspicion had risen and it was then measured on site? If not measured immediately, you can't say it wasn't damaged by potential conditions of use.

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.