Redesign of 60 Hz motor
Redesign of 60 Hz motor
(OP)
The client has imported a Baldor 60 Hz, 7.5 HP, 460 V, 1170 RPM into a 415 V, 50 Hz environment along with the connected equipment. The connected equipment (a clutch) is asking for the original 1170 RPM. He is using a VFD to run this motor. Given the drive input voltage is only 415 V, he is not able to run the motor at 1170 RPM and the motor has already failed within a few hours of running. The drive was tripping on current limit.
I am thinking of redesigning the stator for 415 V, 60 Hz so that he can get his 1170 RPM.
Any opinions ?
The Baldor motor original spec sheet is attached.
I am thinking of redesigning the stator for 415 V, 60 Hz so that he can get his 1170 RPM.
Any opinions ?
The Baldor motor original spec sheet is attached.





RE: Redesign of 60 Hz motor
It's what I'd do. But both would work..
Keith Cress
kcress - http://www.flaminsystems.com
RE: Redesign of 60 Hz motor
I thought about the boost trafos too. But now that the motors (2nd one too failed today) have failed, it would be cheaper to rewind for 415 V, 60 Hz.
RE: Redesign of 60 Hz motor
Keith Cress
kcress - http://www.flaminsystems.com
RE: Redesign of 60 Hz motor
Yes, it will be cheaper to rewind where I am.
RE: Redesign of 60 Hz motor
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Redesign of 60 Hz motor
It's 460 V, 60 Hz. Anyway, now it is all a moot point since the motoes have failed.
Do you any problem in rewinding it for 415 V, 60 Hz ?
RE: Redesign of 60 Hz motor
I can't think of any problems with the voltage change.
T2 = T1 X E2/E1, where: T2 is new turns per coil, T1 is original turns per coil, E2 is new rated voltage and E1 is original rated voltage.
Thanks
RE: Redesign of 60 Hz motor
RE: Redesign of 60 Hz motor
How are you planning to get to 1170 RPM even with the 415V input voltage? You STILL have 50 Hz. If you wind it for 6 poles, it's still going to spin at 975RPM (assuming 2.5% slip from the 1170 RPM value). So to goose that to 1170 you are still going to need to run at 60Hz.
Unless; are you planning to wind it as a 346V motor and then over speed it to 60Hz with a 415V supply?
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RE: Redesign of 60 Hz motor
If I understand the original post correctly the frequency will be the same, only the voltage needs to change. Currently a 460 volt, 60 Hz motor, he wants to go to a 415 volt, 60 Hz motor. The speed should stay the same. (It is a strange voltage/frequency combination).
Thanks
RE: Redesign of 60 Hz motor
RE: Redesign of 60 Hz motor
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RE: Redesign of 60 Hz motor
Yes, it is a very old and very used motor. Changing to a T frame motor would not solve the issue.
The clutch needs 1170 RPM. The drive can output 60 Hz but not the 460 V to go with it since the supply voltage is only 415 V.
RE: Redesign of 60 Hz motor
h
If it could be mounted with 256U adapter (I have heard of some type of U to T frame adapters... not sure how they work), then I think it should be able to provide 7.5hp at voltages down in the range 400vac that you are talking about.
But it sounds like you have a solution that works.
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RE: Redesign of 60 Hz motor
ht
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RE: Redesign of 60 Hz motor
After the motor is rewound for 415 V, 60 Hz, how should I input the drive parameters ?
a. 415 V/60 Hz/1170 RPM or
b. 345 V/50 hz/ 975 RPM
Will the setting (b) affect the torque limit (because running above base speed will reduce torque, at least as the drive sees it) ?
The output speed will be set at 1170 RPM.
RE: Redesign of 60 Hz motor
It looks to me that 256U is indeed mechanically interchangeable with 256T.
256U first line here:
h
256T first line here:
http://www.reliance.com/pdf/pdf/acds/611740-1.pdf
The only difference I could see was term box dimensions which I doubt would make a difference for interchangeability.
So I think you could buy an off the shelf 256T 10hp 1200rpm 460vac 60hz that would do the job and be mechanically interchangeable. (If I am looking at it wrong, anyone please correct me).
Sorry again for the tangent.
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RE: Redesign of 60 Hz motor
Thanks for all the info. I have saved them for future.
The issue here is 460 V is not available to get the 1170 RPM needed by the clutch. The VFD can output only 415 V and to maintain the V/F (and hence the torque), we need 460 V. So any 460 V motor, regardless of HP, isn't going to work. Hence my decision to rewind to 415 V, 60 Hz.
RE: Redesign of 60 Hz motor
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Redesign of 60 Hz motor
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RE: Redesign of 60 Hz motor
The problem with rewinding to 415V 60hz is that your available torque over the zero to 1200rpm range would be lower, assuming the same FLA as at 460V.
If you could rewind with larger conductors to raise the FLA to get the torque back to the original level, you would be ok but it is unlikely the slots will accommodate the larger wire.
Some of the motor rewinders on here surely could comment on that.
RE: Redesign of 60 Hz motor
I am a motor rewinder myself. :0)
Ours is a 415 V world. VFD output voltage is 415 V max. So, how would one get 60 Hz at 415 V ?
Rewinding to 415 V, 60 Hz from 460 V, 60 Hz means a 10% reduction in turns, which will be compensated by increase copper cross section to handle the higher current at 415 V. And the drive too can handle the increased current.
RE: Redesign of 60 Hz motor