Suggest me changing 8 pole 3 phase 7.5kw motor to 2 pole motor advisable.

[b2man63]

We have 3 phase 415 Volts 7.5KW 8 pole 750rpm(Sync) sq.cage induction motor in substantial number in our division. Now we need a 3 phase 415 Volts 7.5KW 2 pole 3000rpm(Sync) motor. Instead of purchasing a new motor, can we do a 2 pole rewinding to the one of the 8 pole motor to meet the new requirement. Please clarify me, changing the low rpm to higher rpm motor is suggested and also clarify me whether any damages occur to a motor designed to run at low rpm is changed to run at high rpm.

 

[theode]

Get a new motor.All the specs will have been designed into the motor.
It will be more expensive,less efficient and maybe a waste of time converting.
There are many things to factor into a rewind conversion.

 

[ScottyUK]

A purpose-built 7.5kW 2-pole machine will be at least one frame size smaller than an 8-pole machine of the same output.

At our facility a 7.5kW motor is in the grey area whether it is more economic to rewind or replace, and that is without any radical alterations to the motor. I agree with theode, this is unlikely to make any kind of economic sense.

 

[zlatkodo]

Hi, b2man63
Perhaps you could try if it is not only a single case.
There are some limitations. For more details fill this form :

Previously, read the explanation:

Winding Design and Data Calculation

 

[itsmoked]

Amazing. Using sex to sell motor winding. Who'da thought?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[crshears]

Clearly I had best not click on any otherwise innocuous-looking links using internet-capable facilities provided by my employer, lest I be subject to disciplinary action up to and including termination...

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[zlatkodo]

Hi, b2man63,
In addition, some things need to know in advance:
- new HP rating could be kept the same (7,5 kW) if constant HP redesign is applied,
- evaluate whether the stator slot - rotor bars combination is suitable for 2 pole ( need to know the stator slots and rotor bars),
- check the new circumferential speed of the rotor ( need to know internal core diameter and Hz),
- check the effect of new rpm on the load ( sometimes increasing the rpm will cause a significant increase in load, for example in pump or fan application),
- since there are lot of variants of pole changeable 8/2 pole windings with only ONE WINDING, ( scroll to find 8/2 pole example here) in some rare cases there is a possibility to reconnect winding from 8 to 2 pole, avoiding rewinding ( need to know an old internal 8 pole connection).

Winding Design and Data Calculation