rebuild syncrounous motor as induction motor

[electricpete]

Can anyone provide general comments about the challenges that would be involved in rebuilding/rewinding a 4KV syncronous motor to be a 13.2kv 324 rpm 3500 hp induction motor.

I realize that I haven't provided enough info to judge the stator rewind (nameplate data for the sync motor and number of slots etc). But I'm interested in general thoughts. Can a sync motor rotor be easily converted into a squirrel cage induction rotor? Doesn't an induction motor require a smaller air-gap? Has anyone ever heard of this type of conversion being done?

 

[raghavan100]

TECHNICALLY POSSIBLE .
BUT YOU HAVE NOT MENTIONED WHETHER IT IS SALIENT POLE OR NON SALIENT POLE CONSTRUCTION. IT IS QUESTION OF DESIGN ASPECTS OF EXISTIG MOTOR VIS A VIS NEW OUTPUT REQUIRED ALONG WITH OTHER PARAMETERS LIKE TORQUE(NORMAL) AND PULLOUT AND STARTING TORQUE REQUIRED

K.S.RAGHAVAN
K.S.RAGHAVAN

 

[rhatcher]

Anything is possible, but I think this may be impractical. I can't imagine any way to accomplish a conversion without replacing the rotor (and it would be a big one, maybe 6 feet in diameter??). I would be interested in hearing more about what Raghavan knows about this type of conversion with respect to the rotor.

 

[electricpete]

I have since found out that the shop would scrap the rotor. More details on the same thread in the power engineering forum. Thanks

 

[jbartos]

Suggestions:
1. There is no need to be discouraged that the industry will not use a high-power low-speed winduction motor. E.g. ships would use plenty of them of your type.
2. I would suggest that you simulate the intended induction motor first by using a suitable software.
3. As an option, the permanent magnet synchronous motor is also a very attractive machine (a "dirty" competition to the squirrel-cage induction motor)
4. There will probably be a need to ground bearings, if you intend to use an AC motor drive to protect bearings from common-mode currents.
5. Consider a double cage rotor.
6. The power rating could be somewhat reduced since the squirrel-cage induction motor may be mechanically more demanding on the stronger stator. This is pending results of the motor simulation.
7. Inquire around, if any motor service/repair firm has done similar conversion to obtain some guidance.