Running 2-winding motor on BOTH windings

[drivechanger]

I have a 2-winding, 2-speed, 4160V induction motor rated for 2100kW/1400kW at 1200/900 RPM, respectively. I need 2500kW at the higher speed. Is it possible to excite the 8-pole windings (900 RPM) at 80 Hz using a medium-voltage inverter, while running the 6-pole windings across-the line? With field-weakening, the 8-pole winding output will be a fraction of 1400kW at 80Hz, but I need only 400kW. Has anyone ever heard of doing this?

 

[aolalde]

I do not recommend the proposed array for the following reasons:

The magnetic circuit is designed to handle the magnetic flux produced by one winding at a time. If you impose a second magnetic flux the magnetic circuit will saturate.
The array is a kind of tandem fluxes to work inducing current in the same rotor bars. The current wave induced by the two systems are totally different making the synchronization almost impossible.
The line powered winding will induce voltage in the 8 pole winding if this winding is now connected to the VFD it could feed back destructive voltages.

May be overloading 20% your actual 4 pole winding will be a better solution, certainly you must monitor the winding temperature and trip the load if the temperature rise exceeds the insulation rating.