A slip ring induction motor 900KW 11KVAC 50HZ failed twice in two years for stater earth fault. Now we are going to repair the faulty 2 slots with 11KV insulation and change its winding connection configurations to 400VAC 50HZ. I will appreciate if any body share such experience and future results.
Really? Did you stop to think about the ever so slight difference in current involved? As a gross estimate, 900kW at 11kV will be about 60A FLC, 900kW at 400V will be in the area of 1900A FLC.
You will never fit enough conductors in the slots of that frame to get 900kW out of that motor at 400V...
No its not problem. The motor is 10 poles 3 coils per set and star connected. So it is possible like this: if you do connect in series 5 bulbs of each 200V 100W and 0.5A, then you can use this 500W (5x100) bulbs on 1000V while total current will be 0.5A. Now if we change the configuration to parallel of same above 5 bulbs, we can use the system volts 200 the current will increase to 500/200=2.5A, but there would be per bulb light will be remain same.