Rewinding a motor will only increase its torque rating if you manage to fit more copper in the stator slots than the original. Changing the number of turns in series/parallel (etc) primarily changes the voltage rating - it is the *total* current through the slot that matter when calculating the torque output. The total current you can put through the slot depends on how much copper you can fit - too much current or too little copper = more heat.

If you just copied the existing winding, but increased the number of turns by the ratio of the new to old voltage rating, then it would be OK. We can go into a lot more detail if you want to, but it's hard to say how much there is to gain from this without actually seeing the motor inside.

Quote Originally Posted by GEOFFREY View Post
Thanks for the reply, but it is not possible to find a suitable replacement VFD. The problem as I understand it is that the spindle (900w max) is a 2 pole 3ph motor with a speed range of 15-60krevs at 15-60volts.
That is well within the rating of the VFD I have designed/made.