Calculating Resistance for Slip-Ring Induction Motors

A resistance box would emit 32kW at half-motor-voltage, so it would need to be a big one! This is the sort of thing that can be found in the electrical equipment suspended from the underside of the chassis of an early electric multiple-unit train.

To go any further, Uncle, we need your supply voltage.

If it's AC, then a much better idea would be a variable-voltage transformer, and a better idea than that would be a variable speed drive.

What sort of mechanical load is this motor attached to?

i'ts supply voltage is 415 v A.C & it is used for hoisting duty in overhead crane.

I would be tempted to ring the crane manufacturer and see what they say.