Regarding Servo Motor Winding Change

Do you have the speed torque characteristics of the servo?

You need to check that because some motors are designed to always rotates at full speed (or is stopped).

servo motor

No. This Servo Motor not wound for full Speed rotation, it has a drive, it can rotate at any speed.

i think it possible by increasing the number of turns & reducing the copper dia.

but i am not getting any technical paper which supports this...

Here is a quick way to check your question. Existing power is 3 Nm. Desired power is 90 Nm. The ratio of force difference that you want is 90/3 or 30 times more torque. Considering that the torque must be constant at any speed, you need a motor that can consume potentially as much 30 times 475 watts or you need to run at 30*50 RPM with gear reduction. Doing the first calculation, you need a motor and controller that is capable of 14,250 Watts for that kind of force at 50 RPM without a gear reduction.

That's like 19.1 horsepower. The expression about 20 lbs. of s _ _ _ in a 5 lb. bag comes to mind.