The problem is the current HAS to be sensed using the 75mv signal only. The motor (and the shunt)is placed more than 50 meters away from this meter and my circuit is to be fitted near this meter.

sorry Unmesh, did nor catch that before answering.
to handle that you must
1) Amplify the signal AT THE SOURCE (the shunt) and, since I bet this will be noisy put a V/f converter there. This circuitry MUST FLOAT i.e. not be referenced to ground. You must label the GROUNDED can holding this circuitry "danger, high voltage inside". Then opto-isolate the pulses from the V/f and run them to your computing unit. Then measure the pulse count every - you find out - (milli)seconds and you have the reading.

Erik