Measuring Power Losses

what is ur supply voltage 220V or 380V

Supply voltage 440V.

what is the rated(written on motor nameplate) current and running current.

Motors don't "deliver" the rated HP unless the load requires it. However, a much larger motor (say 50 HP) to drive a load requiring 10 HP is pretty inefficient, but a 12 HP motor driving a load requiring 10 HP is fairly efficient. Additionally, the 12 HP motor is not being run at maximum and should provide service longer than a 10 HP motor running at full load.

A way to determine how much energy is wasted, measure the current to the motor and multiply it by the supply voltage (using the proper formula depending on whether or not the power is 3 phase or single phase) to get watts.

There are 746 watts per HP for 100% efficiency, so the difference is "wasted."

Actually the motor will draw the current it needs and chanses are you are gaining by using motor upto about twice your actual need. Lower core and resistive losses for sure and even though mechanical losses are bigger for same quality manufactured motor they're a much smaller overall contributor. If your load is constant you could even add cosφ improoving capacitors that will lower the current your source sees as load if you're short on that. We're talking for 3-ph motors right?