Is there any power saving if we will be using a 1400KW motor instead of 1000KW motor. The speed of the motor remaining constant.The load too is constant.After replacing the 1000KW motor with 1400 KW the current has risen from 46 to 54 amps.What is the reason for this?

Is there any relation between the speed and the power consumption of induction motor.

This is a self explanatory the larger your motor the higher the current...

What is relation between speed and power,

There is none. Speed is related to voltage.

There are always losses in the motor. They can be due to resistive or eddy current. The eddy current losses are probably higher. The efficiency of the motor will depend on how it is matched to the load. What if you had a 50 HP motor turning a clock dial vs a motor that is 1/10 of a HP. Which one would draw the least amount of power?

So for a motor that 71% bigger, you got a 17% increase in current consumption.

Power is directly proportional to speed cube!

For the same power rating the current drawn by motor is directly proportional to speed cube! Please find me with its derivation