Induction motors run on a design Volts per Hertz ratio. You didn't specify the rated voltage of the motor, but if it is 50Hz, I'll make the assumption that it is a 380VAC three phase motor. 380 VAC at 50Hz is a ratio of 7.6. Almost all 380VAC rated motors have an insulation system that can safely handle 460 VAC, which is another motor standard voltage. 460 at 60 Hz is a ratio of 7.666, so yes, the speed can be safely increased.
Now, you need to consider some other factors about induction motors. Almost all induction motors under 75KW or 100HP can be safely run up to twice rated speed, but in order to do that, you lose torque. When running over base speed, the stator voltage is kept at the maximum (380 or 460 for example), but the frequency increases. If you were to compare the operation of an induction motor from 0 RPM up to base speed, and then to the extended speed, it would be almost identical to running a DC motor from 0 to rated speed with full field, and then decreasing the field current to increase the motor speed. From 0 to base speed, both operate in the constant torque region. Past base speed, they operate in the constant power (KW or HP) region.
To answer what I think is your actual question, no, do not run a 50Hz motor at an increased voltage unless you increase the frequency to 60Hz to keep the same V/Hz ratio. Increasing the voltage without increasing the frequency leads too excessive winding heating and also reduced cooling capacity from the internal fan (or just the rotor turning).
Other considerations can come into play depending on the mode your VFD is running in, but the above are the basics.
Neglecting voltage drops across field and armature resistances, and assuming supply voltage is not changed:-
The diverter circuit cuts field coil current in half, thereby halving magnetic field strength, doubling Kv, and halving Kt.
Doubling Kv causes speed to increase to 1000rpm. As load torque is proportional to speed squared, torque will increase by 4 times. Since Kt is half, 8 times more current (160A) is required to deliver this torque.
Best Answer
An induction motor is like a transformer with the motor's stator acting as the primary winding and the rotor the secondary. From this basic transformer equation:
it can be seen that the peak flux density is proportional to the voltage divided by the frequency multiplied by the number of turns and the area of the coil. Once the stator has been designed, the number of turns and the core area is fixed, so the flux density is completely determined by the ratio of stator voltage to frequency, V/f. A given core material (type of steel) can support a limited flux density. When the V/f is increased the flux density increases fairly linearly up to a point. Then further V/f increase results in less increase in flux density such that further increase of V/f increases the stator current and heating without providing much additional flux density. Under that condition, the motor is said to be saturated. Induction motors are generally designed so that the rated V/f is at the point where the rate of increasing flux density vs. V/f has begun to decline significantly.