Can Variable-frequency drives be used for driving any 3-phase induction motor at a speed & frequency other than that is mentioned on its name plate? I mean normally induction motors are designed to operate at 50 Hz or 60 Hz at a constant speed as mentioned on their name plates then shouldn't this mean that they can operate only at this frequency as mentioned in their data sheets & name plates.
Moreover, if we operate a 50 Hz motor at 300 Hz frequency using VFD, why is it not damaging to motor? Please explain
Many 3 phase motors have a similar construction in terms of bearings and balance to cover different pole pairs and 50 or 60Hz.
So, its quite common for a small motor (<22kW) to be mechanically OK to 3600rpm, this would be 120Hz on a 4 pole or 180Hz on a 6 pole for example. Of course, vibration increases with speed.
Electrically, you theoretically expect constant torque up to rated voltage and speed, thereafter constant power. In practice, performance in frequencies above the rated (base) varies with motor ratings, particularly peak or pullout torque which is normally higher than stall or pullup torque.
A typical calc for maximum torque is that it reduces as the inverse square multiplied by peak torque at rated speed e.g. if motor TqPk is 240% and you are at 100Hz at 400V on a 50Hz 400V winding, you have half the theoretical voltage for full torque, square this 1/2 and you get 1/4, multiply this by 240%and you get 60% peak torque. This means, constant power would mean 50% torque, if you overload to 60% motor stalls and collapses.
I have run 50Hz windings at up to 200Hz but you have to be careful at higher speeds as torque is very limited and you need to overcome more friction / windage than at lower speeds too.
Also, if fitted with a shaft driven fan, this can be audibly noisy as it is designed to cool at rated speed.
300Hz and more is common for spindles but normally you use a stator wound to a higher frequency.
If you've got something specific in mind, maybe I can assist.
Its quite common to go to 100Hz on 4 pole, obviously you would need to make checks with supplier on 2 pole!
Remember, think too about what's connected to this higher speed as the rest of the drivetrain may not be good for higher speed!
In reply to your last point, I doubt you will reach 300Hz on a 50Hz winding easily, one easy trick is to change to the 230V connection if it exists, then you can calibrate at 400V 87Hz and the 300Hz becomes easier at the cost of 1.732x current (so maybe a larger VFD).
cheers