Since you are in North America, I will confine my answer to NEMA motors.
In the HP range you specify, all of the motors will have cast aluminum rotors. Most will have plastic shaft-driven fans if TEFC. ODP motors will have the fan blades cast into the rotor.
Given the above, on 4, 6, and 8 pole motors, you can, without question, take these motors to 90hz. That would be 150% of nameplate speed. On two pole motors, you can go to 75hz without question and to 90hz if you replace the plastic fan with a metal substitute.
The above guidelines apply to ordinary, commodity grade, high and premium efficiency motors. They do not have to be inverter duty.
For the record, I am simply repeating what many motor manufacturers' sales catalogs have shown for many years.
Now, what happens when you take a motor over its base speed? You cannot, as mentioned above, continue to raise the voltage over the nameplate value. So, above the base frequency of 60hz, the V/hz ratio begins to go down due to the increasing hz but constant voltage. Below 60hz, the ratio had been held constant.
The V/hz ratio determines the motor's current demand under various load conditions which then determines the motor's ability to make torque. By holding the V/hz ratio constant from zero to 60hz, you basically make the motor's torque output potential constant. Above 60hz, since the ratio is going down, the motor's torque output is also going down. In fact, the torque is going down at the inverse of the overspeed ratio so, for example, at 3/2 speed the torque is at 2/3. At 11/10 overspeed (10%) the torque is down to 10/11. Since hp is torque x speed/5250, that makes the hp constant over the overspeed range.
Going beyond 90hz on non-inverter duty rated motors generally doesn't work good because the torque starts to fall off faster than the speed increase so the hp drifts downward. This is due to limits in the coils and magnetics. In inverter-duty motors, the design is sometimes modified so this limit can be moved up to 120hz but, in those cases, the motor nameplate will list performance data for 60 and 120hz.
The potential uses for overspeed are mainly in industrial machines. It is uncommon to find a beneficial use for overspeed in fans and pumps. In industrial machines, it is my practice to design the motor and power train so, at maximum machine speed, the motor is between 75 and 90hz. Many benefits result such as better motor cooling at all speeds, higher starting torque, and reduced speed error in open-loop applications. The only disadvantages I know of are an increase in motor audible noise at the higher speeds and a slight reduction in efficiency due to the fan turning faster.
I routinely use overspeed and have for many years. I have not found any significant reasons not to and it often results in being able to use a TEFC or TENV instead of an auxiliary-cooled TEBC motor as well as a smaller rated VFD.
