What happens if I overdrive an AC motor while connected to the AC whether single phase or three(3) for the dif?
Both AC motors would not burn out by such action. But both coupling gears could damage during engagement. No overload occur in AC supply but motors could be ceased for a while.
What does overdrive mean? What is the rest of your question? Edit: Basically, you are connecting 2 induction motors with a different number of poles (different running speed range) in parallel electrically and physically. Before I answer, an induction motor needs to operate relatively close to the synchronous speed in order to make useful torque; if not there is a large ripple torque and the net torque is zero. In addition, the motor current will be very large if the motor speed is far different than the synchronous speed. So what will happen is that the motor with more torque capability will overpower the other one. I'm pretty sure this will cause excessive current in the smaller motor, and damage it unless some overload protection device kicks in. Don't do it, because it will not do anything useful.
Two AC induction motors mechanically coupled together will run at the speed and torque that represents the intersection of their torque vs. speed curves. Note that the torque vs. speed curves extend to reverse rotation operation and negative torque operation. If the resulting speed is very far from the normal operating speed for either motor, that motor will draw excessive current and overheat or be shut off by overload protection. If the resulting speed is greater than the synchronous speed for either motor, that motor will operate as a generator and return energy to the supply. If the motor is supplied by an electronic source that is not equipped to accept regenerated energy, the source device may be damaged. Two motors of equal synchronous speeds can be coupled together and share a common mechanical load. They may or may not share the load well enough to avoid overloading one of the motors. If a motor connected to mains power is mechanically coupled to a similar motor powered by a variable frequency supply, the supply frequency can be adjusted so that the mains powered motor acts as a generator providing a normal load for the other motor.
