Simple idea to convert induction motor to generator:
By adding capacitors in parallel with the motor power leads, and driving it a little above the nameplate RPM, the motor will generate AC voltage! The capacitance helps to induce currents into the rotor conductors and causes it to produce AC current.
The power is taken off of the motor power leads, or the capacitor leads, since they are all in parallel.
This system depends upon residual magnetism in the rotor to start generating.
Almost all the motors I've tried begin generating just fine on their own, with the appropriate capacitor connected of course! If it doesn't start generating, try speeding the motor up.
That will usually get it going. However, it is extremely rare to find one that doesn't start.
If a motor doesn't start generating on the very first try, then apply 120 vac or even 12 or more volts DC to the motor for a few seconds.
That will usually work to magnetize the rotor and your generator will start by itself from then on.
It is important to not shut the generator down with a load connected to it.This tends to demagnetize the rotor and can cause it to not self-energize. That is, the motor will turn, but it will not produce voltage. It is not a serious problem since the rotor can be demagnetized by following the instructions in the paragraph above.