Complex sentence: For the motor to work as a generator instead of a motor the rotor must be spun faster than its stator's synchronous speed, this will cause the motor to generate power after building up its residual magnetism.
Split into simpler sentences: For the motor to work as a generator instead of a motor the rotor must be spun faster than its stator's synchronous speed. This will cause the motor to generate power after building up its residual magnetism.