A split-phase induction squirrel-cage motor will not start and come up to speed, even though the rated voltage, rated frequency, and rated load are applied. Which of the following troubles would be suspected?

Correct Answer: Option D — an open run or start winding

Split-phase motors rely on both run and start windings to create the rotating magnetic field necessary for starting. An open circuit in either winding disables the phase displacement, causing the motor to hum and fail to start.