Which action determines the rotation direction of a split-phase motor?

Which action determines the rotation direction of a split-phase motor?

• A. Reverse the polarity to the start winding
• B. Reverse the polarity to the run winding
• C. Increase the supply voltage
• D. Add a second capacitor

Answer: (A)

In a split-phase motor, the direction of rotation is set by the relative phase of the two windings: the run winding and the start winding (which is in series with a capacitor to create a phase-shifted current). The start winding produces a secondary magnetic field that leads or lags the run winding, creating the starting torque that kicks the rotor in a specific direction. If you reverse the polarity of the start winding relative to the run winding, that phase relationship is flipped, which reverses the rotating magnetic field and makes the rotor turn the opposite way. Increasing the supply voltage changes how hard the motor can start and run but doesn’t flip the direction. Adding a second capacitor isn’t a standard means to reverse rotation and would affect the starting characteristics in ways that aren’t intended. Reversing the run winding polarity alone could affect direction in some configurations, but the conventional and reliable way to reverse a split-phase motor is to reverse the start winding polarity relative to the run winding.

In a split-phase motor, the direction of rotation is set by the relative phase of the two windings: the run winding and the start winding (which is in series with a capacitor to create a phase-shifted current). The start winding produces a secondary magnetic field that leads or lags the run winding, creating the starting torque that kicks the rotor in a specific direction. If you reverse the polarity of the start winding relative to the run winding, that phase relationship is flipped, which reverses the rotating magnetic field and makes the rotor turn the opposite way.

Increasing the supply voltage changes how hard the motor can start and run but doesn’t flip the direction. Adding a second capacitor isn’t a standard means to reverse rotation and would affect the starting characteristics in ways that aren’t intended. Reversing the run winding polarity alone could affect direction in some configurations, but the conventional and reliable way to reverse a split-phase motor is to reverse the start winding polarity relative to the run winding.