How do you change the direction in a split-phase motor?

How do you change the direction in a split-phase motor?

• A. Switch the connection to the Run winding.
• B. Switch the connection to the Start winding.
• C. Reverse the polarity of supply.
• D. Reverse the rotor.

Answer: (B)

In a split-phase motor, the rotation direction is set by the relative phase between the two windings: the run winding and the start winding (which gets a phase shift from a capacitor or resistor). The rotating magnetic field that drives the rotor comes from how these two fields combine. If you swap which side of the supply each winding’s connection uses for the start winding, you flip that phase relationship. That reversal changes the direction of the rotating magnetic field, so the motor spins the other way. Reversing the supply polarity won’t change which way the field rotates because both windings see the same instantaneous change in polarity, so the relative phase stays the same. Reversing the rotor isn’t something you do to change direction in an induction motor—the rotor just follows the stator’s rotating field. Switching the run winding alone isn’t the standard method to reverse direction, because the essential change is the phase relationship, which comes from the start winding.

In a split-phase motor, the rotation direction is set by the relative phase between the two windings: the run winding and the start winding (which gets a phase shift from a capacitor or resistor). The rotating magnetic field that drives the rotor comes from how these two fields combine. If you swap which side of the supply each winding’s connection uses for the start winding, you flip that phase relationship. That reversal changes the direction of the rotating magnetic field, so the motor spins the other way.

Reversing the supply polarity won’t change which way the field rotates because both windings see the same instantaneous change in polarity, so the relative phase stays the same. Reversing the rotor isn’t something you do to change direction in an induction motor—the rotor just follows the stator’s rotating field. Switching the run winding alone isn’t the standard method to reverse direction, because the essential change is the phase relationship, which comes from the start winding.