Definition
A type of single-phase AC induction motor that uses two separate stator windings — a main (running) winding and an auxiliary (starting) winding — to create the rotating magnetic field needed to start the motor turning. The two windings are wound with different electrical characteristics so that the current in the starting winding is out of phase with the current in the running winding, producing a rotating field at startup. Once the motor reaches about 75% of its rated speed, a centrifugal switch disconnects the starting winding, and the motor continues to run on the main winding alone.
Plain English
A small AC motor that uses a second, temporary winding to give itself a push to start spinning. Once it's up to speed, that extra winding switches off and the motor keeps running on its main winding.
Context Anchor
Seen in aircraft electrical and maintenance discussions involving small AC motors, shop equipment, or motor starting circuits.
Derivation
Split-phase' describes how the single incoming AC phase is electrically 'split' into two phases inside the motor by using two windings with different properties. 'Induction' refers to how the rotor turns — current is induced in it by the rotating magnetic field, rather than being supplied through brushes or wires.
Why Pilots Care
These motors give reliable, low-maintenance starting and running power to essential flight instruments.
Grounding Statement
The key idea is that one-phase power cannot start this motor well by itself, so the motor briefly creates a second, offset push to get rotating.
Intuition Check
Do not read “split-phase” as meaning the aircraft or building supplies two separate power phases. Here, the split happens inside the motor to help it start.
Example Sentence 1
The cabin ventilation blower is driven by a split-phase induction motor that runs on 115-volt AC.
Example Sentence 2
During the instrument check the pilot confirmed the split-phase induction motor was operating because the gyro flag had disappeared.