Definition
A simple, low-power, single-phase AC induction motor in which a small portion of each field pole is wrapped with a heavy copper ring (the shading coil). This ring delays the magnetic field in the shaded section, producing a sweeping field that gives the rotor enough push to start turning in one direction without needing a separate starting winding or capacitor.
Plain English
A small AC motor that uses a copper ring around part of each pole to make it self-starting. It is cheap, simple, and used where only a little power is needed.
Context Anchor
Seen in aircraft electrical and maintenance discussions, especially with small low-power motors such as cooling fans or light-duty equipment.
Derivation
Called shaded-pole because a copper ring placed around part of the pole face shades or delays the magnetic field in that section. The delay creates a moving field that starts the rotor turning.
Why Pilots Care
Pilots and technicians meet shaded-pole motors in small cabin fans, instrument blowers, and gyro-related cooling devices. They are reliable but low-torque, so a sluggish or noisy fan often points to one of these motors wearing out.
Analogy
Think of two people pushing a merry-go-round, but one person pushes a moment later than the other. That slight delay helps create the turning motion. In the motor, the copper band creates that delayed magnetic push.
Intuition Check
“Shaded” does not mean protected from sunlight. In this term, it means part of the motor’s magnetic pole is delayed by a copper band.
Example Sentence 1
The instrument panel cooling fan is driven by a small shaded-pole motor that runs whenever the avionics master is on.
Example Sentence 2
During preflight the pilot heard the shaded-pole motor in the instrument cooling fan start smoothly.