In an electric workshop, I found this motor. It is working when I connect with 110VAC, 60Hz. However, I never saw this motor theoretically. What is this motor called, where can I study theory behind it?

Motor pic 1

Motor pic 2

  • 9
    \$\begingroup\$ shaded pole motor \$\endgroup\$
    – jsotola
    Commented Nov 2, 2021 at 20:38
  • 2
    \$\begingroup\$ en.wikipedia.org/wiki/Shaded-pole_motor \$\endgroup\$
    – Neil_UK
    Commented Nov 2, 2021 at 20:53
  • 1
    \$\begingroup\$ These motors were also used in old turntables (record players). \$\endgroup\$
    – Marla
    Commented Nov 2, 2021 at 21:51
  • \$\begingroup\$ you can easily disassemble the mechanical part of that motor ... give it s good cleaning ... use isopropanol to clean the rotor shaft ... clean the bushings with dry rag ... the bushings could be made from sintered metal and may contain oil ... cleaning them with isopropanol would wash out the oil \$\endgroup\$
    – jsotola
    Commented Nov 2, 2021 at 23:16

1 Answer 1


That is a C-frame, shaded pole motor, a common type of AC induction motor used for small fans like bathroom ceiling fans and kitchen fans. They are made with a range of power ratings that have the same basic mounting dimensions, but have a thicker stack of laminations, a longer rotor and a larger coil for more power. They are 2-pole motors that operate at a bit less than 3600 RPM for 60 Hz.

enter image description here

The theory behind the motor is essentially the same as any other single-phase induction motor. The shading coils serve an auxiliary windings. They are short circuited turns of copper wire or bar that cause the flux in the shaded portion of the pole to lag the flux in the main portion. The result is like a rotating field moving from the shorted portion to the main portion of the pole.

Compared to most induction motors, shaded pole motors have a high slip, perhaps about 20 percent of rated torque. The stall torque is quite low, in the area of 30 or 40 percent of rated. They are not very efficient, perhaps 25 percent. On the positive side, they are inexpensive and do not have the usual high starting current of most motors.

The motor pictured and described has a squirrel-cage rotor similar to the rotors of most other induction motors. It is possible to construct such a motor with a permanent-magnet rotor to make a permanent-magnet synchronous motor. A synchronous-reluctance motor can be made using a salient-pole but unmagnetized rotor. Such motors would presumably be suitable for clocks and other applications requiring an operating speed that has the speed closely held to a constant value determined by the power frequency. C-frame induction motors have significant speed variations due to load variation and power voltage variation.

The motor pictured in the question is assumed to be a squirrel-cage, induction motor because that is, by far, the most common type of shaded-pole motor. Also the condition of the motor suggests that it was used in an exhaust fan.

For more information, look at https://en.wikipedia.org/wiki/Shaded-pole_motor


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