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I am baffled how this motor works...It has a single axial winding that turns a disk. The disk is not a strong magnet but somehow this motor has torque enough to swing a floor fan. I see on the internet that this type of motor is also used for microwave ovens to turn the tray..

The flux is flowing axiallly through the disk but the disk is not conductive so I don't think eddy currents are producing the torque. Somehow the flux is being redirected I guess but how can that be???

From the image you can see the disk is sitting in the center of the many turn winding(covered by the white plastic). There are tabs that come up from the bottom of the motor plate that are used to hold the winding in place. Is it possible that these act as induced stator poles??? enter image description here

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  • \$\begingroup\$ Can you post a photo that shows the windings? \$\endgroup\$ – ThreePhaseEel Nov 22 '16 at 5:17
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It appears that this may be a claw-pole motor. A claw-pole motor would have metal prongs surrounding the rotor that form alternating north and south poles by ever other prong entering the rotor area from opposite sides of the coil. There should be an air gap between the prongs and between each prong and the housing on the opposite side of the coil. There does not seem to be any mechanism to insure that the motor starts in the same direction every time it is turned on. It does not matter which way a microwave oven tray turns. A fan or pump can also be designed so that id doesn't matter which way it turns.

This is not a version of a shaded pole motor. It is either a permanent-magnet synchronous or reluctance synchronous motor.

Here is a picture of the rotor of an automotive alternator. The north and south poles are formed in the same way.

enter image description here

This diagram of a claw-pole stator is a little more difficult to understand, but is shows the same type of construction.

enter image description here

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  • \$\begingroup\$ I concur, pancake round types are claw type, while shaded pole are asymmetry core shapes. Most likely its low AC voltage \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Nov 22 '16 at 5:58
  • \$\begingroup\$ I believe you are correct...there is a top plate with tabs that bend \$\endgroup\$ – user7567 Nov 22 '16 at 7:03
  • \$\begingroup\$ the tabs from the top are interlocking with the tabs from the bottom similiar to the graphic on the left \$\endgroup\$ – user7567 Nov 22 '16 at 7:12
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It starts as an asynchronous AC motor. The turn direction isn't important so one doesn't need a second winding. The irregular poles on the coil and rotor help it starting. Near the synchronous frequency it locks in and acts as a synchronous AC motor from then on.

Also see https://en.wikipedia.org/wiki/Shaded-pole_motor, though your motor is a very simplified version of that.

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  • \$\begingroup\$ OK but how does the flux which is is aligned with the disk axis become redirected to turn the disk?? How are the stator poles induced by this flux??? Or are they induced??? \$\endgroup\$ – user7567 Nov 22 '16 at 3:18

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