I have the following synchronous motor ripped out from an old range hood in my kitchen.

synchronous motor and the rotator

I used new electrician tape to cover up the coils that should form the electromagnet--the old cover is too oily. From wikipedia I know it works by inputting alternative current to produce a rotating magnetic field to drive a rotator made of permanent magnet (the grey thing I partially removed from the stator). But the videos that explain synchronous motor doesn't use a motor similar to my own. Can you explain to me how my synchronous motor works?

Also, can I input DC into the red and blue wire and use this as a electromagnet that produce a field in the iron core as shown by the blue arrow?

synchronous motor


1 Answer 1


It is not a synchronous motor. A synchronous motor requires three-phases. A range hood only has one-phase.

You have a single-phase, shaded-pole, fractional hp, squirrel cage induction motor.

It will not work with DC since the motor needs a changing electruc field to rotate.

The problem with a single-phase motor is the ac produces a pole that oscilates from N to S to N. There is no phase shift to cause motor to spin in one direction, so the copper winding on stator produces a small starting torque which causes the rotor to spin in a specified direction.

From Wikipedia Shaded-pole motor:

enter image description here

  • $\begingroup$ I dont need a rotating magnetic field, all I need is a stationary field that goes in the direction of blue arrow $\endgroup$
    – Faito Dayo
    Aug 4, 2021 at 23:18
  • $\begingroup$ Yes, it will give you a stationary field, with most of it contained in the iron. Iron is a conductor for magnetic flux. There will be very little flux where your arrowhead is located. Be aware that it was designed for an ac signal and a constant high dc voltage may create too much head in winding. $\endgroup$ Aug 4, 2021 at 23:26
  • $\begingroup$ so there wont be any flux going through that circular hole? $\endgroup$
    – Faito Dayo
    Aug 5, 2021 at 2:22
  • $\begingroup$ If you have a lot of steel in the circular hole, yes. But air has 1000 times (from memory) opposition to flux, so very little if no steel. $\endgroup$ Aug 5, 2021 at 16:18
  • $\begingroup$ i am actually wanting to submerge this thing into salt water, and tape two pieces of copper tape (as electrodes) so the electric field and magnetic field is perpendicular to each other. By doing so, i should be able to turn this into a magneto hydrodynamic drive $\endgroup$
    – Faito Dayo
    Aug 5, 2021 at 18:37

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