A shaded pole motor is basically a small squirrel cage motor in which the auxiliary winding is made up of a copper ring or bar that surrounds a portion of each pole. This one-turn auxiliary winding is called a shadow coil. Current induced in this coil by the magnetic field creates a second electrical phase by delaying the phase of magnetic flux changeover so that enough pole to provide a 2-phase rotating magnetic field.
The direction of rotation is from the unshaded side to the shaded side of the post. Since the phase angle between shaded and unshaded sections is small, shade loop motors produce only a small starting torque compared to full speed torque. Shadow motor poles of the asymmetrical type shown are only reversible by dismounting and pulling in the stator, although some similar-looking motors have small auxiliary coils of fine wire cuttable connection instead of copper bars of thickness and can be reversed electrically. Another method of electrical reversal involves four coils.Continue reading »