Shaded-Pole Motor Working Principle

Shaded-pole motors are small (1/100 to 1/20 horsepower) alternating-current mo­tors that are used where very low starting torque is needed (Figure 7). There is little or no resistance (load) imposed on the motor when it tries to get going. With small electric fans and hair dryers, for example, the only resistance the motor encounters is air and that’s not much resistance at all.

A shaded-pole motor has no commutator on its armature and no brushes . The shaded-pole winding consists of solid copper rings on each pole tip. The rings set up a magnetic field which alternately aids and op­poses the main field coil. The effect is a field that produces a turning force and starts the armature spinning.


Figure - In shaded-pole motor, current is induced in copper strap, which sets up mag­netic field across slot, moving armature.