In a shaded pole single-phase motor, the revolving field is produced by the use of
In a shaded pole single-phase motor, the revolving field is produced by the use of
Right Answer is:
Shading coils
SOLUTION
SHADED-POLE MOTORS
- A shaded-pole motor employs a salient-pole stator and a cage rotor.
- The projecting poles on the stator resemble those of DC machines except that the entire magnetic circuit is laminated and a portion of each pole is split to accommodate a short-circuited coil called a shading coil.
- The coil is usually a single band or strap of copper. The effect of the coil is to produce a small sweeping motion (revolving field) of the field flux from one side of the pole piece to the other as the field pulsates.
- This slight shift in the magnetic field produces a small starting torque.
- Thus, shaded-pole motors are self-starting.
The shaded-pole motor has the lowest starting torque of all the single-phase motors. It is relatively inexpensive and is used to turn very small fan blades connected directly to the shaft of the motor. The basic construction of this motor is very simple since no start winding is present. The imbalance in the magnetic field needed to produce rotation is obtained by shading a portion of the run winding with heavy copper wire or band.
When the motor is energized, the strength of the magnetic field is different in the area of the main poles than in the area of the shaded poles, allowing the rotor to turn.