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TitleStarting Method
TagsElectrodynamics Electrical Engineering Relay Power (Physics) Transformer
File Size149.8 KB
Total Pages7
Table of Contents
                            Shaded-pole motor
                        
Document Text Contents
Page 2

http://en.wikipedia.org/wiki/Solid_state_relay
http://en.wikipedia.org/wiki/Transformers
http://en.wikipedia.org/wiki/Relays

Page 6

motor by reversing of two phases at the terminal box. The reversal has to be made when the motor is
stopped and the supply switched off.

The speed reversing starter of 3-Phase Squirrel-Cage Motor is shown below. The circuit uses two
contactors. The method of reversing the motor is simple which is switching any two phases.

Shaded-pole motor

A common single-phase motor is the shaded-pole motor, which is used in devices requiring low
torque, such as electric fans or other small household appliances. In this motor, small single-turn
copper "shading coils" create the moving magnetic field. Part of each pole is encircled by a copper coil
or strap; the induced current in the strap opposes the change of flux through the coil (Lenz's Law), so
that the maximum field intensity moves across the pole face on each cycle, thus producing the required
rotating magnetic field.

A Shaded Pole AC Motor

Here is a photo of a typical shaded pole motor. See the close-up of the notch in the
laminations and the extra heavy winding of two turns creating the phase difference between
the two sections of the laminations, giving the magnetic field a directional motion. The
rotor spins CW as seen from the end with the screw on the shaft. Motors like this are used
in thousands of applications.

Another Shaded Pole AC Motor

Here is a photo of a ceiling fan motor, also shaded pole, but with six windings instead of
only one as seen above. The rotor laminations are skewed to provide smoother torque.
The pole pieces with the windings have a slot in them to create a delayed flux, creating a
direction for rotation.

Applications

http://en.wikipedia.org/wiki/Lenz's_Law
http://en.wikipedia.org/wiki/Electric_fan
http://en.wikipedia.org/wiki/Torque
http://en.wikipedia.org/wiki/Shaded-pole_motor

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