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Characteristics of each part
• Operating principle
When the AD power is connected to the coil of the shading pole
motor, the central axis of the magnetic field shifts in the bold
arrow direction of <Fig. 2>. As the central axis moves, the rotor
moves in the same direction to turn the motor.
Why does the central axis of the magnetic field shift?
<Fig. 1> shows a diagram of AC current changing as time
changes. If you look at changes of magnetic velocity in "a' zone
where the current abruptly increases, the velocity increases as
the current increases in the main pole. But in the shading pole,
the negative effect of the velocity increase is generated from the
shading coil to reduce the velocity shifting the center of the
magnetic field to the main pole. In "b" zone, the change in
current is minimal and the negative effect of shading coil is
minimal to have the center of the magnetic field in the middle as
shown in <Fig. 2>. In "c" zone, the velocity of the main pole
decreases but with the negative effect increasing the velocity
from the shading pole side, the center shifts to the shading pole
side. As shown, the center of the magnetic field shifts from the
main pole to the shading pole to rotate the rotor.
Current
a
<Fig. 1> Change of AC current
Main pole
"a"
zone
"b"
zone
"c"
zone
Removal of magnetic velocity
on the pole surface
<Fig. 2> Change in magnetic velocity
by changes in current
- 49 -
b
c
Time
Shading
Pole
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