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END OF CHAPTER 7
(Induction Motors)
NEXT CHAPTER 10
(Page#633)
Single-Phase and
Special-PurposeMotors
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Split Phase or Resistance Start Single Phase Induction Motor
Not self starting.
Single phase winding produces alternating flux along one
space axis only not revolving.
Stator windings are similar to three phase except wound for
single phase.
Rotor construction is similar to the squirrel cage motor rotor.
Almost constant speed (like 3-phase induction motor)
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How to make it self-starting
Single phase stator winding is temporary (permanent )
converted into two phase for starting.
Starting (or auxiliary) winding is placed in parallel (900 degree
electrical apart) with the stator (or main) windings.
This produces 900 phase difference between the two (Is & Im)
currents, as a result revolving flux is produced.
Centrifugal switch automatically disconnect the startingwindings at 70 to 80 % of the rated speed.
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Xm.>>Xs Hence Im lags Is and applied Voltage (V)
I
V
Is
Im
T
80%Spee
d
200%
Rm
.
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Xm.>>XsRm
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T
80%
Speed
200%
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Transformer
Secondary
Centrifugalswitch
WAPDA1-Phase
220 Volts
50 Hz
Line
Neutral
Xs
Rs
Xm
Rm
I
Is Im
Xm.>>Xs Hence Im lags Is and applied Voltage (V)
Rm.
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Shaded-Pole Single Induction Motor Self-starting due to its
construction. Manufactured in rating of horse power. Rotor
construction is similar to the cage motor. Stator has even
numbers of salient poles connected in series for alternatepolarity.
A.C
Supply
Main
Field
Rotor
Shading pole
N
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Universal Motor
Operated on both on single phase ac and dc at same speed andoutput.
In construction it is exactly like dc series motor.
It has high starting torque ( T I2 ) and variable speed.
They are run on load, without load the speed is very high.
Application
Vacuum cleaner, mixers, drill machines, sewing machines,
automobile starters to crank engine.
Construction
Armature, Field windings, carbon brushes, commutator.
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http://www.radioelectronicschool.net/files/downloads/relay.gif
Relay
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Tacho Meter
(DC Generator)
Accelerometers areone of the latest
application of MEMS
technologies.
The most successful
MEMS accelerometersare based on
capacitive effects.
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Stepper Motors
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Operation principle of stepper motor:
There are many kind of stepper motors. Unipolar type, Bipolar type, Single-
phase type, Multi-phase type... Single-phase stepper motor is often used for
quartz watch. On this page, I will explain the operation principle of the 2-phase
unipolar PM type stepper motor.
In the PM type stepper motor, a permanent magnet is used for rotor and coils
are put on stator. The stepper motor model which has 4-poles is shown in the
figure on the left. In case of this motor, step angle of the rotor is 90 degrees.
As for four poles, the top and the bottom and either side are a
pair. coil, coil and coil, coil correspond respectively. For
example, coil and coil are put to the upper and lower pole. coil
and coil are rolled up for the direction of the pole to become opposite when
applying an electric current to the coil and applying an electric current to thecoil. It is similar about and, too.
The turn of the motor is controlled by the electric current which pours into , ,
and . The rotor rotational speed and the direction of the turn can be
controlled by this control.
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Unipolar Motors
This attracts the rotor into the
position shown. If the power
to winding 1 is removed and
winding 2 is energized, the
rotor will turn 30 degrees, or
one step.
To rotate the motor continuously,we just apply power to the
two windings in sequence.
Assuming positive logic,
where a 1 means turning onthe current through a motor
winding, the following two
control sequences will spin
the motor illustrated in the
figure.
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Animation of Unipolar
Unipolar Half Step
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St M t
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Stepper Motors
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http://sciences-physiques.ac-dijon.fr/documents/MPI/SortiesLogiques/MoteurPasAPas/Moteur3.htm
SWITCHED RELUCTANCE MOTOR
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SWITCHED RELUCTANCE MOTOR
A four-phase 8/6 switched-reluctance motor is shown in
cross section. In order to produce continuous shaft
rotation, each of the four stator phases is energized and
then de-energized in succession at specific positions of therotor as illustrated.
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Irfan :This is another concept of wind energy, generator fitted with balloon in
the air, its only for you information : Read from next slide about this
SEE ANIMATION: with slide show