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7/31/2019 3-Phase Induction Motors
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3-PHASE INDUCTION
MOTORS
Engr. Hassan Mohy-ud-DinInstructor, Electric Machines 3rdSemester
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Induction Motor Action
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Induction Motor: Rotating Field
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Induction Motor Operation
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Rotating Field Sweeping a Rotor Bar
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Induction Motor Construction
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Induction Motor Components
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Induction Motor Components
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Squirrel Cage Rotor
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Squirrel-Cage RotorCast Aluminum Conductors
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Squirrel-Cage RotorBrazed Conductors and End Rings
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Wound Rotor
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Wound-Rotor Induction MotorWhat if Rheostat is reduced to Zero?
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Induction Motor: Stator Winding
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Pole Pitch
Pole Pitch = Stator Circumference / PEquivalently expressed asStator SlotsorStator Arc
Full Pitch WindingCoil Pitch or Coil Span = Pole Pitch
Fractional Pitch Winding
Coil Pitch or Coil Span < Pole Pitch
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Synchronous Speed
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Synchronous Speed
Frequency of Supply Voltage
Frequency of Current inStator Coils
Flux rotates atIncreases Speed
Synchronous Speed
Pole ChangeFrequencyConverter
CONTROL
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Definitions
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Slip-Effect on Rotor Frequency and
Voltage
Assuming ConstantSupply Voltage and Frequency
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Reluctance Synchronous Motor
At no Shaft Load, relative motion b/w rotor androtating flux will be less
Rotor will be magnetized along a path ofMinimum Reluctance
Rotor locked in synchronismwith the RotatingFlux
Slip = 0, Motor Torque = 0
How to pull out of this state?
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Effect of Slip on Rotor Frequency
At blocked rotor, slip = 1, and fBR= fStator
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Effect of Slip on Rotor Voltage
Er= 4.44 N fr max
Er = 4.44 N s fBR max
Er = s EBR
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