armature reaction

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ARMATURE REACTION

• NAME-PANKAJ KR SAHA
• DEPT-ELECTRICAL ENGINEERING
• ROLL-32/11

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WHAT IS ARMATURE REACTION

• Simply effect of armature mmf on main field flux.

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TWO MAIN EFFECTS OF ARMATURE REACTION

• Cross magnetizing effect.
• Demagnetizing effect.

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HOW ARMATURE REACTION OCCURES

• Field flux path at no load condition.
• A)

• Armature flux path at load condition.
• B)

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RESULTANT FLUX DISTRIBUTION WHEN FIELD WINDING
ARMATURE WINDING BOTH ARE EXCITED

• C)

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GNA MNA
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NET EFFECT OF ARMATURE FLUX ON THE MAIN FIELD FLUX

• To distort the main-field flux there by causing
  non uniform distribution un der main poles.
• To shift the MNA in the direction of rotation for
  a generator and against the direction of rotation
  for a motor.
• To reduce the main field flux from its no-load
  value due to magnetic saturation.

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GRAPHICAL REPRESENTATION OF ARMATURE REACTION
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DISADVANTAGES OF ARMATURE REACTION

• Poor commutation.
• Sparking.
• Cost of field winding.
• Iron losses.

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INCREASED FLUX DENSITY IN TEETH IN THE POLE
SHOES
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HOW TO REDUCE ARMATURE REACTION

• Reduction in armature flux.
• Strong main field flux.
• High-reluctance pole tips.
• Interpoles.
• Compensating winding.

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REFERENCE

• ELECTRICAL MACHINE -Dr. P.S.BIMBHRA

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Thank You