Page 209 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Remedy for armature reaction
• Compensating winding embedded the face in the pole shoe in series with armature current is in opposite
direction to armature conductors directly below the pole shoes.
• compensating windings produce magnetic field, which varies directly with armature current.
• compensating winding field oppose the magnetic field of the armature,
• they tend to cancel the effects of the armature magnetic field causing armature reaction

Commutation
Self-induced voltage in coil
Reactance voltage

The changes in the direction of current in a coil after the period of short circuiting the coil is called commutation.
Effects of poor commutation
Sparking
• Commutator Surface carbonization & short circuit
• Damage to commutator
• Increased spark
• Excess heat may result loose connection in riser
Remedy / improving commutation
• Resistance Commutation
• EMF commutation

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CITS : Power - Electrician & Wireman - Lesson 30-37