DC MACHINE CONSTRUCTION
DC Machine construction
1. Pole Body:
• It is made up of Silicon steel laminations.
• The laminations are piled one over another and tightened with bolts and nuts.
• Pole body is attached to yoke by counter sunk screws.
• It supports pole shoe and field winding provides low reluctance path.
2. Pole Shoe:
• Made up of Si Steel laminations.
• Attached to pole body.
• Supports field windings.
• Helps in uniform distribution of flux in air gap.
3. Field Winding:
• Made of copper conductors over which cotton tape is wound and impregnated in
insulating oil and dried.
• On each pole body one field winding is kept and all windings are connected in series so as to make one field winding.
The sense of the windings are kept such that alternately N and S poles are produced around the periphery of the machine.
• It is excited by supply voltage and produces the necessary working flux in them achine.
4. Armature:
• It is made up of Si Steel laminations.
• All laminations are joined by means of nuts and bolts.
• The armature laminations are slotted and carry armature winding.
• The whole assembly of armature is fixed to MS(mild steel) shaft.
• In armature conductors voltage is generated and taken out from the machine by
commutator segments and brushes.
5. Commutator & Brushes
• It is made up of mica inside which copper wedges are fixed around the periphery of
the commutator and it is fixed on MS shaft in front of armature.
• The ends of armature windings are connected to commutator segments.
• Brushes are always pressing the commutator segments by means of spring force to
collect the current through the machine.
• Commutator makes AC voltage generated in the winding as DC voltage to the
external circuit.
• Commutator acts as RECTIFIER.
6. Shaft, Bearings, End covers etc
• Two ball bearings are fixed in two end covers.
• End covers are fitted to yoke.
• The two ball bearings are supported by MS shaft in which armature and
commutator are fixed.
• MS shaft is free to rotate
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