Points: Stator, Yoke, Field Poles, Field Winding, Brushes, Brush Holder Stator consists of

(1) Yokes​

(2) Field Poles

(3) Field winding

(4) Bearings​

(5) Brushes and end covers etc.


1.​ Yoke​

The Cylindrical yoke is made up of unlamented ferromagnetic material and serves the following purpose.

(a) It provides mechanical support for field poles.

(b) It serves as a protecting cover for the whole machine.

(c) It carries magnetic flux, produced by the magnetic poles.



2.​ Field Poles

Field poles are made of stack of steel laminations, (1 to 1.5mm thick) riveted together. The cross-sectional area of pole core where the field winding is wound is less than the area of pole shoe due to the following reasons:​


(a) The reduced cross section of the pole core requires less copper for the field windings.

(b) The large pole shoe area increases the flux per pole entering the armature due to reduction in the air gap reluctances.

(c) Large pole shoe area provides mechanical strength to the field winding.



3.​ Field Winding

Field consists of a number of turns of insulated Copper conductor. These windings are provided on pole core. The function of the field winding is to produce the flux.



4.​ Brushes​ 

The function of brushes is to collect current from the commutator and supply it to the external load circuit (the armature of the machine being connected to the external load circuit via the commutator and brushes). The brushes are rectangular in shape and rest hardness to suit the commutation requirements. They may be classified roughly as carbon, carbon graphite, graphite, metal graphite and copper. The allowable current density at the brush contact varies from 5 A per square cm in the case of carbon to 23 A per square cm in the case of copper. The brushes are housed in brush-holders (usually of the box type) which are mounted or the brush holder studies or brackets.



5.​ Brush Holder

The brushes are housed in a brush holder, which is mounted on brush holder brackets. These brushes are held under pressure over the commutator by spring.