Construction of DC machine

Construction of DC machine:- 

 DC generator can be used as a DC motor without any constructional changes. 

Thus, a DC generator or a DC motor can be termed as a DC machine. The basic constructional details are:-

•Yoke: The outer frame of a dc machine is called as yoke. It is made up of cast iron or steel. It not only provides mechanical strength to the whole assembly but also carries the magnetic flux produced by the field winding.

•Poles and pole shoes: Poles are joined to the yoke. Pole core basically carries a field winding which is necessary to produce the flux.

It directs the flux produced through air gap to armature core, to the next pole.

•Field winding: They are made up of copper. Field coils are  wounded and placed on each pole and are connected in series. They are wounded in such a way that, when energized, they form alternate North and South poles.

•Armature core: Armature core is the rotor part  of a dc machine. It is cylindrical in shape with slots to carry armature winding. The armature is made up of thin laminated circular steel disks for reducing eddy current losses. It may be provided with air ducts for the axial air flow for cooling purposes. 

•Armature winding: It is made up of wound copper coil which rests in armature slots. The armature conductors are insulated from each other and also from the armature core. Armature winding can be wound two methods: lap winding or wave winding.

•Commutator and brushes:  Commutator-brush arrangement. The function of a commutator in a dc generator is to collect the current generated in armature conductors.

In case of a dc motor, commutator helps in providing current to the armature conductors. 

A commutator consists of a set of copper segments which are insulated from each other. 

•Brushes:-Brushes are made up of  carbon or graphite. They rest on commutator segments and slide on the segments when the commutator rotates keeping the physical contact to collect or supply the current.