Essential Parts of a DC Machine
or
DC Generator Construction
A DC generator or DC machine consisted mainly four parts which are given as :-
1- Magnetic field system
2- Armature
3- Commutator
4- Brush
1- Magnetic field system :- The magnetic field system is the stationary part of the machine . It produces the main magnetic flux . The outer frame or yoke is a hollow cylinder of cast steel or rolled steel .
2- Armature :- The rotating part of the DC machine is called the armature . The purpose of armature is to rotate the conductors in the uniform magnetic field . It consists of coils of insulated wires would around an iron and so arranged that electric current are induced in these wires when the armature is rotated in a magnetic field .
3- Commutator :- The Commutator is a form of rotating switch placed between the armature and external circuit and it provides the electrical connections between the rotating armature coils and the stationary external circuit .
4- Brushes :- The function of brushes is to collect current from the commutator and supply it to the external load circuit . The brushes are rectangular in space and reset on the commutator .
Back EMF
During rotation of armature it's conductor cut the magnetic flux , then due to this reason an EMF ( Electromagnetic Force ) is induced . In the conductors according to law of electromagnetic induction , the direction of this induced EMF can be found by Flaming Right Hand Rule and have the direction of opposite to the applied voltage . Therefore this induced EMF is called back EMF and given as -
where P - total no. of poles
N - speed of rotation of armature in RPS
A - no. of parallel path
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