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Construction of DC machine

Construction of DC machine

 The machine which are working on DC supply are known as DC machine. The input of DC machine is always DC but it's not necessary that it always convert into mechanical energy. It is also converted into electrical energy. 

Construction of DC machine


It is work on the principal of current carrying conductor in uniform magnetic field. So, the electric current flows through the electric circuit, which are made up of winding. On the other hand, magnetic fluxes flow through the magnetic circuit which are made up of soft iron core. The soft iron core is less reluctance then air. So, the magnetic flux is easily flow in soft iron core as compared to air.


main parts of DC machine:-

The construction is usually the parts of DC machine. The construction of DC generator and motor are same. So, the workman can't identify the motor or generator when it's assembling. Usually, now these days we can't DC generator because the development of DC current in DC generator is more expanive then rectification of alternative current and also it's in high efficiency. 

All the DC machine have 5 principal component are:-

1. Magnetic field system:- 

The function of producing magnetic field in the entire circuit is Known as magnetic field system. It consist of various parts like yoke, pole, and field winding.

Yoke:- 

Construction of DC machine

The yoke is usually made up of solid cast steel which is used to provide the low reluctance path to the magnetic field lines. It is the outer part of any types of machine whereas the pole pieces are composed of stacked lamination. 

It's also provide the mechanical strength of DC machine. And, carrying the magnetic field flux in it. 

The mmf made of field coils produces a magnetic flow that passes through parts of the pole, air gap, gun and frame. The air gap between armature core and poles are 0.5mm to 1.5mm. 

Poles:-

The are two terms in the pole are:-

Pole core is used to carry the field winding and produce flux in it. Pole core is not laminated but pole shoe is laminated. 

Pole shoe acts as a supports to the field coils and spreads out the flux uniformly over the armature periphery. There are also two types of pole shoe are:-

Arc shaped pole shoe or bradder pole shoe which is used produce flat topped flux field. 

Chamfered pole shoe or eccentric pole shoe produce sinusoidal flux density. 

Field winding:- 

The winding which is used to produce magnetic field in the DC machine is known as field winding. It is wrapped on pole core so, the field which is produce in it with the help of pole shoe transferred to armature. it is usually made up of aluminium or copper metal. 

2. Armature core:- 

It is the main part of machine and rotates between the fields poles. Its also provide housing to the armature winding. Individual lamination coated with a thin insulating film, the purpose of lamination the core is to reduce the Eddy current. 

The winding is placed between slot of armature core. And, teeth is used to provide mechnical security to the armature winding. It's made up of silicon steel stampings to provide low reluctance path.

3. Armature winding:- 

The winding which is wapped on armature is known as armature winding. When the armature core rotates by prime mover, it's cuts the magnetic flux and voltage gets induced in it. The armature coils in a armature winding must be connected in series with each other by the help of back connection. It is usually made up of copper wire. 

4. Commutator:- 


A commutator is a mechanical rectifier which used to convert alternative current to direct current or vica versa. It's made up of hard drawn copper. The function of commutator are use as follows:- 
  • To collect the current from armature windings.
  • To converts internally develop AC emf into DC emf.

To provides unidirectional torque in case of motor. 

5. Brushes:-

The main purpose of brushes to collect  from commutator and supply it to external load. And, also provide the lubrication to the commutator. 

The brush are made of carbon/carbon graphite/graphite or copper, and rest on the commutator. The pressure of brush on commutator is a just by adjustable spring. If the fraction is high between commutator and the brush so, it produce heating or sparking on it. On the other hand, the imperfect connect with the commutator may be produce sparking in it. The brush having always same polarity either positive or negative. 

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Application of DC machine:-

There are various application of DC machine which are as follows:-

1. It is used in traction motor in locomotive, and cranes.
2. It is also used in various machine like pump, car, trimmer, etc.
3. The compound machine is used to increase pressure, shears, convegous, etc.
4. DC machine also used in elevator, heavy planner, for positioning and tracking motor we use servometer.