1. DC Machine
Made by:-Mayank Panwar
Submitted to :-Dr. Krishna Tyagi
Branch:-Electrical Engineering
Roll No.:-20/BEE/006
2. DC Machine
• A DC Machine is an electro-mechanical energy conversion device.
The output of the DC Machine is DC output because they convert
AC Voltage to DC Voltage .
The conversion of this mechanism is known as the commutator ,
thus these machines are also named as commutating machines.
Working principle of DC Machine:
The Working principle of a DC machine is when electric current
flows through a coil within a magnetic filed, and then the magnetic
force generates a torque which rotates the DC motor.
3. Types of DC Machines
Following are two types of DC machines:
• DC Generators.
• DC Motors.
DC Generators:
An Electrical generators is a machine which converts
mechanical power into electrical energy power.
It is based on the principle of production od dynamically induced
e.m.f.
Whenever a conductor cuts magnetic flux , dynamically induced
e.mf. Is produced in it according to Faraday’s Law of Electromagnetic Induction
4. Electromotive force is induced by the relative motion of the armature
conductors and the magnetic field.
CONSTRUCTION:
It consist of following parts:
Stator:
The magnetic fields where the coils spin . This stator is an essential part of
the DC generator , and the main function of this is it provide includes stable
magnets , where two of them are with reverse poles facing . These magnets
are located to fit in the region of the rotor.
Rotor or Armature Core:
Rotor or armature core is the second essential part of the DC generator , and
it includes slotted iron laminations with slots that are stacked to shape a
cylindrical armature core.
5. • Magnetic field : This field envelops the armature and the current within.It
is created by permanent magnets or electromagnets.
• Armature: The armature is a coil of wire that generally consists of many
windings mounted on a shaft.
• Brushes: The brushes are made of carbon . These are rectangular block
shaped . The only function of these carbon brushes of DC generator is to
collect current from commutator segments . The Brushes are housed in the
rectangular box shaped brush holder or brush box.
• Commutator : The commutator plays a vital role in DC generator . It
collects current from armature and sends it to the load as direct current . It
actually takes alternating current from armature and converts it to direct
current and then send it to external load.
6. • It connect between the rotating armature conductors and stationary
external circuit by the brushes.
Faraday’s law of electromagnetic induction
• This law states that when a conductor moves in a magnetic field it cuts
magnetic lines of force , which induces an electromagnetic force (EMF) in
the conductor .
• The magnitude of this induced EMF depends upon the rate of change of
flux (magnetic line force ).This EMF will cause a current to flow if the
conductor circuit is closed.
WORKING PRINCIPLE :
Whenever a conductor is moved within a magnetic field in such a way that
the conductor cuts across magnetic lines of flux, voltage is generated in the
conductor
7. • The AMOUNT of voltage generated depends on: the strength of the
magnetic field, the angle at which the conductor cuts the magnetic
field, the speed at which the conductor is moved, and the length of
the conductor within the magnetic field.
The direction of the current can be determined by Flemming’s right
hand Rule . This rule says that if you stretch thumb, index finger and
middle finger of your right-hand perpendicular to each other , then
thumbs indicates the direction of motion of the conductor, index
finger indicates the direction of magnetic field ,
8. • The waveform of the current through the load circuit is as shown in the
fig. This current is unidirectional.
DC MOTOR:-A DC Motor is an electric motor that runs on direct
current power . In any electric motor , operation is dependent upon simple
electromagnetism.
It is a device which converts electrical energy to mechanical energy.
It works on the fact that a current carrying conductor placed in a magnetic
field experiences a force which causes it to rotate with respect to its original
position.
9. Construction:
• The stator: Every electric motor has two essential parts:one
stationary, and one that rotates. The stationary part is the stator .
Through configuration vary, the stator is most often a permanent
magnet or row of magnets lining the edge of the motor casing.
• The rotator: Inserted into the stator is the rotor, usually consisting
of copper wire wound into a coil around an axle.It is the rotating
part.
• Magnetic filed: This filed envelops the armature and the current
within. It is created by permanent magnets or electromagnets.
• Armature: The armature is a coil of wire that generally consist of
many windings mounted on a shaft.
10. • Brushes:- The Brushes are contacts pressing lightly against the spilt-
ring commutator.They provide the conducting path for the current
from a DC electrical supply to the commutator.
• Spilt-ring commutator:- An electric motor has another important
component, the commutator , which sits at one end of the coil . It is
a metal ring divided into two halves.
11. • It reverses the electrical current in the coil each time the coil rotates
half a turn . The commutator periodically reverses the current
between the rotor and the external circuit , or the battery . This
ensures that the ends of coil do not move in opposite directions, and
ensures that the axle spins in one direction.
• DC CURRENT: A current from an electrical DC supply such as
battery.
• WORKING PRINCIPLE:- The working of DC motor is based on
the principle that when a current carrying conductor is placed in a
magnetic field, it experiences a mechanical force.
12. • The working of the AC (Induction motor and synchronous motor) is
different from DC motor.
13. Consider a part of a multipolar DC Motor as shown in the figure
below . When the terminals of the motor are connected to an external
source of DC supply:
• The field magnets are excited developing alternate North and south
poles .
• The armature conductors carry currents.
