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LOGO
DC MOTOR
ELECTRICAL MACHINE
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Assigned topics
TYPES OF DC MOTOR WORKING PRINCIPLE OF DC MOTOR
CONDITION OFMAX.POWER
DERIVATION OF BACK EMFEQUATION
BACK EMFTOPICS
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Syed Muhammad zaidi TYPES OF DC MOTOR
Syed Muhammad zaidi TYPES OF DC MOTOR
Group members
Muhammad ali
1
2 WORKING PRINCIPLE OF DC MOTOR
RASHID HAMEED Condition of MAX POWER
RASHID HAMEED Condition of MAX POWER
Rehman ali back emf
3
4
Rizwan saeed application of dc motor
Rizwan saeed application of dc motor5
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Here I, brief series wound motor
In series wound motor, field coil is connected
in series with armature.
Because of series connectivity, its armature
and field current is identical.The advantage of a series-wound motor is that
it develops a large torque and can be operated
at low speed.
.
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Shunt wound motor
In shunt motor, field coil is connected in
parallel with armature.
It is used when starting torque is low and
increases with motor speed.
www.themegallery.co
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Compound motor
The compounded motor is desirable for a varietyof applications because it combines thecharacteristics of a series-wound motor and a shunt-
wound motor. The compounded motor has a greatertorque than a shunt motor due to the series field.
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Ali come on the stage please
And present your assigned
topic.
.
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Working Principle of DCMotor
Working Principle of DC Motor
When the coil is powered, a magnetic field is generated around the
armature. The left side of the armature is pushed away from the left
magnet and drawn towards the right, causing rotation. When the coil
turns through 900, the brushes lose contact with the commutator andthe current stops flowing through the coil. However the coil keeps
turning because of its own momentum.
.
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Mr. Rashid
come on thestage please.
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Condition For Maximum Power
The mechanical power developed by the motor
is Pm= EbIaNow Pm=VIa -I
2aRa
Since, V and Ra are fixed, power developed bythe motor depends upon armature current. For
maximum power, dPm/dIa should be zero.
dPm/dIa = V 2IaRa
a a =
Now, V = Eb + IaRa =Eb + V/2therefore Eb= V/2
Hence mechanical power developed by the
motor is maximum when back e.m.f. is equal to
half the applied voltage.
V = applied voltage
Eb = back e.m.f.
Ra = armature resistance
Ia = armature current
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Mr. Rehman
come on thestage please.
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Back emf
Back e.m.f (or) counter e.m.f:
When a D.C supply is given to dc motor its
armature starts rotating.The armature rotates
and cuts the static magnetic flux produced bythe field magnets.Therefore emf is induced in
the armature conductors (Faradays law of
electromagnetic induction ).As per Lenz law
t s n uce em opposes t e supp y
voltage.Hence the emf induced in the armature
is called Back emf (or)counter emf(Eb).Back
emf induced in the armature of the dc motor
Eb = NZP/60A
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Mr. RIZWAN
come on thestage please.
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Applications of DC Motors:
1. D.C Shunt Motors:
Industrial use:Lathes
DrillsBoring mills
Shapers
Spinning and Weaving machines.
. .
compound motors are rarely used because of itspoor torque characteristics.
Industrial uses:
Presses Shears
Reciprocating machine.
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LOGO