BRUSHLESS D.C MOTORS
Prepared by…
FAKHRI KHALIFEH
Contents…
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Abstract.
Introduction.
Basics of a motor.
Classification.
Brushed motors.
BLDCM.
Working procedure.
Applications.
Advantages.
Disadvantages.
Conclusion.
Reference.
Abstract…
• Permanent magnet (PM) brushless DC motors
(BLDCM) are generated by virtually inverting the
stator and rotor of PM DC motors.
• These motors are actually fed by rectangular AC
waveform.
• The advantage is the removal of brushes, leading
to eliminate many problems associated with
brushes.
• Another advantage is the ability to produce a
larger torque because of the rectangular
interaction between current and flux.
Introduction…
• Classical DC motors are no doubt good and
simple but inefficient in some ways.
• Although dc motors possess good control
characteristics and ruggedness, their
performance and applications are inhibited due
to sparking and commutation problems.
• The Permanent Magnet Brushless DC (PMBLDC)
motor is able to overcome the limitations
mentioned above and satisfy the requirements of
a variable speed drive.
MOTOR…
 MOTOR…
>> Converts electrical energy to
mechanical energy.
 ORIGIN...
>> Nicola Tesla introduces electric motor
in December 1889.
>> He identifies the principle of rotating
magnetic field.
Main parts of brushed motor...
 Commutator :
>> Facilitate collection of current
from the armature
conductors.
 Brush :
>> Collects current from the
commutator.
Advantages
• Increased Reliability & Efficiency
• Longer Life
• Elimination of Sparks from Commutator
• Reduced Friction
• Faster Rate of Voltage & Current
Disadvantages
• Requires Complex Drive Circuitry
• Requires additional Sensors
• Higher Cost
• Some designs require manual labor
(Hand wound Stator Coils)
Classification…
BLDCM…
• Has no brushes and
commutators.
• Rotation of the rotor depends
on the accurate position with
stator.
• Detected by Hall Sensor,
mounted on rotor, shifted at
60º or 120º phase shift.
• Electronic commutation used
to vary the PWM duty-cycle
for speed control, using
software.
Working of BLDCM…
 As there is no commutator ,the
current direction of the conductor
on the stator controlled
electronically.
 Rotor consists the permanent
magnet where as stator consist a
no. of windings. Current through
these winding produces magnetic
field and force.
 Hall sensor used to determine the
position during commutation.
Commutation of BLDCM…
 Brushless DC motor requires external commutation circuit to rotate
the rotor.
 Rotor position is very important.
 HALL SENSOR senses the position of the coil accurately.
Working Procedure…
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When electric current passes through a coil in a magnetic field, the magnetic force
produces a torque which turns the motor.
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Force in Motor:
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Torque in Motor:
F=ILB
F = Force
B = Magnetic Field
L = Length of Conductor
I = Current in Conductor
T = IBA sin θ
A = LW
L = Length of Winding
W = Width of Winding
Working Procedure…
 Halls Sensors sense
the position of the coils.
 The Decoder Circuit
turns appropriate
switches on and off.
 The voltage through
the specific coils turns
the motor.
Pros…
 In BLDC motor PM are on the rotor &
electromagnets are on the stator
controlled by software. Thus the
advantages are:
1.
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7.
Because of computer control it is more
precise & more efficient.
There is no sparking & less electrical
noise.
Voltage and current rating is high.
High speed can be achieved.
As there is no brushes it requires no
servicing.
It has longer life.
Low Radio Frequency Interference and
electromagnetic Interference.
Cons…
• Requires Complex Drive Circuitry.
• Requires additional Sensors.
• Expensive.
• Some designs require manual labor.
(Hand wound Stator Coils)
Applications…
• PMBLDC motors are increasingly
being used in a wide spectrum of
applications:
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domestic equipments,
automobiles
information technology equipment
industries
public life appliances
transportation
aerospace, defence equipments, power
tools, toys, vision and sound
equipments
• medical and health care equipment
ranging from microwatts to megawatts.
Reference…
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http://en.wikipedia.org/wiki/Alternator
http://en.wikipedia.org/wiki/Electric_motor
http://www.basler.com
Thompson, Sylvanus P., Dynamo-Electric
Machinery, A Manual for Students of Electro
techniques, Part 1, Collier and Sons, New York,
1902
 White, Thomas H.,"Alternator-Transmitter
Development (1891-1920)".
EarlyRadioHistory.us.
 S.M.L.Kabir, R.Shuttle worth, “Brushless Exciter
Model”.