Brushless DC Motor

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NSPEES 2012

• BRUSHLESS D.C MOTORS
• Prepared by
• 
  Deepak Kumar Mohapatra
• Pijush
  Kumar Banerjee

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Contents

• Abstract.
• Introduction.
• Basics of a motor.
• Classification.
• Brushed motors.
• BLDCM.
• Working procedure.
• Applications.
• Advantages.
• Disadvantages.
• Conclusion.
• Reference.

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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.

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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.

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MOTOR

• MOTOR
• gtgt Converts electrical energy to mechanical
  energy.
• ORIGIN...
• gtgt Nicola Tesla introduces electric motor
• in December 1889.
• gtgt He identifies the principle of rotating
  magnetic field.

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Main parts of brushed motor...

• Commutator
• gtgt Facilitate collection of current from the
  armature conductors.
• Brush
• gtgt Collects current from the commutator.

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Classification
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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.

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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.

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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.

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Working Procedure

• When electric current passes through a coil in a
  magnetic field, the magnetic force produces a
  torque which turns the motor.
• Force in Motor
• FILB
• F Force
• B Magnetic Field
• L Length of Conductor
• I Current in Conductor
• Torque in Motor
• T IBA sin ?
• A LW
• L Length of Winding
• W Width of Winding

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Simulation Of BLDCM
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Output Of Simulation
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Speed Torque Characteristics
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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.

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Pros

• In BLDC motor PM are on the rotor
  electromagnets are on the stator controlled by
  software. Thus the advantages are
• 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.

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Cons

• Requires Complex Drive Circuitry.
• Requires additional Sensors.
• Expensive.
• Some designs require manual labor.
  (Hand wound Stator Coils)

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Applications

• PMBLDC motors are increasingly being used in a
  wide spectrum of applications
• 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.

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Reference

• 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.

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