multi-phase brush-less dc motor and applications
TRANSCRIPT
Multiphase Brushless DC MotorPresented By:
Talha Zahid 2014 EE 169 Zain Ul Abideen 2014 EE 172 Mohammad Rehan Majeed 2014 EE 180 Mohammad Shazil Majeed 2014 EE 181
Contents• Abstract • Classifications• Brushed DC Motors• Definition• Types of BLDC Motor• Brushless DC Motor• Working• 3 Phase Commutation• 5 Phase Commutation• Pros and Cons of Multiphase
BLDCMs• Trapezoidal and Sinusoidal
Constructions
Abstract• BLDCMs are motors which are powered by DC source
via an inverter which produces an electric signal to drivethe motor• High torque and low speed motor
Classification
• DC Motor Brushed Brushless
• Brushless (On the basis of Rotor) IN-RUNNER OUT-RUNNER
Brushed DC MotorContains Commutator and Brushes
Definition of Brushless DC Motor• Brushless motor is a high torque low speed DC motor which has a
rotor of permanent magnet and stator(armature) of electro-magnets. The poles of rotor are attracted or repelled by creating desired poles on the stator winding.• It is type of hybrid motors because it includes both AC & DC.• Flipped inside out the brushed motor
WHY BRUSHLESS???• More efficient• More reliable• Less Noisy• Lighter with same power
output• When we need long life
and reliable operation
Structure• Rotor
Permanent Magnet and Shaft
• Stator Armature
• Electronic Sensor Hall Effect Sensor
Optical Sensor
• DC To AC Inverter
Working • 3 Coil 2 Pole BLDC Motor
Analogy for Rotor Movement
Which coil to energize?When to energize?
Hall Effect Sensor Detects the position of the rotor
Commutation
DC to AC InvertersInverter for 3 Phase
Inverter for N Phase
5 Phase Commutation• Voltage difference of 2π/5• 5 phase 8 pole motor• 5 Hall Sensors• 10 Step Commutation
Increasing Rotor Poles• Size of permanent magnet• Rotor diameter• Torque Increases
Speed Control of BLDC MotorWe can control the speed of this motor by two methods1) No. of stator poles per phase2) Frequency
Speed Control of BLDC MotorWe can find the approx. speed of this motor by the following formula:
Control of BLDC Motor• The waveforms produced by inverters is of two types:1) Trapezoidal waveform2) Sinusoidal waveform
Trapezoidal Control• Motors powered by trapezoidal waveforms produce 10% more torque
then those powered by sinusoidal.• These motors are not much smooth and they have ripples in torque.
Sinusoidal Control• The sinusoidal control is used for low speed because it is smooth and
produces less ripple torque.
Back emf of BLDC Motor• We can also detect the rotor position by motor’s back emf instead of
sensors.• This method is only applicable for high speed motors so that there is
enough bemf amplitude.[2]• As the operating speed of motor increases, the frequency of bemf
also increases, so, the relative speed of switching remains contant.
Trapezoidal Back EMF• We integrate the trapezoidal bemf by controller and thus it can
control current waveform.• The use of sinusoidal wave is not feasible.
Pros of Multiphase BLDC Motor• Minimize torque ripple• Reduced Noise• Increased power density• Improves fault-tolerance w.r.t open circuit lags
3 phase torque
Multi phase torque
• High Efficiency• High Torque to Weight Ratio• Longer Life time• Compact And Lightweight• Better For Environment• Less Maintenance, High Reliability
Cons of Multiphase BLDCM• Complex inverter control scheme • High cost
ApplicationsTransport• Electric Vehicles• Hybrid Vehicles
ApplicationsComputer Applications• PC fans• DVD Players• Floppy Drive
ApplicationsHeating And Ventilation• HVAC And Refrigeration Industries
ApplicationsMotion Control Systems• Pumps• Fans• Positioning• Actuating
ApplicationsAeromodeling• Aircrafts• Helicopters• Best use of High Power to Weight Ratio
ApplicationsRadio Controlled Cars• Less Input Power• More Torque
References[1] Delmar's Standard Textbook of Electricity[2] Power Electronics Handbook: Devices, Circuits and Applications
QUESTIONS
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