1. BRUSHLESS MOTOR COMMUTATION
PRESENTATION BY
SWAPNA.M

2. PRESENTATION OUTLINE OBJECTIVE THE BRUSHLESS DC (BLDC) MOTOR
COMPARISON OF BLDC MOTOR & BRUSHED MOTOR
ADVANTAGES OF BLDC MOTOR
METHODS OF COMMUTATION
TRAPEZOIDAL COMMUTATION
SINUSOIDAL COMMUTATION

3. OBJECTIVE
To investigate different methods of commutation of BLDC motor-Trapezoidal & Sinusoidal

4. The Brushless DC (BLDC) Motor
A modern, much improved, version of the traditional brushed DC motor.
An inside out DC motor with
electronic commutation
Field- permanent magnets- is
on the rotor.
Armature- is on the stator
which has good cooling.
Two types of motor
sinusoidal trapezoidal

5. Sinusoidal motor
Sinusoidal distribution of magnetic flux
2. Sinusoidal current waveforms
3. Sinusoidal distribution of stator conductors.
Trapezoidal motor
Rectangular distribution of
magnetic flux
2. Rectangular current waveform
3. Concentrated stator windings.
Mechanical commutator of brushed
motor replaced by electronic switching of the phases.
Switching - synchronised to absolute rotor position – smooth torque production.

6. Comparison of BLDC Motor & Brushed Motor
Feature
BLDC Motor
Brushed Motor
Commutation
Electronic Commutation based on Hall Sensors
Brushed Commutation
Maintenance
Less
Periodic
Life
Longer
Shorter
Speed/Torque Characteristics
Flat
Moderately Flat
Efficiency
High
Moderate
Output Power
Low
Rotor inertia
Higher
Speed Range
Lower
Electric Noise
Arcs in brushes-generate noise
Cost of Building
Control
Complex & Expensive
Simple & inexpensive
Control Requirements
Controller is always required
No controller is required

7. Advantages of BLDC Motor
Better speed versus torque characteristics
High dynamic response
High efficiency
Long operating life
Noiseless operation
Higher speed ranges
Ratio of torque to size of the motor is higher
Applications Appliances, Automotive, Aerospace, Consumer, Medical, Industrial Automation Equipment and Instrumentation.

8. Commutation of BLDC Motor
Commutation – to energize the appropriate windings in the stator to provide optimum torque generation depending on the rotor position.
Methods of Commutation
Trapezoidal Commutation
Sinusoidal Commutation

9. Trapezoidal Commutation
Simplest method of control for dc brushless motors
Only two phase coils are active at any instant
Commutation –every 60 degree
Hall effect sensors are used

10. Merits 1. Simple control circuits 2. Switching loss is less 3
Merits 1. Simple control circuits 2. Switching loss is less 3. Only one current at a time needs to be controlled. 4. Only one current sensor is necessary. Demerits 1. Overall system efficiency is poor 2. Torque ripple is present at each 60 degree phase commutation 3. Inadequate to provide smooth and precise motor control

11. Sinusoidal Commutation
All three phases are active at any moment.
Attempt to drive - three currents that vary smoothly and sinusoidally as the motor turns
Smooth torque control & accurate position control is required.
An encoder is required