CONTENTS
INTRODUCTION
Cunstruction
BRUSHLESS MOTOR
WORKING OF BLDC
ADVANTAGES & DISADVANTAGES
INTRODUCTION
What is Motor?
It is a machine can converts electrical
energy to mechanical energy.
It may be DC or AC depending upon the
type of power supply.
It has mainly two parts- stator & rotor.
DC motors are of two types-
i) Brushed motor –with brushes and
commutator and
ii) Brushless motor- without brushes.
INTRODUCTION (cont)
What is commutator and brush ?
– Commutator is a cylindrical in
structure, made of copper or carbon
with high conductivity.
– Mounted on the rotor part of the brushed
motor.
– Helps to conduct current
through conductor when the
brushes comes to contact
during rotation.
The electrical contacts to the
rotating ring called brushes.
Conventional DC Motor
Rotor
Images courtesy of How Stuff Works
(http://electronics.howstuffworks.com/motor3.htm)
Magnetic Rotor with
Stator Winding
Brushless DC Motor Commutation
Commutation is performed electronically
using a controller.
Similarity with stepper motor, but with
less # poles
Needs rotor positional closed loop
feedback: With the help of hall effect
sensors, back EMF or photo transistors
Sean DeHart 7
BLDC (3-Pole) Motor Connections
Has 3 leads instead of 2 like brushed DC
Delta (greater speed) and Wye (greater
torque) stator windings
Delta Wye
Sean DeHart 8
Daily life Examples Of Brushless DC
Motors
Applications
CPU cooling fans
CD/DVD Players
Electric automobiles
HDD of PC
Sean DeHart 9
Working of BLDC motor
As there is no commutator ,the current direction
of the conductor on the stator controlled
electronically.
Rotor consists the parmanent 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 BLDC motor
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
Hall Sensor operation
It embedded into the stator on non-driving end of
motor.
Senses accurate position of the rotor to the stator.
Shifts at 60º or 120º phase shift for each of three
coils, yet a time two coils work for 3Φ current
Due to the changing of direction of the current &
applying Fleming’s Left Hand rule force direction can
be determined.
Thus the permanent magnet on rotor moves
clockwise , as well as the rotor of the BLDC also
moves clockwise.
Hall Sensor operation (contd.)
Hall Sensor operation (contd.)
Output of Hall Sensor
Essential Elements of a Typical BLDC Motor & its
Driver
Six-Step Commutation (4-pole)
Hall-Effect Sensors
spaced 60 electrical
degrees apart
6 steps to complete one
electrical cycle
Phase current switching
updated every 60
electrical degrees
BLDC Control
CW
CCW
Disadvantages
Requires Complex Drive Circuitry
Requires additional Sensors
Higher Cost
Some designs require manual labor
(Hand wound Stator Coils)
Advantages of Brushless Motor
In BLDC motor PM are on the rotor &
electromagnets are on the stator controlled by
electronics. Thus the advantages are:
1. Because of electronic control it is more precise
& more efficient.
2. There is no sparking & less electrical noise.
3. Voltage and current rating is high.
4. High speed can be achieved.
5. As there is no brushes it requires no servicing.
6. It has longer life.
7. Low Radio Frequency Interference and
Electromagnetic Interference.
