how a bldcm works & function of controller in motor.

2. BRUSHLESS DC
MOTOR
B HARISH

3.  INTRODUCTION
 WHY BLDC?
 PRINCIPLE
 CONSTRUCTION
 WORKING
 ADVANTAGES
 DISADVANTAGES
 APPLICATIONS
 CONCLUSION

4. MOTORS
Brushed
motor
Brushless
motor
Inrunner Outrunner

5.  It is a machine which converts electrical energy
to mechanical energy.
 Above electrical input can be given to the
brushes and followed by commutator.

6. These are also known as electronically brushless
commutated motors.
 These are powered by direct-current electricity
and having electronic commutation systems,
rather than mechanical commutators and
brushes.
 BLDC motors come in single phase, two phase
and three phase configurations. Out of these
three phase motors are the most popular and
widely used

7. BRUSHED BRUSHLESS
 Brushess &commutator
requires maintainence.
 There is a mechanical
contact between the
brushes & commutator.
 Rotors position is
automatically detected
by brushes
 There are no brushess
and commutator.
 Elecronic switching
using transistors.
 Rotor position is
detected by hall sensor
,optical encoder.

8.  It works on the principle based on “simple
force of attraction between the permanent
magnet and electromagnet”

9.  Just like any other electric motor, a BLDC
motor also has a stator and a rotor. Permanent
magnets are mounted on the rotor of a BLDC
motor, and stator is wound with specific
number of poles. This is the basic
constructional difference between a brushless
motor and a typical dc motor.
 There can be two types of BLDC motor on the
basis of construction : (i) inner rotor design &
(ii) outer rotor design.

10. IN RUNNER OUT RUNNER

11. STATOR ROTOR

12. The stator has a coil arrangament as shown
It has three coils,named as A,B&C.

13. When the coil A is energised the opposite poles of a
rotor are attracted to each other,as a result the rotor
poles move near to the energised stator
 As the rotor the rotor nears the coil A,coil B is
energised.As the rotor nears the coil B, coil C is
energised.After that coil A is again energised with
opposite polarity

14.  This process is repeated and the rotor is
continued to rotate, the DC current required
the each coil is shown in the graph.

15.  Even though this motor works, it has one drawback.
You can notice that, at any instant only one coil is
energized. The 2 dead coils greatly reduce the power
output of the motor. Here is the trick to overcome
this problem. When the rotor is in this position, along
with the first coil, which pulls the rotor, you can
energize the coil behind it such a way that, it will
push the rotor.

16.  With this configuration 2 coils need to be energized
separately, but by making a small modification to the
stator coil, we can simplify this process. Just connect
one free end of the coils together, When the power is
applied between coils A and B, let’s note the current
flow through the coils. it is clear that, the current
flow is just like the separately energized state.

17.  The current form required for the complete 360
degree rotation is shown in the graph below.

18.  The combined effect produces more torque and
power output from the motor. The combined force
also makes sure that a BLDC has a beautiful, constant
torque nature. Such torque nature is difficult to
achieve in any other type of motors.

19.  That’s how a BLDC works. But, you might have
some intriguing doubts in your mind. How do I
know which stator coils to energize? How do I
know when to energize it, so that I will get a
continuous rotation from the rotor? In a BLDC we
use an electronic controller unit (ECU) for this
purpose. A sensor determines the position of the
rotor, and based on this information the controller
decides, which coils to energize.

20.  The schematic figure above shows, how the ECU
controls task of energizing the coil. This task is
known as commutation. Most often, a Hall-effect
sensor is used for this purpose. The Hall-effect sensor
is fitted on the back of the motor as shown in the Fig

21.  No brushes or commutators to wear out
 No generation of EMI
 High torque to inertia ratio
 No winding on the motor but supported by
housing
 High efficiency(up to 97%)
 No sparks & longer life
 Maintenance free
 Good weight/size to power ratio

22.  Higher cost
 Hall effect sensor might not work properly
 Requires additional sensors
 Sudden change in load causes back emf to
become out of synchronous resulting loss of
speed and torque
 Must rotate at minimal speed to generate
sufficient back emf for the drive to sense

23. LOW POWER BLDC HIGH POWER BLDC
1) Medical field
a. Optimising power
density
b. Heat transfer efficient
c. medical analyser
d.sleep apnea treatment
2)Consumer electronics
1)Transport
2)Heating & ventilation
3)Radio controlled cars
4)Industrial engg.

24.  Due to all those advantages BLDC is now
replacing the conventional DC motor &
increasing popularity.
 Various researches are going on for reducing
its complexity in drive circuit with different
types of sensors.
 As sensor less BLDC drives continue to
develop and costs are reduced, the
attractiveness of BLDC motors will continue to
increase.