1. Brushless DC Motors
Sohaib Hasan

2. Motor Basics What is a motor Where did it come from
Converts electrical energy into kinetic energy
Where did it come from
Identification of rotating magnetic field principle by Nicola Tesla in 1882
Introduction of Electric Motor by Nicola Tesla in December 1889 (U.S. Patent )

3. Parts of a Motor End Bell Fastners Shaft Key & Keyways
Bearing & Brushings
End Ball Flanges
Identification Plates
Wire Warnish
Commutators
Brush Holders
Laminations
Conduit Connection Box
Magnets (Ferrites)
Brushless Motor Components
Armature or Rotor
Commutator or Brushes
Lamination stack
Windings
Shaft
Bearings
Brush Type Motor Components
Images courtesy of Hernon Adhesives & Sealents (

4. Parts of a Motor Images courtesy of How Stuff Works(

5. How It Works
When electric current passes through a coil in a magnetic field, the magnetic force produces a torque which turns the motor.
Force in Motor:
F=ILB
F = Force
B = Magnetic Field
L = Length of Conductor
I = Current in Conductor
Torque in Motor:
T = IBA sin θ
A = LW
L = Length of Winding
W = Width of Winding
A simple DC electric motor. When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn toward the right, causing rotation.
The armature continues to rotate.
When the armature becomes horizontally aligned, the commutator reverses the direction of current through the coil, reversing the magnetic field. The process then repeats.
Images courtesy of Wikipedia (

6. Motor Types

7. Brushless DC Motor No Commutators
Position of Coils with respect to the magnetic field is sensed electronically.
Current is commutated through electronic switches to appropriate phases.

8. How it Works 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
Images courtesy of Servo Magnetics (

9. Advantages Increased Reliablilty & Efficiency Longer Life
Elimination of Sparks from Commutator
Reduced Friction
Faster Rate of Voltage & Current
Precision Voltage & Current Applied to Field Coils

10. Applications Low Power High Power Consumer Electronics Medical Field
Industrial Machinery
Vehicles
Airplanes
Consumer: Hard Drives, CD/DVD Drives, PC Cooling Fans, toys, RC airplanes, air conditioners
Medical: Drills, Operating equipment
Industrial: servo drives
Vehicles: electronic power steering
Airplanes: Antares 20E, an electric self-launching sailplane, flies with a 42kW DC/DC brushless motor and Li-Ion batteries and can climb up to 3000m with fully charged cells

11. Disadvantages Requires Complex Drive Circuitry
Requires additional Sensors
Higher Cost
Some designs require manual labor (Hand wound Stator Coils)

12. Useful Links http://en.wikipedia.org/wiki/Electric_motor