Brushless DC Motors

1
Brushless DC Motors

• Sohaib Hasan

2
Motor Basics

• What is a motor
• 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 0416194)

3
Parts of a Motor

1. End Bell Fastners
2. Shaft Key Keyways
3. Bearing Brushings
4. End Ball Flanges
5. Identification Plates
6. Wire Warnish
7. Commutators
8. Brush Holders
9. Laminations
10. Conduit Connection Box
11. Magnets (Ferrites)

Brushless Motor Components
Brush Type Motor Components
Images courtesy of Hernon Adhesives Sealents
(http//www.hernonmfg.com/electricmotor.htm)
4
Parts of a Motor
Images courtesy of How Stuff Works (http//electro
nics.howstuffworks.com/motor3.htm)
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
• FILB
• F Force
• B Magnetic Field
• L Length of Conductor
• I Current in Conductor
• Torque in Motor
• T IBA sin ?
• A LW
• L Length of Winding
• W Width of Winding

Images courtesy of Wikipedia (http//en.wikipedia.
org/wiki/Electric_motor)
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 (http//www.ser
vomag.com/flash/2-pole/2pole-bldc-motor.html)
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
• Consumer Electronics
• Medical Field
• High Power
• Industrial Machinery
• Vehicles
• Airplanes

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
• http//electronics.howstuffworks.com/motor3.htm
• http//www.hernonmfg.com/electricmotor.htm
• http//hyperphysics.phy-astr.gsu.edu/hbase/hframe.
  html
• http//www.servomag.com/flash/2-pole/2pole-bldc-mo
  tor.html
• http//www.engineersedge.com/motors/brushless_dc_m
  otor.htm
• http//www.freescale.com/webapp/sps/site/applicati
  on.jsp?nodeId02nQXGrrlPY7r803B5