February 19, 2017

Do you know which motor is used in the fan present in your computers for ventilation? Do you know which motor is used in the hard drive in your computer?

The answer to both questions is the  brushless DC motor as shown in  Figure-1. Learning the operation of a brushless DC motor is a logical extension of the principles of the permanent magnet stepper motor. The only difference in the architecture of brushless DC motors is the use of position sensors and control devices such as a thyristor that is an electronic gate. The position sensors can be based on Hall effect principles or can be based on optical position sensors. The Hall effect was discovered by Edwin Hall in 1879. Based on the Hall effect, a potential difference (Hall voltage) is created across an electric conductor located in a magnetic field when an electric current flows through the conductor. 

Figure 1-  Brushless DC motor.

The speed of the brushless DC motor is a function of the amplitude and the duration of the firing pulses applied to each of the stator windings. The brushless DC motor is gaining considerable popularity in industry due to the following characteristics: 
  •  The absence of brushes and the commutator means no maintenance is required. 
  •  Longer life. 
  •  Greater reliability.
  • Greater efficiency.
  • Lower inertia and friction which means they can accelerate faster and move to higher speeds quicker. 
  • The armature winding is located on the stator which supports effective cooling.
  • They have low starting torque and high cost; however, their cost reduces as the cost of thyristorized circuits decreases. 

  Other Applications of Brushless DC motor:

  • Video recorders 
  • Computer peripherals 
  • Biomedical instruments 
  • Commercial ovens 
  • Film processing equipment 
  • Printing technology 
  • Material handling equipment 
  • Centrifuges, grinders, and fans 
  • Hybrid vehicles    


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