SLVA654B June   2014  – March 2019 DRV8301 , DRV8301-Q1 , DRV8302 , DRV8303 , DRV8307 , DRV8308 , DRV8312 , DRV8323R , DRV8332

 

  1.   Hardware design considerations for an efficient vacuum cleaner using a BLDC motor
    1.     Trademarks
    2. 1  Suction Principle
    3. 2  Brushless DC Motors (BLDC)
      1. 2.1 Construction of BLDC Motors
      2. 2.2 Working of the BLDC Motor
        1. 2.2.1 Types of Control
          1. 2.2.1.1 Sensor Control
          2. 2.2.1.2 Sensorless Control
            1. 2.2.1.2.1 Sensorless Control: Using Zero Crossing of the Back EMF Signal
          3. 2.2.1.3 Calculations
    4. 3  Microcontrollers
    5. 4  Gate Driver and MOSFETs
    6. 5  Isolation
    7. 6  Power Management (6 to 60-V DC Power Supply)
    8. 7  CAP and QEP interfaces
    9. 8  Enhanced Controller Area Network (eCAN)
    10. 9  High-Resolution and Synchronized ADCs
    11. 10 DRV8323R
    12. 11 Feedback Stage
      1. 11.1 Torque or Commutation Loop
      2. 11.2 Speed Loop
      3. 11.3 Position Loops
    13. 12 Conclusion
    14. 13 About the Author
    15. 14 References
  2.   Revision History

2.2 Working of the BLDC Motor

The starting-current setup in the circuit through the stator windings sets up a magnetomotive force (mmf) which is perpendicular to the main mmf set up by the permanent magnet. According to Fleming’s left-hand rule, a force is experienced by the armature conductors. As the armature conductors are in the stator, a reactive force develops a torque in the rotor. When this torque is more than the load torque and frictional torque, the motor begins rotating. The process of removing current from one circuit and giving it to another circuit is known as commutation.Figure 3 shows the phase current and developed torque in the BLDC motor. In every case there are two phases that are contributing to positive torque and one phase contributing to zero torque. If the torque of each commutation interval is combined, the total torque is a contribution of two torques from two phases that are perfectly flat.

working_bldc_slva654.gifFigure 3. Working of BLDC motor

The commutation process is implemented using a microcontroller. The rotor position must be known for exact commutation. Two methods are used to find the rotor position: sensor control (uses hall effect position sensors) and sensorless control.