Motorola M68HC08 Reference Manual page 14

Introduction
Designer Reference Manual
14
Freescale Semiconductor, Inc.
Once using the semiconductor components, it is opened to replace
classical universal and DC-motors with maintenance-free electrically
commutated BLDC motors. This brings many advantages of BLDC
motors when the system costs could be maintained equivalent.
The advantages of BLDC motor versus universal and DC-motors are:
• high efficiency
• reliability (no brushes)
• low noise
• easy to drive features
To control the BLDC motor, the rotor position must be known at certain
angles in order to align the applied voltage with the back-EMF, which is
induced in the stator winding due to the movement of the permanent
magnets on the rotor.
Although some BLDC drives uses sensors for position sensing, there is
a trend to use sensorless control. The position is then evaluated from
voltage or current going to the motor. One of the sensorless technique is
sensorless BLDC control with back-EMF (electromotive force)
zero-crossing sensing.
The advantages of this control are:
• Save cost of the position sensors & wiring
• Can be used where there is impossibility or expansive to make
additional connections between position sensors and the control
unit
• Low cost system (medium demand for control MCU power)
Introduction
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Go to: www.freescale.com
DRM028 — Rev 0
MOTOROLA