DRM028 — Rev 0
Designer Reference Manual
MOTOROLA
BLDC Motor Control
23
Designer Reference Manual — Sensorless BLDC Motor Control
Section 3. BLDC Motor Control
3.1 Contents
3.2
Brushless DC Motor Control Theory. . . . . . . . . . . . . . . . . . . . . 23
3.3
Used Control Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.4
Application Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.2 Brushless DC Motor Control Theory
3.2.1 BLDC Motor Targeted by This Application
The brushless dc motor (BLDC motor) is also referred to as an
electronically commutated motor. There are no brushes on the rotor, and
commutation is performed electronically at certain rotor positions. The
stator magnetic circuit is usually made from magnetic steel sheets.
Stator phase windings are inserted in the slots (distributed winding) as
shown in
Figure 3-1
, or it can be wound as one coil on the magnetic
pole. Magnetization of the permanent magnets and their displacement
on the rotor are chosen in such a way that the back-EMF (the voltage
induced into the stator winding due to rotor movement) shape is
trapezoidal. This allows a rectangular shaped 3-phase voltage system
(see
Figure 3-2
) to be used to create a rotational field with low torque
ripples.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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