Motorola M68HC08 manual Bldc Motor Control, Brushless DC Motor Control Theory

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

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.

DRM028 — Rev 0		Designer Reference Manual
MOTOROLA	BLDC Motor Control	23
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