Stator Flux Vectors At Six-Step Control - Motorola M68HC08 Manual

BLDC Motor Theory
Designer Reference Manual
22
Freescale Semiconductor, Inc.
Figure 3-6. Stator Flux Vectors at Six-Step Control
The next two figures depict the commutation process. The actual rotor
position in Figure 3-7. Situation Right Before Commutation
corresponds to the Hall sensors' state ABC[011] (see Figure 3-6. Stator
Flux Vectors at Six-Step Control). The actual voltage pattern can be
derived from Table 3-1. Commutation Sequence for
Counterclockwise Rotation. Phase A is connected to the positive
DC-Bus voltage by the transistor Q1; phase C is connected to the ground
by transistor Q6, and phase B is unpowered.
As soon as the rotor reaches a certain position (see
3-7. Situation Right Before
changes its value from ABC[011] to ABC[010]. From
3-1. Commutation Sequence for Counterclockwise Rotation
voltage pattern is selected and applied to the BLDC motor.
As can be seen, using a six-step control technique, there is no possibility
of keeping the angle between the rotor flux and the stator flux precisely
at 90°. The real angle varies from 60° to 120°.
BLDC Motor Theory
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Commutation) the Hall sensors' state
Figure
Table
a new
DRM046 — Rev 0
MOTOROLA