Motorola M68HC08 Reference Manual page 28

BLDC Motor Control
Designer Reference Manual
28
Freescale Semiconductor, Inc.
I
d0
+
u /2 S
=
d
-
+
u /2
=
S
d
-
Figure 3-5. Power Stage — Motor Topology
The second goal of the model is to find how the motor characteristics
depend on the switching angle. The switching angle is the angular
difference between a real switching event and an ideal one (at the point
where the phase-to-phase back-EMF crosses zero).
The motor-drive model consists of a normal 3-phase power stage plus a
brushless dc motor. Power for the system is provided by a voltage
source (U ). Six semiconductor switches (S
d
elsewhere, allow the rectangular voltage waveforms (see
be applied. The semiconductor switches and diodes are simulated as
ideal devices. The natural voltage level of the whole model is put at one
half of the dc-bus voltage. This simplifies the mathematical expressions.
BLDC Motor Control
For More Information On This Product,
Go to: www.freescale.com
S
At
Bt
I
S
Ab Sa
Bb
u u
VA AB
u
VB
u
Sb
u
0
u
Sa
u
u
La
u
Ra
A
S
Ct
I
S
Sb
Cb
u
BC
u
VC
u
CA
B
u
Rb
u
Lb
u
backEMF b
O
u
backEMF c
u
backEMF a
Lc
u
u
Rc
Sc
C
), controlled
A/B/C t/b
Figure
DRM028 — Rev 0
MOTOROLA
I
Sc
3-2) to