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Power stage — motor topology, Figure 3-5, The power stage is usually – Motorola M68HC08 User Manual

Page 28: Bldc motor control, Freescale semiconductor, inc

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BLDC Motor Control

Designer Reference Manual

DRM028 — Rev 0

28

BLDC Motor Control

MOTOROLA

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

d

). Six semiconductor switches (S

A/B/C t/b

), controlled

elsewhere, allow the rectangular voltage waveforms (see

Figure 3-2

) to

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.

B

C

A

backEMF b

backEMF c

backEMF a

Rb

Ra

Rc

Lb

Lc

u

u

u

u

u

u

u

La

u

u

u /2

d

=

+

-

u /2

d

=

+

-

u

AB

I

Sa

I

d0

S

At

S

Bt

S

Ct

S

Ab

S

Bb

S

Cb

I

Sb

I

Sc

u

BC

u

CA

u

Sb

u

Sc

u

Sa

u

0

u

VC

u

VB

u

VA

O

F

re

e

sc

a

le

S

e

m

ic

o

n

d

u

c

to

r,

I

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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