Application Guidelines
50
SECTION
VIII-
APPLICATION GUIDELINES
8.1
Torque
Sharing
Operation of
BRU-Series
Drives
8.
1.1
General Description
The BRU-Series drives
pro
vide the capability
to
operate in a torque-sharing mode
for
applications where
multiple motor shafts are rigidly coupled together
to
dr
iv
e a common load. The torque sharing
configuration may be used with either servo
or
spindle drives.
The torque sharing mode would typically be used in situations where:
1.) A lead screw
or
shaft is driven from each end;
2.) Two
or
more lead screws
must
be
driven;
3.) Drive train torque must be distributed
to
protect the machine mechanics.
Some
of
these cases are illustrated in Figure
8-1
.
The
BRU
-Series servo drives provide a flexible microprocessor-based control which allows operation in the
torque sharing
mode
without requiring additional external hardware. All setup and tuning changes can
be
made using a serial terminal, so there are no components
to
change and
no
potentiometers
to
adjust.
8.1.2 Theory
of
Operation
The torque sharing mode requires that one drive (designated as
th
e master drive) operates
as
a velocity
controller, and one
or
more drives (referred
to
as slave drives) operate as torque controllers. A serial
terminal is used
to
set the mode, scaling, and tuning parameters. Detailed instructions for setup of the
drive using the terminal can
be
found in Section 5
.2.
3.2.
The torque signal (MCO) from the master drive
is
used
as
the command
for
the slave drive. This is a ± 10
Volt signal, where 10 V corresponds
to
the peak current
of
the master drive.
For
example, if a BRU-500
DM
-
50
is used
as
the master drive, a 10 Volt MCO signal corresponds
to
50 amps of
motor
current, and the
polarity
of
the MCO signal determines whether positive
or
negative torque is produced. The scali
ng
of
the
MCO output from the master drive is then 5 Amps per Volt (AjV). The command scali
ng
of
the slave drive,
operating in torque
mode
, is also in
AfV
. For equal sharing
of
the torque, the slave command scaling is set
to
the same value
as
the master drive MCO scaling.
NOTE: If the master and slave motors
ha
ve different torque constants (Kt
),
this
mu
st
be
taken into
account when determining the slave command scali
ng
in order
to
obtain equal torque
sharing.
B
RU-
20
0/B
RU-500 Brushl
ess
Drives In
str
uction Manual
(
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