Trust Automation, Inc. TA333 High Power Linear Servo Amplifier
10-Apr-09 Page 9 of 38
1.4 Command Input
Motion command connections to the TA333 are made at J3. Inputs are provided for two of the three
phases (A and B) and the TA333 can derive the third phase (C = - (A+B)) in sinusoidal applications.
The inputs are common mode terminated at 10K and there is no need to ground an input if it is unused.
The input range is set to ±10V commands.
Differential Inputs
Using differential input helps reduce or eliminate potential noise susceptibility from other sources.
Connect the motion controller ± command outputs to the TA333 ± inputs at J3. For best immunity use a
twisted pair cable. Terminate the motion controller signal ground to the TA333 ISO ground connection
at J3. (See application examples 5.1)
Single-Ended Inputs
Many motion controllers only offer single-ended command signals with a common ground. Single-
ended configurations are accommodated by referencing the A+ and B+ signals to the command output
and referencing the A- and B- signals to the motion controller signal ground. It is good practice to use a
twisted pair cable for the “+” command, terminating the “-” command at the controller signal ground.
Terminate the motion controller signal ground to the TA333 ISO ground connection at J3.
(See application example 5.2)
1.5 Upgrading from a TA320 or TA330
When changing a preexisting application from a TA320 or TA330, the command signal polarity must be
reversed to maintain the applications direction of motion.
The original TA320 and TA330 linear amplifiers operated with inverted outputs, meaning a positive
command induces a negative current. The TA333 is a non-inverting amplifier (positive command =
positive current).
Examples:
• Differential inputs would place the motion controller’s “+” signal on the TA333 “–” command
input and the controller’s “–” signal on the TA333 “+” command input.
• Single-ended configurations place the motion controller’s command output on the TA333 “–”
command inputs and terminate the TA333’s “+” command inputs to the motion controller’s
signal ground and the TA333 ISO ground connection.
1.6 Transconductance Ratio
The TA333 operates in current mode (commonly referred to as Torque mode). For a given input
voltage, the TA333 will output a proportional current by raising the output voltage until the commanded
current is drawn. As current flow in a motor is directly proportional to torque, it is common to refer to this
as “Torque mode”. The ratio between the command voltage and the output current is referred to as the
“Transconductance Ratio,” which is measured in amps per volt and is expressed by the following
equation:
g
m
= I
o
/ V
c
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