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This amplifier provides a continuous output power rating up to 60 watts
with precise servo control of dc servo motors. Operating from a single
rail supply which enables battery operation if required, the unit utilises
a MOSFET based linear output stage with the following operating
advantages:
•
Virtually zero electrical emissions
•
Improved smoothness of motor operation
•
Increased motor life
•
Suitable for low inductance motors without the need for an
additional choke
The differential amplifier based input stage incorporates control
technology based on many years experience in servo design with the
following features:
•
Adjustable peak output current up to 4 amps
•
Independently adjustable continuous output current up to 2amps
•
Choice of velocity control using armature voltage sensing or tacho
feedback
•
Optional torque control or positional control using analogue
positional feedback signal
•
Plug-in personality header to match the drive to specific motor
characteristics
•
Optional automatic velocity ramp for smooth starts using stepped
input signal change
•
Directionally sensitive end of travel limit signal inputs
•
Remote enable signal input
•
Front panel adjustments of servo loop constants for easy
commissioning
•
Front panel diagnostic LED display of drive condition
•
A mother board (268-1875) is available to facilitate simple
connection of amplifier and wiring.
The amplifier has a linear output stage with an output current
proportional to the input voltage. It is also controlled by an enable input
and directional limit inputs. The enable input may be used to enable or
disable the output. The directional limit inputs may be used to prevent
the output driving in a particular direction and therefore may be used as
end of travel limits. The action of these inputs may be inverted by the
switches SW1-1 and SW1-2 (see set up section).
The current limiting stage limits the output to the stage. The peak
current limit is set by resistor RIPeak on the personalisation header.
The peak current limit is the maximum current output that the amplifier
is allowed to produce. The ratio between the nominal current and the
peak current limit (set as above) is set by the resistor RIRatio. The
nominal current limit should be set less than or equal to continuous
current rating of the motor i.e. the rated stall current.
In use, if a current greater than the nominal is demanded, then this will
be available (bounded by the peak current limit) for a time set by the
time constant. The current drawn above the nominal limit is squared
and accumulated over time, and when this exceeds the time constant
set by the resistor RTConst, the output current will be reduced down to
the nominal level. This will therefore allow short bursts of peak current
for acceleration, but restricts the heating of the motor over longer
periods of use.
This output level is available on the Motor Current output for
monitoring.
If the amplifier is to be used as a torque control, the required current is
input on the required current input with SW1-4 off. The sensitivity is
approximately 0.42A/V.
If velocity control is required, then SW1-4 should be closed and the
required current pin may be used as a monitoring output.
The velocity feedback may be derived from either a motor fitted
tachogenerator or the voltage across the motors armature.
For tachogenerator feedback, fit a resistor RTacho as described in the
setting up section. Do not fit link LK Arm.
For armature voltage feedback, fit link LKArm and a resistor RArm as
described in the setting up section. Do not fit resistor RTacho.
The required velocity command signal should be applied to the
RS Stock No.
differential command inputs. This is then fed through a ramp generator,
controlled by the ramp pot. With this pot clockwise, there will be no
ramping. Turning the pot anti-clockwise will increase the ramp time and
263-6027
therefore reduce the maximum rate of change of the required speed.
The speed signal is then scaled by the MAX SPEED pot. Turning this
pot clockwise will reduce the speed demanded for a given input signal.
Turning anti-clockwise will increase the speed. If you cannot get
enough speed with the pot fully anti-clockwise, then the gain can be
increased by closing switch SW1-3.
The ZERO SPEED pot may be used to set the output speed to zero
when no input is applied.
The PROPORTIONAL and DERIVATIVE pots are used to set the
velocity loop response.
Turning the PROPORTIONAL pot anti-clockwise will increase the loop
gain and turning the DERIVATIVE pot anti-clockwise will increase the
derivative action.
If the derivative response is insufficient, then it can be increased by
fitting a capacitor in the CDeriv position of the personalisation header.
Likewise, the integration function may be increased with CInt.
The pots are all thirty turns from end to end.
ENSURE THAT THE AMPLIFIER IS MOUNTED TO ALLOW
SUFFICIENT AIRFLOW AROUND THE HEATSINK, WITH THE
HEATSINK VANES VERTICAL
Set-up
This amplifier may be set up by DIP switch SW1, the personalisation
header SK1 and the edge mounted pots.
Switch 1
Switch 2
Switch 3
Enable polarity selection
Limit polarity selection
Increase speed scaling
Velocity/Torque control selection
Off
On
Enable Polarity Selection.
Drive DISABLED on applying
+10 to +30V to the enable
input
Drive ENABLED on applying
+10 to +30V to the enable
input
Limit Polarity Selection.
Directional limit activated on
applying +10 to +30V to a limit
input
Directional limit deactivated
on applying +10 to +30V to a
limit input
Increase Speed Scaling.
Normal speed scaling
Enhanced speed scaling
(positional mode)
V10752
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