An Overview of the Converter
2-1
590+ Series DC Digital Converter
2
A
N
O
VERVIEW OF THE
C
ONVERTER
How it Works
Note:
Refer to Chapter 9: “Control Loops” for a more detailed explanation.
In
very
simple terms, the Converter controls the dc motor with the use of
Control Loops
- an
inner Current Loop and an outer Speed Loop. These control loops can be seen in the
Application Block Diagram. The block diagram shows all the Converter’s software connections.
Using the Operator Station, you can select the control loops to be used by the Converter to
provide either:
x
Current Control
x
Speed Control (default)
It is usual to supply a Current or Speed Feedback signal to the appropriate loop for more
effective control of the Converter. Current Feedback sensors are built-in, whereas Speed
Feedback is provided directly from the armature sensing circuit (default), or by tachogenerator,
encoder or Microtach connection to the relevant option board.
When in Speed Control,
you can modify the
performance of the
Converter further by
controlling the motor
field, i.e. Field Control.
By weakening the field
current, you can obtain
an increase in motor
speed beyond that
normally achievable for
the rated Armature
Voltage of the dc motor.
The Converter is controlled remotely using digital/analog inputs and outputs, or locally using
the Operator Station.
By plugging in a COMMS Option Technology Box, the Converter can be linked into a network
and controlled by a PLC/SCADA or other intelligent device.
Field Current 5.7A
Voltage 200V
Speed
speed increase
due to field
weakening
armature voltage
remains constant
field current
reduced
base
speed
Armature
REMOTE START/STOP
REMOTE
LOCAL START/STOP
LOCAL
SPEED CONTROL
SPEED CONTROL
DEFAULT
SPEED SETPOINT
SPEED SETPOINT
LOCAL CONTROL
REMOTE CONTROL