Eurotherm Drives 590 DRV Digital, Product Manual, Page: 308 / 318

590 DRV Digital DC Drive Product Manual
App. M - 28
Appendix M Special Blocks and Application Notes
M
Tension
Draw controls speed but does not directly control tension. Tension
control uses an outer control loop to adjust the section speed. The
loadcell provides the feedback signal for the control loop. Speed is
adjusted to keep the feedback signal from the loadcell at a fixed value,
the tension setpoint.
Dancer Position
Dancer position control also uses an outer control loop to adjust the
section speed. The dancer applies force to the web throughout its
range of movement. Loading the dancer, usually by using pneumatics,
determines the force and therefore the tension in the web. To keep the
web tension constant, the drive section must control the web speed so
that the dancer stays in a fixed position.
Additional Features
Line sections often require additional control features. The SC con-
figuration has the following features built in. See the "Using Section
Control" section for details on their use.
Reverse
Reversing allows sections such as coaters and laminators to reverse directions to accomodate a web path change to
coat the other side of the web.
Anti-reverse
Anti-reverse is requried where reversing a section may cause mechanical damage to the machine or may be hazardous
to the operator.
Agitate
Agitate or Sunday drive is a feature used for coater and printer sections to keep the coater turning at a low speed when
the line has stopped to prevent the coating material from solidifying.
Slack Take-up/pay-out
A line in draw control, such as a paper machine, can be difficult to get running. It often needs the ability to speed up or
slow down one section relative to another to remove loops of slack web without disturbing the preset draw. Slack take-
up offers this capability. Similarly, pay-out allows the operator to introduce slack in the web, for example when per-
forming a splice.
Jog
Many sections need individual jog for positioning, clearing wrap-ups, or cleaning.
Ramp
A section ramp, independent from the main line ramp, allows an individual section to accelerate gradually. This per-
mits it to speed up to match the main line and to decelerate smoothly as required by the process.
Figure M.22 - Tension
Figure M.23 - Dancer Position