West Control Solutions Pro-EC44 - Manual (Page 86)

Pro-EC44 2-Loop Graphical Profile Controller & Recorder
Pro-EC44 Product Manual - 59540-1 October 2013 Page 79
the slave setpoint. The oil temperature is reduced towards the new slave setpoint. This
continues until the system becomes balanced. The result is quicker, smoother control with
the ability to cope with changes in the load. Overshoot is minimised and the jacket
temperature is kept within acceptable tolerances.
Normal Cascade Operation
During operation, the master and slave are coupled together and. "Cascade" is displayed.
The master process value and setpoint are most relevant to the user. The master setpoint is
directly adjustable. The process value of the slave controller is displayed for information only.
Cascade-Open
The cascade can be disconnected (via digital inputs or menu selection), switching from
normal operation to direct control of the slave. "Cascade-Open" is displayed. Opening the
c
ascade is “Bumpless”. The current cascade value is used as the initial slave setpoint
(displayed as “SlaveSP”). The process is then controlled and adjusted solely by the slave
controller using this setpoint. Switching back to Cascade is also bumpless.
CAUTION: The master process value is not under control when the
cascade is open, but will be affected by the slave process. The operator is
responsible for maintaining safe conditions.
Manual Mode
The controller can be put into manual mode (via digital inputs or menu selection), switching
from normal operation to direct control of the slave loop’s correcting variable. Manual power
is adjusted from 0% or -100 to 100%. "MAN" is displayed.
CAUTION: Manual mode disables the cascade loop. It also ignores any
output power limits, valve open/close limits and the control enable/disable
setting. The operator is responsible for maintaining the process within safe
limits.
Cascade Tuning
The user can tune the slave and master loops manually, or use the pre-tune feature (see
Controller Tuning on page 99).
In either case the slave control loop must first be optimised on its own, followed by the
master loop in combination with the previously tuned slave.
To automatically pre-tune a cascade:
1. Go to the Automatic Tuning menu
2.
Select “Cascade-Open” from the pre-tune menu to tune the PID set(s) on the slave.
3. After the slave has successfully tuned, pre-tune the master/slave combination by
selecting “Cascade-Closed” from the pre-tune menu.
Note: The cascade remains open until you pre-tune the master or manually
select Cascade-Closed.