Introduction To Heat/Cool Control - ABB C300 Operating Manual

7.3 Introduction to Heat/Cool Control

Cool
Output
(%)
Proportional
Band (Cool)
25.0%
Integral Action
Value (Cool)
Derivative Action Value
Note. Refer to Sections 7.3.2 and 7.3.3 for Crossover Value and Transition
Bandwidth Value examples.
Information.
•
P.I.D. Output –
into two different control elements, one for raising the product temperature (heat
output) and one for lowering the product temperature (cool output).
•
Transition Bandwidth –
the other.
•
Crossover Value –
cool output active. The crossover value is also the centre of the transition and off
hysteresis bands.
•
Output Off Hysteresis Band –
outputs have opposing control actions, i.e. one is direct acting and the other is
reverse. In this configuration both outputs are at 0% within the off hysteresis band.
The band setting is used to prevent oscillation of control changes.
•
Heat/Cool Outputs –
Q Heater = 1.5kW
100
Q Cooler = 0.75kW
90
Max. Cool Output
80
= 75%*
70
60
Output Off
50
Hysteresis Band
40
=15%*
30
20
10
0
0 10 20 30
Crossover
Value
(33%)
0%
is the output value calculated by the controller. The output is divided
used to transfer smoothly from one set of control terms to
defines the changeover point between heat output active and
for the majority of applications the heat and cool
refer to
P.I.D. Output,
Fig. 7.3 Heat/Cool Control – Principle of Operation
Max. Heat
Output = 88%*
40 50 60 70
*User definable limits
P.I.D. Output (%)
Transition
Bandwidth
20%
above.
7 CONTROL LEVEL...
100
Heat
Output
(%)
0
80 90 100
100%
Proportional
Band (Heat)
20.0%
Integral Action
Value (Heat)
Derivative Action
Value
25