Introduction To Heat/Cool Control - ABB C1900 Series Operating Manual

5.10 Introduction to Heat/Cool Control

100
90
80
70
Cool
60
Output
(%)
50
40
30
20
10
0
0
Crossover Value (33%)
0%
Proportional Band
(Cool) 25.0%
Integral Action Value
(Cool)
Derivative Action Value
Note. Refer to Sections 5.10.2 and 5.10.3 for Crossover Value and Transition Bandwidth Value examples.
Information.
• PID Output – is the output value calculated by the controller. The output is divided into two different control elements one
for raising the product temperature (heat output) and one for lowering the product temperature (cool output).
• Transition Bandwidth – used to transfer smoothly from one set of control terms to the other.
• Crossover Value – defines the changeover point between heat output active and cool output active. The crossover value
is also the centre of the transition and off hysteresis bands.
• Output Off Hysteresis Band – for the majority of applications Outputs 1 and 2 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 – refer to PID Output, above.
Q Heater = 1.5kW
Q Cooler = 0.75kW
Max. Cool
Output = 75%*
Output Off
Hysteresis Band
=15%*
10 20 30 40
Transition
Bandwidth
20%
Fig. 5.18 Heat/Cool Control – Principle of Operation
Max. Heat
Output = 88%*
50 60 70
*User definable limits
PID Output (%)
5 CONTROL OPERATION...
100
Heat
Output
(%)
0
80 90 100
100%
Proportional Band
(Heat) 20.0%
Integral Action Value
(Heat)
Derivative Action Value
31