Chromalox 1020 User Manual

32
12 Extrusion Model Only Features
12.1 Non-Linear Cooling Function
The initial cooling effect with water cooling can be
very strong when water first flows into a hot process.
Evaporation extracts significant amounts of heat en-
ergy making the effective cooling power dispropor-
tionally high at nominally low levels of cooling output.
This makes process control more difficult, particularly
if “over-cooling” during the transition from heating to
cooling causes the heating to be reactivated. Non-Lin-
ear Cooling can be used to counteract these effects by
applying the cooling more gradually at first.
To enable the Non-Linear Cooling function the Output
1, Output 2 or Output 3 Usage parameter needs to be
set to Non Linear Cooling.
>Output 1
Usage
Heat Power
Cool Power
Non Linear Cooling
Alarm 1
Alarm 2 Alarm 1 or 2
Loop Alarm
Heat Power
This table lists the Control sub-menu parameters re-
lated to non-linear cooling.
Title Description
Minimum
Cooling
The minimum temperature for non-
linear cooling to operate
Impulse
Length
The fixed “On” pulse duration with
non-linear cooling
Minimum Off
Time
The minimum “Off” duration with
non-linear cooling
Non-Linear
Adjust
Adaptation of characteristics of the
non-linear cooling
12.2 Method
The cooling characteristic is altered so that the control-
ler output is weak until approximately 70% of nominal
cooling demand. Beyond this level, the correcting vari-
able rapidly rises to the maximum cooling allowed.
Cooling is inhibited entirely until the Minimum Cool-
ing temperature has been exceeded. After that it turns
ON with fixed duration pulses (adjustable with Impulse
Length parameter). The OFF time between pulses is
varied to adjust the cooling effort, but is never off for
less than Minimum Off Time value whenever cooling is
active. This ratio limits the maximum effective cooling.
The maximum effective cooling is calculated as fol-
lows:
Impulse Length + Minimum Off Time
Max Cooling= x 100%
Impulse Length
The Non-Linear Adjust parameter can be reduced if the
corrective action is too severe by reducing the non-lin-
earity of the effective output. See the examples below.

Chromalox 1020 Specifications

General

Brand	Chromalox
Model	1020
Category	Temperature Controller
Language	English