Ropex RES-445 - Principle of Operation

Principle of operation
Page 6 RES-445
•etc.
The use of RESISTRON temperature controllers
results in:
• Repeatable quality of the heatseals under any con-
ditions
• Increased machine capacity
• Extended life of the heatsealing bands and teflon
coatings
• Simple operation and control of the sealing process
3 Principle of operation
The resistance of the heatsealing band, which is tem-
perature-sensitive, is monitored 50x per second (60x at
60Hz) by measuring the current and voltage. The tem-
perature calculated with the help of these measure-
ments is displayed and compared with the set point.
The primary voltage of the impulse transformer is adju-
sted by phase-angle control if the measured values
deviate from the set point. The resulting change in the
current through the heatsealing band leads to a change
in the band temperature and thus also its resistance.
This change is measured and evaluated by the
RESISTRON temperature controller.
The control loop is closed: ACTUAL temperature = SET
temperature. Even minute thermal loads on the heatse-
aling band are detected and can be corrected quickly
and precisely.
The thermoelectric control loop which is formed has a
highly dynamic response because purely electrical
variables are measured at a high sampling rate. A high
secondary current can be controlled with only minimal
power loss because power is controlled on the primary
side of the transformer. This allows optimum adaptation
to the load and to the required dynamic range despite
the exceptionally compact dimensions of the controller.
PLEASE NOTE!
RESISTRON temperature controllers play a significant
role in enhancing the performance of modern
machines. However, the full benefit can only be
obtained from the advanced technology offered by this
control system if all the system components, in other
words the heatsealing band, the impulse transformer,
the wiring, the timing signals and the controller itself,
are compatible with one another.
We will be pleased to
contribute our many
years of experience
towards optimizing your
heatsealing system.
R=f(T)
+
_
Set point
Start
Indicators
and
controls
or
bus interface
Actual value
LINE
RESISTRON controller
Heatsealing band R = f (T)
Current
transformer
Impulse transformer
U
R
I
R
prim.
U
1
sec.
U
2