Closed Control Loop With Subordinate Control - JUMO 709061/8-01-032 Operating Manual

6.5.2 Closed control loop with subordinate control

2
U control
V1.04/EN/00561071 [Thyristor Power Switch TYA 201]
sponse of the temperature control loop and increases its output level (y
the furnace reaches the original temperature (250 °C) again.
To avoid power variations caused by mains voltage fluctuations, a subordi-
nate control loop is built into the power controllers. The subordinate control
loop immediately counterbalances any fluctuations in the amount of supplied
power. This means that the power controller always provides a power level at
the output (y) that is proportional to its input signal (y
subordinate control loop is shown in Figure .
w
Controller
-
x
A distinction is made between U
most applications. There are, however, some applications where an I
control has advantageous control-loop characteristics (requires recording of
the current in the power controller).
The three different types of subordinate control are described in the following
chapters.
Considering the power Pl
by the voltage on the load, U
Equation 3 shows that, for a constant load resistance, the power in this resis-
tance is proportional to V
A power controller with a U
voltage is proportional to the signal input (e.g. 0 to 20 mA) to the controller.
2
∼
U Eingangssignal des Leistungsstellers
Last
Combining equations 5 and 4, we can see that the power in the load resis-
tance is proportional to the input signal to the power controller.
6 Special device functions
power controller
y
R
subordinate
control loop
2 2
, I , and P control loops. V
in a resistive load, we know that it is determined
oad
and the resistance of load, R, as follows:
load
2
U
Last
P =
------------ -
Last
R
2
.
load
2
∼
P U
Last Last
2
control will regulate so that the square of the load
). The principle of an
R
Voltage supply
SCR
y
2
control is used in
) until
R
Controlled
system
Sensor
2
or P
(3)
(4)
(5)
85