JUMO TYA 202, Руководство по эксплуатации

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6 Special device functions
74 2011-07-01/00561073 [SCR Power Controller TYA202]
The controller recognizes the deviation through the relatively slow response of
the temperature control loop and increases its output level (yR) until the
furnace reaches the original temperature (250°C) again.
6.5.2 Closed control loop with a subordinate control
To avoid power variations caused by supply voltage fluctuations, a
subordinate control loop is built into the controller system. This makes an
instant correction for variations in the amount of energy provided. The result is
that the power controller always provides a power level (y) at the output that is
proportional to its input signal (yR). The principle of subordinate control loop is
shown in Figure .
A distinction is made between U
2
, I
2
and P control loop. U
2
control is used in
most applications. There are however some applications where an I
2
or P
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
sections.
U
2
control Considering the power PLoad in a resistive load, we know that it is determined
by the voltage on the load, ULoad and the resistance of load, R, as follows:
Equation 3 shows that, for a constant load resistance, the power in this
resistance is proportional to U
Load2
.
A power controller with a U
2
control will regulate in such a manner that the
square of the load voltage is proportional to the signal input (e.g. 0 ... 20mA) to
the controller.
Combining equations 5 and 4, we can see that the power in the load
resistance is proportional to the input signal to the power controller.
Controller
Sensor
Controlled
system
SCR
power controller
Voltage supply
subordinate
control loop
y
R
x
y
w
-
P
Load
U
Load
2
R
----------------- =
(3)
P
Load
U
Load
2

(4)
U
Load
2
Eingangssignal des Leistungsstellers

(5)