Stange SE-707 Скачать руководство пользователя страница 120

Страница: 120 / 244

Program Controller SE-707

120

Subject to technical modifications

Control Zone Optimization

In the case of modern, gas-heated industrial furnaces is often worked with high heating power whereby two control technical

problems may occur:

1.)

Break-point at the temperature set value is reached during program execution (beginning of the hold phase):

Here it often comes to substantial overshoots with high performance burners.

2.)

During the furnace is on set temperature the furnace door is opened in order to take out or insert new parts. The

controller heats with full burner capacity against it which leads then in consequence to substantial overshooting of

the furnace temperature and then takes a long time until these increased temperatures are reduced again.

In the following measures are described how to get this behaviour under control with the STANGE SE-707 program controller.
The control zone configuration offers two easy activatable and settable parameter, the “I-Brake”

(description see above)

and the

“PID-ON plus/minus Range”

(description see above)

, which help to achieve a lot. “X-Tracking” is a further parameterizing

possibility

(description see above)

, which makes considerable improvements possible by combination of different device

functions.

1.)

Foresighted controller manipulation at the beginning of the hold phase

Before the hold phase the furnace is typically "run up" with maximum performance in order to reach a short as possible

warm-up time. Afterwards the hold phase begins usually with a “break” in the set value process. Through this break it comes

to a strong temperature overshooting and the controller hardly tries to reduce this overshooting again; particularly because

of today's very well isolated furnaces.
The method of resolution is here a soft "interception" of the set value rise before reaching the hold phase.
For this purpose a tolerance is used in the SE-707 that recognizes if the temperature actual value approaches the target set

value up to a certain measure. Then the X-tracking of the controller is started, this drives the controller set value "softly" up

to the target set value and avoids an overshooting of the furnace temperature to a large extent.
The tolerance value must be large enough in order to enable an interception of temperature within the tolerance range. If

overshooting is still present the tolerance must be selected more largely.
In addition to the tolerance the x-tracking must be configured accordingly; the ramp slope is particularly important. It must

be selected in such a way that the furnace is able to follow the ramp gradient controlled by the controller in any case. The

approximation of controller set value and target set value is still optimizable with the progression factor and interval.
The following graph displays the reaction to a rapid set value ramp: Approx. 50 K before reaching the target set value the X-

tracking intercepts the controller set value (orange curve) and leads it softly to the target set value (red curve) whereby a

regulating without overshooting (green curve) is reached.

Configuration notes on the following page!