Automation and Drives - SCE
2.6 Controlled Systems without Inherent Regulation
The controlled variable continues to grow after a fault, without aiming for the high range value.
Example: Level Control
In the case of a container with a drain whose inflow volume stream and outflow volume stream are the same, a constant level is the result. If the flow rate of the inflow or the outflow changes, the liquid level rises or falls. The larger the difference between inflow and outflow, the faster does the level change.
The example shows that in practice, the integral action usually has limits. The controlled variable rises or fills up only so long until it has reached a limit that is contingent on the system: the container overflows or empties, the pressure reaches the plant maximum or minimum, etc..
The figure shows the trend of an I-system when there is an abrupt change of the input variable, as well as the block diagram derived from it.
Block Diagram
If the step function at the input changes into any function xe(t), the following happens:
integrating controlled system
integral coefficient of the controlled system
| Preface | Fundamentals | Discontinuous Action Controller Controller Block (S)FB41 | Setting the System Appendix |
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| T I A Training Document | Page 17 of 64 | Module | ||
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| B3 | |
Issued: 02/2008 |
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| Control Engineering with STEP 7 | ||