Abstract
Different types of automatic regulators can formally be represented by differential equations between the deviation from normal of the controlled variable and the displacement of the power device of the regulator. The equations are derived for the “floating-and-proportional”, the “proportional-position”, the “floating”, and the “first and higher derivative” control, and the characteristics for drooping and non-drooping control are described. The paper shows that identical results may be obtained by self-contained regulators and by control equipment consisting of separate units which may comprise a regulator proper, a servo-motor, and sometimes also one or more impulse transformers. Such composite control equipment has the advantage of greater flexibility, as the same elements may be used in various arrangements producing entirely different control actions.
The regulator equations by themselves give no information on the ultimate behaviour of a regulator, if applied to a particular plant, as this depends just as much on the characteristics of the plant itself. Information regarding stability of control, maximum deviation, and period of oscillation can be obtained only by combining the regulator equation with the equation describing the plant to which the regulator is applied.
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