# Kapp’s Regulation

Kapp had designed a diagram shown in Figure 1.42 to determine the regulation at any power factor. The description of the construction of the diagram is shown below.

**Figure 1.42** Kapp’s Diagram

Load current (*I*_{2}) is taken as a reference phasor. OA representing *V*_{2} is drawn at angle *θ*_{2} with *I*_{2}. AB represents *I*_{2}*R*_{02} drawn parallel to *I*_{2}, whereas BC represents *I*_{2}*X*_{02} drawn perpendicular to AB, i.e., *I*_{2}. Here OC represents secondary emf (_{0}*V*_{2} = *E*_{2}) at no-load. The circle 1 known as often circuit EMF circle is drawn with O as centre and OC as radius. The line OO^{′} is drawn parallel to AC representing *I*_{2}*Z*_{02}. With O^{′} as centre and OA as radius, the circle 2 known as terminal voltage circle is drawn, which intersects with circle 1 at the points D and E. The region above and below the reference line represents the lagging and leading power factors region, respectively. The point D is the point corresponding to zero regulation. The intercept FG gives the maximum regulation, which is drawn through O and drawn parallel to AC. The regulation at any power factor angle *θ* is obtained by extending OA to meet the outer circle at H. The regulation at the required power factor cos*θ* is represented by AH, which is the intercept between the two circles.