Kapp Regulation Diagram of a Transformer and Its Uses

Kapp regulation diagram (or in short Kapp diagram) - a graphical method of determining the voltage regulation in a transformer caused by changes in load and power factor.

The Kapp diagram is helpful in finding the voltage reduction or increase (voltage regulation).

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

Figure: Kapp’s Diagram

Load current (I2) is taken as a reference phasor. OA representing V2 is drawn at angle θ2 with I2. AB represents I2R02 drawn parallel to I2, whereas BC represents I2X02 drawn perpendicular to AB, i.e., I2. Here OC represents secondary emf (0V2 = E2) at no-load. 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 I2Z02. With O as a centre and OA as a radius, 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. 

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 cosθ is represented by AH, which is the intercept between the two circles.

You may know the details about the electrical transformer from the following articles:

 

1. Working Principle of Transformer;
2. Transformer Construction;
3. Core-type Transformers;
4. Shell-type Transformers;
5. Elementary Theory of an Ideal Transformer;
6. E.M.F. Equation of Transformer;
7. Voltage Transformation Ratio;
8. Transformer with losses but no Magnetic Leakage;
9. Transformer on No-load;
10. Transformer on Load;
11. Transformer with Winding Resistance but no Magnetic Leakage;
12. Equivalent Resistance;
13. Magnetic Leakage;
14. Transformer with Resistance and Leakage Reactance;
15. Simplified Diagram;
16. Total Approximate Voltage Drop in Transformer;
17. Exact Voltage Drop;
18. Equivalent Circuit Transformer Tests;
19. Open-circuit or No-load Test;
20. Separation of Core Losses;
21. Short-Circuit or Impedance Test;
22. Why Transformer Rating in KVA?;
23. Regulation of a Transformer;
24. Percentage Resistance, Reactance, and Impedance;
25. Kapp Regulation Diagram;
26. Sumpner or Back-to-back-Test;
    
27. The efficiency of a Transformer;
28. Condition for Maximum Efficiency;
29. Variation of Efficiency with Power Factor;
30. All-day Efficiency;
31. Auto-transformer;
32. Conversion of 2-Winding Transformer into Auto-transformer;
33. Parallel Operation of Single-phase Transformers;
34. Questions and Answers on Transformers;
35. Three-phase Transformers;
36. Three-phase Transformer Connections;
37. Star/Star or Y/Y Connection;
38. Delta-Delta or ∆/∆ Connection;
39. Wye/Delta or Y/ Connection;
40. Delta/Wye or ∆/Y Connection;
41. Open-Delta or V-V Connection;
42. Power Supplied by V-V Bank;
43. Scott Connection or T-T Connection;
44. Three-phase to Two-Phase Conversion and vice-versa;
45. Parallel Operation of 3-phase Transformers;
46. Instrument Transformers;
47. Current Transformers;
48. Potential or Voltage Transformers.