xii LIST OF ILLUSTRATIONS 



II... IIIIK. I'X'.K 



20.21. Types of Sections of Transformer Ooree .... 45 

 22 '2'). Types of Sectioiis of Transformer Corel .... Hi 

 L'i. CJore Section for Elliptical-shaped Ooil . . .46 



27. Curvr> showing tin- llelation between the Output and the Wilth 



t' Winding S]ure 47 



28. Section of 20-kw 5000 -JOO- volt Transformer Core (Dimensions 



in Centimeters) 48 



29. Section of Winding and Core of 20-kw 5000/200-volt Trans- 



former (Dimensions in Centimeters) . . . . .49 



30. Simple Concentric Winding . . . . . . >~>\ 



31. Triple Concentric Winding 51 



32. Sandwich Winding ... . . . . .52 



33. Simple Concentric Winding with Subdivided Primary . . .~>'2 



34. 35. Curves showing Relation between Space Factor of Winding 



Window and Rated Output for Various Primary Voltages 

 (Fig. 34, Rectangular Core Section; Fig. 35, Cruciform 



Core Section) ><J 



Sketch of Core for 20-kw 5000/200-volt 50-cycle Transformer . 58 

 Annual Efficiencies of 20-kw Transformers at Various Load 



Factors .......... 63 



38. Profit to Electricity Supply Company in per cent, of Cost of 



Power supplied to 20-kw Transformers at Various Load 

 Factors ' . <>(> 



39. No-Load Current Diagram 69 



40. Curve showing Variation of Power Factor with the Load for 



a 20-kw Transformer ........ 72 



41. 42. Characteristic Curves of 20-kw Transformer (Fig. 41, Con- 



Loss = 190 watts; Copper Loss =360 watts. Fig. 42, Core 

 Loss =360 watts; Copper Loss =190 watts) . . . 73 



43. Curves showing the Relation between the No-Load Current 



and the Rated Output for Transformers having (a) High 

 Grade and (b) Ordinary Grade Laminations ... 75 



44. Curves showing the Relation between the Iron Loss and the 



Rated Output for several Lines of Designs for different 

 Periodicities by Various Firms A, B, C, D and E . . 76 



45. 46. Curves showing the Influence of Varying the Periodicity 



and Primary Pressure upon the Core Loss and No-Load 



( 'in-rent of a 20-kw Transformer 77 



47. Curves showing the Relation between the Regulation and 



the Rated Output for several Lines of Designs for 

 Different Periodicities by Firms A, B, ( 1 and D . . . 79 



48. Curves showing ratio of Labour Cost to Cost of Active 



Material for Natural Air-cooled and Oil-cooled Trans- 

 formers NO 



1!>. Outline Drawing showing the Arrangement of the Windings 



of the 20-kw 5000/200-volt Transformer . . . . 82 



