THE TRANSFORMER 



211 



tension coil. This requires 9.1 amp. in the high-side coil which 

 is now acting as primary. The line current from the supply 

 must be 100.1 amp. If the transformer losses are neglected, the 

 power supplied 



Pi = 2,200 X 100.1 = 220,220 watts 

 r delivered 



P 2 = 2,420 X 91 = 220,220 watts 

 power transformed = 91 X 220 = 20,000 watts. 



Assume 97 per cent, efficiency for the transformer. This 

 means that the loss is 0.03 X 20,000 = 600 watts. 

 The efficiency of the system is 

 220,220 



= 99 ' 8 



cent ' 



220,220 + 600 



It is to be noted that a device of this type is very similar to the 

 series booster described in Vol. I, page 304, Par. 204, but that it 

 is much simpler and much more efficient. When an ordinary 

 lighting transformer is used in this manner the low-side winding 

 should be grounded at one point as the insulation between tin* 

 low -ide and core is not designed to withstand full high-side 

 potential. 



91. Transformer Connections. There are several methods of 

 connecting: three-phase transformer banks, as for example, 

 Y-Y, A-A, A-Y, Y-A, V-V, T-T, etc. 



load 



Fio. 201. Y-Y ...im.ti. ,n <>f (r:i reformers. 



in -01 >h<>\\> a Y-Y mmi'Tird transformer hank, which 

 may be either a step-up or a st. p-doun l.;mk. I nl ss the 

 prim;irv ni-uiril i- connected to the ueneratnr neutral, thiscnn- 



" floating" neutral. An 



extreme oaae i> illu-n-at.-d by attempting to place a load from 

 'he n. uti.il on the secondary side. This power must 



