THE REGULATION OF TRANSFORMERS 101 



The result indicates that in order to send full-load current of 

 100 amperes through the short-circuited secondary of our 

 20-kva transformer, a primary pressure of 1 % 2"> volts will be 

 required. 



Let us study the influence of the two component drops on 

 the regulation of a tran>former. In actual practice these 

 components constitute but a very small percentage of the 

 terminal pressure, but for our examination of the subject, it 

 will be preferable to take a case in which the component drop- 

 are quite considerable. Let the transformer have a 1 : 1 ratio of 

 transformation and let the secondary pressure be 100 volts at 

 no load. Then at no load the primary pressure will also be 



too 



: 



1 i;. 59. Transformer diagram with no reactance, but with an I R drop of 



l."i per criit. 



100 volts. Let the resistance drop at full load be 15 per cent, 

 of the secondary pressure. 



If the transformer had no reactance drop, then in <>i 



t.i have, at full load and unity power factor, a pressure of 100 



the terminals of the secondary winding, it would he 



necessary to apply a pressure of 115 volts at the terminals of 



winding. Or if at all loads we maintain a OOn- 



' pressure of 115 volts at th< trrminals of the primary 



windiiiL'. thru as the load is ii; the pressure at the 



terminals of the secondary winding (which is 115 volts at no 



load) will gradually decrease until at full load the secondary 



will only b- 100 rolt& Thi- is >hown dia-rammat ieally 



in 1 .id of having a negligible reactance drop 



at full load, , in addition to the resistance drop ,,f 



15 volts, also a reactance drop of 30 volts, then if,-r unity 



power factor of the external < -in -uit supplii <1 ir- -m the 



