CHAPTER II 



ALTERNATING-CURRENT TRANSMISSION 



ONE of the chief reasons why the electrical develop- 

 ment of the past thirty years has been more rapid than 

 has ever been the case with any other phase of engineer- 

 ing is that electricity offers the cheapest and most con- 

 venient means of supplying energy according to the vari- 

 ous needs and occasions of the users. A consumer can 

 withdraw from a common supply amounts of energy, 

 either large or small, at any time and at almost any loca- 

 tion, which he desires. In this quality of flexibility of 

 application, electricity is superior to steam, gas, shafts, 

 or ropes, for delivering energy. 



The main difficulty connected with most methods of 

 energy transmission is that the form in which the energy 

 is most economically transmitted is quite different from 

 the form in which it must be applied. This is true, also, 

 of electric power, but, fortunately, the transformation 

 from high voltage, which is most suitable for transmis- 

 sion, to low voltage for ordinary application, is very 

 easy and inexpensive. An alternating-current trans- 

 former is one of the most efficient pieces of apparatus 

 built, and one of the cheapest, considering the amount 

 of power passing through it. 



The design of electric circuits is largely determined 

 by the distance between the point of supply and the 

 point of application of energy. For short distances of 

 only a few hundred feet, electric circuits for ordinary 



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