Niagara Falls 



1894 Before finally deciding on what system of transmission to use, 



•* the Cataract Construction Company asked for plans for a system 

 for the purpose from a number of electrical engineering estab- 

 lishments. Twenty-four distinct ones were submitted, more than 

 one of the tendering companies having sent several different plans 

 to be chosen from. No individual one was, however, accepted 

 in toto, but instead a design was adopted embodying such points 

 of value as could be assembled in one suitable type of machine, 

 and the Westinghouse Company received the contract for it. 

 The system on which the generators work is the Tesla two-phase, 

 and is notably peculiar on account of the low periodicity of 

 alternation. 



The number of pulsations of commercial alternating currents 

 is usually over one hundred per second and is frequently double 

 that amount. The reasons for this high frequency are mainly 

 two: The first, that with any given alternating-current dynamo 

 the number of alternations depends directly on the speed, and, 

 as this must usually be high in order to get as much work as pos- 

 sible out of the machine, the periodicity is also high. The second 

 reason is that in lighting work it is, of course, highly undesirable 

 to employ a current of which the pulsations are so slow as to 

 leave the incandescent filament or the arc visibly dimmer between 

 separate beats, as we may call them, than during the passage of 

 the full current strength. In the case in hand one is impressed 

 with the effort that has been made to steer a middle course in 

 the design of the generators so as to obtain a portion of the advan- 

 tage of the direct current for motor work and of the alternating 

 for transformation. The periodicity for the first portion at least 

 of the electrical equipment is to be as low as twenty-five per 

 cent, and this at once limits the scope of the use of the current 

 in the matter of electric lighting. Prof. Forbes states that light- 

 ing by the current direct is a comparatively small portion of the 

 work in contemplation, and that the plant is rather to be regarded 

 as essentially for power distribution. The expression, " lighting 

 by the current direct," is used because a very important branch 



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