CHAPTER IX. 

 ELECTRIC DISTRIBUTION AND WIRING. 



111. Series and parallel systems of distribution. The con- 

 stant-voltage method of electrical distribution is briefly discussed 

 in Art. 41 and the system of connecting lamps and motors in 

 parallel between the supply mains in the carrying out of the 

 constant-voltage method is shown in Fig. 69. This is called the 

 parallel system of distribution. The constant-current method of 

 electrical distribution is also briefly discussed in Art. 41, and the 

 system of connecting lamps in series in the carrying out of the 

 constant-current method is shown in Fig. 68. This is called the 

 series system of distribution. The parallel system of distribution 

 is used in the great majority of electric installations both for 

 direct current and for alternating current. In the case of alternat- 

 ing-current distribution the use of transformers, and especially the 

 employment of several phases of voltage and current, complicates 

 the scheme of connections to some extent as described in the 

 second volume of this text. The series system of distribution is 

 generally used for street lighting in cities and in some cases for 

 power transmission by series generators and motors.* 



Combinations of series and parallel connections, (a) Connection 

 of series-groups in parallel. When the voltage of supply in the 

 constant-voltage method of distribution is greater than can be 

 conveniently used for operating single lamps, the lamps are usually 

 arranged in groups, each group consisting of a number of lamps 



*Thury's System of Direct-current Power Transmission. See London Electrician. 

 Vol. 38, pages 683-687, March 19, 1897; Zeitschrift fur Electrotechnik (Vienna), 

 Vol. 1 6, pages 5-10, 1898 ; Bulletin de la Societe International des Electriciens, 

 Vol. 17, pages 9-93, January, 1900; and Electrical Review (New York), January, 

 1901. 



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