CHAPTER IX 



SYNCHRONOUS MOTORS IN LOCAL DISTRIBUTION 



SYNCHRONOUS motors are most valuable for control- 

 ling the voltage of long transmission lines. For this pur- 

 pose, as has been shown, it is economical to purchase 

 large synchronous machines and run them without 

 mechanical load, merely for the sake of their reactive 

 current. Where the distances of transmission are shorter, 

 the economies produced by synchronous motors are not 

 so great, but it is often possible to utilize the controlling 

 features of motors which are driving mechanical loads. 

 This is done by giving a bonus to energy consumers who 

 install synchronous motors and operate them correctly. 

 The bonus can be made automatic by the installation of 

 certain instruments and the insertion of power-factor 

 clauses in the power contracts. 



With long transmission lines, voltage control is of 

 great value largely because there are limitations to the 

 use of high voltage and, as has been shown, voltage 

 variation is the chief difficulty when the voltage is low 

 in proportion to the distance of transmission. With 

 short distances, other difficulties become prominent, and 

 among these are the disadvantages of low power-factor 

 due to the wide-spread use of induction motors. 



In the early days of the central station industry, the 

 loads supplied were composed almost entirely of incan- 

 descent lamps, and were of practically 100 per cent 



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