SYNCHRONOUS MOTORS IN LOCAL DISTRIBUTION 61 



cause, when they are operated as voltage regulators, they 

 also furnish good service as power-factor correctors. 



Where voltage variation is troublesome, the supply 

 company wishes synchronous motors to be installed and 

 adjusted for constant voltage, since this reduces the in- 

 vestment in power lines and feeder regulators. This 

 result could be obtained by paying a definite amount as 

 a bonus for each Kva. of synchronous motors available 

 for power-factor control. With isolated customers this 

 would be all that was necessary, since if they did not 

 adjust their voltage properly, they would be practically 

 the only sufferers. In general, however, it would be 

 necessary to impose penalties for poor voltage adjust- 

 ment, as shown by a graphic voltmeter, since poor 

 adjustment by one customer would be detrimental to 

 the service of neighboring customers, and to the opera- 

 tion of the entire transmission system. 



A common method of insuring that synchronous mo- 

 tors are always correctly adjusted for constant voltage 

 is to equip them with automatic voltage regulators, 

 which operate in the same way as with A. C. gener- 

 ators. Although some care must be taken not to 

 reduce the excitation of the motors enough to make 

 them unstable, this method is frequently used and gives 

 successful operation. 



In conclusion, the most advisable power-iactor clause 

 for power contracts under average conditions is merely 

 to give a bonus for the installation of synchronous mo- 

 tors in proportion to the reactive Kva. which they 

 can furnish, and to impose penalties when a graphic 

 voltmeter shows that they are not adjusted for con- 

 stant voltage. 



