122 THE DIRECT-CURRENT MOTOR CH, V 



cally it will run equally well at any speed, since the 

 terminal tension is not fixed. 



The practicability of this system depends entirely 

 upon the design of the automatic governor. Power trans- 

 missions on the constant-current principle are now being 

 successfully worked with the aid of the Thury regulator, 

 an account of which may be found in the ' Electrician ' of 

 March 19, 1897. This regulator will keep the speed 

 variation within one-half per cent, from no load to full 

 load. In Genoa, 1,400 horse-power is transmitted for a 

 distance of twenty miles on this system. 



Example 30. At Chaux-de-Fonds, where the in- 

 stallation contemplates a tension of 14,400 volts being 

 used over a distance of 30 miles, the current employed is 

 150 amperes. Fora motor running at 600 r.p.m., with 

 a load of 1,200 inch-pounds, M must be 56'8, and if 

 J?=0'003, the terminal tension would be 57'2 volts, and 

 the output would be 11 *4 horse-power. 



