88 THE DIRECT-CURRENT MOTOR CH. IV 



torque loss of 7,210 watts in the generator. If expressed 

 as torque, we find that it amounts to 5,800 inch-pounds. 

 (Compare the results of tests of a 200 k.w. generator at 

 the Nice Central Lighting Station, described in the 

 'Industrie Electrique' for October 10, 1896, where the 

 losses were given as follows : c 2 R loss, 3*75 k.w. ; hysteresis 

 and eddy loss, 7 '83 k.w.) 



When two coupled motors with constant induction 

 factors have their armatures connected in series, the effect 

 is as if there were one motor with an induction factor 

 equal to the sum of the two. Thus two motors with 

 induction factors of 6 and 4 placed in series will act as a 

 single motor with an induction factor of 10, the resistance 

 being the sum of the two resistances. 



We have already seen that when two motors are 

 connected in parallel, the combination acts as one motor 

 with an induction factor equal to the mean of the two 

 induction factors if the resistances are equal. Hence we 

 have the following possible combinations of two 

 motors, enabling us to get as many different speeds as 

 there are combinations. 



Let the induction factors be 6 and 4 respectively, the 

 resistances equal, and the tension of the line 120 volts. 



1. A only; maximum speed 1,200 r.p.m. 



2. B only; maximum speed 1,800 r.p.m. 



3. A and B in parallel ; maximum speed 1,440 r.p.m. 



4. A and B in series ; maximum speed 720 r.p.m. 



In this way we can get four different speeds by 

 connecting up two motors in four different ways. If the 

 induction factors were 3 and 5 w r e could get speeds of 

 600, 860, 1,200. and 2,000 r.p.ni. on a tension of 100 

 volts. 



