CH, V SERIES-WOUND MOTORS 111 



induction factors increases. Now considering the two 

 motors together, the current from the line will dimmish 

 as the speed increases, so that the difference between 

 the induction factors will increase with the speed. If 

 the induction factors were equal, the induced tensions 

 would also be equal and the tension between a and b 

 the same as that between c and d if we increase the 

 induction factor of one motor, say of A, and reduce 

 that of the other, the tension between a and b is greater 

 than that between c and d, since they are running at the 

 same speed, and a current therefore flows from a to c 

 and from d to b. For a certain difference in the induction 

 factors A would be drawing no current and B would be 

 doing all the work. Any further increase in the difference 

 would cause A to generate current ; and only so much 

 more current would be drawn from the line as would be 

 required to make up the increased heat losses. 



If two motors driving a car are connected up in this 

 way, the change in the relative values of the induction 

 factors takes place automatically as the car speeds up. The 

 result is that a large current circulates in the closed circuit 

 acdb, quite independently of the work being done on the 

 car. The difference in the induction curves may be very 

 great, especially if the magnets are made of steel. 



As soon as one motor begins to generate current the 

 torque due to the current resists the rotation of the wheel 

 to which that motor is geared, and when a certain speed 

 is attained the wheel will be suddenly stopped. 



When this difficulty is experienced it will be necessary 

 either to alter the method of connecting the motors 

 or to avoid the use of steel in the construction of the 

 magnets, 



