THE CONTINUOUS CURRENT GENERATOR 145 



amperes and No. 2 80 amperes and the load is therefore 

 210 amperes. 



Equalization of Load. Suppose it is now desired to 

 equalize this load between the two machines, so that each 

 machine carries 100 amperes. This may be done either by 

 increasing the field current of No. 2 (cutting out some of 

 its field rheostat) or by decreasing the voltage of No. 1 

 (by increasing its field rheostat resistance). Suppose that 

 the voltage of No. 2 is increased by increasing its field 

 current, until its external characteristic crosses that of 

 No. 1 at 100 amperes; the external characteristic of No. 

 2 is raised throughout the whole range of the curve and is 

 shown by the dotted line ACS, in Fig. 92. When the 

 load is 200 amperes, each machine wil Itake one-half of the 

 load but at lighter loads No. 2 will now take more current 

 than No. 1; when the load is 120 amperes for example, 

 No. 2 takes 80 amperes and No. 1 only 40 amperes. 



Generators of Different Capacities. If the two external 

 characteristics coincided with each other throughout their 

 length and the load was once equally divided, it would be 

 equally divided for all loads. It may be, however, that the 

 two machines are not of the same capacity; No. 1 might 

 have a full load capacity of 100 amperes and No. 2 of only 

 50 amperes, in which case we would want the division of 

 load to be proportional to the capacities. In this case 

 the two characteristics must fe similar in shape and the 

 no-load and full-load voltage of the two machines must be the 

 same; if No. 1 gives 110 volts at no load and 105 volts when 

 carrying 100 amperes No. 2 should give 110 volts at no 

 load and 105 volts when carrying 50 amperes. With such 

 external characteristics No. 2 would always carry one-half 

 as much current as No. 1. 



Disconnecting a Generator from the Bus-bars. If it is 

 desired to disconnect one generator from the bus-bars its 

 load is first reduced to zero by increasing the resistance of 

 its field rheostat until its generated e.m.f. is the same as the, 



