6 THE DIRECT-CURRENT MOTOR CH. I 



the machine as there are in one polar division of the arma- 

 ture ; when this is the case the armature is said to be con- 

 nected in parallel. 



If, however, the armature is connected in series, the 

 conductors lying under one pole being placed in series 

 with those lying under another pole, the force and the 

 torque must be multiplied by a quantity p, expressing the 

 number of polar divisions of the armature thus connected 

 in series. Equation 3 may then be written 



............... (4). 



Example 1. A four-pole dynamo has 440 surface 

 conductors with 16'1 x 10 6 lines per pole. The armature 

 is series connected, giving p=2. The torque for 300 

 amperes is 60,000 inch-pounds. 



Example 2. A ten-pole dynamo has 28-6 x 10 6 

 lines per pole and 1,440 surface conductors; the armature 

 is parallel connected, giving p=l. The torque for 800 

 amperes is 465,000 inch-pounds. 



Equation 4 may be written 



*=l-41cJ/ ..................... (5). 



M being given by 



.................. (6). 



where A is the number of surface conductors, p is the 

 number of polar divisions of the armature connected in 

 series, and N is the number of useful lines per pole. 



We shall call M the Induction Factor of the 

 dynamo. 



Example 3. A two-pole dynamo has 200 surface 

 conductors and 2'1 x 10 6 lines per pole. The induction 

 factor is 4-2. 



