22 Mr. W. M. Mordey on the Dynamo 



of motors, or, in other words, of how the missing power is 

 expended. In what particulars a good motor should resemble 

 a good dynamo, and in what they should differ from one 

 another, are also interesting questions of great importance 

 which await answers. 



The writer having, with Mr. C. Watson — who is his assistant 

 in the works of the Anglo-American Brush Electric Light 

 Corporation — given some attention to the matter from a prac- 

 tical point of view, a great necessity was felt for some founda- 

 tion on which to work, similar in character to the broad general 

 principles which serve to guide the practical constructor of 

 dynamo machines. In the search for such general principles, 

 all those ways of considering the actions which depend on the 

 idea of magnetic poles in the armature were abandoned, and the 

 conclusion was arrived at that the armature should have no polar 

 action whatever, that the iron of the armature should have only 

 the function of a conductor of lines of force, and that the power 

 of the motor should be due to the simple action between the 

 lines of force of the magnetic field and the armature- wires con- 

 veying currents at right angles to those lines of force. This 

 mode of regarding motor action is convenient on several 

 grounds, and leads to certain conclusions, which, if correct, 

 form substantial bases for practical construction. Thus the 

 armature, instead of being, as hitherto, considered as a strong 

 electromagnet placed in the field of another electromagnet, 

 is to have its electromagnetic functions reduced as much as 

 possible, or preferably suppressed altogether. 



The field is to be very strong. 



As with such an arrangement there is no polar effect in the 

 armature except that due to the direct magnetic induction of 

 the field-magnets, it follows that the maximum power is 

 obtained with any given current when the brushes occupy an 

 absolutely neutral position, or, in other words, when there is 

 no " lead " and no distortion or rotation of the field. These 

 conditions do away with the most troublesome and prolific 

 cause of the sparking at the brushes, which is so often an 

 objectionable feature of most electric motors. 



But by working backwards in this way it was seen at once 

 that the conditions which seemed to be best for a motor were 

 precisely those which the would-be designer of a perfect 

 dynamo would set before him as his goal. 



Certain perfect analogies had been arrived at. In both 

 dynamos and motors, according to this briefly sketched 

 view : — 



(1) The field should be a very strong, the armature a very 

 weak electromagnet. 



