28 



ELECTRICAL MACHINERY 



part named the armature core revolves when the machine is 

 in operation. In an alternating current machine (taken 



FIG. 3. Sketch to Show Magnetic Circuits of a Bipolar Machine. 



up in the later chapters) the field frame generally rotates 

 while the armature is stationary. In either case it is seen 



FIG. 4. Sketch to Show Magnetic Circuits of a Four-pole Machine. 



that the field frame is that part of the machine which carries 

 the field coils through which current is passed to produce 



