xvi LIST OF SYMBOLS 



W - power watts. 

 W = width of brush (circumferential). 

 W a = brush width (arc) referred to armature periphery. 

 w = a portion of the total (circumferential) width of brush. 



Wc \ = cooling coefficients (armature temperature). 



Wd ) 



X = reactance (ohm). 



Z = impedance (ohm). 



Z = number of inductors in series per phase (A.C. generator). 

 Z = number of inductors on armature (D.C. generator). 

 Z r = total number of inductors (A.C. generator). 



a = angle denoting slope of coil side in end connections of armature 



winding. 

 a = angle of phase displacement of developed e.m.f . due to armature 



cross magnetization. 



= angle of lag of current behind phase of open-circuit e.m.f. 

 A = current density; amperes per square inch. 

 A w = maximum current density over contact surface of brush. 

 6 = clearance between coil sides in end connections of armature 



windings. 



* = length of actual air gap tooth top to pole face. 

 6 t = length of equivalent air gap in machines with toothed armatures. 

 6, = deflection of shaft (inches). 

 6 = an angle. 



$ = angle of lag (cos 6 = power factor). 

 X = slot pitch. 

 M = permeability = B/H. 

 ir = 3. 1416 approximately. 

 T = pole pitch (usually in inches). 



* = magnetic flux (maxwell). 



* = total flux entering armature from each pole face. 

 * a = flux per pole actually cut by armature conductors. 



* c = total flux entering teeth comprised in commutating zone. 



*i = flux entering armature core through roots of teeth (commuta- 

 tion). 



* = total flux cut by one end of armature coil during commutation. 



*. = total flux cut by end connections (both ends) of polyphase 

 armature winding. 



*. = "equivalent" slot leakage flux (magnetic circuit closed through 



roots of teeth). 



*'. = "equivalent" slot flux (magnetic circuit closed through tops of 

 teeth). 



*j = leakage flux (maxwells). 



*, = total slot leakage flux. 



*\ = flux entering armature in space of one tooth pitch. 

 ^ = internal power-factor angle. 



f = "apparent" internal power-factor angle. 



