xiv LIST OF SYMBOLS 



H = intensity of magnetic field; magnetizing force (gilberts per 



centimeter; or gauss). 

 hp. = horsepower. 



7 = current, amperes. 

 7 = current per phase (or per conductor) in alternator armature 



winding. 



7 C = current per conductor in armature (D.C. machines) 

 7 m = mean or average value of current, 

 t = instantaneous value of current. 

 i, = instantaneous value of current in armature conductor (for slot 



leakage calculations). 

 k = a constant; any whole number. 

 k = cooling coefficient. 



k = distribution factor (A.C. armature windings), 

 pole arc. 



k = ratio 

 k as ratio 



armature core length. 



permissible current density at brush tip. 



average current density over brush contact surface, 

 k.v.a. = kilovolt-amperes. 

 k.w. = kilowatts. 



L = inductance; coefficient of self-induction (henry). 

 L c length of cylindrical surface of commutator (inches). 



I = a length, usually expressed in centimeters. 



I = y^ (commutation). 

 V = axial projection of armature end connections beyond slot (A.C. 



generator). 



I" = a length expressed in inches. 

 la = gross length of armature core. 

 l c = total axial length of brush contact surface. 

 l e = length of end portions of armature coil. 

 If. = leakage factor. 



In = net length of iron in armature core (usually inches). 

 IP = axial length of commutating pole face. 

 I, = total axial length taken up by vent ducts. 



M = thickness of commutator mica. 

 (M ) = circular mils per ampere, 

 (ra) = circular mils, 

 m.m.f. = magnetomotive force (gilbert). 



A T = number of revolutions per minute. 

 N = number of revolutions per second. 

 n = number of radial air ducts in armature core. 

 n = number of slots per pole. 

 n, = number of slots per pole per phase. 



