LIST OF SYMBOLS 



A = area of cross-section; area of surface. 



A = area of one lobe of periodic wave plotted to polar coordinates. 

 Ac = ampere-conductors in pole pitch, 

 a = coefficient in resistance-temperature formulas. 



B = magnetic flux density (gauss). 

 B,, or B" = magnetic flux density (maxwells per square inch). 



B a = instantaneous average value of air-gap density over the arma- 

 ture conductors of one phase. 



B e = average air-gap density in zone of commutation. 

 B e = average or equivalent flux density in pole cores. 

 B g = flux density in air gap (gausses). 

 B = average air-gap density over tooth pitch. 

 B p average air-gap density under commutating pole. 

 Bt = actual flux density in teeth. 

 B. & S. = Brown and Sharpe wire gage. 

 b = number of brush sets. 



C = electrostatic capacity (farads), 

 c = coefficient of friction. 

 c = length of pole (radial). 



D = diameter of armature core (including teeth). 

 D e = diameter of commutator (inches). 

 d = diameter of magnet core. 

 d = inside diameter of armature core. 

 d = maximum value of equivalent sine-wave. 

 d = depth of armature slot (length of tooth). 

 d c = equivalent length of tooth. 



E = electromotive force (e.m.f.); difference of potential (volt). 

 E a = volts per phase in armature winding. 

 E e SB volts per conductor. 

 E e = e.m.f. generated in end connections of short-circuited coil 



during commutation (volts). 

 E m = mean or average value of e.m.f. 

 EQ = terminal voltage when load is thrown off. 

 E t = reactance voltage drop per phase (slot leakage only). 

 E t = terminal voltage. 

 e = instantaneous value of e.m.f. (volts). 

 e e = instantaneous e.m.f. per armature inductor, 

 e.m.f. = electromotive force. 



/ = frequency (cycles per second), 

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