Circuits, Formulas and Tables Electrical Engineering  Basic vocational knowledge (Institut für Berufliche Entwicklung, 201 p.) 
11. Basic symbols and formulas of electrical engineering 

frequency 
_{}  

T = cycle duration in s  
gyrofrequency 
_{}  
phase angle 
_{}  
instantaneous value of a sinusoidal a.c. voltage 
_{}  
instantaneous value of a sinusoidal a.c. current 
_{}  
maximum value 
 

 of a sinewave voltage 
_{} 

U = virtual value 


 of a sine current 
_{} 

I = virtual value 


inductive resistance 
_{} 
(inductive reactance) 
L in H  
capacitive resistance 
_{}  
(capacitive reactance) 
C = capacity in F 
Series connection
impedance 
_{} 
[W] 
ohmic drop in voltage 
U_{R} = I · R 
[V] 
inductive voltage drop 
U_{L} = I · X_{L} = I · w L 
[V] 
capacitive voltage drop 
_{} 
[V] 
Ohm’s law for alternating current 
_{} 
[A] 
Powers in case of singlephase alternating current
apparent power 
S = U · I 
[VA] 
active power 
P = U · I · cos z 
[W] 
reactive power 
Q = U · I · sin z 
[Var] 
power factor 
_{}  
Powers in case of threephase alternating current
apparent power 
_{} 
[VA]  
active power 
_{} 
[W]  
reactive power 
_{} 
[Var]  
power factor 
_{}   
efficiency for motors and generators 
_{}   

P_{e} = effective power   

P_{i} = indicated power   
speed calculation of threephase motors rotating field speed 
_{} 
_{}  

p = number of pole pairs   
slip 
_{} 
[%]  

n = rotor speed 
