 | Circuits, Formulas and Tables Electrical Engineering - Basic Vocational Knowledge |
 |  | 11. Basic symbols and formulas of electrical engineering |
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11.5. Alternating current engineering
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frequency |
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T = cycle duration in s | |
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gyro-frequency |
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phase angle |
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instantaneous value of a sinusoidal a.c. voltage |
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instantaneous value of a sinusoidal a.c. current |
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maximum value |
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- of a sine-wave voltage |
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U = virtual value |
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- of a sine current |
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I = virtual value |
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inductive resistance |
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(inductive reactance) |
L in H | |
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capacitive resistance |
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(capacitive reactance) |
C = capacity in F | |
Series connection
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impedance |
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[W] |
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ohmic drop in voltage |
UR = I · R |
[V] |
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inductive voltage drop |
UL = I · XL = I · w L |
[V] |
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capacitive voltage drop |
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[V] |
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Ohm’s law for alternating current |
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[A] |
Powers in case of single-phase alternating current
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apparent power |
S = U · I |
[VA] |
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active power |
P = U · I · cos z |
[W] |
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reactive power |
Q = U · I · sin z |
[Var] |
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power factor |
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Powers in case of three-phase alternating current
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apparent power |
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[VA] | |
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active power |
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[W] | |
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reactive power |
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[Var] | |
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power factor |
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efficiency for motors and generators |
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Pe = effective power | | |
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Pi = indicated power | | |
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speed calculation of three-phase motors rotating field speed |
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p = number of pole pairs | | |
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slip |
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[%] | |
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n = rotor speed |
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