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close this bookCircuits, Formulas and Tables Electrical Engineering - Basic vocational knowledge (Institut für Berufliche Entwicklung, 201 p.)
close this folder11. Basic symbols and formulas of electrical engineering
View the document(introduction...)
View the document11.1. General direct current engineering
View the document11.2. Magnetic field
View the document11.3. Law of induction
View the document11.4. Electric field
View the document11.5. Alternating current engineering
View the document11.6. Calculation of power

11.5. Alternating current engineering

frequency


T = cycle duration in s


gyro-frequency

phase angle

instantaneous value of a sinusoidal a.c. voltage

instantaneous value of a sinusoidal a.c. current

maximum value



- of a sine-wave 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

UR = I · R

[V]

inductive voltage drop

UL = I · XL = I · w L

[V]

capacitive voltage drop

[V]

Ohm’s law for alternating current

[A]

Powers in case of single-phase 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 three-phase alternating current

apparent power

[VA]

active power

[W]

reactive power

[Var]

power factor


efficiency for motors and generators



Pe = effective power




Pi = indicated power



speed calculation of three-phase motors rotating field speed


p = number of pole pairs


slip

[%]


n = rotor speed