Contents - AP Technology

Technical Guidelines
Basic electrical-engineering formulas
Voltage drop (power engineering)
Symbol Designation and unit Formula
u voltage drop in V
Rated voltage (continuous rated voltage is expressed by statement of
two AC values U 0 /U in V)
U0 /U = conductor earth/conductor line-to-line voltage
U0 voltage between conductor and Earth or metallic sheath
(screening, reinforcement, concentric conductor)
U voltage between the outer conductors
U0 U/3 for three-phase moments
U0 U/2 for single-phase and AC moments
U0 /U0 one outer conductor earthed, for single-phase
and AC moments
16.086
at given current
- for AC
- for single-phase AC
- for three-phase current
at given power
- for AC
- for single-phase AC
- for three-phase current
operating current in A
l single length of power cable in m
(Kappa) conductivity of conductor (m/·mm 2 )
(-Cu-conductor: 56, -Al-conductor: 33)
u voltage drop in Volt (V)
U operating voltage in V (V)
P power in Watt (W)
q conductor cross-section in mm 2
Mathematical symbols
= equal to < smaller than sin sine
not equal to > greater than cos cosine
~ proportional to smaller than or equal to tan tangent
appr. equal to ≥ greater than or equal to cot cotangent
sum, total infinite intersection
difference (3,14) set union
u =
u =
u =
u =
u =
u =
2··l
·q
2··cos·l
·q
1,732··cos·l
2··P
·q·U
2··P
·q·U
·P
·q·U
·q
Conductor cross-section (power engineering)
Symbol Designation and unit Formula
q conductor cross-section in mm 2
at given current
- for DC
and single-phase AC
- for three-phase current
at given power
- for DC
and single-phase AC
- for three-phase current
operating current in A
l single length of power cable in m
(Kappa) conductivity of conductor (m/ ·mm 2 )
(-Cu-conductor: 56, -Al-conductor: 33)
u voltage drop in Volt (V)
U operating voltage in V (V)
P power in Watt (W)
q conductor cross-section in mm 2
Electrical energy
Abbreviation Designation Symbol Formula
W electr. energy Ws W = P·t
P
t
l
electr. power
time (duration)
current
W
S
A
U voltage V W = l2 U2·t
W=
R
·R·t
R resistance Ω W = U·l·t
Example given t = 0,05 s, U = 220 V, l = 0,25 A
required electrical energy Ws (wattseconds)
Calculation route W = U·l·t
W = 220 V·0,25 A·0,05 s = 2,25 Ws
q =
q =
u =
2·· l
· u
1,732··cos·l
2··P
q =
·u·U
·P
·u·U
·u