Your One-Stop Solution For Cable & Wire Accessories!

RoHS Compliant Cable & Wire
Technical Information

Contact Us About Us  
LinkedIn Facebook Twitter You Tube Hi-Tech Controls Blog
Cables & WiresEnclosures (Plastic & Metal)Pneumatic Components Liquid Tight Strain Relief FittingsCircular ConnectorsConduit System (Tubing, Fittings, etc.)Accessories & Adapters, Reducers, Enlargers
*Zip Code
Please answer the security question:
(*) Required Fields
Catalogs / Samples, Full Quote & Contact Information

Formulas of Power Engineering

for direct - and single phase alternating current
(current given)
q = 1 x I x l (mm²)
κ x u
for three-phase current
q = 1.732 x I x cosφ x l (mm²)
κ x u

for direct - and single phase alternating current
(capacity given)
q = 2 x I x P (mm²)
κ x u x U
for three-phase current
q =     l x P     (mm²)
κ x u x U

Voltage drop
For low voltage cable network of normal operation, a voltage drop of 3-5% is adviseable.
Exeption: higher values (7%) can be permitted in case of network extension or in short circuit.

for direct current (current given)
u = 2 x I x l (V)
κ x q

single phase alternating current (current given)
u = 2 x I x cosφ x l (V)
κ x q

for three-phase current (current given)
u = 1.732 x I x cosφ x l (V)
κ x q

for direct current (capacity given)
u =   2 x l x P   (V)
κ x q x U

single phase alternating current (capacity given)
u =   2 x l x P   (V)
κ x q x U

for three-phase current (capacity given)
u = l x P   (V)
κ x q x U

u = Voltage drop (V)
U = Operating voltage (V)
P = Power (W)
RW = Effective resistance (Ω/km)
L = Inductance (mH/km)
ωL = Inductive resistance (Ω/km)
    ω = 2 π f at 50 Hz = 314
q = Cross-section (mm²)
I = Working current (A)
l = Length of line (m)
κ = Electrical conductivity of conductors
    (m/Ω x mm²)
    κ Copper: 58
    κ Aluminum: 33
Nominal voltage
The nominal voltage is to be expressed with two values of alternating current U0/U (in V).
U0 = voltage between conducter and ground or metallic covering (shield, armoring, concentric conductor)
U = voltage between two outer conductors
U0 = U/√3 for three-phase current systems
U0 = U/2 for single phase and direct current systems
U0/U0 = 1 outer conductor is grounded for single phase and direct current systems
Nominal current
I in A

Active current
IW = I x cosφ

Reactive current
I0 = I x sin φ

Active power
S = U x I                             for single phase current
S = 1.732 x U x I                 for three-phase current

Apparent power
P = U x I x cosφ                   for single phase current
P = 1.732 x U x I x cos φ      for three-phase current
P = U x I                             for direct current

Reactive power
Q = U x I x sin φ                 for single phase current
Q = 1.732 x U x I x sin φ     for three-phase current
(Voltampere reactive)           Q = P x tan φ

Phase angle
φ is a phase angle between voltage and current
cos φ = 1.0 0.9 0.8 0.7 0.6 0.5  
sin φ = 0 0.44 0.6 0.71 0.8 0.87  
Insulation resistance
RInsu = SInsu x In Da x 10-8 (MΩ x km)
l d

Specific insulation resistance
RS = R x 2π x l x 108
In Da
Da = Outer diameter over insulation
d = Conductor diameter
di = Inner diameter of insulation
l = Length of the line
SInsu = Spec. resistance of insulation materials (Ω x cm)
Mutual capacity
for single conductor, three-cond. and H-cable
CB =     ξr x 10³     (nF/km)
18 In Da

0.4 x ( In Da  + 0.25)    mH/km

0.2 x ( In Da  + 0.25)    mH/km
Da = Distance mid to mid of both conductors
r = Conductor radius
ξr = Dielectric constant
0.25 = Factor for low frequency
Ground capacitance
EC = 0.6 x CB

Charging current
(only for three-phase)
ILad = U x 2 π f x CB x 10-6 (A/km per conductor at 50Hz)

Charging power
PLad = ILad x U

Leakage and loss factor
G = tanδ x ωC(S)
tanδ = G/ωC

ω = 2 π f
C = Capacity
tanδ = Loss factor
S = Siemens = 1/1Ω
Dielectric loss
DV = U² U x 2 π f x CB x tan x 10-6 (W/km)

It should be noted that for the current load of the insulated cables and wires of selected cross-section, the power ratings are to be considered.
To estimate the voltage drop of insulated cables and wires with large cross-sections of single and three-phase overhead line, the active resistance as well as indictive resistance must be considered.

Formula for single phase:
U = 2 x l x I x (RW x cosφ + ωLx sinφ) x 10-3 (V)

Formula for three-phase
U = 1.732 x l x I x (RW x cosφ + ωLx sinφ) x 10-3 (V)
f at 50Hz
tanδ PE/VPE cables ~ 0.0005
EPR ~ 0.005
Paper single conductor, three-conductor, H-cable ~ 0.003
Oil-filled and pressure cable ~ 0.003
PVC-cable ~ 0.05
Items For Quote

Sealcon is the Exclusive Importer of HUMMEL products. We offer over 6,000 different Types and Sizes of RoHS Compliant Liquid Tight Strain Relief Fittings, Cord Grips, Cable Glands, Circular Connectors, Conduit System, Industrial Enclosures and Other Related Cable Management Products which are rated the best in the industry.
7374 S. Eagle Street
Centennial, CO 80112-4221 USA
Toll Free: 800-677-8942 / 303-680-5159 FAX: 303-680-5344
Valid XHTML 1.0 Transitional
To Top of Page Top of Page

Copyright © 2018 Hi-Tech Controls Inc. All Rights Reserved
|Domestic & International Cables|Enclosures |Liquid Tight Strain Relief Fittings & Accessories|
|Circular Connectors|Conduit System|Pneumatics|Cable Index|Enclosure Index|Search|
|Media|Site Map|Company Overview|Contact|Privacy Policy|Copyright Notice|