Calculators tailored to electrical work: understand the fundamentals, size the cable, work out power and load, and see the economics. Enter your own values — the result updates live.
Start here: Ohm's law and power — the relationship between voltage, resistance, current and power.
Voltage, resistance, current and power
The fundamental relationship in any electrical installation: U = R · I and P = U · I. Enter voltage and resistance — current and power are computed live. Assumes a purely resistive load.
Spænding, strøm og omsætningstal
Den klassiske idealtransformer-sammenhæng U₁/U₂ = N₁/N₂ = I₂/I₁. Indtast primærspænding og omsætningstal — sekundærspænding og strømomsætning beregnes live. Antager en idealtransformer uden tab; reale transformere har ≤ 99,5 % virkningsgrad (læg 0,5–3 % på ved præcis strømdimensionering).
Size the cable: calculate the voltage drop and find the smallest cross-section that stays within the limit.
Voltage drop over a cable run
Calculate the voltage drop ΔU from length, current, cross-section and conductor material, and see it as a percentage of nominal voltage. Reactance is not included — current-carrying capacity and short circuit must be checked separately.
Minimum cross-section based on the permitted voltage drop
Find the smallest conductor cross-section that keeps the voltage drop below a chosen limit, and the nearest standard cross-section. Sizes for voltage drop ONLY — verify current-carrying capacity and short-circuit performance against the tables.
Calculate power in single-/three-phase systems and add several circuits together with a diversity factor.
Active, apparent and reactive power
Calculate the power in a 1- or 3-phase system from voltage, current and cos φ. Shows active P [W], apparent S [VA] and reactive Q [var] from the power triangle. Applies to a symmetrical, balanced load.
Design power and current for multiple groups
Sum several groups and multiply by a diversity factor of your own choosing — get the design power and current. An estimate: the correct diversity depends on the installation and is looked up in the applicable standards.
Current for a known power — 1-phase, 3-phase or motor
Beregn dimensioneringsstrømmen IB ud fra effekt, spænding og cos φ — og for motorer også virkningsgraden η. IB er grundlaget for grundreglen IZ ≥ In ≥ IB: vælg sikring og kabel ud fra denne strøm.
Inrush-faktor og peak-strøm ved start
Kvantificér startstrømmen (inrush) når en motor starter: I_start ≈ I_nominel × k. Inrush-faktoren k er dit eget input — typisk 5–8 ved direkte start (DOL), 2–3 med soft-starter. Vejledende tal; check spændingsfald under start separat mod DS/HD 60364-5-52.
Kontrollér sikkerheden: tåler lederen kortslutningen (K²S² ≥ IK²·t), og vælg RCD/HPFI så berøringsspændingen holder i TT-systemet.
Thermal capacity K²S² ≥ IK²·t
Check whether the conductor withstands the short-circuit current within the disconnection time, and find the smallest cross-section that does. Uses the K-values from DS/HD 60364-4-43 table 43A (Cu/Al × PVC/XLPE). Adiabatic assumption — valid for short times.
Rated tripping current from earth resistance
Find den største tilladte mærkeudløsestrøm I_ΔN så berøringsspændingen holdes under 50 V i et TT-system (R_A·I_ΔN ≤ 50 V), og tjek 0,3×-lækstrømsgrænsen. Personbeskyttelse kræver desuden maks. 30 mA.
Convert power and run time into kWh and cost using your own electricity price.
Dimensionér lampeanlæg efter EN 12464-1: find lux på arbejdsfladen eller antal lamper for at nå din mållux.
Guidet flertrins-vejviser: fra ønsket effekt til en konkret standard-transformerstørrelse og maks. spændingsfald — ren geometri på dine svar plus citeret standard-række.