Result
Preliminary calculation: This tool is for quick sizing and information. Electrical installation designs and cable and protection selection must be done according to the relevant standards and by an licensed electrical engineer. Results are approximate.
Formulas
Three phase: S [mm²] = √3 × L × I × cosφ / (κ × ΔU_V)Single phase: S [mm²] = 2 × L × I × cosφ / (κ × ΔU_V)Line loss P = n × I² × L / (κ × S)On long lines voltage drop becomes the deciding factor; at motor start the voltage drop is even higher and can cause contactor pull-in problems. The allowed drop value is set according to installation standards and the project specification; the 3% in the tool is only a starting example.
What to look at when selecting the cross-section
- Current-carrying capacity (installation type and ambient temperature)
- Short-circuit withstand and protective device coordination
- Motor starting voltage drop
- Connection and terminal compatibility with aluminum
Frequently asked questions
What percentage should the voltage drop be?
It is determined by installation standards and the project specification. The value in the tool is adjustable; enter the limit your standard allows.
Is the cross-section selected by voltage drop alone?
No. Current-carrying capacity, short circuit and protection are also checked; the cross-section is selected according to the largest of these.
Can aluminum cable be used?
It can be used with suitable terminals and a suitable connection method; a larger cross-section is needed for the same current.