Electrical and engineering
Current, conductor size, voltage drop and machine rating. Every page shows the formula it used and asks for the coefficients — power factor, ampacity, conductivity, the diversity a set is actually carrying — because those decide the answer and belong to your installation, not to a general reference.
Two things get a wrong electrical figure published. The first is a formula applied with a coefficient nobody checked: a three-phase current computed as if the load were single phase, a voltage drop computed without the factor of √3, a kVA turned into kW with a power factor borrowed from a different class of machine. Each of those returns a clean number that is wrong by a fixed and substantial margin, which is worse than an obviously wrong one.
The second is treating a calculation as a standard. The current these pages give you is the current your load draws; the conductor that may carry it is chosen from the manufacturer’s and the regulations’ tables for the insulation, the grouping, the ambient temperature and the way the cable is laid, none of which this page can see. So an ampacity here is a field you fill from a table you have read, and where the computed need exceeds the rating you entered, the page says so instead of quietly resizing the cable for you.
Rating a transformer, a generator or a solar array is the same argument one level up. Nameplate ratings are published in steps — the next size exists, the size in between does not — and the step series belongs to the manufacturer. The load’s diversity, the margin for machines not yet installed and the irradiance at your site are yours to state; what these pages give back is the number those inputs imply, and the advice to order the next published rating above it.
Every tool in Electrical and engineering
- Wire and cable size calculator by load The current a load draws and the conductor cross-section that has to carry it, from the ampacity of the way it is installed.
- Cable size calculator with voltage drop The conductor size a long run needs so the far end still gets its voltage, from the run length and the conductivity of the metal.
- Single phase power calculator Active, apparent and reactive power on one phase, and the angle between voltage and current that separates them.
- Three phase power calculator kW, kVA and kVAR on a balanced three-phase load from line voltage and line current.
- Transformer kVA calculator The kVA a load demands, the rating that carries it inside its continuous loading limit, and the margin for what comes later.
- Generator size calculator The kVA a set must carry after diversity, at the load's power factor, with room for what may be added later.
- Solar panel size calculator How many kilowatts of array a day's consumption needs, and how many panels that is, from sun hours and a performance ratio you supply.
- Motor HP to kW and current calculator The shaft power a horse-rated motor delivers, the power it takes from the supply, and the current that implies.