function performKvaConversion() {
var kva = document.getElementById("inputKva").value;
var pf = document.getElementById("inputPf").value;
var resultDiv = document.getElementById("kva-result-area");
var kwOutput = document.getElementById("kwResult");
var formulaOutput = document.getElementById("formulaPath");
if (kva === "" || pf === "") {
alert("Please enter both kVA and Power Factor values.");
return;
}
var kvaVal = parseFloat(kva);
var pfVal = parseFloat(pf);
if (pfVal > 1 || pfVal < 0) {
alert("Power Factor must be between 0 and 1.");
return;
}
var kw = kvaVal * pfVal;
kwOutput.innerHTML = kw.toFixed(3) + " kW";
formulaOutput.innerHTML = "Calculation: " + kvaVal + " kVA × " + pfVal + " PF = " + kw.toFixed(3) + " kW";
resultDiv.style.display = "block";
}
Understanding kVA and kW Conversion
In electrical engineering, distinguishing between kVA (kilovolt-amps) and kW (kilowatts) is essential for sizing generators, transformers, and industrial UPS systems. While both units measure power, they represent different aspects of electrical energy.
The Difference Between kVA and kW
kVA (Apparent Power): This is the total amount of power being used by a system. It includes both the power that does work and the "reactive" power that creates magnetic fields in motors and transformers.
kW (Real Power): This is the actual power that performs work (such as lighting a bulb or turning a shaft).
Power Factor (PF): This is the efficiency ratio, expressed between 0 and 1. It represents the fraction of apparent power that is actually doing useful work.
The kVA to kW Formula
To convert from apparent power to real power, use the following mathematical formula:
kW = kVA × Power Factor
For most commercial generators, the standard power factor used for rating is 0.8. This means the engine can provide 80% of the total kVA capacity as usable kilowatts.
Practical Examples
If you have a 100 kVA generator with a power factor of 0.8, the conversion is:
100 kVA × 0.8 = 80 kW
If you are dealing with a purely resistive load (like a heater), the power factor is 1.0. In this case:
100 kVA × 1.0 = 100 kW
Quick Conversion Table (at 0.8 PF)
Apparent Power (kVA)
Real Power (kW) @ 0.8 PF
10 kVA
8 kW
50 kVA
40 kW
100 kVA
80 kW
250 kVA
200 kW
500 kVA
400 kW
Why This Calculation Matters
Sizing electrical equipment based only on kW can lead to overloading if the kVA requirements are higher than the system can handle. Conversely, buying a generator based on kVA without considering your actual kW needs might lead to insufficient power for your machinery. Always check the nameplate of your equipment for the specific Power Factor to ensure accurate calculations.