In short. Four calculations come up on almost every generator job: converting between kW and kVA, working out the current a set delivers, understanding power factor, and estimating how long the fuel will last. Each guide below shows the formula, a worked example with real Indian site values (415 V, 50 Hz, 0.8 PF), and the common mistakes that lead to an undersized set or a dry tank.
Where to start
| If your question is… | Start with |
|---|---|
| Converting kW to kVA and back | kW ↔ kVA Guide |
| Full-load current for cable and breaker sizing | Generator Current Guide |
| What power factor means for a generator | Power-Factor Guide |
| How long the fuel will last | Fuel Runtime Guide |
All 4 guides in this section
- kW ↔ kVA Guide — Understand the difference between kW and kVA, convert between them with the right power factor, and see why kVA is only the first step in generator sizing.
- Generator Current Guide — Calculate generator full-load current from kVA and voltage for three-phase and single-phase supplies, with a 415 V reference table and the limits of the figure.
- Power-Factor Guide — What power factor means for a diesel generator, how lagging and leading loads affect the alternator and AVR, and how to handle capacitor banks on generator.
- Fuel Runtime Guide — How to calculate how many hours a diesel generator will run on the fuel it really has, allowing for unusable volume, reserve, load profile and refuelling.
Questions engineers ask
How do I convert kW to kVA for a generator?
Divide kW by the power factor. Generators are rated at 0.8 PF, so 100 kW of load needs at least 125 kVA before any margin for motor starting or growth.
What is the full-load current of a 125 kVA generator at 415 V?
About 174 A, from kVA × 1000 ÷ (√3 × 415).
Engineering content reviewed by Srinivas Reddy, Managing Partner, Reddy Generators. For advice on your own site, send us your requirement or call 098852 01608.