In short. A useful generator technical article defines one engineering problem, explains the principle that governs it, lists the inputs needed, shows the method with a labelled illustrative example and says how to verify the result on site. It ends with a practical next decision and states what remains uncertain. Articles here follow that structure and are written for Indian conditions: 415 V, 50 Hz, CPCB IV+ sets and high ambient temperatures.
What a technical article must do
An article is not a brochure and not a site design. Its job is to teach a method well enough that an engineer can apply it to a different plant and know where the method stops working. That requires five parts, in order: the governing principle, the required inputs, the method, the assumptions, and the verification. Equations carry defined variables and units. Examples state their operating conditions. Results lead to a decision, such as whether a load study is needed or whether a soft starter would let a smaller set work, and the article says plainly what it cannot settle without equipment data.
| Part of the article | What it contains | Question it answers for the reader |
|---|---|---|
| Problem | The symptom or decision, stated precisely | Is this my problem? |
| Principle | The physics or rule that governs it | Why does it happen? |
| Inputs | Data needed, with units and source | What do I need to collect? |
| Method | Steps and formula with a worked example | How do I calculate it? |
| Verification | Test or measurement that proves the result | How do I know it is right on my site? |
| Limits | Where the method fails or needs a study | When do I need more than this? |
Start with the problem, not the product
A sizing question rarely concerns steady load alone. It may involve motor starting, non-linear loads such as UPS and VFDs, step loading after a transfer, and future expansion. A continuity question may involve UPS behaviour, generator start time, ATS logic and the distribution system downstream. An article that jumps to a kVA rating without walking through these has skipped the engineering. The Power Engineering Centre groups the calculations by problem so that the inputs are identified before any equipment is selected.
An example of the method in practice
Consider the most common article topic: converting a real-power demand into a generator rating. The principle is that the generator must supply apparent power, and its rating is stated in kVA at 0.8 power factor.
kVA = kW / PF
Here kW is the real power drawn by the load, PF is the load power factor, and kVA is the apparent power the alternator must supply. Worked example (illustrative): a workshop draws 160 kW at a power factor of 0.85. The apparent power is 160 / 0.85, about 188 kVA. Allowing a margin of around 20 to 25 percent for load growth and to keep the set off its limit gives roughly 225 to 235 kVA, so a 250 kVA set is the first candidate. That is not the end of the article. The next section must ask whether the largest motor starts on this set within an acceptable voltage dip, and whether the site ambient requires derating. Only then is the recommendation defensible. The relationship is explored further in generator sizing.
Topics engineers ask for most
- Motor starting on a diesel generator: DOL, star-delta, soft starter and VFD, and the starting kVA each demands.
- Voltage and frequency dip on load steps, and how the governor and AVR recover.
- UPS and VFD loads on generators: harmonics, alternator heating and controller interaction.
- Derating for ambient temperature and altitude, including summer conditions in Telangana and Andhra Pradesh.
- AMF and ATS sequencing, transfer times and what the UPS must bridge.
- Fuel consumption, runtime and tank sizing from measured load.
- CPCB IV+ sets: what changed in the engine and what it means for service and fuel quality.
- Earthing and neutral arrangements when a generator replaces the DISCOM transformer as the source.
Each topic links to the relevant calculator so the reader can repeat the method with site figures.
Sources, editions and examples
For a specific product, the controlling document is the manufacturer’s current data sheet and its revision. For regulation, it is the notification for the jurisdiction, read with its commencement date. General engineering material explains the subject but does not replace those records. Articles therefore name the type of source they rely on, such as an ISO 8528 performance class definition or an IS standard for earthing, and point to the Technical Library for the reference itself. A worked example distinguishes illustration from recommendation; a figure such as a typical transient reactance or a typical specific fuel consumption is given as a range and flagged for confirmation against the actual machine.
How articles are reviewed
Each article is checked by an engineer with field experience before release. The review asks whether every equation has defined units, whether the example’s conditions are stated, whether any number could be read as a promise, and whether the conclusion still holds for the common variations an Indian site will throw at it, such as a weak DISCOM supply, a monsoon-damp generator room or a set running at 30 percent load for months. Articles are revised when a standard, an emission stage or field experience changes the recommendation, and the revision is recorded. No article title, author or date is listed until that review is complete.
Common mistakes
- Applying a kVA conversion without checking motor starting; the set is adequate on paper and stalls the first time the largest compressor starts.
- Using an example’s derating factor at a different site; a set that was fine at 30 degrees overheats at 45 degrees in an enclosed room.
- Reading a typical figure as guaranteed; the actual alternator reactance or fuel curve differs and the result shifts.
- Quoting an article in a tender specification without checking its edition; the referenced standard or emission norm has since been revised.
What to send us
If you want an article on a specific problem, or need a method applied to your plant, send a short description of the equipment and the unresolved question, plus any data you already hold: the load list, nameplate photographs, single-line diagram, or measured readings from a power analyser. Tell us which figures are measured and which are estimated. Send your application engineering enquiry and we will say what can be answered from the data you have.
Questions engineers ask
Why do generator ratings use kVA instead of kW?
The alternator’s heating depends on current, which follows apparent power, while the engine’s limit follows real power. Rating in kVA at 0.8 power factor covers both for typical loads. A load with a power factor below 0.8 can overload the alternator before the engine is fully loaded.
Can I size a generator from the connected load?
Connected load overstates running demand on most sites, sometimes by half. Size from the expected simultaneous running load, then check motor starting and step loads. A maximum-demand reading from the DISCOM meter is a useful starting point for an existing building.
Are the worked examples safe to use directly?
No. They are labelled illustrative and exist to show the method. Repeat the calculation with your own measured inputs and confirm equipment-specific values against manufacturer data.
Do the articles cover 60 Hz equipment?
They assume 50 Hz Indian supply. Where an export or special-equipment case needs 60 Hz, the relevant article notes the difference in engine speed and alternator output and links to the 60 Hz guidance.
Technical content reviewed by Srinivas Reddy, Managing Partner, Reddy Generators. Last updated 19 October 2026.