In short. A manufacturing generator project succeeds when it keeps the process safe and restartable, not when it matches the plant’s connected kVA. The scope must say whether the generator supports full production, selected lines or only a safe shutdown, and the design must handle motor starts, step loads and non-linear drives. Claims about reduced downtime or higher output need a measured baseline; an energised generator alone proves neither.
Three different scopes that all get called backup power
Factories in the Patancheru, Pashamylaram, Jeedimetla and Medchal industrial areas ask for generators for three quite different purposes, and confusing them is the root of most poor projects. The first is full production continuity, where the generator carries every line through a DISCOM outage. The second is selected-load continuity, where the generator keeps critical utilities running, such as process cooling, compressed air for instruments, furnace holding power or cold rooms, while production lines stop. The third is safe shutdown and restart, where the generator only needs to bring the process to a safe state and restart it in order. A 2,000 kVA plant may need 2,000 kVA of generation for the first, 600 kVA for the second and 250 kVA for the third. The production manager, not the electrical contractor, should decide which applies. Manufacturing power describes typical load classes by sector.
| Scope | Generator sized for | Main design risk | Evidence of success |
|---|---|---|---|
| Full production | Running load plus largest motor start plus growth | Cost, low load factor during partial production | Load test at production load, transfer test |
| Selected loads | Critical utilities and their starting sequence | Wrong loads on the generator bus | Transfer test with selected loads, segregation check |
| Safe shutdown and restart | Shutdown loads, then sequenced restart | Restart attempted all at once | Recorded shutdown and restart sequence |
Motor starting and step loads
Industrial loads reach the generator as steps: a compressor starting, a chiller loading, a press or a mixer engaging. The alternator must hold voltage well enough that contactors stay closed, and the engine must recover frequency before the next step. Turbocharged diesel engines accept load in increments rather than as a single block, so the project must confirm the manufacturer’s load acceptance capability against the plant’s actual starting sequence.
kVA_required ≈ (P_running / PF) + (S_start,largest − S_run,largest)
P_running is the running load in kW that is already connected, PF its power factor, S_start,largest the starting kVA of the largest motor and S_run,largest that motor’s running kVA. Worked example (illustrative): a plant segment running 280 kW at 0.85 power factor has about 330 kVA of running load. If its largest motor is a 75 kW screw compressor on star-delta, with starting demand around 210 kVA against 90 kVA running, the starting margin is about 120 kVA, giving a requirement near 450 kVA before growth and derating. The result should be confirmed against the alternator’s voltage dip curve. See generator sizing.
Drives, harmonics and sensitive equipment
VFDs, induction furnaces, rectifiers and UPS systems draw non-linear currents that distort generator voltage more than they distort the stiffer DISCOM supply. CNC machines and PLCs may react to the resulting voltage distortion or to frequency excursions during step loads. Where non-linear loads form a large share of the generator load, the alternator may need to be oversized or fitted with a permanent magnet excitation system for better voltage stability, and harmonic filters may be justified. A UPS on the controls protects them from the transfer gap; it does not extend generator runtime and does not cover the drives themselves.
Synchronised sets for variable production
Plants whose load swings widely between shifts often benefit from two or more synchronised generators rather than one large set. At night, one set runs at a healthy load factor; during full production, a second set synchronises and shares load. That also allows one set to be serviced while the other covers the critical utilities. The trade-off is a synchronising panel, load sharing controls and protection that must be engineered and tested. Synchronising panels describes the equipment involved.
What a manufacturing project record should prove
A credible record states which production functions were in scope, what the generator was tested to carry, and in what sequence. Claims about downtime need a defined baseline: outage hours before and after, measured on the same basis. A repaired or newly energised generator does not by itself prove an improvement in output; process outcomes outside the power scope stay outside the claim. No approved manufacturing case is presented in this category at present; when one is added, it will follow these rules. Cases from other sectors are listed under verified projects and healthcare power projects.
Common mistakes
- Sizing the generator on the sanctioned contract demand. The plant pays for capacity it never uses and the set runs at a low load factor.
- Connecting all motors to restart automatically on generator supply. The combined inrush trips the set and the plant faces a second outage.
- Ignoring VFD and furnace harmonics in alternator selection. The alternator overheats and voltage distortion disturbs PLCs and CNC machines.
- Claiming reduced downtime without a measured baseline. The claim cannot be defended when management or auditors ask for the numbers.
What to send us
Send the load list with motor ratings and starting methods, the list of drives and other non-linear loads, the production sequence, details of the existing DISCOM connection and transformer, and records of outage frequency and duration over the last year. State whether you need full production, selected loads or safe shutdown. Send a generator sales enquiry.
Questions engineers ask
How much larger than the running load should a factory generator be?
There is no fixed margin; it depends on the largest motor start, the step-load sequence, the non-linear share and growth. A common starting point is 20 to 25 percent above running kVA, then checked against the motor starting study and the alternator’s voltage dip curve.
Can one generator support two plants on the same premises?
Yes, if the combined load and starting sequence is within its capability and the changeover arrangement keeps the supplies separate from the DISCOM. Separate metering and a clear load priority are needed so one plant cannot overload the set at the expense of the other.
Is a CPCB IV+ generator suitable for heavy industrial loads?
Yes. CPCB IV+ sets use electronically controlled engines and aftertreatment, and their load acceptance is specified by the manufacturer like any other set. Low-load operation needs more attention, because aftertreatment works best at moderate to high load.
Should we use one large generator or two synchronised sets?
Two synchronised sets suit plants with variable load and a need for maintenance without losing backup. A single set is simpler and cheaper when the load is steady and a short loss of backup during maintenance is acceptable.
Generators by rating
- Under 15 kVA generators
- 15–50 kVA generators
- 50–125 kVA generators
- 125–250 kVA generators
- 250–500 kVA generators
- 500–1000 kVA generators
- 1–2 MVA generators
- 2 MVA and above generators
Technical content reviewed by Srinivas Reddy, Managing Partner, Reddy Generators. Last updated 19 October 2026.