Build a controlled UPS and VFD load sheet, define operating events, and require quote-specific generator evidence before comparing suppliers.

Total kW and kVA do not qualify a generator quote for an uninterruptible power supply (UPS), variable-frequency drive (VFD), rectifier, charger, or other nonlinear load. Identify each exact device, its source-side input data, and every material operating event, then require the supplier to tie its check to that controlled input and the exact offered generator-set build. If the identities, events, method, result, and acceptance source do not share one basis, return or stop the quotation.

This is an RFQ and comparison method, not a final sizing calculation or compatibility approval. Harmonic, transient, protection, grounding, and whole-system limits remain project-specific and need their named technical owners.

Separate steady totals from operating events

A load total shows one stated point, not how each power-conversion unit draws current or changes state. Separate steady totals from transfer, recharge, rectifier ramp, bypass, pre-charge, speed change, or regenerative events that actually occur in the project.

Split the load schedule into three groups before asking for a generator recommendation:

  • Common loads with a known operating state.
  • Power-conversion loads that need source-side input data.
  • Loads whose input data or operating state is still OPEN.

Use the industrial generator sizing guide for the full load and case plan. The task here is narrower. Turn the power-conversion loads into a clear supplier input.

Do not fill a data gap with a stock oversize or derate factor. The same rule applies to a fixed UPS-to-set or VFD-to-set ratio. A factor cannot name the unit type, event order, source point, or exact set build it is meant to cover.

Turn each category label into an exact input record

For this quote review, treat a unit as nonlinear when one steady kW or kVA value does not fully describe its source-side current. Its input may change with switching, charge mode, power conversion, load point, controls, and the rest of the power system.

That is a flag to request data, not a verdict about suitability. “UPS,” “VFD,” and “charger” are broad labels. They are not full input records, and two units with the same category name may require different source-side evidence.

Eaton's overview of harmonic sources gives broad context. For the project, use the current maker document for the exact unit. A broad guide cannot prove that a BEAR set, one load, or the whole system is suitable.

Eaton harmonic-sources webpage listing variable frequency drives, rectifiers, computers, and chargers as nonlinear-load examples
Source context captured from Eaton's “What causes harmonics” page on September 2, 2026. It identifies broad nonlinear-load categories; it is not a generator-sizing rule or proof that a quoted set suits a project.

For each key power-conversion load, record:

  • Maker, exact model, option codes, quantity, and any hardware or software version that changes the input.
  • Source document title, number, version, date, page or section, and owner.
  • Input voltage, frequency, phase, wiring, kW, kVA, current, and power factor at the named load point.
  • Input type, if documented, plus waveform or harmonic-current data, pre-charge or inrush data, and source rules.
  • Filters, reactors, transformers, switching paths, and controls that change the event.
  • Data status: CONFIRMED, PARTIAL, ASSUMED, or UNAVAILABLE.

Do not swap in the UPS output rating, VFD motor-side current, or motor nameplate. Use one of those values only if the equipment maker links it to the source-side input for that exact build.

Build one revision-controlled qualification sheet

Put the records into one Nonlinear-Load Qualification Sheet with a project number, issue date, version, writer, reviewer, status, load-list version, quote version, and change log. This is the comparison control: a technically sound check still fails procurement review if it uses an old drive option, UPS module plan, or set offer.

Use this minimum structure:

Record block. Buyer-controlled fields. Completion rule.
File control. Project, site, owner, issue/version, load-list link, quote link, status, and change log. You can trace each file used in the check.
Load ID. Unique ID, load type, maker, exact model/build/version, count, and owner. No key power load is left as a broad label.
Input basis. Voltage, frequency, phase, wiring, input kW/kVA/current, power factor, input type, input curve, and load point. Each value names its source, mode, unit, and point.
Run states. Normal and peak-use modes; needed UPS rectifier ramp, recharge, transfer, and bypass states; needed VFD pre-charge, speed-up, slow-down, regenerative, and bypass states. Real project states are named; unused states are marked.
Fitted parts. Filters, reactors, transformers, switches, load-shed controls, phase split, neutral plan, and location. Each item has an exact ID, scope, location, and owner.
Acceptance basis. Metric, test point, load point, event, needed result, source file, and criterion owner. No limit comes from a broad article or an unscoped chart.

Use the generator voltage and frequency checklist to set the electrical basis for the target market. This guide does not choose that basis or design the wiring system.

Keep gaps in view. OPEN — equipment maker to confirm is more useful than a likely number with no clear source.

Map every material operating event

A load list is static, while the set and its loads move through states. Make an event record for each change that may alter source demand or must keep key loads online. Keep simultaneous and staged changes separate unless a controlled project rule joins them.

Each event needs an ID. Add these fields:

  • Trigger: Grid loss, set start, transfer, a process command, recharge, fault reset, a site test, or another real project action.
  • Start state: Set status, loads online, unit modes, and load points just before the change.
  • Change: Units that connect, transfer, ramp, charge, use bypass, speed up, slow down, feed power back, or drop off.
  • Sequence and timing: Joint or staged changes, based on a project rule or controlled maker file.
  • Loads kept online: Load IDs that must stay online, plus the source of that need.
  • Test point: Where current, voltage, frequency, waveform, unit status, or another stated result is read.
  • Recovery state: What must settle or stay in range. Also name the file that sets the rule and the party that owns the decision.

If VFD bypass starts the motor direct from the generator, keep that event as a separate case. Use the motor-starting kVA, inrush, and voltage-dip guide for the extra input and return fields.

A load-bank test may stand for one stated site-test step. It does not copy the input behavior of the fitted UPS, VFD, rectifier, or charger by itself. State what the bank stands for. List the real power loads in the test and the events it leaves out.

Require a quote-specific generator-set return

Ask the supplier to name the full generator set behind each claim and cite the Qualification Sheet revision it used. A family name is not enough. Nor is an alternator-only curve, a broad “VFD ready” line, or a result for a different build.

Multiple alternator assemblies held in a metal parts cage in a workshop
Similar-looking alternator assemblies still require exact configuration records. The image does not establish winding, source impedance, harmonic performance, transient response, UPS or VFD compatibility, rating or suitability for a stated event.

A showroom view can show product formats. It cannot identify the alternator, controls, winding, rating basis, or electrical build behind a quote.

BEAR showroom wall with portable and enclosed generator products on display
BEAR showroom display. The visible generator formats provide appearance context only; the photograph does not identify the quoted model or configuration, or establish ratings, components, UPS/VFD compatibility, waveform performance, testing, certification, or project suitability.

Require the supplier to return:

When the nonlinear-load review depends on alternator selection, winding, AVR, controller, monitoring, filters, or other supplier-specific scope, carry those exact build and interface fields into the BEAR OEM and private-label project review.

Return block. Quote-specific response required.
Offer ID. Quote number/version, set model/build, rating terms, and site/duty basis used.
Set build. Alternator model and build, winding and wiring, excitation or AVR, engine speed control, set control, voltage, frequency, phase, neutral plan, output point, and key set loads.
Input IDs. Qualification Sheet version, load-list version, load IDs, event IDs, maker files, and acceptance sources used.
Method. Load sum, calculation, model, part curve, prior project record, factory test, site test, or other named method. Give the file or report ID and version.
Result. Metric, test point, load point, event order, result, test method, tool where needed, and source of the acceptance rule.
Limits. Assumptions, items left out, valid range, untested states, build changes that void the result, open gaps, and the owner of each next input.

Proof for one part stays tied to that part. An alternator curve alone does not show how the engine, alternator, controls, wiring, and real loads work as one system.

Keep inputs, evidence, and approval owners separate

Assign every input and approval to its real owner; do not ask one party to invent another party's facts or accept another party's risk. Keep four proof lanes:

Owner. Provides. Must not silently decide.
Buyer or EPC. Load list, project states, key-load needs, site/scope data, future growth, file order, and open-item owner. Load behavior or supplier test results.
UPS, VFD, charger, or equipment maker. Exact unit ID, needed input data, operating modes, source rules, and controlled maker files. The exact generator-set build on offer.
Generator-set supplier. Exact offered set, included scope, check method, inputs used, results, items left out, and open gaps. Final whole-system sign-off beyond its stated scope.
Project electrical authority. Open questions on the power system, source impedance, protection, grounding or earthing, parallel work, acceptance rules, and final system approval. Claims with no product proof or missing maker data.

Keep buyer calculations and buy/no-buy calls in a fifth lane. A supplier return can be complete when it names a system gap for another owner. It is not complete when it hides that gap.

Apply a COMPARE, RETURN, or STOP gate

Do not force weak proof into a yes/no compatibility label. Use three procurement outcomes.

Decision flow checking exact load identity, operating events, quote-specific generator configuration, supplier evidence, and unresolved system interfaces before compare, return, or stop
“Compare” means the quotation bases are aligned. It does not mean the generator or integrated system has received final engineering approval.
  • COMPARE: the Qualification Sheet and source files are controlled. Key events are set. The exact set, method, test point, load state, acceptance source, gaps, and owners share one basis.
  • RETURN: the data may exist, but a model, version, run state, event, set build, method, result point, or owner is missing or unclear. Send the package back for more work.
  • STOP: the answer needs missing load data, an unknown key event, clashing source rules, or a system gap with no owner. Send it to the project electrical authority. Do not claim fit.

Return or stop if a quote rests on a broad fit label or one-size factor. Do the same for a bare waveform or harmonic figure. Stop for motor-side VFD data used as source-side proof, a missing UPS recharge or bypass state, family-level set proof, or a load-bank result used as real UPS/VFD proof. A method with no test point, acceptance source, or list of open gaps also fails.

Send a controlled RFQ and require the same-basis return

Send the current Qualification Sheet with the RFQ or technical inquiry. Add the project and duty basis, load list, unit IDs, and controlled maker files. Add the stated voltage, frequency, phase, and wiring.

List all fitted filters, reactors, transformers, switches, and controls. Then add the event list, key-load need, acceptance sources, and open-item list.

Ask the supplier to return the quote version and exact set build. It should fill each return block and list the buyer inputs used. It must also name the method, results, acceptance sources, assumptions, gaps, and owner for each open system point.

The final set rating and choice remain outside this guide. So do the harmonic or source-impedance study, UPS/VFD setup, system design, protection, grounding or earthing, parallel work, site work, legal checks, site tests, and whole-system approval. The project must name qualified owners for them.

For a BEAR quote review, send Miya the controlled load sheet, event list, maker files, project site, electrical basis, target market, order count, and open-item list. Ask BEAR to return the exact offer, input revisions used, method, result points, source files, exclusions, and owner for every open interface. An incomplete input package or broad compatibility statement does not prove fit.