Freeze a generator electrical configuration by load, voltage, frequency, phase, connection, grounding, interfaces, protection, environment and signed evidence.
Do not release a generator electrical setup from a country table, mixed voltage label, or headline kW value. Start with the actual loads, then fix the voltage points, frequency, phase, wires, neutral, transfer scheme, interfaces, test rules, site conditions, and source revisions. Offers are comparable only when those fields are clear and consistent; otherwise the configuration remains on hold.
This is a buying control, not site work advice. A qualified professional must design and approve the generator and transfer system for the real site. That work includes protection, grounding, wires, commissioning, and local legal duties.
Installation and load schedule
The first question is not “50 Hz or 60 Hz?” Define what the generator must supply, how it will connect, and what happens during the hardest load event.
Build a load schedule containing:
| Load field | Buyer or engineer input |
|---|---|
| Equipment identity | Make and model, or a controlled description. Add the quantity. |
| Electrical input | Voltage, frequency, phase, line current or power, and power factor when relevant. |
| Operating pattern | Groups that run together, sequence, hours, cycles, and future growth. |
| Starting/transient behavior | Starting current or kVA, method, duration, and allowed voltage or frequency dip. |
| Nonlinear/sensitive behavior | Rectifiers, UPS, VFD, electronics, chargers, and maker limits for the power source. |
| Phase allocation | Planned spread of single-phase loads on a three-phase source. |
| Criticality | Loads that must stay on, allowed break, and recovery sequence. |
| Environment | Altitude, heat, humidity, dust, corrosion, enclosure, airflow, and site class. |
A nameplate may not show motor starting, charger behavior, or the power quality a device needs. Get maker data. If risk calls for a site measure, have a qualified person run it.
Use the rated-versus-peak guide to keep sustained rating, temporary capability and starting-load analysis separate.
Authoritative project evidence for voltage and frequency
Country plug lists help early research, but they are not the order baseline. Factory sites, split-phase service, remote grids, old wiring, and dedicated loads may differ from a home-power summary.
IEC 60038:2009+A1:2021 gives preferred voltage values for system and equipment design. Its preview says that national groups and single systems may set values within that framework. It does not prove the voltage at one site, the outlet needed, or the output of the quoted generator.
Confirm the project values through the site owner, utility, electrical drawings, equipment manufacturers and the competent local designer. Record:
- nominal voltage at the point of use.
- frequency.
- allowed steady and short-term changes for the loads.
- source and load phase setup.
- wires and system connection.
- voltage at each required outlet or terminal.
- whether the generator supplies isolated loads, temporary cord-connected loads, a transfer system or another defined network.
Never write “220/380 V,” “230/400 V,” or “120/240 V” alone. Name the two points used for each measure and the system setup.
Phase, line-to-line and line-to-neutral values
Single-phase, split-phase, and three-phase systems do not fit in one voltage cell. Three-phase line-to-line and line-to-neutral values describe different links. The presence of a neutral and the way loads spread across phases also change the offered setup.
The electrical return should explicitly state:
| Field | Example of the required form, not a universal value |
|---|---|
| Phase/system | Single-phase two-wire. Single-phase three-wire or split-phase. Three-phase three-wire or four-wire. |
| Nominal values | ___ V line-to-line. Add ___ V line-to-neutral when it applies. |
| Connection | Wye or star, delta, or another exact setup when relevant. |
| Neutral | State whether it exists. The application engineer defines its wire and bond setup. |
| Phase sequence | Required order and test method for three-phase loads. |
| Load balance | Allowed imbalance and planned spread of single-phase loads. |
| Output interface | Exact outlets, terminals, connector ratings, and pin or wire plan. |
A selector switch or reconnectable alternator does not prove full rated output at every listed voltage. Protection, outlets, and files may also change. Get the maker's exact connection and rating table for the offered set.
The factory image below shows why a visual check is only a start. Panel and outlet layouts differ across built units. Controlled records still need to prove the exact voltage, frequency, phase, and protection.
Use the diesel generator range and buyer guide to identify exact candidates for the electrical return. Compare them only after voltage, frequency, phase, connection, protection and outlet fields are tied to the same quoted build.
Frequency, engine speed, and voltage
Frequency is an output need. Some generator designs use engine speed to produce it. In a standard synchronous machine, pole count and shaft speed follow this formula:
synchronous speed (r/min) = 120 × frequency (Hz) ÷ number of poles
This formula is an engineering identity, not a selection rule. An inverter generator can rectify and rebuild the AC output. Other designs and controls work in other ways. Get the maker's output-control method and test proof instead of guessing from engine sound or a label.
Do not change a set from 50 Hz to 60 Hz by speed alone. The exact maker instructions must approve the full change. It may affect voltage control, alternator links, engine power, cooling, controller settings, protection, outlets, labels, rating, and conformity proof.
For motors and other frequency-sensitive loads, get the equipment maker's approval for both voltage and frequency. A fixed volts-per-hertz ratio does not prove operation at another frequency. Speed, cooling, magnetic design, torque, the driven load, and controls still matter.
Waveform and dynamic performance requirements
Nominal voltage and frequency do not describe power quality. Sensitive and nonlinear loads may set limits for harmonic distortion, wave shape, frequency drift, short dips or rises, recovery time, imbalance, and DC offset.
The official scope of ISO 8528-5:2025 covers design and performance rules for an engine and AC generator working as one set. The standard does not prove that a specific generator meets a class. The quote and proof must name the rule, edition, build, and test conditions.
Ask for exact-model returns such as:
- claimed performance class and standard edition, if applicable.
- steady voltage and frequency at defined loads.
- load-on and load-off steps, power factor, and recovery rules.
- total harmonic distortion, with metric, phases, load type, and load points.
- behavior with the buyer's UPS, VFD, charger, IT, or other nonlinear load.
- allowed load imbalance and neutral current.
- test report or method that identifies the offered configuration.
Do not assume AVR proves a wave result or inverter proves one THD limit. Use the inverter generator buying guide for design-specific decision gates.
Neutral, grounding, and transfer
Neutral bonding and grounding depend on the generator, transfer gear, distribution system, and local rules. A “floating neutral” or “bonded neutral” label is a design input. It is not one answer for every site.
OSHA's US workplace portable-generator grounding fact sheet gives a narrow case where the frame can serve as the ground electrode under set cord-and-plug conditions. OSHA's wiring rule treats portable-generator cases and separately derived systems in different ways. These are US work rules, not global wiring instructions. The actual site design remains decisive.
The project electrical drawing should establish:
- generator neutral setup and accessible terminals.
- frame and equipment grounding, plus the protective-wire path.
- whether local rules treat the source as separately derived.
- transfer switching of phase wires and neutral when required.
- an interlock that prevents unsafe parallel links or backfeed.
- ground-electrode and bond setup.
- fault-current path and protection response.
- inspection, test and labeling requirements.
Never connect a portable generator to building wires without proper transfer gear and qualified site work. Carbon monoxide, fire, shock, and backfeed risks remain separate from voltage choice.
ATS, terminals, and protection interfaces
Break “ATS compatible” into physical and control links. The generator, controller, start system, breaker, charger, and transfer gear must work as one system. Use the electric-start, remote-start, and ATS auto-start guide to separate the initiator, command path, generator response, and transfer-system ownership before comparing that claim.
Request controlled details for:
| Interface | Questions to close |
|---|---|
| Power output | Terminal or outlet type, wire capacity, neutral and earth terminals, breaker rating, and access. |
| Remote start/stop | Contact logic, control voltage, terminal IDs, start steps, and stop or cooldown action. |
| Transfer system | Exact ATS or switchgear model, poles, ratings, neutral setup, and interlock. |
| Protection | Overcurrent, short circuit, earth or ground fault when needed, voltage, frequency, overload, heat, and engine protection. |
| Monitoring | Meter values, alarms, event log, and link protocol when requested. |
| Auxiliary power | Battery, charger, heater, and standby supply needs. |
| Commissioning | Settings owner, test plan, load-bank or site-load test, and handover record. |
Portable receptacle use and building-transfer use are different approval cases. A socket image cannot prove ATS readiness, conductor capacity or protective coordination.
Environment, derating, and load sequence
Maker ratings use stated reference conditions. Altitude, heat, humidity, airflow, exhaust limits, fuel, enclosure, load steps, and power factor may reduce usable output. They may also change cooling and site needs.
Ask the exact-model manufacturer or responsible engineer to return:
- reference conditions for the stated rating.
- derating method and resulting project rating.
- allowed load steps and start sequence.
- enclosure or room airflow and heat-rejection data.
- exhaust limits and route needs.
- fuel, battery, start, and cold-weather needs.
- protection from corrosion, dust, rain, or other site risks.
- restrictions on nonlinear or unbalanced load.
Do not copy a generic percent from another engine or generator. Keep the formula, conditions, and project math in the approval file.
Cross-document configuration freeze
The final configuration should appear consistently in the commercial, technical and production records:
- quotation and purchase order.
- generator-set data sheet.
- single-line diagram and connection drawing.
- control and ATS interface drawing.
- nameplate and panel or terminal labels.
- manual and site instructions.
- relevant conformity and test records.
- FAT, inspection, and commissioning records.
- packing list when electrical accessories are separate packages.
Use a match-up matrix instead of trusting a familiar filename. One record may cover a part or model family. Another may control the exact built set. State what each file proves. The generator document checklist explains how to manage those scopes and revisions.
If the buyer first needs a broad shortlist, compare the checked electrical return with the current generator categories. Keep the exact model open until its files match.
Electrical configuration return and decision
Send each bidder the same blank return. Do not send a market example that can be copied as the answer. The supplier enters the offered value, condition, status, and source for each field. The site designer checks the distribution, transfer, grounding, protection, and load basis.
| Return block | Minimum fields |
|---|---|
| Site and loads | Market, site type, conditions, running groups, start sequence, nonlinear or sensitive loads, power factor, imbalance, and growth. |
| Output | Duty and rated need. Add V L-L, V L-N, Hz, phase, wires, connection, neutral, and exact output point. |
| Interfaces | Outlets or terminals, cable or bus limit, breaker, ATS start, sense and poles, monitoring, and auxiliary power. |
| Performance | Named steady, transient, wave, imbalance, and load-event rules, with source and test basis. |
| Protection and grounding | Engineer-set protection, bond or earth, transfer, interlock, and backfeed control. |
| Evidence | Exact offered model and build, rating basis, drawings, alternator link table, controller and ATS files, manual, plate, labels, test method, results, and revisions. |
| Exceptions | Mark each field CONFIRMED, CONDITIONAL, NOT OFFERED, or OPEN. Add the gap, owner, due date, and affected decision. |
Use the hardest planned load event as a check. Name what is already running, what starts or changes, and what must stay on. Then name the project rules that judge the response. “Stable” is not enough when the load evidence gives limits that can be measured. Record the agreed event in the load plan and test basis.
Summarize the controlled answer on a one-page power card. Link each field back to its source. The card is an index for buying and design review, not a wire plan. Mark the offer HOLD if any source conflicts on voltage, frequency, phase, connection, outlet, neutral, ATS, protection, rating, or load event. Keep the hold until controlled revisions close the mismatch. Mark NO FIT only when the offered build cannot meet a fixed project need under the proper review.
Do not release the PO while a key electrical field, source conflict, or qualified design review is open. To request an exact-model return without assuming supply, send Miya the market, load schedule, distribution and transfer context, required connection, and open return rows.
