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A 1 000 kVA transformer is the rating most commercial and mid-size industrial sites land on. It is large enough to serve a substantial plant or a battery storage and solar step-up duty, and small enough to arrive as a single skid-mounted unit rather than as a site-assembled substation.
Transformers are built to order, so this page is about what has to be specified rather than what is on the shelf. It covers the rating decision, the electrical values your network depends on, and what the site has to provide.
The rating is a thermal question, not a load number
The most common specification error is to size a transformer from the connected load. The rating is chosen from the load profile and the diversity factor: how much of the connected equipment actually runs at once, and for how long.
- Demand assessment uses measured or engineered simultaneous demand. Do not apply a generic diversity percentage to solar export, storage charge/discharge or a process that can operate at full load.
- Loading profile matters because the rating is thermal. A unit that runs at 80 percent for three hours a day ages differently from one that runs at 80 percent continuously.
- Future headroom is worth stating at enquiry stage, because adding it later means a second unit rather than a larger one.
Send the load or generation profile, required reactive-power duty and planned future capacity. The selected kVA must cover the design duty under the stated thermal conditions; any diversity or overload allowance needs an engineering basis.
Specifications
Configuration reference
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| Parameter | Typical value | What it depends on |
|---|---|---|
| Rated power | 1 000 kVA | Load profile and diversity factor |
| Type | Oil-immersed ONAN, or cast-resin dry-type | Indoor or outdoor, and fire risk |
| Primary voltage | Up to 34.5 kV; 13.8 kV and 4.16 kV common | Your utility supply voltage |
| Secondary voltage | 480Y/277 V or 400 V | Plant voltage and earthing arrangement |
| Phases and frequency | Three-phase, 60 Hz | Local network standard |
| Impedance voltage | Typically 5.75 percent | Prospective fault level and parallel operation |
| Vector group | Dyn11 or YNd11 | Parallel operation, harmonics and earth faults |
| Cooling | Confirm cooling designation for the selected oil or dry-type design | Rated duty, ambient conditions and manufacturer design |
| Insulation | Class A, 65 degrees Celsius rise | Ambient temperature and loading |
| Losses | Specify applicable efficiency requirements and measured load/no-load losses | Transformer scope, destination market and delivery requirements |
| Enclosure | Outdoor NEMA 3R or IP54 | Siting and local requirements |
| Compliance documents | Confirm applicable transformer standards and required third-party documents | Exact design, utility specification and inspection requirements |
| Approximate weight | 3 000 to 3 600 kg | Final type and options |
Figures are selection references. Confirm the final ratings, dimensions, available certifications and warranty against the current datasheet and written proposal for the selected model or system.
What arrives in a typical order
- The selected oil-immersed or dry-type transformer, routine-tested and prepared for the agreed transport and installation arrangement.
- Routine test report to IEEE C57 or IEC 60076 for that unit, not a type report.
- Nameplate data, wiring diagram and the vector group confirmed on the drawing.
- Installation, oil handling and maintenance documentation.
- Packing list and delivery documentation.
Where the project needs it, the medium-voltage switchgear, the low-voltage distribution board and the protection settings are quoted on the same order so the fault rating and discrimination are settled together.
Where a 1 000 kVA unit usually goes
- Commercial and industrial service entrances stepping the utility voltage down to plant voltage.
- Battery storage and solar step-up duty, matching the inverter output to the interconnection voltage.
- Campus and multi-building distribution as the primary substation unit.
- Replacement of a failed or obsolete unit, where the footprint and the vector group have to match what is there.
What the site has to provide
- A level, load-bearing pad or foundation, built to the drawing we issue.
- For oil-immersed units, oil containment and the separation your fire authority requires.
- Crane or heavy-capacity handling, and an approach route that takes the delivery vehicle.
- Clearance and access for terminations on both sides, and for future maintenance.
Sizing notes before you order
- State the losses you want, not just the rating. Load loss and no-load loss are separate line items, and evaluating on purchase price alone is what makes a cheap unit expensive over twenty years.
- Confirm the vector group against any unit it will run in parallel with. Getting it wrong only shows up at energisation.
- Confirm the impedance against your fault study. Lower impedance improves regulation but raises the fault current the switchgear downstream has to withstand.
- Decide oil-immersed or dry-type early: dry-type indoors or where fire risk is the constraint, oil-immersed outdoors at this rating for cost.
Documentation to confirm for your order
- Routine test report for the specific unit, to IEEE C57 or IEC 60076.
- Dimensional drawing, nameplate data and the wiring diagram with the vector group marked.
- Loss figures measured, not catalogue values.
- Installation, oil handling and maintenance documentation, and the warranty terms.
Questions buyers ask
Oil-immersed or cast-resin dry-type?
Dry-type is specified indoors or wherever fire risk is the constraint. Oil-immersed is more economical outdoors at this rating. We size and price both so you compare total cost rather than unit price.
How long does it take to build?
Common ratings are in U.S. stock and ship with dispatch timing confirmed for the selected model and delivery address. Engineered ratings are built to your specification and quoted with a firm date rather than a range, because the date depends on the production slot.
Is there a minimum order quantity?
No. Transformers are built to order, so the quotation is driven by rating and specification rather than by quantity. One unit is a normal order.
Which losses should we specify?
Specify both load and no-load losses and compare lifetime cost using the expected duty. Confirm the efficiency requirements applicable to the selected transformer type and destination market on the quotation.
Can it match an existing transformer we are paralleling with?
Yes, provided the vector group, impedance and voltage ratio are matched. Those three have to be confirmed from the existing nameplate before the new unit is built, not after.
What to send us
Send the primary and secondary voltages, the load profile or the connected load with the diversity you assume, indoor or outdoor, and your target date. We come back with the rating recommendation, the losses, and a firm build date.
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Send the rating, the voltage and the site conditions
With the kVA rating, primary and secondary voltage, altitude, ambient range and whether the installation is indoor or outdoor, we confirm the cooling class, enclosure and test documentation.
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