Transformer Selection for Commercial Buildings
Reviewed by the Fengguang engineering team · Last updated 8 Nov 2026
Commercial Buildings projects typically use 10/20 kV indoor distribution. Select the transformer on load profile, ambient, protection and interface; confirm the final rating on the datasheet.
Load and duty
Commercial Buildings loads are not all the same. Define the maximum demand, cyclic or continuous duty, motor starting, harmonic content and future expansion. The transformer must carry the real profile, not the connected load.
Recommended configuration
A typical starting point is Dry-type cast-resin, 500-2,000 kVA. The final choice depends on the site, fire strategy, fault level and maintenance capability. For outdoor or compact sites, a prefabricated station may reduce civil works.
Protection and interface
Confirm the transformer impedance, LV breaker rating, relay settings, earthing and cable entry. The transformer is part of a system; the protection study and the single-line diagram must agree.
Common mistakes
Common errors include sizing on connected load, ignoring ambient derating, specifying a generic IP rating, leaving no cable-entry space and forgetting the transport route. Each of these becomes a site problem after delivery.
Site conditions and enclosure
Confirm the ambient temperature, altitude, dust, humidity, salt spray and solar gain. For outdoor duty, specify the IP rating, corrosion class, cable entry and ventilation. For indoor duty, confirm the room heat balance and fire strategy.
Acceptance checks
Review the approved drawing, nameplate, routine test report and accessories before shipment. On site, check the foundation, earthing, cable termination, oil level (if applicable), protection settings and commissioning records.
| Input | Why it matters |
|---|---|
| Maximum demand | kVA and load factor |
| Duty | Continuous, cyclic or bidirectional |
| Ambient / altitude | Cooling and derating |
| Fault level | Impedance and protection |
| Layout | Station, cable entry and access |
FAQ
What transformer is used for Commercial Buildings?
Typically Dry-type cast-resin, 500-2,000 kVA. The exact rating, impedance and cooling must be confirmed from the load and site data.
Can a standard transformer be used?
Often a standard platform can be adapted, but the ambient, duty, protection and interface must be checked. A generic catalogue unit is not a design review.
What should be in the enquiry?
Maximum demand, voltage class, frequency, duty, ambient, altitude, fault level, required standards, documents and delivery schedule.
How do I compare options?
Compare guaranteed losses, impedance, cooling stage, dimensions, mass, protection and document scope on the same load case.
What is the most common specification error?
Sizing on connected load and ignoring the site ambient or altitude. Both lead to a unit that is either oversized or thermally limited.
Related pages
Need this applied to a project?
Send the application, voltage class and site conditions through the inquiry form. The team will check the transformer family and the document scope.
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