A 100 % electronic load, an absolute continuity requirement, a closed room: the data center combines everything that puts a generic transformer in difficulty. The right specification comes down to four decisions.
Servers, UPS systems and switch-mode power supplies massively distort the current. Those harmonics create extra losses, particularly in the windings and metal parts, that a classic "kVA" sizing ignores: a standard transformer loaded at 70 % can run as hot as at full load. The answer is a K-rated unit (commonly K-13 for a typical IT hall), designed to carry that spectrum without derating. The full reasoning is in the K-factor & harmonics guide.
In an N+1 or 2N architecture, each supply chain must be able to pick up the other's load: in normal operation every transformer therefore runs around 40–50 % of its rating. The direct design consequence: no-load losses (P₀), paid 24/7, weigh proportionally more than load losses. A unit optimised for low no-load losses (up to and including an amorphous core) pays back all the faster when the PUE is watched closely.
In an occupied building, fire safety governs the technology choice. Two routes: the cast resin dry-type transformer (fire behaviour class F1: self-extinguishing, limited smoke), the standard for indoor electrical rooms; or an ester-filled oil-immersed unit (K-class fluid, fire point above 300 °C) when you want the advantages of a liquid. Mineral oil, for its part, stays outside.
A data center measures everything; the transformer is no exception. On dry-type: PT100 probes per winding plus a temperature controller reporting over RS485/Modbus to the BMS/DCIM, with alarm and trip thresholds. On oil-immersed: a DGPT2 relay wired to the protection. These options appear as such in the "Protections / accessories" field of our configurator.
From a few hundred kW, the supply runs through an MV delivery substation (in France under NF C 13-100, with the connection processed by the DSO), often a compact prefabricated substation to control schedule and footprint. Power, number of transformers and growth path are set with the design office at sketch stage: the moment when everything is still simple.
General design pointers; the exact K class, technology and architecture are determined with your design office from the real IT load and the site's requirements.
Indoors, cast resin F1 dry-type is the reference choice: no liquid, controlled fire behaviour. Ester-filled oil-immersed units have their case in a dedicated technical room or outdoors. Mineral oil stays in outdoor substations away from the building.
K-13 covers most IT halls; a load that is very predominantly electronic can call for K-20. The right figure follows the actual harmonic spectrum (measurement or UPS data). State data center in the configurator and we set it together.
Because harmonics do not dilute proportionally, and a big under-loaded transformer pays high no-load losses around the clock. A suitable K rating, a right-sized power and, if useful, AN/AF for growth is more reliable and cheaper over time.
No: it is the price of availability in an N+1 or 2N architecture. The design adapts to it: low no-load losses weigh most at that operating point, which is precisely what we optimise for.