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Transformer for battery storage (BESS)

Battery storage imposes truly bidirectional flow and harmonic-rich converters: the transformer is specified for that duty from the start — not patched afterwards.

• Bidirectional flow  • K-adapted  • Tier 2  • Delivered in 15–18 weeks

Containerised units · high-voltage chamber

What changes with a BESS

A conventional distribution transformer is designed for downward flow and a roughly sinusoidal load. A battery system charges and discharges — the flow reverses several times a day — and the PCS converters inject harmonics that heat the windings beyond the apparent RMS current. The engineering answer: a K-adapted design (thermal oversizing of the windings), screens and vector group chosen for inverter duty, and endurance against repeated thermal cycling.

Tell us in your request: PCS rating and number of units, harmonic spectrum (THDi), cycling profile (cycles/day), dedicated or shared transformer, site constraints (outdoor, coastal, altitude).

Specification benchmarks (indicative)

ParameterTypical BESS range
Power630 – 3,150 kVA per conversion unit
Impedance6 – 8 % depending on PCS requirement
K-factorK4 – K13 depending on harmonic spectrum
Vector groupDyn11 (others per conversion scheme)
Dielectricmineral oil · ester (enhanced fire safety) · cast resin
Delivered lead time15 to 18 weeks — production + shipping

Indicative pre-sizing values — the final specification follows your requirement and the actual PCS duty, confirmed at quotation.

Frequently asked

Can a standard transformer feed a BESS?

Technically it will run, but it ages prematurely: converter harmonics create additional losses its thermal design never accounted for. A K-adapted design costs little at the design stage and avoids an early replacement.

One transformer per PCS?

Both architectures exist: one transformer per conversion unit, or a shared multi-winding unit. The choice follows the project's electrical scheme — tell us yours and we will quote both if useful.

Is ester mandatory for a battery site?

No, but it is often chosen: high fire point and biodegradability strengthen the fire-safety case for a storage site. Mineral oil, ester or cast resin — we quote against your risk analysis.

Ready to quote

A BESS project with a specification?

Select “Storage / BESS” in the Application field of the configurator, or send your specification — first reply within 48 h.

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