The Use Case

A gym is importing custom Italian boxing training rigs that require 480 V three‑phase power. The facility only has standard 208/240 V single‑phase service. To bridge the gap, two 6 kVA autotransformers (208 V→480 V) are needed, plus a phase converter to generate the three‑phase waveform.

What Usually Matters for Sizing

  1. Transformer kVA rating – Each 6 kVA transformer can safely handle about 10 A at 480 V. Multiply by two if the equipment draws power from both phases.
  2. Total load (kW) – Determine the combined wattage of all boxing equipment; ensure it stays below the aggregate 12 kVA capacity (≈20 A at 480 V).
  3. Voltage conversion – Autotransformers step up 208 V single‑phase to 480 V three‑phase; they must be compatible with the converter’s output voltage and phase angle.
  4. Phase converter rating – The converter must supply enough three‑phase current for both transformers plus any additional loads (e.g., lighting). A 15–20 HP AutoLink unit is typical for a 12 kVA load.
  5. Single‑phase input capacity – The site’s service must provide the combined amperage of the converter and transformer losses (often ~30 A at 240 V).

Common Mistakes to Avoid

  • Skipping the autotransformer step – Feeding a 480 V‑only device directly from a 208 V converter will cause undervoltage and possible damage.
  • Undersizing transformer kVA – Overloading a 6 kVA unit leads to overheating, reduced lifespan, and nuisance trips.
  • Using a bare NL converter for high‑inrush loads – The boxing equipment may have motorized resistance bands or pneumatic actuators that draw spikes; an AutoLink model is safer.
  • Neglecting harmonics – Autotransformers can amplify voltage distortion from the converter; choose a converter with low THD (Total Harmonic Distortion).

Practical Phoenix Recommendation

Based on the call where a customer requested “two 6 kVA 208 V→480 V autotransformers” and was matched with Maddox 6 kVA 3‑Phase Autotransformer, the recommended solution is:

  1. Select two Maddox 6 kVA autotransformers – Ensure they are rated for 208 V primary, 480 V secondary, three‑phase output.
  2. Pair with a GP15NL AutoLink converter (≈15 HP) – This provides enough headroom for the combined transformer load and any ancillary equipment.
  3. Install a single‑phase input breaker sized at 40 A on the 240 V side to accommodate converter draw plus transformer losses.
  4. Run balanced three‑phase cabling from the converter through the autotransformers to the boxing rigs, keeping conductor length under 100 ft to limit voltage drop.

If space permits, a larger GP20NLA (20 HP) can be used for extra margin and future expansion.

What to Have Ready Before Calling

  • List of equipment with nameplate kW or HP.
  • Desired three‑phase voltage (480 V).
  • Existing single‑phase service rating (amps at 208/240 V).
  • Confirmation that the primary side of the autotransformers will be fed from a 208 V source.
  • Any plans to add more three‑phase loads later.

Final note: Verify final sizing against each piece of equipment’s nameplate, total kVA demand, voltage, and any starting currents before ordering. A correctly sized AutoLink converter plus two Maddox 6 kVA autotransformers will give reliable 480 V three‑phase power for the Italian boxing system on a single‑phase supply.