The Use Case

A mid‑size fabrication shop runs a variety of heavy‑duty machines—CNC mills, press brakes, hydraulic presses, and other shop floor equipment. Each piece is rated for three‑phase power (often 460/480 V) but the building only supplies 230 V single‑phase. The owner wants to keep the existing machines, avoid costly rewiring, and maintain production throughput.

What Usually Matters for Sizing

  1. Horsepower per machine – Heavy equipment can range from 5 HP up to 30 HP or more. Each motor’s nameplate HP is the primary sizing factor.
  2. Voltage rating – Most shop machines are 460/480 V three‑phase; if the site only has 230 V single‑phase, a transformer package may be required to step the input up before conversion.
  3. Full‑load amps (FLA) & Locked‑rotor amps (LRA) – These values dictate the converter’s internal transformer rating and its ability to start large motors without voltage sag.
  4. Starting method – Some CNC drives use soft starters or variable‑frequency drives (VFDs); others have direct‑on‑line starts that demand high LRA. Knowing this helps decide whether a standard NL model suffices or if an “auto‑link” (compressor‑duty) configuration is needed for repeated starts.
  5. Duty cycle – Continuous operation (e.g., a press running 8 hours/day) requires more thermal capacity than intermittent use.

Phoenix typically recommends the GP10NLA family for most shop‑floor loads up to about 10 HP when the input voltage matches the motor rating. For larger or more demanding machines, stepping up to a GP12NLA or GP15NLA provides extra transformer headroom.

Common Mistakes to Avoid

  • Overlooking voltage mismatch – Trying to run a 480 V motor directly from a 230 V converter will cause severe undervoltage and damage. Include a step‑up transformer if needed.
  • Using “bare NL” SKUs for heavy starts – Bare neutral‑leg units lack the internal overload protection required for repeated high‑LRA starts typical of presses or CNC spindles. Choose an auto‑link or compressor‑duty rated converter instead.
  • Ignoring cumulative load – When multiple machines share a single converter, add their HP and LRA values together; undersizing leads to frequent trips.
  • Skipping final nameplate verification – Even if the shop’s paperwork lists “10 HP,” the motor may be derated for 230 V operation; always confirm the exact rating on the nameplate.

Practical Phoenix Recommendation

For a typical mixed‑load shop with machines ranging from 5 HP to 15 HP, start with a GP12NLA rotary phase converter. This model provides:

  • Three‑phase output at 460/480 V (or 230 V if the machine is rated lower).
  • An internal neutral leg for balanced loads and reduced harmonic distortion.
  • Sufficient transformer capacity to handle simultaneous starts of two medium‑size CNC spindles or a press brake plus a mill.

If any equipment requires 30 HP or higher, consider pairing the GP12NLTA package with a step‑up transformer package (e.g., 230 V → 460 V, 6 kVA) to meet voltage and power demands safely.

Final sizing must be confirmed against the machine nameplate, motor HP, voltage, LRA/FLA when applicable, and starting behavior.

What to Have Ready Before Calling

  1. Nameplates for every machine you plan to connect (HP, volts, FLA, LRA).
  2. Electrical service specs – single‑phase voltage, breaker size, distance from panel to machines.
  3. Load schedule – which machines will run simultaneously and which are intermittent.
  4. Space & ventilation details for the converter and any transformer package.

Providing these details lets a Phoenix specialist calculate the exact converter model, determine if a transformer is required, and give you an accurate quote without back‑and‑forth.