The Use Case

A metal‑fabrication shop has a 170‑ton CNC press brake whose motor is rated 40 HP at 230 V three‑phase. The facility was built with only 120/240 V single‑phase service, and upgrading the entire building to three‑phase would be cost‑prohibitive. The owner needs a reliable phase conversion solution that can handle the high starting torque of the press brake’s motor while maintaining precise speed control.

What Usually Matters for Sizing

  1. Motor horsepower – At 40 HP, Phoenix recommends a converter rated at ≈2 × HP, i.e., an 80‑90 HP unit, to provide ample start‑up torque and voltage stability during heavy load changes.
  2. Locked‑Rotor Amps (LRA) / Full‑Load Amps (FLA) – Large press brakes can draw several hundred amps at lock‑rotor; the converter must sustain this surge without excessive voltage sag.
  3. Voltage – Both source and motor are 230 V, so no transformer is required; the converter will generate a balanced third leg at the same line‑to‑line voltage.
  4. Starting behavior – Press brakes often start under load (the ram may be positioned), creating high instantaneous torque demand. A larger idler reduces voltage drop and protects the motor windings.
  5. Service capacity – The building’s main breaker must accommodate the converter’s input current, which for an 80 HP unit can be 150–180 A at 240 V. An upgrade to the service panel may be necessary.

Common Mistakes to Avoid

  • Undersizing the converter – A 40 HP‑rated converter will likely stall or cause voltage imbalance during heavy presses.
  • Ignoring LRA – Failing to account for the massive inrush can damage both motor and converter.
  • Skipping breaker coordination – The input breaker must be sized for the converter’s draw; otherwise you’ll experience nuisance trips.
  • Assuming a small transformer will help – Since voltage is already 230 V, adding a transformer only adds loss without solving start‑up torque.

Practical Phoenix Recommendation

The call evidence (E038) points to the GP100NL, a 100 HP “Phase‑Only” rotary converter. For a 40 HP press brake, this model offers:

  • Ample idler capacity – Provides more than double the required horsepower, ensuring stable voltage during high‑torque starts.
  • Robust construction – Designed for heavy industrial loads with continuous duty cycles.
  • Three‑phase output at 230 V – Matches the press brake’s motor rating without needing a transformer.

Final sizing must be confirmed against the press brake’s nameplate (HP, voltage, LRA/FLA) and the facility’s service capacity. If the existing panel cannot support the converter’s input current, a service upgrade or dedicated feeder may be required.

What to Have Ready Before Calling

  1. Press brake motor nameplate – HP, voltage, LRA, FLA, and any start‑up torque specifications.
  2. Existing electrical service data – Main panel amperage, available breaker slots, and single‑phase voltage (120/240 V).
  3. Load profile – Frequency of presses per hour, typical load conditions (ram position) to gauge starting demand.
  4. Physical layout – Distance from converter to press brake for cable sizing and ventilation planning.
  5. Any future equipment you may add that will share the same three‑phase bus.

Providing these details lets a Phoenix engineer verify that the GP100NL is the appropriate 100 HP solution, confirm any necessary service upgrades, and generate an accurate quote quickly.