3 HP Phase Converter — 7 Things You Need to Know

A 3 HP rotary phase converter is the smallest rotary unit in Phoenix's lineup — and it is the right choice for a specific set of small shop machines. Here is everything you need to know before ordering.

1. What Equipment Does 3 HP Cover?

The GP3NL handles single three-phase motors up to 3 HP on easy-to-medium starting loads. Common applications include:

  • Small bench grinders and drill presses (up to 3 HP)
  • Small lathes (1.5–2 HP max — 1.5x multiplier)
  • Small milling machines (1–1.5 HP spindle)
  • Light-duty conveyors

2. The Sizing Multiplier Still Applies

3 HP is the converter rating, not the motor HP you can run for every application. Hard loads (CNC, lathes) use a 2x multiplier — so a 3 HP converter only covers a 1.5 HP lathe motor. Easy loads (grinders, saws) use 1x — a 3 HP converter covers a 3 HP grinder.

3. It Will Not Run a Bridgeport Reliably

A standard 2 HP Bridgeport milling machine needs at least a 5 HP converter (2 HP x 2.0 multiplier). The GP3NL may start a lightly loaded Bridgeport but will struggle under combined spindle and power feed load. Go GP5NL for a Bridgeport.

4. Auto-Start NL Series

The GP3NL is an NL Series converter — it starts automatically when single-phase power is applied. No button required. When you turn on your machine's disconnect, the converter energizes and is ready within 2–3 seconds.

5. 230V Input, 230V Output

The GP3NL requires 230V single-phase input and delivers 230V three-phase output. It is not suitable for 460V equipment.

6. Lifetime Warranty Included

Like every Phoenix Phase Converter, the GP3NL includes a lifetime warranty. If a capacitor fails years down the road, call us and we will get you the right part.

7. When to Step Up to 5 HP

If you are on the fence between 3 HP and 5 HP, go 5 HP. The price difference is modest, and the extra headroom means reliable starts, less voltage sag on the generated leg, and longer converter life. Call (800) 417-6568 if you want a second opinion on sizing.

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3 HP Converter — FAQ

Is the GP3NL powerful enough for a small machine shop?

For a single small machine (grinder, small drill press, small lathe under 2 HP), yes. For a shop with multiple machines or anything larger than a small benchtop unit, step up to GP5NL or GP10NL.

Can I add more equipment later if I start with a 3 HP converter?

Not without upsizing the converter. Each converter is rated for a maximum total load. If you expect to grow, buy larger now — it is more economical than replacing the converter in 6 months.

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Questions? Talk to an engineer.

Free sizing help. Made in Phoenix, AZ. Lifetime warranty on every unit.

Shop Phase Converters

(800) 417-6568