Lathes demand consistent, balanced three-phase power for smooth spindle rotation. Imbalanced or dirty power causes vibration, chatter marks, and poor surface finishes. A rotary phase converter produces true sinusoidal three-phase power — the same clean power your lathe was built to run on.

Many modern lathes have built-in variable frequency drives or servo motors. VFDs stacked behind another VFD (as a phase converter) creates harmonic issues that corrupt the lathe's own drive electronics. A rotary converter feeds clean utility-grade power into your lathe's existing controls — no interference.

Interrupted cuts and heavy roughing passes create sudden load spikes. The rotary converter's idler motor acts as a flywheel, absorbing and delivering surge power without tripping breakers or stalling the spindle. This is something static converters simply cannot do.

Quality lathes cost $5,000 to $150,000+. Running them on underpowered or harmonically distorted power shortens motor life, damages bearings, and degrades spindle accuracy over time. A properly sized rotary phase converter protects your lathe investment for decades.

• South Bend, Clausing, Leblond, Monarch
• Typical range: 1–10 HP
• Geared head or variable speed
• Most common home/job shop lathe
• Standard NL converter is perfect

• Haas, Mori Seiki, Okuma, Mazak, Doosan
• Typical range: 10–50 HP
• Built-in servo drives and coolant pumps
• Need clean power — rotary converter ideal
• Often 460V — use NLT/NLTA package

• Warner & Swasey, Lodge & Shipley, American Pacemaker
• Typical range: 5–30 HP
• Heavy-duty production and maintenance
• High inrush on startup
• Oversize converter by 1 step

Check the nameplate on the main spindle motor — it lists the HP, voltage, and phase. For CNC lathes, check the electrical panel door or the machine's specification sheet. If you can't find it, call us at (800) 417-6568 with the lathe's make and model and we'll look it up.

You need an NLT or NLTA converter package. This takes your 230V single-phase input and produces 460V three-phase output — the exact voltage your CNC lathe requires. No separate step-up transformer needed.

Absolutely. Size the converter for the total HP of all machines running at the same time. Example: 5 HP lathe + 3 HP mill + 2 HP surface grinder = 10 HP → use a GP10NL. This is one of the biggest advantages of a rotary converter over a VFD.

No — in fact, a rotary converter produces cleaner, more balanced power than many utility feeds. There's no harmonic distortion, no electronic noise, and the flywheel effect of the idler motor actually smooths out power fluctuations. Your lathe will run as well or better than it would on utility three-phase.

NL series is our most popular for lathes — it runs continuously and you start/stop your lathe normally. PL series adds a magnetic starter with start/stop control — better if you want the converter to shut down when you're not using the lathe, or for safety compliance in commercial shops.

Technically possible for some simple engine lathes, but you'll lose roughly 1/3 of the motor's power and torque. Heavy cuts will stall the spindle. CNC lathes absolutely will not run on static converters — the control electronics require balanced three-phase power.