Best Rotary Phase Converters for Up to 20 HP and Beyond
Rotary phase converters provide a reliable bridge between single-phase power and three-phase equipment, enabling CNC machines, VFDs, lathes, and other heavy tools to run from standard electrical service. This guide highlights five capable models from American Rotary and Pro-Line that cover common 5–20 HP ranges, with notes on performance, start behavior, and ideal use cases. Whether you’re upgrading a shop or expanding a small manufacturing setup, these products illustrate how modern rotary converters balance startup power, continuous load capability, and ease of integration.
| Product | HP Range | Best For |
|---|---|---|
| Rotary Phase Converter AD20 | Up to 20 HP | 10 HP loads; CNC, VFD, EDM, battery chargers |
| American Rotary AR20-20 HP | 20 HP | General purpose, motor and mixed loads |
| American Rotary AR5 | 5 HP | Light to moderate loads, general purpose |
| American Rotary AR10-10HP | 10 HP | Mid-range motor loads, light to moderate |
| Rotary Phase Converter AR15-15HP | 15 HP | General purpose with higher headroom |
Rotary Phase Converter AD20
The AD20 model is a 20 HP rotary phase converter designed to start up to 10 HP of load with strong performance for CNC, VFD, and resistive applications. It includes digital controls for precise operation and supports a 28 amp resistive or similar load. Recommended for users who require reliable 10 HP class performance on mixed loads, including rectified and computer-based equipment. This converter is positioned to handle CNC and EDM work as part of a broader 208-240V system.
American Rotary AR20-20 HP
The AR20-20 HP converter is a 1 to 3 phase device designed to handle up to 10 HP of load on light operation and up to 28 amps at 208-240V on a 20 HP rating. It is suitable for general-purpose motor loads and combination loads, with the aim of scaling to moderate power requirements. This unit emphasizes versatility for shops with varied equipment demands and a need for dependable startup performance on mid-range HP loads.
American Rotary AR5
The AR5 is a compact 5 HP rotary phase converter intended for light to moderate loads. It supports general-purpose motor loads and CNC or resistive applications up to about 2.5 HP in a single-motor equivalent. Designers use AR5 when upgrading smaller workshops or needing a reliable 208-240V 3-phase supply for light equipment.
American Rotary AR10-10HP
The AR10-10HP converter provides a bridge for 5 HP loads and light to moderate combinations, making it a solid mid-range option. It’s suitable for 208-240V systems and supports CNC, VFD, and motor-driven tools with a focus on consistent single-phase to three-phase conversions. This unit is commonly used where a balance of startup power and running efficiency is needed.
Rotary Phase Converter AR15-15HP
The AR15-15HP unit is designed for higher headroom within a 208-240V environment, enabling up to 7.5 HP light loads or more with stable operation. It is a strong option for shops with a mix of 7.5 HP CNC machines or other equipment that requires consistent 3-phase power without relying on utility-grade three-phase service. This converter emphasizes reliability for mid-to-large scale hobbyists and small manufacturers.
PL-5 Pro-Line 5HP Rotary Phase Converter
The PL-5 Pro-Line is a 5 HP rotary phase converter designed to generate 3-phase power for up to 7 amps at 208-240 volts. It is built to start and run a 2.5 HP motor or equivalent loads, with a two-piece configuration including an electrical control panel and an idler motor. This option suits small workshops that require efficient 3-phase supply for compact CNC or resistive loads and seek straightforward setup.
Buying Guide: Key Considerations For Choosing A Rotary Phase Converter
- Load rating and headroom: Match the converter’s HP rating to the peak load of your tools, and allow additional headroom for startup surges. Higher HP units handle heavier, mixed loads with less risk of voltage dips.
- Phase balance and voltage stability: Look for models with stable output at 208-240V and robust regulation under varying loads. Balanced secondary phase helps extend motor life and performance.
- Startup method: Some models offer “soft start” or digital controls to ease initial current draw, while others rely on traditional mechanical idlers. Choose based on the sensitivity of your equipment to startup transients.
- Floor vs. benchtop vs. integrated: Floor units (AR20F, AR15-15HP) are common for shop floors, while compact or panel-mounted designs suit tighter spaces and integrated production lines.
- Compatibility with CNC and VFD loads: If your shop runs CNC, EDM, or VFD devices, ensure the unit can handle resistive and rectified loads with sufficient amperage capacity.
- Maintenance and assembly: Some models require assembly or come with pre-wired control panels. Factor in setup time, accessibility for service, and any optional accessories.
- Warranty and support: Check for manufacturer warranties and availability of technical support, which can be crucial for high-use environments.
- Physical dimensions and installation environment: Ensure adequate space for the idler motor and cooling requirements, especially in high-temperature shops or enclosed areas.