Digital Phase Converters 101
A digital phase converter uses solid-state electronics to convert single-phase power into clean, balanced three-phase power with no rotating parts, so you can run CNC machines and other voltage-sensitive three-phase equipment wherever utility three-phase power is unavailable.
What is a digital phase converter?
A digital phase converter is a solid-state device that converts single-phase power into three-phase power electronically, without the rotating motor used in other converter types. Where a rotary converter spins an idler generator to create the missing third phase, and a static phase converter only helps a three-phase motor start, a digital phase converter uses high-speed solid-state switching and a microprocessor to produce a smooth, continuous three-phase output.
Proudly made in the USA, NAPCco digital phase converters maintain phase-to-phase voltage balance within 2% under any load condition. That precision, combined with quiet operation and high efficiency, makes them the ideal choice for CNC machines, VFDs, and other voltage-sensitive equipment.
How does a digital phase converter work?
A digital phase converter converts the incoming single-phase supply to DC power and then electronically rebuilds it into three-phase AC power using solid-state switching. There are no moving parts in this type of phase converter. A built-in microprocessor continuously monitors the output voltage and corrects it in real time, maintaining output voltage within 2% of the input, regardless of load.
Because the output is regulated electronically rather than mechanically, a digital converter delivers a clean, continuous sine wave with minimal heat generation and low standby power consumption. That efficiency makes a digital converter a cost-effective choice for equipment that runs unattended for extended periods, such as elevators, pumps, and air compressors.
Digital Phase Converter vs Rotary Phase Converter: What’s the difference?
Both a digital phase converter and a rotary phase converter convert single-phase power into three-phase power, but they do it in very different ways. The right choice depends on your equipment and your budget.
| Feature | Digital Phase Converter | Rotary Phase Converter |
|---|---|---|
| How it works | Solid-state electronic switching, no moving parts | Spins an idler generator motor to create the third phase |
| Voltage balance | Within 2% under any load | Within 5% |
| Power quality | Clean, continuously regulated sine wave | Balanced three-phase, corrected by run capacitors |
| Noise and moving parts | No moving parts, slight electrical hum | Rotating idler motor, some running noise |
| Efficiency | High efficiency through minimal heat generation | Efficient under load, the idler runs continuously |
| Best for | CNC, voltage-sensitive and precision equipment, unattended loads | General motor, resistive and inductive loads, multiple simultaneous loads |
| Capacity range | 5 HP – 75 HP | 3 HP to 100 HP |
| Warranty | 1-year parts and labor, extended available | 10-year parts / lifetime labor |
| Relative cost | Premium | Mid-range |
| Shop | Shop Digital Phase Converters | Shop Rotary Phase Converters |
For a full breakdown of every converter type, including static converters, see Phase Converters 101.
Is a digital phase converter right for you?
A digital phase converter is the best fit for voltage-sensitive equipment and loads that run for long, unattended periods. Use the table below to see if your setup is a typical fit.
CNC Machines
Common Equipment: CNC mills, CNC lathes, CNC plasma cutters, CNC routers
Why a digital phase converter suits it: CNC machines require tight, balanced voltage to operate, and computer-operated machinery is sensitive to voltage fluctuations. A digital phase converter supplies the load with power balanced to within 2% phase-to-phase.
Elevator Applications
Common Equipment: Residential elevators in single-family homes and apartment buildings, commercial elevators
Why a digital phase converter suits it: Digital phase converters are ideal for equipment that runs throughout the day because they use less standby power when idle. An elevator may run for around 4 hours a day and sit idle for the other 20, making a digital converter the most cost-effective solution.
HVAC Equipment
Common Equipment: Rooftop air conditioning units, VRF systems
Why a digital phase converter suits it: Most rooftop and VRF systems are built for three-phase power but are often installed in apartment buildings or commercial settings that only have single-phase power. Because these units run for long periods, often 24/7, they benefit from a digital converter’s energy-efficient design.
Automated Systems
Common Equipment: Conveyors, air compressors, pumps
Why a digital phase converter suits it: Automated systems often run for prolonged periods, known as a continuous duty cycle, and are frequently left unattended, so they suit a digital converter’s efficient, low-standby operation.
Equipment with VFDs or Drives
Common Equipment: Machinery with built-in variable frequency drives
Why a digital phase converter suits it: Equipment with built-in VFDs or drives is often very sensitive to voltage fluctuations, much like CNC machines, so the three-phase output voltage needs to be as close as possible to the single-phase input voltage.
Woodworking Equipment
Common Equipment: A wide range of woodworking machines
Why a digital phase converter suits it: Runs a wide variety of woodworking equipment, much like the Pro-Line rotary phase converter.
Sizing Your Digital Phase Converter
Proper sizing is critical. A digital phase converter is sized to the amperage or horsepower of the equipment it will run, so an undersized unit will struggle to sustain full three-phase output, particularly if you run multiple machines at once. Use the tool below or call us at 877-545-2926 for free sizing help.
For model-by-model amperage and full specifications, see the digital phase converter range.