What Is a Phase Converter? How It Converts Single-Phase Power to Three-Phase Power
Introduction
Many industrial machines, motors, pumps, compressors, and other equipment are designed to operate on three-phase power. However, some facilities, workshops, and locations may only have a single-phase electrical supply available.
A phase converter provides a way to obtain three-phase power from a single-phase source, allowing compatible three-phase equipment to operate where a direct three-phase utility connection is unavailable or impractical.
Depending on the equipment and application, phase conversion can be accomplished using different technologies, including rotary and solid-state/digital phase converters. The correct solution depends on the connected load, motor starting requirements, voltage, frequency, and required power quality.
What Is a Phase Converter?
A phase converter is an electrical device designed to convert an available single-phase electrical supply into a three-phase output for compatible three-phase equipment.
For example, a facility may have a single-phase supply but need to operate a three-phase motor or industrial machine. A properly selected phase converter can provide the required three-phase output without requiring an immediate upgrade to a three-phase utility service.
A phase converter should not be confused with a conventional transformer. A transformer primarily changes voltage levels and/or provides electrical isolation, while a phase converter addresses the number and configuration of electrical phases.
Why Convert Single-Phase Power to Three-Phase?
Three-phase power is widely used for industrial equipment because it provides a practical way to supply motors and other loads continuously.
A phase converter may be considered when:
Three-phase utility power is unavailable
Upgrading the utility service is costly or impractical
A workshop needs to operate three-phase machinery
A facility needs to operate three-phase motors
Pumps or compressors require three-phase power
Industrial equipment was purchased with a three-phase input
A temporary or remote installation requires three-phase power
The suitability of a phase converter depends on the specific equipment and electrical system.
How Does a Phase Converter Work?
The basic concept is straightforward:
Single-Phase Input → Phase Conversion → Three-Phase Output → Three-Phase Equipment
However, the actual conversion method depends on the type of phase converter.
Different technologies can generate the required third phase and provide different characteristics in terms of voltage balance, motor starting performance, efficiency, controls, and compatibility with electronic equipment.
For this reason, selecting a phase converter based only on the horsepower of a motor may not be sufficient.
What Is a Rotary Phase Converter?
A rotary phase converter uses a rotating electrical machine, commonly referred to as an idler motor or generator, to produce a three-phase output from a single-phase supply.
Rotary phase converters have traditionally been used for applications such as:
Machine shops
Pumps
Compressors
Industrial motors
Lathes
Milling machines
Grinders
Manufacturing equipment
The converter must be properly sized for the connected equipment, particularly where motors have significant starting-current requirements.
What Is a Static or Digital Phase Converter?
Another approach uses electronic power conversion rather than a rotating machine.
Modern solid-state phase converters can electronically generate the required three-phase output. Some systems can also regulate voltage and, depending on the design, frequency.
These systems may be appropriate where the application requires tighter control of the output or where the connected equipment contains sensitive electronics.
The important point is that not every phase converter has the same output characteristics. The converter should be selected according to the equipment manufacturer's requirements.
Can a Phase Converter Run a Three-Phase Motor?
Yes, a properly selected phase converter can be used to operate compatible three-phase motors.
However, motor starting is an important consideration.
A motor can draw substantially more current during starting than during normal operation. Hard-starting equipment such as compressors, pumps, and certain machinery may require additional consideration when sizing the phase converter. For more information about motor starting requirements, see our article on What Is a Motor Starting Transformer?
Motor horsepower or kW
Motor voltage
Full-load current
Starting current
Starting method
Number of motors
Whether motors start simultaneously
Continuous operating load
Other equipment connected to the converter
What Equipment Can Use a Phase Converter?
Phase converters may be used with many types of three-phase equipment, including:
Industrial Machinery
Machine tools, production equipment, and other industrial machinery may require three-phase power.
Motors and Pumps
Three-phase motors are common in pumps, compressors, fans, and industrial machinery.
CNC Equipment
CNC machines may have specific power-quality requirements, so converter selection should consider both the motor and the machine's electronic controls.
Compressors
Compressors can have significant starting demands and should be evaluated based on their starting characteristics.
Workshops
A workshop with only single-phase utility service may use a phase converter to operate selected three-phase machines.
Single-Phase vs. Three-Phase Power
Feature Single-Phase Three-Phase
Number of phases 1 3
Common use Residential and smaller loads Industrial and commercial equipment
Motor applications Smaller motors and equipment Industrial motors and machinery
Power delivery Pulsating More continuous
Typical industrial equipment compatibility Limited for some equipment Widely used
Phase conversion Can be converted to three-phase Direct three-phase supply
The actual electrical characteristics depend on the voltage, frequency, system configuration, and application.
How Do You Size a Phase Converter?
Correct sizing is one of the most important parts of phase-converter selection.
The converter should not simply be selected based on the motor's nameplate horsepower.
Consider the following:
1. Input Voltage
Determine the available single-phase supply voltage.
2. Required Output Voltage
Determine the voltage required by the three-phase equipment.
3. Frequency
Confirm whether the equipment requires 50 Hz or 60 Hz.
4. Equipment Capacity
Determine the motor horsepower, kW, kVA, or electrical current requirement.
5. Starting Requirements
Identify whether the equipment has a high starting-current demand.
6. Total Connected Load
If multiple machines will operate from the same converter, evaluate the combined load and operating sequence.
7. Power Quality Requirements
Equipment containing sensitive electronic controls may have different requirements from a basic three-phase motor.
8. Installation Conditions
The enclosure, ventilation, ambient temperature, protection, disconnects, and other installation requirements should also be considered.
When evaluating the overall electrical load, it is also important to understand how kVA, load demand, voltage requirements, and motor starting affect equipment sizing. See our guide on How to Choose the Right Transformer Capacity for Your Facility.
Phase Converter vs. Transformer
A phase converter and transformer perform different functions.
Device Primary Function
Transformer Changes voltage and/or provides electrical isolation
Phase Converter Converts available electrical phases
Voltage Regulator Helps maintain voltage within a desired range
Variable Frequency Drive Controls motor speed and frequency
Phase Converter + Transformer Can be combined when both phase conversion and voltage transformation are required
In some projects, a transformer may be part of the overall system, but it does not by itself convert single-phase power into three-phase power.
If you want to understand electrical isolation in more detail, see What Is an Isolation Transformer? Uses, Benefits, and Applications.
Can 220V Single-Phase Become 220V Three-Phase?
It can be possible to configure a phase-conversion system with 220V single-phase input and 220V three-phase output, depending on the converter technology and equipment specifications.
The input and output voltage should always be confirmed against:
Available utility voltage
Equipment nameplate voltage
Required phase configuration
Frequency
Converter specifications
Applicable electrical requirements
The exact configuration should be determined before purchasing or installing the equipment.
If voltage stability is also a concern for your equipment, learn more about What Is a Regulated Voltage Transformer? Uses, Benefits, and Applications.
What Information Is Needed to Specify a Phase Converter?
For a proper quotation or engineering evaluation, provide as much of the following information as possible:
Input voltage
Input phase
Input frequency
Required output voltage
Output phase
Output frequency
Motor horsepower or kW
Motor full-load current
Number of motors
Starting method
Equipment type
Continuous or intermittent operation
Indoor or outdoor installation
Enclosure requirements
Ambient conditions
Available electrical protection
Any special control or monitoring requirements
This information allows the converter to be matched to the actual application rather than simply selecting a unit based on a single rating.
When Should You Consider a Phase Converter?
A phase converter may be worth evaluating when:
Your facility has single-phase power but your equipment requires three-phase power
Installing a new three-phase utility service is impractical
You are adding three-phase machinery to an existing workshop
You need to operate three-phase motors, pumps, or compressors
You need a customized single-phase-to-three-phase solution
Your equipment has specific voltage and power requirements
For larger or more complex installations, an electrical assessment should be performed before selecting the converter.
VERIL Phase Converter Solutions
At VERIL Transformer Sales and Services, phase-converter solutions can be specified according to the requirements of the application.
Depending on the project, specifications can include:
Custom kVA capacity
Single-phase input
Three-phase output
Required input and output voltage
50 Hz or 60 Hz operation
Enclosure requirements
Application-specific configuration
Industrial equipment requirements
Because every installation is different, providing the equipment nameplate information and electrical requirements helps ensure the proposed solution is properly matched to the application.
Need a single-phase to three-phase solution for your equipment?
Contact VERIL Transformer Sales and Services for a quotation and application assessment.
Frequently Asked Questions
Can a phase converter convert single-phase power to three-phase power?
Yes. Phase converters are specifically designed to provide three-phase output from a single-phase source, depending on the converter technology and application.
Can I use a phase converter for a three-phase motor?
Yes, provided the converter is properly selected for the motor's voltage, current, starting requirements, and operating conditions.
Is a phase converter the same as a transformer?
No. A transformer changes voltage and/or provides isolation. A phase converter changes the phase configuration.
Can a phase converter run multiple machines?
Some systems can support multiple loads, but the total connected load, starting sequence, converter capacity, and equipment characteristics must be evaluated.
What information should I provide when requesting a quotation?
Provide the equipment nameplate, input power available, required output voltage, motor horsepower or kW, current, frequency, and any other available electrical specifications.
