A phase converter is a device that converts electric power provided as
single phase Image:Single-phase-pole-transformer-d335.jpg, 173px, A single-phase polemount stepdown transformer in Canada. One supply phase (phase-to-neutral) from the utility is converted to split-phase for the customers. In electrical engineering, single-phas ...
to multiple phase or vice versa. The majority of phase converters are used to produce
three-phase electric power Three-phase electric power (abbreviated 3φ) is a common type of alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct ...
from a single-phase source, thus allowing the operation of three-phase equipment at a site that only has single-phase electrical service. Phase converters are used where three-phase service is not available from the utility, or is too costly to install due to a remote location. A utility will generally charge a higher fee for a three-phase service because of the extra equipment, including transformers, metering, and distribution wire.

Conversion systems

Three-phase induction motors may operate adequately on an unbalanced supply if not heavily loaded. This allows various imperfect techniques to be used. A single-phase motor can drive a three-phase generator, which will produce a high-quality three-phase source but with high cost for apparatus. Several methods exist to run three-phase motors from a single-phase supply, these can in general be classified as: *
Rotary phase converter 200px, A simple homemade phase converter A rotary phase converter, abbreviated RPC, is an electrical machineIn electrical engineering, electric machine is a general term for machine A machine is a man-made device that uses power to apply f ...
s constructed from a three-phase electric motor or generator "idler". These normally require some kind of starting aid and capacitors to improve phase balance and power factor. This is a two-motor solution. One motor is not connected to a load and produces the three-phase power, the second motor driving the load runs on the power produced. * Electronic means of creating three phases where the incoming power is rectified, and the three-phase power is synthesized with electronics. Power electronic devices directly produce a three-phase waveform from single-phase power, using a
rectifier A rectifier is an electrical device that converts Religious conversion is the adoption of a set of beliefs identified with one particular religious denomination A religious denomination is a subgroup within a religion Religion is a ...

inverter A power inverter, or inverter, is a power electronic device or circuitry that changes direct current Direct current (DC) is the one directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct curren ...
combination. This also offers the advantage of variable frequency. * A digital phase converter uses a rectifier and inverter to create a single voltage with power electronics, which is added to the two legs of the single-phase source to create three-phase power. Unlike a phase-converting VFD, it cannot vary the frequency and motor speed, since it generates only one leg, which must match the voltage and frequency of the single-phase supply. It does have the advantage of a sine-wave output voltage and excellent voltage balance between the phases. More details about these methods are explained in the patents Medagam et. al. “Active Single Phase to Three Phase Power Converter” US Patent 10,333,420 and Meiners et. al. “Phase Converter” US 6,297,971. * Static conversion techniques in which the motor is run at less than full efficiency mainly on two of the legs of the three-phase motor. Current is sometimes injected into the third leg with a capacitor or transformer arrangements that provide imperfect phase shift. In these systems the motor must be derated.

Rotary phase converter

rotary phase converter 200px, A simple homemade phase converter A rotary phase converter, abbreviated RPC, is an electrical machineIn electrical engineering, electric machine is a general term for machine A machine is a man-made device that uses power to apply f ...
is an economical way to create three-phase power in an area where three-phase utility power is not available or is cost-prohibitive to bring in. A rotary phase converter uses a control panel with a start circuit and run circuit to create balanced, clean power without excessive voltage. A three-phase motor produces the third leg of power. Some rotary phase converters are digitally controlled, enabling them to produce balanced power that is clean enough to run on voltage-sensitive loads such as a CNC machine, welder, or any other computer-controlled load. A rotary phase converter does not change the voltage, but it can be paired with a transformer to step the voltage up or down depending on what is needed. 

Digital Phase Converter

A ''digital phase converter'' creates a three-phase power supply from a single-phase supply. A
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(DSP) is used to control power electronic devices to generate a third voltage, which along with the single voltage from the supply creates a balanced three-phase power supply. AC power from the utility is converted to DC, then back to AC. The power-switching devices used in this process are
insulated-gate bipolar transistor An insulated-gate bipolar transistor (IGBT) is a three-terminal power semiconductor device primarily used as an electronic switch, which, as it was developed, came to combine high efficiency and fast switching. It consists of four alternating lay ...
s (IGBT). In one type of digital phase converter, the input rectifier consists of IGBTs in series with inductors. The IGBTs are controlled by software in the DSP to draw current from the single-phase line in a
sinusoidal A sine wave or sinusoid is any of certain mathematical curves that describe a smooth periodic oscillation Oscillation is the repetitive variation, typically in time Time is the indefinite continued sequence, progress of existence and ev ...

fashion, charging capacitors on a constant-voltage DC bus. Because the incoming current is sinusoidal, there are no significant harmonics generated back onto the line as there are with the rectifiers found in most VFDs. The controlled rectifier input allows power factor correction. The output inverter consists of IGBTs that draw on the power of the DC bus to create an AC voltage. A voltage created by power-switching devices like IGBTs is not sinusoidal. It is a pulse-width modulated (PWM) waveform very high in harmonic distortion. This PWM voltage is then passed through an inductor/capacitor filter system that produces a sine-wave voltage with less than 3%
total harmonic distortion The total harmonic distortion (THD or THDi) is a measurement of the harmonic distortion present in a signal and is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency Fundamental may re ...
(standards for computer grade power allow up to 5% THD). By contrast, VFDs generate a PWM voltage that limits their versatility and makes them unsuitable for many applications. Software in the DSP continually monitors and adjusts this generated voltage to produce a balanced three-phase output at all times. It also provides protective functions by shutting down in case of utility over-voltage and under-voltage or a fault. With the ability to adjust to changing conditions and maintain voltage balance, a digital phase converter can safely and efficiently operate virtually any type of three-phase equipment or any number of multiple loads. The solid-state design results in a relatively small package with no moving parts except for small cooling fans. The converters operate at 95%–98% efficiency.
Active-Phase Converter for Operation of Three-Phase Induction Motors on Single-Phase Grid
,IEEE Transactions on Industry Applications ( Volume: 53 , Issue: 6 , Nov.-Dec. 2017 )
When the converter is energized with no load, it consumes very little power.

Electric railways

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, electricity is normally generated as three-phase AC at 50
hertz The hertz (symbol: Hz) is the unit Unit may refer to: Arts and entertainment * UNIT Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the science fiction television series ''Doctor Who'' * Unit of action ...

. Five European countries:
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Austria Austria (, ; german: Österreich ), officially the Republic of Austria (german: Republik Österreich, links=no, ), is a landlocked Eastern Alps, East Alpine country in the southern part of Central Europe. It is composed of nine States o ...

Switzerland , french: Suisse(sse), it, svizzero/svizzera or , rm, Svizzer/Svizra , government_type = Federalism, Federal semi-direct democracy under an assembly-independent Directorial system, directorial republic , leader_title1 = Fe ...

Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål (, ; literally "book tongue") is an official written standard for the Norwegian language Norwegian (Norwegian: ''norsk'') is a Nort ...

Sweden Sweden ( sv, Sverige ), officially the Kingdom of Sweden ( sv, links=no, Konungariket Sverige ), is a Nordic country The Nordic countries, or the Nordics, are a geographical and cultural region In geography, regions are areas that ...

have standardised on single-phase AC at 15 kV 16⅔ Hz for
railway electrification A railway electrification system supplies electric power to Rail transport, railway trains and trams without an on-board Prime mover (locomotive), prime mover or local fuel supply. Electric railways use either electric locomotives (hauling pas ...

railway electrification
. Phase converters are, therefore, used to change both the phase and the
frequency Frequency is the number of occurrences of a repeating event per unit of time A unit of time is any particular time Time is the indefinite continued sequence, progress of existence and event (philosophy), events that occur in an apparen ...
. {{Citation needed, date=October 2009

See also

Rotary phase converter 200px, A simple homemade phase converter A rotary phase converter, abbreviated RPC, is an electrical machineIn electrical engineering, electric machine is a general term for machine A machine is a man-made device that uses power to apply f ...
Variable frequency drive A variable-frequency drive (VFD) or adjustable-frequency drive (AFD), variable-voltage/variable-frequency (VVVF) drive, variable speed drive (VSD), AC drive, micro drive or inverter drive is a type of motor drive used in electro-mechanical In ...

Variable frequency drive
Scott-T transformer A Scott-T transformer (also called a Scott connection) is a type of circuit used to produce two-phase electric power (2 φ, 90 degree phase rotation) from a three-phase In electrical engineering, three-phase electric power systems h ...



*RadioWorld Magazine featured article: Harris Impressed by Phase Technologies PT355 by Terry Cockerill, 12.31.200

*Wine Business Monthly featured article: What's Cool: Digital Phase Converters November 15, 200
Whats Cool: Digital Phase Converters
*January/February 2008 Vineyard & Winery Management Magazine Featured article "The Digital Converter; A New Way to Generate Three-Phase Electricity for a Winery"] by Ben Guthrie.
United States Patent #6297971Circuit and method for reducing inrush current of phase converter motor
"Circuit and Method for Reducing Inrush Current of Phase Converter Motor" Inventor Glen Floreancig, Phoenix Phase Converters.
US Patent for Active single phase to three phase power converter Patent (Patent # 10,333,420 issued June 25, 2019) - Justia Patents SearchPhase converter
Electrical engineering AC power