A frequency changer or frequency converter is an

electronic Electronic may refer to: *Electronics, the science of how to control electric energy in semiconductor * ''Electronics'' (magazine), a defunct American trade journal *Electronic storage, the storage of data using an electronic device *Electronic co ...

electromechanical In engineering, electromechanics combines processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focuses on the interaction of electrical and mechanical systems as a whole and how the two systems ...

device that converts

alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...

( AC) of one

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

of another frequency. The device may also change the

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...

, but if it does, that is incidental to its principal purpose, since voltage conversion of alternating current is much easier to achieve than frequency conversion. Traditionally, these devices were electromechanical machines called a motor-generator set. Also devices with mercury arc rectifiers or vacuum tubes were in use. With the advent of

solid state electronics Solid-state electronics means semiconductor electronics: electronic equipment using semiconductor devices such as transistors, diodes and integrated circuits (ICs). The term is also used as an adjective for devices in which semiconductor electr ...

, it has become possible to build completely electronic frequency changers. These devices usually consist of a

rectifier A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The reverse operation (converting DC to AC) is performed by an inve ...

stage (producing

direct current Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or ev ...

) which is then inverted to produce AC of the desired frequency. The

inverter A power inverter, inverter or invertor is a power electronic device or circuitry that changes direct current (DC) to alternating current (AC). The resulting AC frequency obtained depends on the particular device employed. Inverters do the opp ...

may use

thyristor A thyristor () is a solid-state semiconductor device with four layers of alternating P- and N-type materials used for high-power applications. It acts exclusively as a bistable switch (or a latch), conducting when the gate receives a current ...

s, IGCTs or

IGBT 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. If voltage conversion is desired, a

transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...

will usually be included in either the AC input or output circuitry and this transformer may also provide

galvanic isolation Galvanic isolation is a principle of isolating functional sections of electrical systems to prevent current flow; no direct conduction path is permitted.John Huntington ''Show Networks and Control Systems: Formerly Control Systems for Live ...

between the input and output AC circuits. A

battery Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...

may also be added to the DC circuitry to improve the converter's

ride-through In electrical power engineering, fault ride through (FRT), sometimes under-voltage ride through (UVRT), or low voltage ride through (LVRT), is the capability of electric generators to stay connected in short periods of lower electric network vol ...

of brief outages in the input power. Frequency changers vary in power-handling capability from a few

watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...

s to megawatts.

Applications

Frequency changers are used for converting bulk AC power from one frequency to another, when two adjacent power grids operate at different

utility frequency The utility frequency, (power) line frequency (American English) or mains frequency (British English) is the nominal frequency of the oscillations of alternating current (AC) in a wide area synchronous grid transmitted from a power station to ...

. A

variable-frequency drive A variable-frequency drive (VFD) is a type of motor drive used in electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency and, depending on topology, to control associated voltage or current va ...

(VFD) is a type of frequency changer used for speed control of AC motors such as used for pumps and fans. The speed of a

Synchronous Synchronization is the coordination of events to operate a system in unison. For example, the conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are said to be synchronou ...

AC motor is dependent on the frequency of the AC power supply, so changing frequency allows the motor speed to be changed. This allows fan or pump output to be varied to match process conditions, which can provide energy savings. A

cycloconverter A cycloconverter (CCV) or a cycloinverter converts a constant amplitude, constant frequency AC waveform to another AC waveform of a lower frequency by synthesizing the output waveform from segments of the AC supply without an intermediate DC lin ...

is also a type of frequency changer. Unlike a VFD, which is an indirect frequency changer since it uses an AC-DC stage and then a DC-AC stage, a cycloconverter is a direct frequency changer because it uses no intermediate stages. Another application is in the

aerospace Aerospace is a term used to collectively refer to the atmosphere and outer space. Aerospace activity is very diverse, with a multitude of commercial, industrial and military applications. Aerospace engineering consists of aeronautics and ast ...

and airline industries. Often airplanes use 400 Hz power so a 50 Hz or 60 Hz to 400 Hz frequency converter is needed for use in the ground power unit used to power the airplane while it is on the ground. Airlines might also utilize the converters to provide in-air wall current to passengers for use with laptops and the like. Radio and combat systems equipment on Navy warships is often also powered by 400 Hz to reduce noise on the DC signal after rectification. In

renewable energy Renewable energy is energy that is collected from renewable resources that are naturally replenished on a human timescale. It includes sources such as sunlight, wind, the movement of water, and geothermal heat. Although most renewable energy ...

systems, frequency converters are an essential component of

doubly fed induction generator Doubly-fed electric machines also slip-ring generators are electric motors or electric generators, where both the field magnet windings and armature windings are separately connected to equipment outside the machine. By feeding adjustable freque ...

s ( DFIGs) as used in modern multi-megawatt class wind turbines.Renewable Energy World (May 2008), "
Excited About Power Quality
'" An

HVDC A high-voltage direct current (HVDC) electric power transmission system (also called a power superhighway or an electrical superhighway) uses direct current (DC) for electric power transmission, in contrast with the more common alternating curre ...

-system can serve as frequency converter for large loads.

Alternate uses

Frequency converter may also refer to a much-lower-powered circuit that converts

radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the up ...

signals at one

to another

, especially in a

Superheterodyne receiver A superheterodyne receiver, often shortened to superhet, is a type of radio receiver that uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original car ...

. See

Frequency mixer In electronics, a mixer, or frequency mixer, is an electrical circuit that creates new frequencies from two signals applied to it. In its most common application, two signals are applied to a mixer, and it produces new signals at the sum and di ...

. The circuit usually consists of a

local oscillator In electronics, a local oscillator (LO) is an electronic oscillator used with a mixer to change the frequency of a signal. This frequency conversion process, also called heterodyning, produces the sum and difference frequencies from the frequenc ...

and

frequency mixer In electronics, a mixer, or frequency mixer, is an electrical circuit that creates new frequencies from two signals applied to it. In its most common application, two signals are applied to a mixer, and it produces new signals at the sum and di ...

(analog multiplier) that generates sum and difference frequencies from the input and local oscillator, of which one (the

Intermediate frequency In communications and electronic engineering, an intermediate frequency (IF) is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception. The intermediate frequency is created by mixing the carrier sig ...

) will be required for further amplification, while the others are filtered out. The same result was achieved historically by the

pentagrid converter The pentagrid converter is a type of radio receiving valve (vacuum tube) with five grids used as the frequency mixer stage of a superheterodyne radio receiver. The pentagrid was part of a line of development of valves that were able to take an ...

or a

Triode A triode is an electronic amplifying vacuum tube (or ''valve'' in British English) consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate (anode). Developed from Lee De Forest's ...

and Hexode in a single tube, but can be implemented in transistor radios economically by a single transistor functioning as a self-oscillating mixer.

References

External links

What is Frequency Conversion
{{Authority control

Applications

Alternate uses

See also

References

External links