A frequency changer or frequency converter is electronic or

electromechanical Electromechanics combine processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focus on the interaction of electrical and mechanical systems as a whole and how the two systems interact with each ...

equipment that converts

alternating current Alternating current (AC) is an electric current that 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 w ...

( AC) of one

frequency Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...

of another frequency. The equipment may also change the

voltage Voltage, also known as (electrical) potential difference, electric pressure, or electric tension, is the difference in electric potential between two points. In a Electrostatics, static electric field, it corresponds to the Work (electrical), ...

, 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 were electromechanical machines called a motor-generator set. There were also mercury arc rectifiers or vacuum tubes in use. With the advent of solid state electronics, it has become possible to build completely electronic frequency changers. These 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 process is known as ''rectification'', since it "straightens" t ...

stage (producing

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

) 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 op ...

may use

thyristor A thyristor (, from a combination of Greek language ''θύρα'', meaning "door" or "valve", and ''transistor'' ) is a solid-state semiconductor device which can be thought of as being a highly robust and switchable diode, allowing the passage ...

IGCT The integrated gate-commutated thyristor (IGCT) is a power semiconductor device, power semiconductor electronics, electronic device, used for switching electric current in industrial equipment. It is related to the gate turn-off thyristor, gate tu ...

s or

IGBT An insulated-gate bipolar transistor (IGBT) is a three-terminal power semiconductor device primarily forming an electronic switch. It was developed to combine high efficiency with fast switching. It consists of four alternating layers (NPNP) that ...

s. If voltage conversion is desired, a

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

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. Energy or information can still be exchanged between the sections by other means, suc ...

between the input and output AC circuits. A battery may also be added to the DC circuitry to improve the converter's ride-through 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 (physics), 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 quantification (science), quantify the rate of Work ...

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 t ...

. A

variable-frequency drive A variable-frequency drive (VFD, or adjustable-frequency drive, adjustable-speed drive, variable-speed drive, AC drive, micro drive, inverter drive, variable voltage variable frequency drive, or drive) is a type of AC motor, AC motor drive (sys ...

(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 synchrono ...

or induction 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 Alternating current, AC waveform to another AC waveform of a lower frequency by synthesizing the output waveform from segments of the AC supply without an ...

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 astron ...

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 (also called green energy) is energy made from renewable resource, renewable natural resources that are replenished on a human lifetime, human timescale. The most widely used renewable energy types are solar energy, wind pow ...

systems, frequency converters are an essential component of

doubly fed induction generator Doubly fed electric machines, Doubly fed induction generator (DFIG), or 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 ...

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 uses direct current (DC) for electric power transmission, in contrast with the more common alternating current (AC) transmission systems. Most HVDC links use voltages betwe ...

-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 u ...

signals A signal is both the process and the result of Signal transmission, transmission of data over some transmission media, media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processin ...

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, the term local oscillator (LO) refers to an electronic oscillator when used in conjunction with a Frequency mixer, mixer to change the frequency of a signal. This frequency conversion process, also called Heterodyne, heterodyning ...

and

(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 (telecommunications), transmission or reception. The intermediate frequency is ...

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

triode A triode is an electronic amplifier, amplifying vacuum tube (or ''thermionic valve'' in British English) consisting of three electrodes inside an evacuated glass envelope: a heated Electrical filament, filament or cathode, a control grid, grid ...

and hexode in a single

tube Tube or tubes may refer to: * ''Tube'' (2003 film), a 2003 Korean film * "Tubes" (Peter Dale), performer on the Soccer AM television show * Tube (band), a Japanese rock band * Tube & Berger, the alias of dance/electronica producers Arndt Rör ...

, 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