View source for Electric power conversion

{{Short description|Conversion of electric energy from one form to another}}
{{For|generic power conversion (e.g., [[heat]] to [[electric energy]])|Energy transformation}}
{{Power engineering}}
In all fields of [[electrical engineering]], '''power conversion''' is the process of converting [[electric energy]] from one form to another. A '''power converter''' is an electrical or [[electro-mechanical]] device for converting electrical energy. A power converter can convert [[alternating current]] (AC) into [[direct current]] (DC) and vice versa; change the [[voltage]] or [[frequency]] of the current or do some combination of these. The power converter can be as simple as a [[transformer]] or it can be a far more complex system, such as a [[resonant converter]]. The term can also refer to a class of electrical machinery that is used to convert one [[utility frequency|frequency]] of [[alternating current]] into another. Power conversion systems often incorporate [[redundancy (engineering)|redundancy]] and [[voltage regulation]].

Power converters are classified based on the type of power conversion they perform. One way of classifying power conversion systems is based on whether the input and output are alternating current or direct current. Ultimately, the task of all power converters is to "process and control the flow of electrical energy by supplying voltages and currents in a form that is optimally suited for user loads".<ref>{{Cite book|last=Petrocelli|first=R.|url=https://cds.cern.ch/record/1641409|title=Proceedings of the CAS–CERN Accelerator School: Power Converters|publisher=[[CERN]]|year=2015|isbn=9789290834151|editor-last=Bailey|editor-first=R.|location=Geneva|page=15|chapter=One-Quadrant Switched-Mode Power Converters|arxiv=1607.02868|doi=10.5170/CERN-2015-003|s2cid=125663953 }}</ref>

==DC power conversion==

===DC to DC===
{{Main|DC-to-DC converter}}

The following devices can convert DC to DC:{{Explain|date=May 2017}}
*[[Linear regulator]]
*[[Voltage regulator]]
*[[Motor–generator]]
*[[Rotary converter]]
*[[Switched-mode power supply]]

{{Expand section|date=May 2017}}

===DC to AC===
The following devices can convert DC to AC:{{Explain|date=May 2017}}
*[[Power inverter]]
*[[Motor–generator]]
*[[Rotary converter]]
*[[Switched-mode power supply]]
*[[Chopper (electronics)]]

{{Expand section|date=May 2017}}

==AC power conversion==

===AC to DC===
The following devices can convert AC to DC:{{Explain|date=May 2017}}
*[[Rectifier]]
*Mains [[power supply]] unit (PSU)
*[[Motor–generator]]
*[[Rotary converter]]
*[[Switched-mode power supply]]

{{Expand section|date=May 2017}}

===AC to AC===
{{Main|AC-to-AC converter}}

The following devices can convert AC to AC:{{Explain|date=May 2017}}
*[[Transformer]] or [[autotransformer]]
*[[Voltage converter]]
*[[Voltage regulator]]
*[[Cycloconverter]]
*[[Variable-frequency transformer]]
*[[Motor–generator]]
*[[Rotary converter]]
*[[Switched-mode power supply]]

{{Expand section|date=May 2017}}

==Other systems==
{{Main|Three-phase electric power}}

There are also devices and methods to convert between power systems designed for single and three-phase operation.

The standard power voltage and frequency vary from country to country and sometimes within a country. In North America and northern South America, it is usually 120 volts, 60&nbsp;[[hertz]] (Hz), but in Europe, Asia, Africa, and many other parts of the world, it is usually 230 volts, 50&nbsp;Hz.<ref>[http://www.kropla.com/electric2.htm Electric Power Around the World] {{webarchive|url=https://web.archive.org/web/20090906064026/http://www.kropla.com/electric2.htm |date=2009-09-06}}, Kropla.com</ref> Aircraft often use 400&nbsp;Hz power internally, so 50&nbsp;Hz or 60&nbsp;Hz to 400&nbsp;Hz frequency conversion is needed for use in the ground power unit used to power the airplane while it is on the ground. Conversely, internal 400&nbsp;Hz internal power may be converted to 50&nbsp;Hz or 60&nbsp;Hz for convenience power outlets available to passengers during flight.

Certain specialized circuits can also be considered power converters, such as the [[flyback transformer]] subsystem powering a [[cathode ray tube|CRT]], generating high voltage at approximately 15&nbsp;kHz.

Consumer electronics usually include an [[AC adapter]] (a type of [[power supply]]) to convert mains-voltage AC current to low-voltage DC suitable for consumption by microchips. Consumer [[voltage converter]]s (also known as "travel converters") are used when traveling between countries that use ~120 V versus ~240 V AC mains power. (There are also consumer "adapters" which merely form an electrical connection between two differently shaped [[AC power plugs and sockets]], but these change neither voltage nor frequency.)

==Why use transformers in power converters==
{{tone|section|date=September 2022}}
Transformers are used in power converters to incorporate electrical isolation and Voltage step-down or step up.

The secondary circuit is floating, when you touch the secondary circuit, you merely drag its potential to your body's potential or the earth's potential. There will be no current flowing through your body. That's why you can use your cellphone safely when it is being charged, even if your cellphone has a metal shell and is connected to the secondary circuit.

Operating at high frequency and supplying low power, power converters have much smaller transformers as compared with those of fundamental frequency, high power applications. '''Usually, in power systems, transformers transmit power simultaneously, no charge!''' 

The current in the primary winding of a transformer help to sets up the mutual flux in accordance with Ampere's law and balances the demagnetizing effect of the load current in the secondary winding.

'''Flyback converter's transformer works differently, like an inductor.'''
In each cycle, the flyback converter's transformer first gets charged and then releases its energy to the load. Accordingly, the flyback converter's transformer air gap has two functions. It not only determines inductance but also stores energy. For the flyback converter, the transformer gap can have the function of energy transmission through cycles of charging and discharging.
:<math>W_{e}=\frac{1}{2}BH=\frac{1}{2} \frac{B^2}{\mu}</math>

The core's relative permeability <math>\mu_r</math> can be > 1,000, even > 10,000. While the air gap features much lower permeability, accordingly has higher energy density.

==See also==
*[[Power supply]]
*[[Cascade converter]]
*[[Motor-generator]]
*[[Resonant converter]]
*[[Rotary converter]]

==References==
{{Reflist}}
*Abraham I. Pressman (1997). ''Switching Power Supply Design''. McGraw-Hill. {{ISBN|0-07-052236-7}}.
*Ned Mohan, Tore M. Undeland, William P. Robbins (2002). ''Power Electronics: Converters, Applications, and Design''. Wiley. {{ISBN|0-471-22693-9}}.
*Fang Lin Luo, Hong Ye, Muhammad H. Rashid (2005). ''Digital Power Electronics and Applications''. Elsevier. {{ISBN|0-12-088757-6}}.
*Fang Lin Luo, Hong Ye (2004). ''Advanced DC/DC Converters''. CRC Press. {{ISBN|0-8493-1956-0}}.
*Mingliang Liu (2006). ''Demystifying Switched-Capacitor Circuits''. Elsevier. {{ISBN|0-7506-7907-7}}.

==External links==
*[https://web.archive.org/web/20051217120256/http://www.powerdesigners.com/InfoWeb/design_center/articles/DC-DC/converter.shtm A general description of DC-DC converters]
*[http://www.hzfrequencyconverter.com U.S. based 50 Hz, 60 Hz, and 400 Hz frequency converter manufacturer] {{Webarchive|url=https://web.archive.org/web/20200221214752/http://www.hzfrequencyconverter.com/ |date=2020-02-21 }}
*[https://web.archive.org/web/20140709030157/http://en.globtek.com/glossary.php GlobTek, Inc. Glossary of electric power supply and power conversion terms]

[[Category:Electric power conversion| ]]
[[Category:Electric power systems components]]
[[Category:Electronic engineering]]