Editing Microwave oven (section)

== Components ==
[[File:Magnetron2.jpg|thumb|A magnetron with section removed (magnet is not shown)]]
[[File:-125wiki.jpg|thumb|Inner space of a microwave oven and its control panel]]
A microwave oven generally consists of:
* a high-voltage DC power source, either:
** a large high voltage [[transformer]] with a [[Voltage doubler#Villard circuit|voltage doubler]] (a high-voltage [[capacitor]] and a [[diode]])
** an electronic [[power converter]] usually based around an inverter.
* a [[cavity magnetron]], which converts the high-voltage DC electric energy to microwave radiation
* a magnetron control circuit (usually with a [[microcontroller]])
* a short [[Waveguide (electromagnetism)|waveguide]] (to couple microwave power from the magnetron into the cooking chamber)
* a turntable and/or [[mode stirrer|metal wave guide stirring fan]]
* a control panel

In most ovens, the magnetron is driven by a linear transformer which can only feasibly be switched completely on or off. (One variant of the GE Spacemaker had two taps on the transformer primary, for high and low power modes.) Usually choice of power level does not affect intensity of the microwave radiation; instead, the magnetron is cycled on and off every few seconds, thus altering the large scale [[duty cycle]]. Newer models use ''inverter'' power supplies that use [[pulse-width modulation]] to provide effectively continuous heating at reduced power settings, so that foods are heated more evenly at a given power level and can be heated more quickly without being damaged by uneven heating.<ref>{{cite web|url=http://www.thetelegram.com/opinion/columnists/a-notable-advance-in-microwave-technology-135137/|title=A notable advance in microwave technology|work=[[The Telegram]]|date=September 22, 2013|access-date=May 10, 2018|archive-url=https://web.archive.org/web/20180502233757if_/http://www.thetelegram.com/opinion/columnists/a-notable-advance-in-microwave-technology-135137/|archive-date=May 2, 2018|url-status=dead}}</ref><ref name=":3" /><ref name=":2" /><ref name=":4" />

The microwave frequencies used in microwave ovens are chosen based on regulatory and cost constraints. The first is that they should be in one of the [[ISM band|industrial, scientific, and medical (ISM) frequency band]]s set aside for unlicensed purposes. For household purposes, 2.45&nbsp;GHz has the advantage over 915&nbsp;MHz in that 915&nbsp;MHz is only an ISM band in some countries ([[ITU Region]] 2) while 2.45&nbsp;GHz is available worldwide.{{citation needed|date=January 2013}} Three additional ISM bands exist in the microwave frequencies, but are not used for microwave cooking. Two of them are centered on 5.8&nbsp;GHz and 24.125&nbsp;GHz, but are not used for microwave cooking because of the very high cost of power generation at these frequencies.{{citation needed|date=May 2019}} The third, centered on 433.92&nbsp;MHz, is a narrow band that would require expensive equipment to generate sufficient power without creating interference outside the band, and is only available in some countries.{{citation needed|date=May 2019}}

The cooking chamber is similar to a [[Faraday cage]] to prevent the waves from coming out of the oven. Even though there is no continuous metal-to-metal contact around the rim of the door, [[Waveguide flange#Choke connection|choke connections]] on the door edges act like metal-to-metal contact, at the frequency of the microwaves, to prevent leakage. The oven door usually has a window for easy viewing, with a layer of conductive mesh some distance from the outer panel to maintain the shielding. Because the size of the perforations in the mesh is much less than the microwaves' wavelength (12.2&nbsp;cm for the usual 2.45&nbsp;GHz), microwave radiation cannot pass through the door, while [[visible light]] (with its much shorter wavelength) can.<ref>{{Cite web|last=Staff|first=Straight Dope|date=November 4, 2003|title=What keeps microwave radiation from leaking out the oven door?|url=https://www.straightdope.com/21343269/what-keeps-microwave-radiation-from-leaking-out-the-oven-door|access-date=March 1, 2021|website=The Straight Dope|language=en}}</ref>

=== Control panel ===
Modern microwave ovens use either an analog dial-type [[timer]] or a digital [[Control panel (engineering)|control panel]] for operation. Control panels feature an [[LED]], [[LCD]] or vacuum fluorescent display, buttons for entering the cook time and a power level selection feature.  A defrost option is typically offered, as either a power level or a separate function.  Some models include pre-programmed settings for different food types, typically taking weight as input.  In the 1990s, brands such as Panasonic and GE began offering models with a scrolling-text display showing cooking instructions.

Power settings are commonly implemented not by actually varying the power output, but by switching the emission of microwave energy off and on at intervals. The highest setting thus represents continuous power. Defrost might represent power for two seconds followed by no power for five seconds. To indicate cooking has completed, an audible warning such as a bell or a beeper is usually present, and/or "End" usually appears on the display of a digital microwave.

Microwave control panels are often considered awkward to use and are frequently employed as examples for user interface design.<ref>{{cite web|url=https://www.theguardian.com/technology/2015/jul/13/microwave-oven-user-interface-digital-complicated |title=User Interfaces: Why are Microwave Ovens All So Difficult to Use?|work=[[The Guardian]]|date= July 13, 2015|access-date= January 4, 2019}}</ref>