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1、inverter, is anelectrical power converterthat changesdirect current（DC） toalternating current（AC）.1The input voltage, output voltage, and frequency are dependent on design.Static inverters do not use moving parts in the conversion process. Some applications for inverters include convertinghigh-volta

2、ge direct currentelectric utilityline power to AC, and deriving AC from DC power sources such asbatteries.Contentshide 1Typeso 1.1Output waveforms 1.1.1Modified sine wave 1.1.2Sine waveo 1.2Resonanceo 1.3Grid tie 1.3.1Solar 2Applicationso 2.1DC power source utilizationo 2.2Uninterruptible power supp

3、lieso 2.3Induction heatingo 2.4HVDC power transmissiono 2.5Variable-frequency driveso 2.6Electric vehicle driveso 2.7Air conditioningo 2.8Electroshock weapons 3Circuit descriptiono 3.1Basic designso 3.2o 3.3Advanced designso 3.4Three phase inverters 4Historyo 4.1Early inverterso 4.2Controlled rectif

4、ier inverterso 4.3Rectifier and inverter pulse numbers 5See also 6Referenceso 6.1General references 7External linksTypesedit source|editbetaStatic inverters use switching devices arranged in anH bridge. The large switching devices for power transmission applications installed until 1970 predominantl

5、y usedmercury-arc valves. Inverters for consumer use as well as power transmission systems commissioned after 1970 aresolid state.2The sameH bridgebasic design is used in smaller-scale consumer devices as well.3Output waveformsedit sourceAn inverter can produce square wave, modified sine wave, pulse

6、d sine wave, or sine wave depending on circuit design. The two dominant commercialized waveform types of inverters as of 2007 are modified sine wave and sine wave.There are two basic designs for producing household plug-in voltage from a lower-voltage DC source, the first of which uses a switchingbo

7、ost converterto produce a higher-voltage DC and then converts to AC. The second method converts DC to AC at battery level and uses aline-frequencytransformerto create the output voltage.4Modified sine waveedit sourceThe waveform in commercially available modified-sine-wave inverters is a square wave

8、 with a pause before the polarity transition, which only needs to cycle through a three-position switch that outputs forward, off, and reverse output at the pre-determined frequency.4The peak voltage toRMSvoltage do not maintain the same relationship as for a sine wave. The DC bus voltage may be act

9、ively regulated or the on and off times can be modified to maintain the same RMS value output up to the DC bus voltage to compensate for DC bus voltage variation.The ratio of on to off time can be adjusted to vary the RMS voltage while maintaining a constant frequency with a technique calledPWM. Har

10、monic spectrum in the output depends on the width of the pulses and the modulation frequency. When operating induction motors, voltage harmonics is not of great concern, however harmonic distortion in the current waveform introduces additional heating, and can produce pulsating torques.5Most AC moto

11、rs will run on MSW inverters with an efficiency reduction of about 20% due to the harmonic content.dubiousdiscuss6A proposal suggested inPower Electronicsmagazine utilizes two voltages as an improvement over the common commercialized technology which can only apply DC bus voltage in either direction

12、s or turn it off. The proposal adds an additional voltage to this design. Each cycle consists of sequence as: v1, v2, v1, off/pause, -v1, -v2, -v1.7Sine waveedit sourceA sine wave inverter produces a sine wave output, with atotal harmonic distortionunder 3%citation needed. Sine wave inverters are mo

13、re complex and have a higher cost than a modified-sine-wave type of the same size.7Resonanceedit sourceMain article:Resonant inverterResonantinverters produce sine waves withLC circuitsto remove the harmonics from a simple square wave. Typically there are several series- and parallel-resonant LC cir

14、cuits, each tuned to a different harmonic of the power line frequency. This simplifies the electronics, but the inductors and capacitors tend to be large and heavy. Its high efficiency makes this approach popular in largeuninterruptible power suppliesin data centers that run the inverter continuousl

15、y in an online mode to avoid any switchover transient when power is lost.A closely related approach uses a ferroresonant transformer, also known as aconstant voltage transformer, to remove harmonics and to store enough energy to sustain the load for a few AC cycles. This property makes them useful i

16、nstandby power suppliesto eliminate the switchover transient that otherwise occurs during a power failure while the normally idle inverter starts and the mechanical relays are switching to its output.Grid tieedit sourceGrid-tie inverters are designed to feed into the electric power distribution syst

17、em. They transfer synchronously with the line and have as little harmonic content as possible. They also need a means of detecting the presence of utility power for safety reasons, so as not to continue to dangerously feed power to the grid during a power outage.Solaredit sourceA solar inverter can

18、be fed into a commercial electrical grid or used by an off-grid electrical network. Solar inverters have special functions adapted for use withphotovoltaicarrays, including maximum power point tracking and anti-islandingprotection.Applicationsedit sourceDC power source utilizationedit sourceInverter

19、 designed to provide 115 VAC from the 12 VDC source provided in an automobile. The unit shown provides up to 1.2 amperes of alternating current, or enough to power two sixty watt light bulbs.An inverter converts the DC electricity from sources such asbatteries,solar panels, orfuel cellsto AC electri

20、city. The electricity can be at any required voltage; in particular it can operate AC equipment designed for mains operation, or rectified to produce DC at any desired voltage.Micro-invertersconvert direct current from individual solar panels into alternating current for the electric grid. They are

21、grid tie designs by default.Uninterruptible power suppliesedit sourceAnuninterruptible power supply（UPS） uses batteries and an inverter to supply AC power when main power is not available. When main power is restored, arectifiersupplies DC power to recharge the batteries.Induction heatingedit source

22、Inverters convert low frequency main AC power to higher frequency for use ininduction heating. To do this, AC power is firstrectifiedto provide DC power. The inverter then changes the DC power to high frequency AC power.HVDC power transmissionedit sourceWithHVDCpower transmission, AC power is rectif

23、ied and high voltage DC power is transmitted to another location. At the receiving location, an inverter in astatic inverter plantconverts the power back to AC. The inverter must be synchronized with grid frequency and phase and minimize harmonic generation.Variable-frequency drivesedit sourcevariab

24、le-frequency drivevariable-frequency drivecontrols the operating speed of an AC motor by controlling the frequency and voltage of the power supplied to the motor. An inverter provides the controlled power. In most cases, the variable-frequency drive includes aso that DC power for the inverter can be

25、 provided from main AC power. Since an inverter is the key component, variable-frequency drives are sometimes called inverter drives or just inverters.VFDs that operate directly from an AC source without first converting it to DC are calledcycloconverters. They are now commonly used on large ships t

26、o drive the propulsion motors.Electric vehicle drivesedit sourceAdjustable speed motor control inverters are currently used to power thetraction motorsin someelectricdiesel-electricrail vehicles as well as somebattery electric vehicleshybrid electrichighway vehicles such as theToyota Prius,BYD e6Fis

27、ker Karma. Various improvements in inverter technology are being developed specifically for electric vehicle applications.8In vehicles withregenerative braking, the inverter also takes power from the motor （now acting as a generator） and stores it in the batteries.Air conditioningedit sourceInverter

28、 air conditioningAn inverterair conditioneruses ato control the speed of the motor and thus the compressor.Electroshock weaponsedit sourceElectroshock weaponstasershave a DC/AC inverter to generate several tens of thousands of V AC out of a small 9 V DC battery. First the 9VDC is converted to 400200

29、0V AC with a compact high frequency transformer, which is then rectified and temporarily stored in a high voltage capacitor until a pre-set threshold voltage is reached. When the threshold （set by way of an airgap or TRIAC） is reached, the capacitor dumps its entire load into apulse transformerwhich then steps it up to its final output voltage of 2060 kV. A variant of the principle is also used inelectronic flashbug zappers, though they r