inverter

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inverter
explain dc to ac conversion
okay a little clarification, are you asking ac to dc conversion or an inverter whic is the opposite?
an inverter changes dc voltage, nearly always from batteries, into standard household ac voltage so that it can be used by common tools and appliances. essentially, it does the opposite of what a battery charger or "converter" does. dc is usable for some small appliances, lights, and pumps and is usually suitable for small home or cabin systems, rv's and boats. however, nearly all larger home systems should include an inverter. although some dc appliances are available, with the exception of lights there is not a wide selection - and many are expensive and/or poorly made compared to their ac cousins. the most common battery voltage inputs for inverters are 12, 24, and 48 volts dc - a few models from some companies are also available in other voltages.
there is also a special line of inverters called a utility intertie or grid tie, which does not usually use batteries - the solar panels or wind generator feed directly into the inverter and the inverter output is tied to the grid power. the power produced is either sold back to the power company or (more commonly) offsets a portion of the power used. these inverters usually require a fairly high input voltage - 48 volts or more. some, like the sunny boy, go up to 600 volts dc input.
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how does an inverter work?
an inverter takes the dc input and runs it into a pair (or more) of power switching transistors. by rapidly turning these transistors on and off, and feeding opposite sides of a transformer, it makes the transformer think it is getting ac. the transformer changes this 12, 24, or 48 volts "alternating dc" into 115 volts ac at the output. depending on the quality and complexity of the inverter, it may put out a square wave, a "quasi-sine" (sometimes called modified sine) wave, or a true sine wave. square wave inverters are usually only suitable for running some type of electrical tools and motors and incandescent lights.
quasi-sine (modified sine, modified square) wave inverters have more circuitry beyond the simple switching, and put out a wave that looks like a stepped square wave - it is suitable for most standard appliances, but may not work well with some electronics, such as bread makers. also, some of the chargers used for battery operated tools (such as makita) may not shut off when the battery is charged, and should not be used with anything but sine wave inverters unless you are sure they will work.  sine wave inverters put out a wave that is the same as you get from the power company - in fact, it is often better and cleaner. sine wave inverters can run anything, but are also more expensive than other types. the quality of the "modified sine" (actually modified square wave), quasi-sine wave, etc. can also vary quite a bit between inverters, and may also vary somewhat with the load. the very bottom end put out a wave that is nothing but a square wave, and is too "dirty" for all but universal motor driven tools, coffee makers, toasters, and other appliances that have only a heating element.
one solution to the problem of a few small appliances not working well with modified sine wave inverters is to get a large standard inverter, and a small (such as the exeltech 250 watt) true sine wave for use only with that equipment. this would also allow you to keep the small appliance (such as an answering machine) powered up without having to run the larger inverter full time.