Does anybody know how inverters work? I heard it turns AC into DC then into 3-phase power to run motors. How does it do this?

 

Forget the AC to DC for the time being.
Google for 3 Phase Invertors to start with.

 

Does anybody know how inverters work? I heard it turns AC into DC then into 3-phase power to run motors. How does it do this?

When you say "run motors" it sounds like your talking about what is called a VFD, variable frequency drive, not what is normally referred to as an inverter. Inverter usually mean something that takes DC and makes AC. So Google VFD and there will be many links.

 

Indeed there will be thousands of links, mostly for folks wanting to sell you an inverter, even if they have no clue what an inverter might be.
An inverter, in this area of functionality, includes an oscillation circuit and a power circuit, usually fed with DC power, either from batteries or from rectified mains power. If you have an application for an inverter you can describe the application and folks here can certainly provide lots of information and some good advice. The more fully you describe what you seek the more specific the advice can become.

 

Well, I am trying to understand how an inverter on an air conditioner works. On the outside condenser in a split system, there is an inverter board. It drives the motor in the compressor. The motor I heard is a brushless dc motor. Inverters are said to be good because the compressors are variable. They save a lot of electricity.

 

OK, now I can supply information specific to this system. THANKS!
For this type of inverter drive system, which is a variable power variable speed system, the first step is rectifying the single phase AC supply power. Next, there is a controller, which may include a microprocessor, or not. Following the controller is an oscillator circuit that has it's frequency controlled by that controller, based on the cooling demand.. The oscillator usually includes logic to produce a 3-phase set of waveforms to drive the power output section of the system. There may be position sensors on the motor to allow for better control of the phase switching, although if the motor runs as an induction motor those parts are not needed.Others can probably deliver a far more detailed description of how it works.