What's an inverter microwave

[The-Maxx]

I see a lot of ads right now for inverter microwaves, all of which say it's better, but don't explain what's better about it. What does inverter refer to here, and how does it work?

[Liberal]

According to Panasonic (http://www.panasonic.com.au/about/press/October_2000/ret2030bn.pdf) (PDF):

The benefits offered by Inverter microwaves include more even cooking and better cooking control through `true' selectable power levels; up to 1200 watts of power for faster cooking; and increased internal capacity of up to 44 litres that allows a larger turntable size for bigger dishes as well as permitting two-level cookingHere's their how it works page (http://www.selectappliance.com/exec/ce-tidbits/panasonic).

[mangeorge]

Regular microwaves don't really vary the power level, they cycle on and off. The inverter types actually vary the power level of the microwave energy.
Peace,
mangeorge

[GaryM]

My folks have one of these. It seems to be good in theory, and actually works quite well at the lower power levels, but the programming for time and power level is not as straight forward as other "conventional" microwave ovens I've owned.

[Balthisar]

Hmmm... Panasonic's website wasn't really that useful. And GaryM, there are crappy UI's on microwaves and computers -- probably some human-interface guy didn't do a good job -- not necessarily the inverter's fault.

So, here's a brief microwave course. Microwaves (and RADAR) have a tube called a magnetron. You pump in current, and a very specific frequency and power-level of microwave current comes out. You can paint an enemy plane or point it at food to get it hot. Too little input power, though, and the magnetron won't work. Too much input power, and you burn out the magnetron. So you adjust the "heat" of the magnetron by turning it on and off (incidently this is how a resistance welder using SCRs/thyristors works).

An inverter, though, is any device that takes DC power and turns it back into an alternating form. In the case of a microwave, you'll take 110VAC sine in, rectify it, and invert it into whatever frequency and waveform you want. Let's say the inverter is a set of four large transistors -- IGBT's for example (think I Got Big Transistors). Well, given a DC power source, you can control the voltage level, frequency, and wave shape of the ouput power. Feed this to a modern magnetron, and you get true power control. Incidently, this is how a modern resistance welder using inverter technology works.

There's a lot more to it, but my military work with RADAR and both these technologies contributed directly to my current work with resistance welding controls. The only difference is a welder has no receiver and isn't at 9GHz.