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Old 11-22-2002, 12:59 PM
The-Maxx The-Maxx is offline
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What's an inverter microwave

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?
Old 11-22-2002, 01:43 PM
Liberal Liberal is offline
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According to Panasonic (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 cooking
Here's their how it works page.
Old 11-22-2002, 02:27 PM
mangeorge mangeorge is offline
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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.
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Old 11-22-2002, 02:57 PM
GaryM GaryM is offline
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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.
Old 11-24-2002, 12:41 PM
Balthisar Balthisar is offline
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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.
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Old 12-29-2013, 07:25 AM
Chronos Chronos is online now
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I once saw a "how things work"-type article about microwaves that explained that the physics of microwaves made it inherently absolutely impossible to vary the power of microwaves (which I recognized as balderdash immediately). I wonder if the author of that article has since retracted, given how common it is now?
Old 12-29-2013, 10:32 AM
JWT Kottekoe JWT Kottekoe is offline
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This seems to be marketing buzz by Panasonic.

Since a magnetron only works efficiently at a fixed power output, microwave ovens adjust the power level by turning the magnetron on and off. The Panasonic microwave oven uses a power inverter (DC to AC converter) to accomplish this by modulating the width of the "on" pulses. There is nothing fundamentally different about their approach, but there may be advantages in energy efficiency or in speeding up the power cycling.

As long as the cycling time is much shorter than the total cooking time, it should make very little difference how fast you switch the power on and off.

Last edited by JWT Kottekoe; 12-29-2013 at 10:33 AM.
Old 12-29-2013, 11:01 AM
Colibri Colibri is online now
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Note: This thread is from 2002, and was bumped by a spammer.

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Old 01-19-2017, 11:00 PM
epbrown01 epbrown01 is offline
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I did a search and this is the only one that came up, and I decided to bump it rather than start a new one. I ordered one of these from Amazon and I'm wondering if any Dopers have one and how they like it. My brother and I have been jousting about this via Google, with his position being I should have gone for a convection/microwave oven combo. My own second thoughts lean towards a toaster oven/microwave combo myself.
Old 01-19-2017, 11:41 PM
Iggy Iggy is offline
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I bought an inverter microwave for my niece to take with her to college. It gets good marks from her though I suspect she probably doesn't use it to the fullest of its capabilities. Still it really didn't cost much more and will serve her well when she sets up her own household in a few years.

Where inverter units have an advantage is in lower powered cooking. If all you want to do is blast something as fast as possible and you don't normally use lower power settings then just buy a traditional microwave.
Old 01-19-2017, 11:53 PM
Francis Vaughan Francis Vaughan is offline
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More for the OP than the bump question. But maybe useful.

Magnetrons produce microwaves when run at a specific anode voltage. Run outside this voltage they swiftly cease to efficiently produce microwaves. So, first up, any arguments about varying voltage with an inverter are wrong.

The answer seems to be that a switching power supply (ie an inverter) can efficiently switch the anode voltage on and off very quickly - quickly enough that a pulse width modulated stream of microwaves is emitted. Thus allowing close to infinite variability in power output. Older or cheaper ovens seem to use little more than a relay on the input side of the power supply, something that only allows the most rudimentary of PWM, with a period in tens of seconds.
This means that an inverter oven actually does have the effect of a low power input into the food, whilst an old style oven really gives the food a solid blast for a few to tens of seconds and then sits for a while before repeating. For short term heating or cooking of small items this is going to matter. Especially for food items that contain lots of oil or fat - as these can reach very high temperatures very quickly. The simple ovens run for a short length of time (say to head something little) cannot vary their power as there isn't enough total cooking time to turn the magnetron on and off in.

ETA - the other way of varying power in some vacuum devices (eg X-Ray tubes) is to vary the filament current - which then varies the forward current through the tube. However you may well run into cathode stripping problems if this is done in a power magnetron.

Last edited by Francis Vaughan; 01-19-2017 at 11:58 PM.
Old 01-20-2017, 12:34 AM
panache45 panache45 is offline
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I have one, a Panasonic, and it hasn't worked since shortly after the warranty was up. The temperature is no longer adjustable. Regardless of the setting, everything cooks at a continuous 1200 watts, and I have to manually adjust the time accordingly. Lots of things come out overcooked... dry or burnt. It can't even make simple popcorn without burning it. I totally recommend against buying this piece of shit.
Old 01-20-2017, 06:41 AM
epbrown01 epbrown01 is offline
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Originally Posted by panache45 View Post
I have one, a Panasonic, and it hasn't worked since shortly after the warranty was up.
Panasonic seems to be the only game in town. And this seems to be the way of small appliances nowadays. My old Sharp lasted a decade (and I bought that used), but everything since has lasted 2-3 years; the 'wave I'm replacing was bought 2 years, 3 months ago.

Last edited by epbrown01; 01-20-2017 at 06:43 AM.
Old 01-20-2017, 07:11 AM
ftg ftg is offline
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Originally Posted by Francis Vaughan View Post
More for the OP than the bump question. But maybe useful.
Re: The OP.

"Last Activity: 12-31-2003 05:22 PM"

But I like a good update anyway on a question like this. Helps get new people to visit the board and see what it's like. (Assuming they have an ad blocker.)
Old 01-20-2017, 08:08 AM
bob++ bob++ is offline
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So - essentially the "inverter" just pulses the m'waves; so that for a given time, there can be different amounts of nuke applied. My simple one has a choice of powers; 90, 180, 360, 900 watts. All it does is cycle from mostly off at 90 all the way up to continuous at 900.

The only time I ever use a low setting is for defrosting.

Last edited by bob++; 01-20-2017 at 08:09 AM.
Old 01-20-2017, 08:21 AM
Atamasama Atamasama is offline
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I use the low setting for reheating almost everything. Here's an XKCD on the subject:

On a lower power level I'm less likely to have food cold on the inside and overcooked on the outside.

Also: Don't microwave cut grapes (not sure why you would, just don't).

Last edited by Atamasama; 01-20-2017 at 08:23 AM.
Old 01-20-2017, 10:55 AM
epbrown01 epbrown01 is offline
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Originally Posted by Atamasama View Post
On a lower power level I'm less likely to have food cold on the inside and overcooked on the outside.

Also: Don't microwave cut grapes (not sure why you would, just don't).
I'm pretty sure I've never cut a grape for anything, certainly not with an intent to microwave it.
Old 01-20-2017, 11:36 AM
Atamasama Atamasama is offline
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You might slice grapes if they were included in ambrosia salad but you wouldn't want to microwave that either; it would turn into soup.
Old 01-20-2017, 01:11 PM
chorpler chorpler is offline
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Originally Posted by Atamasama View Post
Also: Don't microwave cut grapes (not sure why you would, just don't).
I'll tell you why: because it's SUPER FUN! Just like putting fire in a microwave. Although you probably shouldn't use a microwave you aren't willing to destroy.


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