Reduce power of a microwave oven?

My Panasonic has an inverter. Works OK, and and an energy meter confirmed that it doesn't just cycle from full power to off when running at lower power levels.

But it does tempt you to experiment. Even though the guidebook warns against trying to "boil" a perfectly cooked egg in its shell, I thought it worth trying using lower power levels. The first egg was perfect, using a rather complicated cooking schedule. The second was very soft - barely cooked. The third I'd rather forget, but it took a long time to clean the oven, and SWMBO wasn't amused as she was standing almost next to the door when it was blown open. It also took me some time to repair the safety lock...

--

Jeff

Why do things right, when you can whine online? ;-)

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You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

Then stick a damn glass of water in the oven to adsorb some of the energy.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

I suppose the issue could go round 'n round (usenet style), but the term cooked means different things in different contexts.

Not raw.. safe to eat. Beef color changed from pink to grey. Internal temp of 180 F.

Cooked, meaning not raw, is hardly properly prepared to taste. A piece of beef could be boiled to an internal temp of 180 F, and it's cooked, but I wouldn't care to eat it prepared that way.. some people do.

If beef doesn't sear from being in contact with blazing hot air/reflected IR heat (real oven), metal and/or fire, ya might as well be eating soy. Beef roasted in a real oven will brown on the top/outside, but not in a typical MWO.

For my tastes, the searing/browning of meats is what gives them good flavor, not so much the seasoning.. with a few exceptions, fried chicken, for example.

I prefer real oven or covered grill baked potatoes (or roasted in hot coals) over microwaved potatoes.. it's a matter of preference. I haven't been able to get crispy skins in a MWO. Sure, the MWO potatoes are edible, but far less flavorful.

Many MWO dishes are pre-cooked processed stuff anyway.. not good food when taken out of the package, but better when eaten warm/hot.

-- Cheers, WB .............

On 1/19/2011 9:24 AM William Sommerwerck spake thus:

... which should give further pause to those who claim that Wikipedia is full of good, accurate information ...

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Comment on quaint Usenet customs, from Usenet:

   To me, the *plonk...* reminds me of the old man at the public hearing
   who stands to make his point, then removes his hearing aid as a sign
   that he is not going to hear any rebuttals.

Put in a smaller high voltage capacitor?

Get an oven with inverter power control, like a Panasonic?

You're just DETERMINED NOT TO READ the original posting...where I mentioned that too. Although, I'd not considered adsorption as a relevant process.

more

in,

of

It is. No one is claiming it's always absolutely perfect.

When I ask a question on line, I go to great lengths to describe the issue in detail to keep the discussion from running off in all directions. It rarely works, but I keep hoping that people will actually read the info before shooting from the hip.

With this, and every other low-end non-inverter microwave oven I've ever encountered, the power is adjusted by pulsing the magnetron in bursts of approximately 15 seconds followed by an off-time required to get the average power you programmed. The RELEVANT number is the 15 second MINIMUM on-time. Doesn't matter what buttons you push, you can't get an on-time less than 15 seconds unless you program a single burst that's shorter. If 15 seconds is long enough to boil the liquid in part of the payload, defrosting can make a mess of things.

In this case, the "defrost" button has some algorithm that they don't disclose and I've been too lazy to reverse-engineer, but the minimum on-time is still about 15 seconds. It's a fundamental property of the design.

Reminds me of this interesting video showing how microwave energy is distributed inside a standard microwave...

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-Scott

Well, that's what I was asking about. I don't think there's anything you can do in the primary circuit. The magnetron filament runs off the same transformer as the high voltage. If you reduce the average input, you also reduce the average filament voltage/temperature. There are two basic issues that I can think of.

1) It takes time for the filament to come up to temperature. 2) The more you thermal-cycle the filament, the shorter the life. The 15-seconds is a compromise that mostly works.

If you want to pulse the anode, you have to have a separate transformer for the filament to keep it up to temperature while you pulse the anode. Conceptually trivial, but it adds to the cost.

As I mentioned in the original posting, you probably can change the value of the secondary cap, but that takes a high-voltage switch. I'm interested to learn if anybody's done that. Or if there's any theoretical basis for concluding that it's a bad idea.

It's worse than that. A triac can fix the relay issue. The problem is the thermal time constant of the magnetron filament.

Thanks for repeating one of my suggested options. Can you be a little more theoretical? One reference suggested that the cap is actually sized to resonate with the transformer. That would make the change of cap value much more sensitive than just a power ratio. Relevant input? Thanks, mike

Simple matter of price ;-)

and

The filament winding is on the same transformer as the HV, so the filament turns off when the transformer isn't powered; and magnetrons are a diode, it ONLY has the HV electrode available to control the power. If there were separate filament and HV transformers, the price would reflect this 'feature' in unpleasant ways.

Ineed, the patent I referred to shows the filament secondary as part of the main transformer. But the system presumably works.

I can't imagine a separate filament transformer being /that/ expensive.

he

But, you need to get multikilovolt safety testing on two magnetic parts, you need safe wiring in case the 'extra' wires come loose, and you then require a media campaign to trumpet the added feature, and a new model number for the finished product, which has to have a snazzy front-panel rework to distinguish it from the unenhanced model (which now sells at a different price point)... and the markup on this $2 technical improvement can easily get you to $120 addon at the retail store. The marketing department would like that to be $225.

Yes, it's hard to imagine a separate filament transformer as expensive. The marketing department has expert imaginers to do the heavy work of imagining the price upward. Ever upward. Excelsior!

You're right: Adsorption is definitely not relevant in this context!

Martin

On 1/19/2011 12:55 PM mike spake thus:

I guess I'm showing my ignorance here, as I don't know much about magnetrons, but why can't you just let the filament burn while you cycle the HV, like you'd do with any other ordinary tube? I mean, with other tubes, it's OK to apply power to the heater without any anode voltage, right?

--
Comment on quaint Usenet customs, from Usenet:

   To me, the *plonk...* reminds me of the old man at the public hearing
   who stands to make his point, then removes his hearing aid as a sign
   that he is not going to hear any rebuttals.

All correct by my experience, also

Arfa