minute,
cycle
What do you mean by excessive? If a magnetron can be modulated by varying its B+, why shouldn't each PWM cycle be just one or two seconds long? You DO NOT want the magnetron running at full power for "long" periods, followed by even longer periods off (eg, one minute, four minutes off, for 20%).
My GE has six instant-start buttons, for one through six minutes.
Mine cycles over 10 seconds.
-- You can't fix stupid. You can't even put a Band-Aid? on it, because it's Teflon coated.
If you like switching a kilowatt sized transformer on and off every second, power to you. Same for a reed relay rated at kV at hundreds of mA.
It would obviously be easier with one of those switching power supply microwaves, but that's not how the old microwaves worked.
As far as I know, my 10-year-old GE is a "newer" model.
This has become one of those "inquiring minds want to know" questions. There are leakage meters, which would show changes in level. Does anyone make a power meter you can place in the cavity?
You might get by with a cup of water and a light bulb. Neon lights with the leads twisted together was the standard "indicator" for microwaves when I last touched these things. You really want the cup of water as a dummy load when putting weird stuff in a microwave.
I just ran at test like that on my made in 1981 samsung microwave. It surprisingly has a digital clock and numeric keypad- space age stuff for the time. This thing was clearly made when they were terrified of microwave leaks. There are a whopping 20 torx screws alone holding the glass in the front door, plus more holding the door together.
Anyways, in defrost mode, the magnetron is clearly cycled on and off in 15 second intervals. I could tell when it was on from when the small lightbulb lit up.
Connect a voltmeter across the power line. You will see the voltage change as the oven switched between a couple Watts to 700-1100 Watts. I can hear a change in the hum from the HV transformer on my oven.
-- You can't fix stupid. You can't even put a Band-Aid? on it, because it's Teflon coated.
Cydrome Leader wrote in news:iqs93v$lv7$ snipped-for-privacy@reader1.panix.com:
No,it's longer than that. probably a minimum of ~10 seconds. you can tell by the change in sound of the oven,the magnetron loads more when it's cooking.
Maybe it's cheaper to use a digital timer than a mechanical timer. Although ISTR seeing some low-end MW ovens that still had the mech.timer.
But people want the flexibility of using their MW for more than simple reheating/cooking tasks. My GE has all sorts of functions I never use,mostly sensor cooking.
-- Jim Yanik jyanik at localnet dot com
The problem -- as I've repeatedly stated -- is that if the "on" part of the variable-power cycle is more than a few seconds -- possibly as short as 5 seconds, and /definitely/ 10 -- you're going to have localized boiling.
I occasionally see the oven's lights changing brightness, and hearing various "cycling" noises. I'm going to have to check into this...
1.panix.com:
I started using my combo oven turbo/microwave and I was disappointed it only had 15 second increments. Later I found out Turing the dial while it's cookin, you can reset the time in fin increments which is really neat, without having to stop and start.
In one case I replaced a digital timer with a mechanical timer, which both me and dad really liked. It was just like the old heath kit oven.
Greg
he
Our Panasonic cycles in the 5 - 15 second range.
There are a few things you can do. Use containers with straight vertical sides. The thinnest part of the material boils first in a typical bowl. I've been acquiring HUGE ceramic coffee mugs to cook soup. The other thing you can do is siphon off the energy with a cup of water. Varying the amount of water and the power cycling can accommodate most needs.
In some cases, a microwave browning dish can average the long-duration PWM of the oven.
I've done some experiments with a dish that looks like a lemon juicer. The donut shape of the liquid gets energy from all sides and can help moderate the edge boiling. You'd really not want any thickness of the subject material to be any thicker than the microwaves can penetrate.
I use huge ceramic cereal bowls. Heating soup or oatmeal at full power still causes localized boiling.
With my oven, simply lowering the power does the trick. A big bowl of oatmeal cooks in 6 minutes at 50% power, with no boilover.
It seems to me that's exactly what you want.
Percent power may not be related to actual duty cycle. 50% is not 50% on and 50% off. The ON time may be longer based on service info for a Sharp Microwave, It takes time for the filament to warm up and there may be reduced or no output. This is taken into account.
Which still results in a 50% on to off output from the Magnetron. Just how long do you think it takes for the filament to reach full operating temperature? We aren't talking about 12 volt tubes with 150 mA filaments that take ten seconds to warm up.
-- It's easy to think outside the box, when you have a cutting torch.
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