Higher powered microwaves would require higher powered electric
outlets, probably 220VAC (in the USA).
Also it is questionable whether higher powered ovens would be
practical for use. Getting warming times down to a couple of
seconds might not be a good idea. More speed is not always better.
On Saturday, December 29, 2018 at 9:23:42 AM UTC-5, Bill Gill wrote:
That about covers it. Not sure how useful more power would be. For exampl
last night I was thawing out a tomato sauce in a quart plastic container.
The Panasonic has a defrost mode that uses about 30% power and cycles that.
Even so, after a couple mins you have to check, because the bottom gets
hotter and the plastic can soften or melt. Other things tend to heat uneve
as well, eg you can have one area starting to spatter, while the other is
lower temp. If you had more power, those issues just become worse. And
for sure the fact that receptacles are 15 or 20 amps limits the practical
upside as well. If people had a MW and it trips the breaker when they
use another small appliance, they wouldn't be very happy.
That was true of the first generation of Microwaves, but the current
"inverter" driver units actually CAN throttle the power. Inverter
microwaves are much better for defrosting AND cooking.
We've had ours for about 2 years now - replacing our original that we
bought in about 1985.
BIG difference (but the old one would likely still be working by the
time this one dies)
Why is it called an invertor? I thought an invertor was a device to increase the voltage - like running 240V devices off a 12V car battery.
And why on earth would you not want to cook on full power? I've never had a reason to lower the power from the maximum of 800W. I want the meal as soon as possible!
So they rectify the AC, then boost the DC voltage as required by the user setting?
But even without an invertor, surely you could have a few tappings on a transformer to change the AC voltage to the magnetron? It's not like you need infinite control, just 3 or 4 would do.
On Sat, 29 Dec 2018 12:27:21 -0600, Arthur Conan Doyle
No, the inverter still produces AC - but the AC is variable. The AC
in both systems is rectified to DC for the magnetron.
The inverter produces a lot higher frequency AC than line frequency.
High frequency produces a much easier to filter DC .
Both styles actually take AC incoming mains, raise it to 5k or so,
and convert it with a single diode mind you, to DC to feed the
magnetron. The filament is fed by low voltage AC. Neither of them can
or do vary the voltage going to the magnetron. That's just not how it
works. You can't lower the voltage to reduce microwave energy. And
you can't raise it to get more microwave energy, either. The
magnetron requires voltage within a certain range to function. More
than that will burn the magnetron up. Less will prevent it from
making viable microwaves.
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On Monday, December 31, 2018 at 9:43:22 AM UTC-5, Max Demian wrote:
He abundantly and mostly correctly explained that in his previous post,
including the one you copied. The inverter type still pulse the magnetron,
just at a very fast rate, so that for all practical purposes, it's
like being continuous. It's like dimming a 100W bulb. If you turn it
on and off half the time in 1 second cycle times, you will see it blinking.
If you do that with a very fast cycle time you will see a dimmed but
continuous light. That's how bulb dimmers work too.
I built a PWM dimmer as a project I did in college. The improved
efficiency was obvious if you felt the heat in the power transistor. Too
low a switching frequency would show the light on for part of the time.
Also, with AC, a diode in series reduces the brightness (approx. 49%
duty cycle). This works on some LED lights as well. I have them on some
Christmas lights that are normally too bright (green tape lights around
tree and light pole in picture below).
Microwaves do not penetrate all the way through larger volumes of
food - the heating is done in the outer 1-2cm. Heating the middle
is done by conduction (and by convection if the food is a fluid).
If you pile in energy faster than it can conduct all the way through,
you will have a burned outside and a cold middle.
Domestic microwave food products are not designed to be heated in
2kW ovens. Many would fail to cook properly/safely.
Commercial microwave food products (some anyway) are designed to be
heated in 2kW microwaves.
And in reference to your other post, it's not simply a matter of
dividing the cooking time by two. The amount of energy absorbed by
a food product also depends on the surface area exposed to the
microwaves (1 pea in a 2kW oven will not absord 2kW), so the cooking
time in a 2kW oven depends on the size and shape of the item - it
would have to be calculated by the manufacturer and included on the
packaging, but in practice, most domestic food products will not have
sufficient heat conduction to be able to absord 2kW and cook properly.
[email address is not usable -- followup in the newsgroup]
As usual, you are so stupid that you havent even noticed
that most words have more than one meaning.
In most ovens, the magnetron is driven by a linear transformer
which can only feasibly be switched completely on or off. (One
variant of the GE Spacemaker had two taps on the transformer
primary, for high and low power modes.) Usually choice of
power level doesn't affect intensity of the microwave radiation;
instead, the magnetron is cycled on and off every few seconds,
thus altering the large scale duty cycle. Newer models use inverter
power supplies that use pulse-width modulation to provide
effectively continuous heating at reduced power settings, so that
foods are heated more evenly at a given power level and can be
heated more quickly without being damaged by uneven heating.
Yeah, you know it all, no microwave designer knows anything.
There's been a lot of nitpicking in this thread.
All microwaves reduce power by cycling between 0 and 100% power.
The relative power level is the duty factor of that on/off cycle.
Older microwaves switch the INPUT to the power transformer.
That also runs the filament. The time to heat up the filament
is the limiting factor in how short you can make the on-time.
You get a minimum of about 10 seconds on-time.
That minimum time is plenty to make food explode.
Better microwaves are called "Inverter" microwaves.
I believe they're all licensed from Panasonic.
When I bought mine, it seemed that all the licensees had
dried up leaving Panasonic as the only locally available units.
It's my understanding that they heat the filament independently
and can have very short on-times. Duty factor is the same as
the older microwaves, but the on-time can be much shorter.
Foods don't explode on low power like they used to.
Food is not uniform. The effectiveness of microwaves decreases
as the food thickness increases. There's a thermal time constant.
So, if you cook at lower average power for longer time,
you can warm the inside without seriously overcooking the outside
or having local boiling that makes food explode.
The minimum on-time really helps with that. I haven't had food
explode since I got an Inverter microwave. The defrost cycle
really does work well.
They're slightly more expensive, but it's worth it.
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