View Single Post
  #78   Report Post  
Posted to alt.home.repair,uk.d-i-y,alt.electronics,alt.sci.physics
mike[_22_] mike[_22_] is offline
external usenet poster
 
Posts: 1,243
Default Slow microwave ovens

On 12/29/2018 10:16 AM, William Gothberg wrote:
On Sat, 29 Dec 2018 17:38:04 -0000, Clare Snyder
wrote:

On Sat, 29 Dec 2018 08:07:42 -0800, Bob F wrote:

On 12/29/2018 6:37 AM, trader_4 wrote:
On Saturday, December 29, 2018 at 9:23:42 AM UTC-5, Bill Gill wrote:
On 12/29/2018 7:43 AM, William Gothberg wrote:
Shouldn't we have faster microwaves by now giving out a few kW? They
were invented decades ago.
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.

Bill

+1

That about covers it. Not sure how useful more power would be. For
example,
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.


It gets the 30% power by cycling the 100% power on 30% of the time.

(By the way, adjusting the level does not actually change the wattage.
It simply means the microwave will pulse on and off at its fixed wattage
until the desired level is reached.)

https://lifehacker.com/5974788/famil...-cooking-a-joy

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!


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.