Re: microwave oven power cooking levels?

From: Repeating Rifle (salmonegg_at_sbcglobal.net)
Date: 12/09/04 

Date: Thu, 09 Dec 2004 00:52:43 GMT

in article 41b7823f@clear.net.nz, wave at wave@waving wrote on 12/8/04 2:38
PM:

> Have spent over 2 hours trying to find out if most or all microwaves do true
> variable power output as opposed to the traditional cycling on & off to
> attain different power levels, panasonic call this inverter technology, they
> make it sound like they are the only ones that do it, have not been able to
> determine if this is so yet, I searched webpages as well as the newsgroup
> archives but frustratingly I could not find the answer to what I would have
> thought would be a common question.
>
>
I was intrigued by this and other posts on the subject. Here is what I
conclude off the top of my head. I may be wrong in part. It sure is
difficult to glean specific information from the Panasonic web pages.

The inverter substitutes high frequency electronic switching and a SMALL
transformer for a much heavier magnetic transformer to provide the high
voltage necessary to operate a magnetron. The switching also allows varying
the voltage applied to the magnetron. In turn, that varies the magnetron's
output level. A conventional transformer's output voltage is not easily
changed. The down side is that efficency is reduced somewhat, especially at
low cooking level. That is, a larger fraction of the electrical power you
pay for ends up heating things other than food you are trying to heat.

Running transformers at high frequencies, what the inverter does, reduces
the size and weight required to handle large powers. The cost of electronic
devices such as transistors has dropped as manufacturing techniques
improved. Magnetic components such as transformers have not dropped much, if
any, in price. To a large extent, cost and size for these components vary
together.

Bill

Relevant Pages

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    ... A textbook about 10 years old says that inverter units increase the input power from 60 Hz to several thousand Hz, then can use a smaller transformer to step down to the welding voltage, then convert that high freq power to low freq AC or to DC for welding. ...
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