Mike Harrison <mike <at> whitewing.co.uk> writes:

>... cheap transformer

In fact the transformer is built to saturate and thus limit power transfer to
the magnetron (and also to limit heater current when this is cold). The
magnetron is a current driven device (it can be modelled like a giant zener
diode in its operating area).

But the bottom line is that one can only put a 500 Watt heater into a cup of 
water with difficulty. Ditto smaller things. Therefore microwave heating is the 
most efficient for small (portion sized) food items when all factors are 
accounted for. A normal heater (electric plate) will have a lot more losses and 
waste the heat used to heat itself (its own mass) when used cyclically.

The magnetron itself is considered a class C rf amplifier for calculation
purposes (that means efficiency > 90% is possible). I think that the dc-dc
driven supplies in new ovens try to get close (probably >70%).

Peter P.


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