Contrabasso - 14-9-2008 at 12:40
I want to use a conventional microwave oven in a low power situation, -12v battery and inverter. However all the ovens I have seen are 800w or larger
and do reduced power by time proportional switching. Is there a way of running a microwave at 100% duty cycle but say 50% power. Perhaps the
equivalent of driving the PSU off a Variac, half volts meaning reduced power?
I also want to protect the inverter against switch on nasties.
Who knows what? Please.
Twospoons - 14-9-2008 at 13:49
AFAIK reducing the cathode voltage on a magnetron will reduce the output power. The tricky bit is you need the cathode heater current to stay the
same. Most domestic microwaves have one transformer supplying both heater current and cathode bias, so to get variable poewr you need to add another
tranformer and spearate the two.
Alternately, I know Panasonic make a range of "inverter" microwaves, which use a variable switchmode supply internally to bias the cathode, so
running at 50% really is half power, not "half on/ half off". One of those may be your best bet.
I've got one at home, and it works really well ( best defrost performance I've seen on a microwave)
[Edited on 15-9-2008 by Twospoons]
not_important - 14-9-2008 at 18:29
Earlier thread, including an article in which a true power adjustment microwave was used
https://sciencemadness.org/talk/viewthread.php?tid=9221&...
I suspect such models are expensive, perhaps using electronic switching to changes duty cycling from number of seconds on/off to number of power line
AC cycles on/off would give something closer to true power output control without the difficulty of actually adjusting the power level.
Twospoons - 14-9-2008 at 19:13
I don't recall the inverter microwave being particularly expensive. It certainly wasn't the cheapest, but it was a long way from the dearest. In a
$100 to $1200 shop range, the inverter microwave was placed about $350.
Contrabasso - 15-9-2008 at 10:20
OK I'll look for a LV oven on the market somewhere. It's such a pain when the microwave tries to draw full power then nothing every few seconds when
you are using small gensets or even smaller inverters.
tentacles - 15-9-2008 at 14:41
We got an inverter microwave for x-mas, I think they're selling them for a crippling $89 at walmart. We have this model in white: http://www.walmart.com/catalog/product.do?product_id=8466190 Looks like the price is up a bit. It's a 1300w inverter type microwave.
I have to agree with Twospoons, these defrost superbly.
edit: Update, I plugged the micro into my kill-a-watt. Here's what I found: at power level 1, it draws ~700W and then cycles off for a bit (probably
at level 2 or 3 it stays at 700W continuously). At full power it draws a staggering 1975W! At P6 it pulled a continuous 1200W.
[Edited on 16-9-2008 by tentacles]