2x Panasonic Inverter Microwaves - what to salvage, dangers?

[Michelle_]

Hi,

I found a couple of these by the bins and moved them to the garage for later. I understand they might have useful components such as diodes or "beefy IGBTs", but I can't find much information on them compared to regular microwaves.

I know regular microwaves have a HV capacitor to watch out for, and a transformer that can be useful.

What are the Dos and Don'ts of inverter microwaves?

[Twospoons]

I had one, and it blew the IGBT and main diode bridge. So don't go hoping to salvage those parts, thats probably why the microwaves are dead.

[Michelle_]

I had one, and it blew the IGBT and main diode bridge. So don't go hoping to salvage those parts, thats probably why the microwaves are dead.

Could be. I want to poke around in there and see but I just wanted to double check that there won't be any dangerous surprises, mainly.

I've also read they may contain a flyback transformer.

[Michelle_]

Took this and tossed the rest

[Mads Barnkob]

Being a inverter, rather than a big lump of iron, a microwave inverter is not as sturdy and can stand up to abuse.

Look up the load impedance of a magnetron and you got an idea of how much you load the output. They are most likely only rated for full power for a 5-10 minutes, with forced air cooling.

All that being said, it is a nice small 2300 VAC inverter, on/off controlled, maybe something like power supply for a marx generator.

[rikkitikkitavi]

The transformer is designed to take the full load more or less continously I would say.

The drive stages will overheat rather quickly considering the size of the heatsinks. The transformer would saturate immediately if driven with too high V*t . Windings heat upp quickly  due to the low mass. Any magnetic losses  (proximity effect etc) will show upp quickly too. Even if the oven is normally used to run att full power for say 5 mins it has to be designed for more, atleast the magnetics and the transformer because it is not very easy to measure the temperature of a 2300VAC winding

The drive stage is monitored or limited somehow, and probably a heat sink temperature sensor but that has a delay.

I say it is safe to load it around 50% or so. Say 400W output? Like Mads said , not forgiving if driven out of spec. The silicon will release its magic smoke and stop working immediately with acoustic, optical and olfactory signals in such a manner that you can not miss it.

But silicon can be replaced even if it is impossible to put the magic smoke back inside.

A normal iron core transformer I say is safe to load at 25% continously for a 800W microwave, but even in idle, ie no load losses will make it rather warm. . It is disturbingly undersized  to save on magnetic iron and copper windings. And shipping costs...

But they are robust. Hell, we have all shorted iron-core transformes one way or the other. It takes a while for it to overheat.

If you find a microwave oven in the bin and it is not clearly having a heavy transformer inside (the weight is more or less evenly distributed) most likely silicone is gone. It could be repaired though for a few bucks (in most currencies) with all likelyhood. Just as the average induction top for significantly more money.