New Microwave Oven Amps

[xrunner]

I bought a new microwave oven yesterday - a Panasonic "inverter" technology unit which does power level differently than the older microwave designs. It doesn't "pulse" the power level to reduce total power to the food, it actually reduces the output microwave power level. If you want to know more see the link -

https://www.choice.com.au/home-and-living/kitchen/microwaves/articles/what-is-an-inverter-microwave

It also does several other things my older one can't do but I digress ...

The unit works very well and I'm pleased with it so far. Anyway, I wanted to check if it was really doing the power levels the newer way or if they were loose with their claims of the product. I first checked the amperage with a Kill A Watt plug-in power checker while looking at several power levels. I did find that it really was changing the power levels like you would think.

However, I noticed on full power it pulled ~16 Amps. This did not agree with the labeling which states "12.4 A, 1480 W" (see manual screen shot, the label on the product also states the same info). My mains voltage here is 123 V, and that equates to 1968 W, which also agrees with the Kill A Watt reading.

I wondered if the Kill A Watt was measuring correctly. It's only supposed to go up to 15 A and was beeping while it was measuring 16 A, warning the user it was over range.

I set up another way to measure amps with a short extension cord test rig that I could get my clamp-on ammeter on to. It also measured ~ 16 A at full power. Yet the label states 12.4 A. What do I not understand here?

[dietert1]

Can you find out whether the "inverter" includes "PFC"? I'd guess for a high power device like that microwave PFC is required by law, but who knows. I'm trying to construct some explanation. Without PFC the peak current of the bridge rectifier will be much more than expected and the relatively simple devices you are using for measurement may be fooled into high measurements. You would need a "true RMS" meter to determine power consumption of a non-PFC inverter.
Another explanation might be the difference between power input and output (inefficiency). I mean 1900 W could be required as input to output 1400 W. But then again as far as i remember most household microwave ovens have 600 or 800 W output. So it should consume 1400 W to radiate 800 or 1000 W of heat into the meal.

Regards, Dieter

[xrunner]

Thanks for your questions.

Can you find out whether the "inverter" includes "PFC"? I'd guess for a high power device like that microwave PFC is required by law, but who knows.

No I can't easily find out.

I'm trying to construct some explanation. Without PFC the peak current of the bridge rectifier will be much more than expected and the relatively simple devices you are using for measurement may be fooled into high measurements. You would need a "true RMS" meter to determine power consumption of a non-PFC inverter.
Another explanation might be the difference between power input and output (inefficiency). I mean 1900 W could be required as input to output 1400 W. But then again as far as i remember most household microwave ovens have 600 or 800 W output. So it should consume 1400 W to radiate 800 or 1000 W of heat into the meal.

Regards, Dieter

Well it does state the cooking power is 1200 W, which should be less than the total input power consumption. And it is, the label states 12.4 A, 1480 W. So that makes sense. I find it difficult to believe that the label would have the wrong amps listed, I mean this Panasonic model has been in production for years. I dunno, that's why I'm asking because I don't know everything about all things. 

This morning I'm doing some tests and comparing the heating of the more modern design with my older unit, using some water filled cups, and using my IR camera. This is just for fun and my own interest. I will post them later if I remember.

[xrunner]

I opened the new microwave to see what bulb part they used so I can locate a replacement LED substitute. To open it I had to remove five screws - three of the five were T20 torx security screws, which I already had a bit for. The other two were regular Philips screws. Why they were not all security screws I don't know. Probably would have cost 2/10 of a cent more. My old microwave did not have any security screws on the back cover.

The bulb part is a very cheap standard POS thing, which is held on simply by two bent tabs of metal - yee-haw.  The bulb does not unscrew from the base. I easily found a replacement LED part so I ordered that.

Replacement LED for Microwave

While it was opened I inspected all the wiring. It's pretty much as you would expect. Very cheap mass-produced assembly. There is a fuse in a fuse holder on the input power board, but it's not meant to be user-replaceable by the average consumer because it's behind a cover with security screws (so is the incandescent bulb). For what it was I didn't find any really bad issues to the eye. I put the cover back on until the LED bulb arrives.