X-No-Archive: Yes

I have one of those "inverter" type microwave oven made by
Panasonic. It uses an inverter instead of the traditional iron core
transformer to power the magnetron.

I just noticed that this thing draws a lot more power & current than it
should. The manual specifies "120V AC 12.7A, 1460W" and 1,300W cooking
power.

Measurement with either true RMS or regular ammeter shows actual
current draw is around 16A. Based on the specifications given, the
power factor comes to around 0.956. Given that, it probably has a
harmonics correction so the reading from even an ordinary ammeter
should be reasonably accurate.

One possibility is that the interference from the inverter is causing
the meter to read abnormally high but given rather unrealistic
specifications, I believe my result is reasonable.

It is rather unrealistic that the calculated system efficinecy is
89%(1300W output over 1460W input). 89% efficinecy is unrealistically
high when you factor in the loss in drive circuit and magnetron. More
realistic answer is: A.) the unit is drawing more than the rated power.
B.)the unit is putting out less than the rating C.) combination of
both.

Assuming my measurement is correct, what's the permissibility of
something with NEMA-15P plug drawing in excess of 15A for more than a
split second?

If you have an inveter microwave oven, I'd like to know how your unit's
current draw compares to the official specification.