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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.

the power delivered and the power consummed probably changes with the
load.

what is in the oven?

did you try something else?

there may be a "standard load" that is used for these ratings.

Mark

I am thinking that your meter is being effected by some harmonics. I have
seen this before. If your circuit breaker for the outlet is a 15 Amp rated,
it would be in a short time that it should become opened.

The inverter ovens are using switching power supply technology. The current
pull from these under load is difficult to accurately measure. If the oven
seem to be working okay, I would think it is okay.

--

Jerry G.
======


wrote in message
oups.com...
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.

X-No-Archive: Yes


Jerry G. wrote:
I am thinking that your meter is being effected by some harmonics. I
have
seen this before. If your circuit breaker for the outlet is a 15 Amp
rated,
it would be in a short time that it should become opened.

The inverter ovens are using switching power supply technology. The
current
pull from these under load is difficult to accurately measure. If the
oven
seem to be working okay, I would think it is okay.

--

Jerry G.
======


I just went to FCC site and searched its FCC ID. I poked around the
exhibits Panasonic has submitted to FCC and one of the repots did say
"120V 16.7A 2004W"
Go to this link:
https://gullfoss2.fcc.gov/prod/oet/cf/eas/reports/ViewExhibitReport.cfm?mode=Exhibits&RequestTimeout =500&calledFromFrame=N&application_id=314929&fcc_i d='ACLAP6K51'

^that's one large line if it gets wrapped.
Download the PDF document Test Report Application index and summary.

Bottom of page 5 shows the specification for model # NN-S654BF. This
one says 120V 12.7A which is consistent with my instruction manual.

Bottom of page 8 shows test result for the same model # microwave.
120V 16.7A 2004W input, which is consistent with my measured result.

Last I checked, there's no way 16.7A appliace would be permitted with a
NEMA-15P plug with an intent to be used on a 15A circuit. But I could
be wrong..

wrote in message
oups.com...
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.


+ or - 20% is typical

Also if your line voltage is low, the amps will go up with a switcher, to
keep power constant.

It is better to have a transformer, it is far more reliable and more
efficient, about 97% or more than a switcher especially for 13 amps ac.

wrote in message
oups.com...
X-No-Archive: Yes


Jerry G. wrote:
I am thinking that your meter is being effected by some harmonics. I
have
seen this before. If your circuit breaker for the outlet is a 15 Amp
rated,
it would be in a short time that it should become opened.

The inverter ovens are using switching power supply technology. The
current
pull from these under load is difficult to accurately measure. If the
oven
seem to be working okay, I would think it is okay.

--

Jerry G.
======


I just went to FCC site and searched its FCC ID. I poked around the
exhibits Panasonic has submitted to FCC and one of the repots did say
"120V 16.7A 2004W"
Go to this link:

https://gullfoss2.fcc.gov/prod/oet/cf/eas/reports/ViewExhibitReport.cfm?mode=Exhibits&RequestTimeout =500&calledFromFrame=N&application_id=314929&fcc_i d='ACLAP6K51'

^that's one large line if it gets wrapped.
Download the PDF document Test Report Application index and summary.

Bottom of page 5 shows the specification for model # NN-S654BF. This
one says 120V 12.7A which is consistent with my instruction manual.

Bottom of page 8 shows test result for the same model # microwave.
120V 16.7A 2004W input, which is consistent with my measured result.

Last I checked, there's no way 16.7A appliace would be permitted with a
NEMA-15P plug with an intent to be used on a 15A circuit. But I could
be wrong..


A 15A circuit breaker may hold for a very long time or even indefinitely
with 16A running through it. A device which draws 16A would not damage a
15A circuit, nor trip a 15A breaker, if its duty cycle is low. If that
microwave does draw that much and Panasonic is allowed to put a 15A cord on
it, maybe that's the reason why.

j

According to circuit breaker tripping curves, a c.b does not trip with the
nominal current, but with 50% more current than nominal in 2 hours.Thus,
15+7.5=22.5 A and that for 2 hours.

--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "Jerry G." Ýãñáøå óôï ìÞíõìá
...
I am thinking that your meter is being effected by some harmonics. I have
seen this before. If your circuit breaker for the outlet is a 15 Amp
rated,
it would be in a short time that it should become opened.

The inverter ovens are using switching power supply technology. The
current
pull from these under load is difficult to accurately measure. If the oven
seem to be working okay, I would think it is okay.

--

Jerry G.
======


wrote in message
oups.com...
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.