Why does microwave trip breaker?

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A friend with a Panasonic microwave, Inverter model, physcially a big one, says it is tripping the circuit breaker after about 5 minutes of running.
They've reset the breaker several times and it's the same each time.
What's your best guess?
I havent' looked at it yet, but my best guess from afar is that some of the primary windings in the transformer have shorted, and thus the impedance of the primary has decreased and it's drawing more current than it should, more than 15 amps. Does this sound reasonable? If not reasonable, then possible?
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On 12/12/2013 10:48 AM, micky wrote:

They may have other devices on the breaker which they should remove.
If there are NO other devices on that circuit and you do not have an AC ammeter, temporarily try the microwave on some completely different circuit. If that circuit breaker blows too, then the microwave may very well be bad. OTOH: If it does not blow, then the breaker is weak OR the wiring going to it is loose or burned and getting hot!
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That i thought of, but I didn't get a satisfactory answer. The electric coffee maker is on the same circuit and they've had to unplug that, but it isn't plugged in now. But when I tried to bring up other things plugged in to the same circuit, I got some words I didn't understand.

That I didn't think of, and I should have. He said around 3 that he'd found one, in the paper or online, a lot like this one, and he was going to buy one today. I told him I would ask online, but he still went shopping. I read your replies about 5, and after all of you brought up the breaker, I called and he wasn't home. I called his cell and got voicemail. I called his wife at home and he was just coming in but had to go out and had no time to talk!
She told him it might be the breaker and I could hear him say, That's a good idea"
I could hear him tell her that the new one was in the car. It's safe enough he can leave it in the car all night, but I have a feeling he will bring it in, open it up, and cook something, when he gets home tonight. .

I was explaining this to the wife, but she raised something I hadn'ty thought of, and before I discounted it, she'd was in a hurry and said goodbye too.
Maybe I'll know something tomorrow, but experience in general tells me that when someone gets this head up about buying something, he'll buy it whether he needs it or not.
Thanks philo and all of you.
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On 12/12/2013 04:32 PM, micky wrote:

<snipped for brevity>

If you can get them to go through all those steps I'm sure they will get it sorted out.
If the do replace the breaker they need to be sure the wire going to it is not burned...if it is tarnished, the problem will just start all over again.
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Okay.
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wrote:

it on a separate dedicated circuit??? What wattage is the oven? My suspiscion would point to the breaker if it is less than 1700 watts and on a dedicated circuit. If not on a dedicated circuit, what else is on with it???
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On 12/12/2013 8:48 AM, micky wrote:

called and inverter. It's so light, they should move it to another circuit and try it.
The time delay is the breaker getting warm enough to open. I suspect a worn out breaker! Replace it and all should be ok.
Paul
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Paul Drahn wrote:

First question to ask is, Did the unit work well and started tripping breaker lately or they got new one and try to start use it?
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wrote:

It's a few years old, and worked fine until a day or two ago.
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On Thu, 12 Dec 2013 10:14:04 -0800, Paul Drahn

No kidding! I wondered about the name.

That's what they should do all right. Based on your post, I told his wife it was light

I told her it might be that and she told him, but I think they'll buy a new one anyhow. Oh, well, I tried. And at least I learned a couple new things.

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On 12/12/2013 10:48 AM, micky wrote:

Microwaves are notoriously mean and will trip anyone coming by them. ^_^
TDD
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On 12/12/2013 11:48 AM, micky wrote:

box. Put ammeter on the wire, and see for real. In real time. Or use a splitter where the plug goes into the wall.
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On Thu, 12 Dec 2013 18:04:25 -0500, Stormin Mormon

Splitter?
You remind me that I had bought a Kill-o-watt, or whatever to measure wattage. Haven't used it. Only bought it then to put myself over 25 dollars for free amazon shipping. (Now you have to spend 35 dollars for that) He's supposed to call this morning. I'll suggest it. Except we'll have to stare at it for 5 minutes to see if it's high when the breaker trips. Iwonder if it remembers a max value. .
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On 12/13/2013 5:40 AM, micky wrote:

AC clamp on ammeter only goes around one of the power wires (power or neutral). As such, we use a splitter, so you can clamp one of the wires but not the other. If you clamp the entire microwave cord, you read zero amps of current.
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On Fri, 13 Dec 2013 07:17:08 -0500, Stormin Mormon

Oh, yeah. I get it.
I used to have a clamp-on attachment, but I bought a cheap clamp-on meter from HF and sold the attachment for a dollar at a hamfest. STill haven't used that either. But I probably will if I live long enough.
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On 12/13/2013 9:34 AM, micky wrote:

I use ammeter, now and again while working on equipment. Can be very useful information.
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Stormin Mormon wrote:

Ammeter has to in sereis with circuit duo you ct wires or put it between equipment breaker(switch) poles?
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On 12/13/2013 10:36 AM, Tony Hwang wrote:

I use a new gadget called a "clamp on ammeter" which goes around a single wire which carries current.
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Stormin Mormon wrote:

AC ammeter, Wow! when you use it do you cut the wires to put in the circuit or connect to breaker(switch) terminals for the equipment under test.
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wrote:

extension cord with one of the wires cut and brought out to connect the ammeter. - makes it a "plug in ammeter"
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