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Usual failure modes of magnetrons?

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Paul Hovnanian P.E.
Guest

Thu Apr 16, 2020 9:45 pm   



tabbypurr_at_gmail.com wrote:

Quote:

The short only occurs if the primary interlock switches fail, no other
situation. At which point no-one cares what it does to equipment life
expectancy.


The shorting monitor switch closes every time the door opens. If the timer
shuts off the magnetron and you open the door a few seconds later, there is
no effect. If you open the door on a running oven, even if the series
interlock switch removes AC power from the HV transformer, the shorting
switch may close within milliseconds of that. So what is the time constant
of the decaying field in the transformer? And what hapens if you give that
field a shorted winding?


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Cydrome Leader
Guest

Thu Apr 23, 2020 6:45 am   



Paul Hovnanian P.E. <paul_at_hovnanian.com> wrote:
Quote:
tabbypurr_at_gmail.com wrote:


The short only occurs if the primary interlock switches fail, no other
situation. At which point no-one cares what it does to equipment life
expectancy.

The shorting monitor switch closes every time the door opens. If the timer
shuts off the magnetron and you open the door a few seconds later, there is
no effect. If you open the door on a running oven, even if the series
interlock switch removes AC power from the HV transformer, the shorting
switch may close within milliseconds of that. So what is the time constant
of the decaying field in the transformer? And what hapens if you give that
field a shorted winding?


The delay in the mechanical timing of those switches is clearly always enough. If there
was overlap, you'd blow the fuse every time.

fun fact, the monitor swtich as it's being called here is these days (at least the past
decade if not longer) is a non-snap action switch in a standard microswitch form factor.
The only rating is 1 use and enough current to blow the mains fuse. They never switch any
load during the life of the microwave unless there is a fault condition. Microwave ovens
are sort of like cars and have every possible extra cost engineered out. Polaroid instant
cameras were like that too. It was amazing how many parts they tweaked out of the design.

three_jeeps
Guest

Fri Apr 24, 2020 12:45 pm   



Link points to a website that is under construction???

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