Microwave transformer inrush current solution?

"Martin Riddle"

** That would be a first in a microwave oven. ** Really ? Got a link for that ? ** Looks like more transformer Mumbo Jumbo ...

** Transformers routinely saturate at switch on - that is why " slo- blo" fuses always have to be used. Over the next few cycles the core demagnetises and settles down to a steady magnetising current level - with toroidals this is a very low value.

Problems arise with larger transformers ( particularly toroidals over

500VA ) because the primary resistance is less than 2ohms and this leads to very large current peaks during the first half cycle after switch on - no matter what the previous state of the core.

There are two ways a core may become highly magnetised:

1. The fuse blows at switch on, due to inrush.
2. AC switch contacts bounce just after an inrush.

... Phil

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Since when does a fuse "trip"??? They either open or not, but in English th e word, trip, implies it is resettable, so maybe you're talking about circu it breakers??? Who would know? And who would know of it's a plurality of "f uses" or a single fuse, wherein a singular fuse is indicative of a miswired installation.

Not practical for the usual duty cycle modulated installation.

uld

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Absolute last thing anyone would want to do.

rn

Yep, TRIACS are hardly ever used for power control, it's amazing the compon ent even exits it's so cumbersome to use.

Saturated transformer peak inrush current is winding resistance limited so it makes no difference whether it got there by being cycled through zero or peak reinforcing residual magnetization. The only difference is a cycle of exra integration time. The installation power distribution and circuit protection are miswired and selected badly.

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The correct answer is to quit screwing around and upgrade the wiring to properly support the load. Failure to do so can have legal consequences, particularly in case of a fire.

Just ask your local fire marshall.

?-)