tracing out schematics

From: der Mouse <mouse_at_Rodents.Montreal.QC.CA>
Date: Sat Nov 20 20:01:24 2004

>> OK, with the chopper array disconnected (plus everything downstream
>> of it) the bulb lights very brightly when power's initially applied,
>> then gradually extinguishes over a period of about 5 seconds.
> Maybe OK. It could just be the charging current of the smoothing
> caps (they'll cahrage a lot more slowly with the lamp in series).

If we consider the lamp to nominally draw ?A[%], that means we have
roughly two coulombs of energy stored in the capacitors. I've seen
capacitors of relatively large rated farads*volts, but not often and I
think not as big as 2 coulombs. Based on what I have seen I'd expect
such a thing to be pretty big (200 cubic inches would be my minimum
size guess). How large are the caps in question? That should give
some idea how reasonable it is that for what you saw to be just
charging current.

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[%] Tony said 100W, and Jules didn't say. Since both the people
    involved are UK people, I take this to be running on 220V, this
    reinforced by the statement that the filter caps were running at
    about 300V; assuming a simple rectifier circuit, that means the
    input voltage was about 300/sqrt(2)=212+ volts plus diode drops.
Received on Sat Nov 20 2004 - 20:01:24 GMT

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