Re: Convert an AC to a DC Welder

In article <QEJoj.12$EK3.8@trndny04>, "James Sweet" <jamessweet@xxxxxxxxxxx> wrote:


If the input to the bridge is AC each set of two diodes conduct for 1/2
cycle.
On the other half they are NOT conducting and cooling down.
If in that 1/2 cycle two diodes carry 100 amps, then the average
of 8.4 msec. zero amps, and 8.4 msecs 100 amps, I calculate 50.

How else do you do it ?


On an AC line driven Xmas light st, the LED is on for 50% of the time
If the peak current is 30 ma. then the average is 15 ma. !! ??

greg

The average current is less than the peak current, but when talking current
ratings of semiconductors, it's the peak current that matters. 100A
rectifier needs 100A diodes, because they still have to carry 100A,
regardless of how much time they spend actually doing it. It isn't just a
matter of heating.



When you say you want a 3 amp bridge. You get a 3 amp bridge.
Nothing was said about peak current. Very rarely do I worry about peak current.
In most circuits the current is limited by other resistances or Z's.
OK the 3 amp bride has a 200 amp peak.

greg

.

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