[sdiy] blowing fuses

[Sarah Thompson]

Yep, linear supplies can eat current like it went out of fashion. Go for a
slow blow and you should be fine.

On Sun, Feb 16, 2020 at 9:45 PM Richie Burnett <rburnett at richieburnett.co.uk>
wrote:

> > How does this magnetized transformer problem work? Doesn't that
> magnetism dissipate after a short time?
>
> If the AC mains voltage happens to be crossing through zero at the instant
> when the transformer is connected to the mains line, then the transformer
> core sees asymmetric magnetisation and soon saturates.  This means it loses
> most of its inductance and the primary current is limited only by the
> winding resistance.  The larger the transformer the bigger the current
> surge due to this effect because the windings are thicker and have lower
> resistance. Low resistance makes the current surge larger and last longer
> before the transformer core moves out of saturation and returns to normal
> operation.
>
> Some additional resistance in series with the primary of the transformer
> reduces the magnitude of the current surge and also makes it go away
> quicker. This resistance can be bypassed to minimise losses once the Inrush
> event has passed. An NTC thermistor in series with the transformer primary
> is another common method to limit Inrush.
>
> -Richie,
>
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-- 
[s]
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