fusible link questions

[Tom Parker]

KD6JDJ <KD6JDJ at aol.com> wrote:

>  [[ I am curious about how a professor has determined that automotive
>alternator diodes will have a forward voltage drop of 2 volts.]]

Most people think that a forward biased diode drops a constant voltage no
matter what the current. This is not true. There is a small rise in resistance
as the current increases.

I have measured this over a few orders of magnatude of current.

I'm not sure, but I seem to remember that there is an exponential rise in
resistance, but I can't really remember.

The diodes in the alternator are passing 100A or more, so even a small
increase in resistance with current can produce a significant drop.

2V at 100A seems reasonable to me. The only way to tell is to measure it
though.

--
Tom Parker - tparker at nznet.gen.nz
           - http://www.geocities.com/MotorCity/Track/8381/