BoatBanter.com - View Single Post

On Sat, 19 Mar 2005 00:31:02 -0500,
wrote:

On 24 Jul 2003 15:35:55 -0700, (Jim Balsley)
wrote:

"Ed Price" wrote in message news:DPtQa.417$ Extraordinary claims demand extraordinary proof. I wanna see a schematic, I
wanna see suppressed transient waveforms, show me why Zap-stop is better
than a zener or MOV or SiC or Transorb or a gas tube!

Ed

I believe the zap stop is just a zener in series with a slow blow
fuse. You could make one for a lot less than they charge

There are several ways to approach this, depending on the alternator.
I don't like integrated regulators because they are hard to safely
control. Particularly those that supply their own field current when
they are running (get starting current through the charge lamp) and
ground the field internally through the regulator. By disconnecting
the trio diodes internally from the regulator, you can convert many of
these alternators to ecternally excited units -supply field current
through the "L" terminal.

External regulator units are obviously simpler.

Now you just need a "crowbar" circuit (like the zap-stopper) on the
regulator feed, with a fuse between the crowbat and the battery/ign
switch. If the voltage excedes 15 volts (or whatever voltage you
design for) the circuit clamps the field and blows the field supply
fuse - guaranteeing you will NOT get overvoltages. Now, if you want to
fuse the output, you need to have an NC relay in the field circuit
controlled by the output of the alternator, and you need to charge the
battery though a diode so when the fuse blows there is no voltage to
the relay coil, and the field drops. Final piece of the puzzle is to
provide startup current to the field, so the alternator can produce
power to close the relay to energize the field. This can be done by
providing power directly to the field(alternator side of field relay)
or to the coil of the relay during cranking.

And what do you do about the already charged field in the alternator
when the battery gets disconnected? It is already too late.
That's why the zap stop goes across the output of the alternator.

Regards
Gary