[HAM] Converting to a SS rectifier

[Drew Hoelscher]

The ones I use in all of my circuits (and of course I'm home now and 
can't remember the part number...) is basically a power Zener without a 
sharp knee.  I use them in crowbars.  The part I use starts to conduct 
at about 18 - 22VDC which knocks-down any input transients.  In forward 
bias, they are a diode...and pop the fuse (crowbar) when a reverse 
voltage is applied to the power input.  Tomorrow I'll post  a link to a 
spec sheet.

They are used in automotive for "load dump" (counter EMF).  Your car has 
at least 1.

For high-voltage (like lightening) I would use a MOV (metal oxide 
varistor).  MOV's work in a circuit like Transorbs, (Transorbs are 
faster) but tend have a higher breakdown voltage.  Also, Transorbs have 
a tenancy to fry at high-voltages (work once then die, like any good 
solid state device).  MOV's can work over repeated hits.  Surge 
suppressor outlets normally have 3 MOV's in them (Hot to cold, hot to 
ground, cold to ground).

Duh!  I'm just not all that familiar with tube circuitry (however I did 
design a 300VDC class A solid state linear power supply for the AO28, if 
anyone is insane enuf to build it...).  The idea of putting a low 
resistance high wattage resistor in series with the output of a full 
wave rectifier bothers me.  But since the surge that is being discussed 
is a current surge, (ic = C dv/dt) a Transorb wouldn't be the right 
device to use (a PTC might work...).

- Drew


Ted Thompson wrote:
> Interesting, yet another item that I am unfamiliar with.  Would you 
> have any technical data on this "Transorb"?  All I found was info 
> related to power protection for avionics, and that frankly looks like 
> nothing more then a zener diode.
>
> Cheers!
>
> Ted Thompson
> General Manager - Speakeasy Vintage Music
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> dahoelscher at charter.net wrote:
>> A transorb would be the device of choice over a resistor.
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