Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!husc6!hao!noao!arizona!caset!catuc!doug
From: doug@catuc.UUCP (doug)
Newsgroups: sci.electronics,comp.misc,misc.consumers,rec.audio
Subject: Re: Power supplies & 3B1's
Message-ID: <2626@catuc.UUCP>
Date: Wed, 25-Nov-87 16:04:33 EST
Article-I.D.: catuc.2626
Posted: Wed Nov 25 16:04:33 1987
Date-Received: Sun, 29-Nov-87 10:46:03 EST
References: <942@woton.UUCP> <1805@ukecc.engr.uky.edu> <2257@kitty.UUCP> <2803@ncrcae.Columbia.NCR.COM>
Organization: Computer Automation, Tucson, AZ
Lines: 17
Keywords: secondary surge lightning arrestor
Xref: mnetor sci.electronics:1817 comp.misc:1696 misc.consumers:3549 rec.audio:4486

In article <2803@ncrcae.Columbia.NCR.COM>, ralph@ncrcae.Columbia.NCR.COM (Ralph Hightower) writes:
> I am in the process of collecting material and references for my previous
> request of Lightning Protection (lacking some ANSI/IEEE and NFPA standards).
> 

I did some research into this area and was told that MOV's have a prpblem
in that they degrade each time they absorb a surge and that the amount of
energy they can absorb each time becomes less and less. Eventually they
become ineffective. The bad part is that one cannot often tell if the
part has absorbed any surges and how much useful life it has left. This
means they they should be replaced periodically but that no one can tell
you when. The gas discharge tubes can work repeatedly but are not very
fast hence the reason they are often employed alongside the faster MOV's.
One solution I'm told is to use a device called a transorb
(Panasonic/Digikey sells them.) These are beefed up back-to-back zener
diodes that can work repeatedly if not stressed beyond their maximum
energy rating.