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.