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From: wolfgang@mgm.mit.edu (Wolfgang Rupprecht)
Newsgroups: sci.electronics
Subject: Re: MOVs
Keywords: computer power protection line conditioning
Message-ID: <6000@bloom-beacon.MIT.EDU>
Date: 4 Jul 88 16:33:22 GMT
References: <219@nfsun.UUCP>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: wolfgang@mgm.mit.edu.UUCP (Wolfgang Rupprecht)
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Organization: Freelance Software Consultant, Boston, Ma.
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>What exactly is the difference between buying a $150 line conditioning box
>and soldering a couple of MOV capacitors [sic] across the outlet?  

about $140

Seriously you can buy lots of MOVs for the price of one of those
nicely packaged anti-surge outlets.

Remember, NEVER connect an MOV across a powerline without putting some
sort of fuse protection upstream of the MOV.  Not unless you really
want to cash in on your fire insurance. ;-)

(If you really want to see what an MOV does when it "blows" plug a
100V-peak one into a normal wall outlet sometime.  Instant arc-light
and mucho smoke and flames.)

For a really deluxe surge suppressor box, get 
    1) fuse, for the "hot" [black] lead
    1) inductive-capacitive line-filter (such as a Cornell-Dublier) 
       for filtering noise
    3) MOVs for major surges
    3) gas-discharge voltage clamps to parallel across the MOVs
       for slightly faster response times.
   (and... lots of colored LEDs or neon bulbs for that special
   high-tech look!)

PS. MOVs aren't capacitors at all.  They are much more like a
statistical network of zener diodes.  The thicker the MOV is, the
longer the mean-path through it is, and the higher it's effective
zener voltage is.  MOVs are such robust voltage clamps because they
fail "gracefully".  The failure of any small number of its 10's of
thousands of constituent zeners hardly matters at all.

---
Wolfgang Rupprecht	ARPA:  wolfgang@mgm.mit.edu (IP 18.82.0.114)
TEL: (617) 267-4365	UUCP:  mit-eddie!mgm.mit.edu!wolfgang