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From: bkoball@cup.portal.com (Bruce R Koball)
Newsgroups: sci.electronics
Subject: Re: Are switches supposed to spark?
Message-ID: <33111@cup.portal.com>
Date: 23 Aug 90 02:32:52 GMT
References: <27155@pasteur.Berkeley.EDU>
  <1990Aug22.171934.24558@zoo.toronto.edu> <3964@kitty.UUCP>
Organization: The Portal System (TM)
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re: the comments of other posters on strategies for arc suppression on
switch contact opening....contactors (large switches used in industrial
applications, usually for switching large inductive loads) have a number
of interesting approaches....

arc chutes -- these are shaped pathways designed to extinguish large arcs
and contain the hot gases generated. one strategy involves breaking the
large arc into numerous smaller ones with an array of parallel plates in
the chute

blow out coils -- these are used in DC circuits. the current being carried
is also routed through a short, heavy-gauge coil wound around a "blowout
core." this core has pole piece extensions which bracket the contact area.
when the contact is opened the magnetic field of the blowout coil forces
the arc perpendicular to the direction of it's current flow (the ol' right
hand rule) thus extinguishing it.

Bruce Koball
Motion West
2210 Sixth Street
Berkeley, CA 94710
415-540-7503
bkoball@cup.portal.com