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MMD > Archives > June 1997 > 1997.06.27 > 07Prev  Next


Electrical Safety - Solid State Relays
By Pat Mullarky

Regarding Solid-state Relays:  SSRs are *the* way to go.  The major
problem is finding a source for them, as they are very much a "specialty"
item, even in the electronics/electrical world.  I'd call DigiKey,
1-800-344-4593 , and ask for a catalog.  There is a huge selection of
Crydom SSRs in the catalog -- and at DigiKey you can order small
quantities! A properly selected SSR will last essentially forever.  They
are not a "restoration" item of course; they're new technology.

For a perfect restoration, you'll have to rebuild the old relays.
A few (a very few) motor rebuild shops can do this for you if they have
absolutely nothing better to do.

Regarding "melting" relays: there is indeed a problem with the newer,
cheap-o relays commonly sold, even if they have silver contacts.  The
answer is either a SSR (above) or a high-quality "contactor" type of
relay designed for motor switching.  A motor-switching relay can and
should last decades if it is selected with the appropriate rating (which
for me is double- everything!).  Think of your refrigerator: it uses a
motor relay -- and you never unplug it.

Grainger's Motor Supply (Yellow Pages) has pages and pages of
motor-control relays in their catalog.  Just select twice as big a relay
as you think you need.  They're big and ugly and not an aesthetic or
restoration replacement, but -- safety first!

My two cents....

Pat Mullarky

Patrick Mullarky
NW Computer Engineering
pat@nwce.com  www.nwce.com
206 451-7916   206-453-9699 fax


(Message sent Fri 27 Jun 1997, 19:02:08 GMT, from time zone GMT-0800.)

Key Words in Subject:  Electrical, Relays, Safety, Solid, State

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