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RE- Re: Short circuit/Control Panel
Subject: RE- Re: Short circuit/Control Panel
Date: Sat, 07 Jun 1997 10:26:37 GMT
From: robert.michaels-at-online.sme-dot-org (Robert Michaels)
Organization: Society of Manufacturing Engineers
To: tesla-at-pupman-dot-com
Excellent, excellent, overall posts (no surprise there
considering the poster).
[ ... ]
-> While 1350 watts is only about 11 or 12 amps at 120 volts, it has
-> been my experience that inrush currents can easily be double this and
-> more. You will *not* experience the effects of inrush current if you
[ ... ]
Good point. If someone doggedly and abjectly refuses to
take Fr. McGahee's advice (or mine - see other post), then
for catsake and cryin'outloud do get yourself a switch
which is specificly and clearly rated for inductive loads
(or for motor-starting which is even more demanding).
-> circuit breakers (not fuses). My main control panel has a bank of
-> circuit breakers of several different values. I just "activate"
-> several in parallel to reflect the maximum current I want to allow.
-> For example, if I want 40 amps, then I activate two 20 amp breakers.
-> Just because my electrical service can supply me with 100 amps is no
-> reason to use a 100 amp breaker! Four 20 amp breakers and one 10 amp
-> breaker and two 5 amp breakers allow me to adjust from 5 to 100
-> amps in 5 amp increments.
Uh, er, I'm not too sure about this. It may well suffice
for casual coiling. It is assuredly not acceptable in
in professional practice:
Paralleling two fuses or two breakers to double the current
interruption capability is shakey at best. I'm not at
liberty to give a lengthy dissertation on why at the moment
(nor either would most want to read it). Suffice to say
it does not automatically give you 20-amps of protection
to run two 10-amp fuses or breakers in parallel in one
(or both) sides of the line.
Fuses and breakers are used for either of two
ways: To =allow= current or to =limit=
current. In the latter case, there is usually
some sensitive/expensive/difficult-to-replace
equipment which must =never= be subjected to
to overcurrents (fast blo fuses usually used
here). In this case especially it would be
exceedingly unwise to parallel fuses.
If one is going to parallel fuses/breakers for casual coiling
=at least= make certain the fuses/breakers are identical in
type, rating, mfg'r.
[ ... ]
-> system down from a remote position. This remote panic button is
-> mounted in a box and attached via a cable to the control panel. The
-> panic button is "portable" in the sense that I can move it anywhere I
-> want.
-> PANIC buttons should be a LARGE pushbutton, and preferably
-> illuminated so that you can't miss it in the dark! Place it where you
-> can slam it quickly in case of an emergency.
[ ... ]
The idea of a panic button is a super-excellent one.
I would propose that the panic button (more professionally
stated: emergency-stop button or E-Stop as they are widely
called { =real= professionals would never actually panic,
you understand} ) be mounted in a small box at the end of
a long cable, preferably shielded cable or cable in flexible
conduit, conduit or shield grounded.
Cradle the panic button box in your hand at all times when
operating under power. That way if you panic (er -- I mean
experience an untoward event) you can hit the button instantly.
Dr. Tesla counseled keeping one hand in one's
pocket at all times. Taking a page from Fr.
McGahee's book (or rather post) I'd say: one hand
in one's pocket and the other on one's panic button.
Calmly coiling, in --
Detroit, USA
Robert Michaels