Residual current device (detector?)

Basically an mcb type device that opens if the difference between phase &
neutral current exceeds a specified amount (5, 10 & 30mA are typical). The
difference current is assumed to be finding an alternative path via earth
and could then represent a hazard.

Richard

> -----Original Message-----
> From: Sean H. Breheny [mailto:shb7@CORNELL.EDU]
> Sent: Tuesday, September 14, 1999 9:41 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [OT] Muscle contraction. was: cats! -Reply
>
>
> Once again I must plead ignorance: Could someone please tell
> me what an RCD
> is?
>
> Thanks,
>
> Sean
>
> At 07:48 AM 9/14/99 +1200, you wrote:
> >All this out of my head - probably approximately correct but
> don't trust
> >your life to it:
> >
> >Defibrillation (or more properly here, fibrillation) depends
> not only on
> >current but also on duration. RCDs are designed to
> disconnect power within a
> >critical period. I think it's within 50mS (which fortunately
> makes sense in
> >the context of 50Hz (or higher) mains frequencies) and
> corresponds to a
> >critical period during the heart's cycle. In fibrillation
> the normal voltage
> >patterns of the heart are disturbed and while it may still
> oscillate it may
> >subsequently do so in a  mode which is not conducive to
> pumping blood. The
> >television (and real life) "300, joules, clear, zap" routine
> is designed to
> >polarise the muscle, clear all oscillation patterns and let
> the oscillator
> >try and start clean again. (Master Reset).
> >
> >As you'll well appreciate if you've "field tested" one, an
> RCD does not stop
> >you receiving a shock (the kick is not necessarily pleasant)
> but strictly
> >limits the duration.
> >
> >
> >
> >RM
> >
> >
> >
> >From: G.C. <gary.cadman@TIUK.TI.COM>
> >
> >>I think that these figures air on the side of caution. An
> RCD usually has a
> >trip of 30mA all though you can get them in many sizes.
> >>When I last looked at these type of figures I recall a
> statement that 30mA
> >at 40V was sufficient to cause defiblaration.
> >>
> >>Jim Main wrote:
> >>>
> >>> I found the following pertinent info in a mag the other
> day, detailing
> >>> whether or not you'd be able to let go a live source - it
> depends on the
> >>> amount of current that's flowing through the muscle.. and gave the
> >following
> >>> rough guidelines..
> >>>
> >>> 1mA   - tingling feeling - no problem letting go
> >>>
> >>> 10mA - probably still able to let go
> >>>
> >>> 16mA - borderline able to let go
> >>>
> >>> 20mA - you're locked to it!
> >>>
> >>> Jim
> >
> |
> | Sean Breheny
> | Amateur Radio Callsign: KA3YXM
> | Electrical Engineering Student
> \--------------=----------------
> Save lives, please look at http://www.all.org
> Personal page: http://www.people.cornell.edu/pages/shb7
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>