Newsgroups: rec.arts.theatre.stagecraft
Subject: Re: Two cables in one plug ?
References:   <[email protected]>  <[email protected]>  <[email protected]>      <[email protected]>   <[email protected]>
"Frank Wood"  writes:

> Use of unshrouded 13A plugs and unswitched sockets would represent an
> unacceptable hazard in a domestic environment though, since normal
> working
> practice is not to kill the power to your ring main whilst plugging in
> a
> kettle!
> 
> It all depends on where you are. In France, Germany, and Italy, there
> is no such thing as a switched socket outlet.The connector design is
> such that you can't get your fingers to the live pins. With UK 13A or
> 15A outlets, to BS1363 ir BS655, you can, if you are careless.
> 
> On the other hand, the UK fused plugs provide a higher standard of
> protection. I am always slightly worried when in plug a table lamp,
> wired in 3A cable, into a socket protected by a 16A fuse. This offers
> no protection to the cable.

The design philosophy of e.g. the German system (Schuko) is thata room
(or a small number of rooms) has a 10 A or 16A fuse in the mains
distribution panel, and all leads and plugs are designed to withstand
any short-circuit current that will not yet blow the fuse (today
usually circuit breakers are used, not fuses). 

If equipment has 1.5mm^2 cabeling, then the main fuse is enough, since the
wires in the wall are also 1.5mm^2 and these are rated for 16A
continous current and several thousands for a short duration
short-circuit. 

It is also permissible to use lighter cables (0.75mm^2)
for lighter equipment. This type of cable should still be able to
stand 16A for some time. The equipment powered in this way are 
fused (or othewise built in this way) that there will not be 
possiblity for long time overload of the cable.
If there is short circuit inside equipment, then there will 
be for short time high short circuit current that burns the 
10A or 16A fuse on the main distribution panel. 
There is a limitation where this kind of thin device 
wires can be put and how long they are allowed to be. 
The siatuation ot to guarantee that in case of short 
circuit inside the device or in the cable them main 
fuse (10-16A) burns before the equipment able catches fire...


-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/