Newsgroups: sfnet.keskustelu.kuluttaja,sfnet.harrastus.elektroniikka
Subject: Re: VAROITUS vaarallisesta FI-hyv�ksytyst� 0-luokan pistokkeesta
References:       <[email protected]>  
"Lu-lu"  writes:

> "mikko kurko" < kirjoitti
> > Hmmm. johtimen terminen kest�vyys huomioonottaen
> > SFS6000 vissiin sanoo kiinteist� asennuksista poiskytkent�ajat.
> > Vaan kannettavien kojeiden ja laitteiden liitynt�johdoista ei
> > puhuta senk��n vertaa.  Saati sitten EU direktiiveiss�.
> 
> 
> 
> Aivan! ...
> ja mit� tuo tarkoittaa esim. tulipalon syttymisvaaraa ajatellen?
> 
> pienehk� vikavirta laitteen ohuessa liitynt�johdossa ei ehk�
> polta sulaketta, mutta sulattaa kyll� helposti johdon eristeet
> ... ja voip' my�s sytytt�� johdon ymp�rill� olevat sytykkeet?
> liitynt�johdon kokoinen aukko direktiiveiss�

Kyll� noita liitynt�johtojakin on ajateltu jollakin tasolla. 
Kun itse laitteessa on suojaus ylikuormitukselle, niin 
todenn�k�isin vikaantuminen joka voi aiheuttaa johdon 
ylikuormitusta on se ett� liitynt�johtoon tulee oikosulku. 
Oikosulkutapauksessa pit�� sit� oikosulkuvirtaa sitten 
synty� sen verran ett� se polttaa sulakkeen ennen kuin 
johto kuumenee liikaa. T�st� syyst� ohuimmat laitekaapelit 
ei voi olla kovin pitki� ett� turvallisuus t�yttyisi 
(esim. ohuet partakoneiden jne. johdot).   
Paksummasta johdosta tehdyt voi olla pitki� ilman vaaraa. 

On noista liitynt�johdoistakin ohjeita/m��r�yksi� olemassa...


http://www.epanorama.net/links/wire_mains.html#europe
There are requirement for a fuse in the equipment itself, depending on
what type of equipment it is and what kind of cable it has. If it has
1.5mm^2 cabling, then the mains penel fuse is enough to protect
equoment wiring, since the wires in the wall are also 1.5mm^2 and
these are rated for 16A continous current and several thousands
amperes short circuit currengt for a short duration short-circuit
(before mains panel fuse blows). You can see this kind of arrangement
in many heavier devices like heaters, coffee makers, lamps etc. Many
electronic equipment have fuses in them to protect their transformers
and electronic components. Even though the mains panel fuse protecting
the outlet and wiring connected to it can be as high as 16A, the are
cases where thinner than 1.5 mm^2 cable is connected to the outlet. It
is 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 that has thin cable has fuse or other means
of protection that makes sure that the equipment cannot permantely
overload the cable even in case of damage. In case of full short
circuit inside equipment or in the connection cable, there will be a
high short circuit current, that will burn the mains panel fuse before
the thin connection cable overheats. You can see often 0.75 mm^2 cable
on many small lamps and small electronic devices, and even thinnner
cable on some special equipment (razors etc..). There are specific
limitations where you can use that thinner that 1.5 mm^2 thin cable
for the equipment and there are also limitations how long this thin
cable can be maximally be (make sure that it's resistance is so low
that the short circuit will quicly blow the mains panel 16A fuse).

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