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Ever thought about ... ?

gkenyon
I was asked a series of interesting questions this week about fault protection and overload protection for a particular application. Some of these really make you think, and the physics doesn't always lead you where you think you'd go.


Dropping out of all this, was me pointing out something interesting which I wonder whether it's ever crossed the minds of contributors to this Forum ... so here goes.


Ever thought about what, in typical UK installations, protects the electronics in a plug-in [to a standard BS 1363-2 socket-outlet] phone charger / wall-wart type power converter against:

(a) Fault current (consider both cases of L-N and L-PE); and

(b) Overload current ?




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  • 0
    Sparkingchip:

     





    The same as used for the design of the new RCD sockets and FCU?






    This may appear to be a bit of a random comment, but I have it in mind that one of the selling points of these new fittings is that they are rated similar to consumer unit devices for big bangs.


    I have tried an internet search to find the ratings, but have not come up with an answer, though I remember seeing it somewhere.


    In my garage there’s a couple of double sockets immediately under the consumer unit connected to a B 32 MCB with around 300 mm of  4.0 mm twin and earth, the consumer unit is adjacent to the meter and intake. 


    I’m not poking about out in the garage tonight measuring the PSC on the sockets, but it’s probably the same as the consumer unit.


    So if I swap one of those sockets in the garage for one with a built in USB charger the potential current flowing in a big bang event is probably around 1.500 kA, which is probably going to make it disappear in a puff of smoke and may not do the adjacent consumer unit  with a plastic enclosure much good either.


    It’s probably best to install a USB socket with a few metres of cable between it and the consumer unit. 


Reply
  • 0
    Sparkingchip:

     





    The same as used for the design of the new RCD sockets and FCU?






    This may appear to be a bit of a random comment, but I have it in mind that one of the selling points of these new fittings is that they are rated similar to consumer unit devices for big bangs.


    I have tried an internet search to find the ratings, but have not come up with an answer, though I remember seeing it somewhere.


    In my garage there’s a couple of double sockets immediately under the consumer unit connected to a B 32 MCB with around 300 mm of  4.0 mm twin and earth, the consumer unit is adjacent to the meter and intake. 


    I’m not poking about out in the garage tonight measuring the PSC on the sockets, but it’s probably the same as the consumer unit.


    So if I swap one of those sockets in the garage for one with a built in USB charger the potential current flowing in a big bang event is probably around 1.500 kA, which is probably going to make it disappear in a puff of smoke and may not do the adjacent consumer unit  with a plastic enclosure much good either.


    It’s probably best to install a USB socket with a few metres of cable between it and the consumer unit. 


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