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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
    kfh:

    If they are so safe why do so many cheap clone power supplies burst into flames?


    I realise that cheap components used in a design based on lowest possible price rather than safety or longevity will be primarily to blame but my question is a genuine one. 


    Because they are cheaply made, with no attempt to follow recognised safety standards.


    A well-designed power supply will provide its rated current all day without overheating.  It will ensure that the power supply shuts down if it's overloaded.


    A cheap power supply will use under-sized components that run very hot, and will have no overload protection.  The gaps between the mains side and the ELV output may also be under-sized.


Reply
  • 0
    kfh:

    If they are so safe why do so many cheap clone power supplies burst into flames?


    I realise that cheap components used in a design based on lowest possible price rather than safety or longevity will be primarily to blame but my question is a genuine one. 


    Because they are cheaply made, with no attempt to follow recognised safety standards.


    A well-designed power supply will provide its rated current all day without overheating.  It will ensure that the power supply shuts down if it's overloaded.


    A cheap power supply will use under-sized components that run very hot, and will have no overload protection.  The gaps between the mains side and the ELV output may also be under-sized.


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