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Why fuse in computer power cables(leads)

Discussion in 'Electronic Basics' started by [email protected], Jan 10, 2005.

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  1. Guest

    In India power leads for computers do not have any fuse in them, 5amp
    or 13amp.

    Do not know about USA but in UK these leads have fuse in them, mostly
    5amp.

    What can happen in a Computer that will cause fuse in cable to blow up?

    HP sells its servers with power cable that cannot have fuse in the
    cable.

    What could be HP's assumption?
     
  2. CJT

    CJT Guest

    that probably varies by country to satisfy local laws
    it's probably following the law
     
  3. Kevin R

    Kevin R Guest

    I think you will find the fuse is also there to protect the cable as well
    encase its cut through or a short on the cable the fuse does not just
    protect the computer
     
  4. Dont forget the UK has a lot of ring main GPO ccts, so thats why they use
    the fused plugtops.
     
  5. Guest

    Short circuiting in a cmputer that is running continuously for years in
    Datawarehouse should be very rare I believe.
     
  6. Guest

    In the environment of Datawarehouse chances of cable getting cut and
    short circuiting should be highly unlikely.
     
  7. Guest

    Can you please explain "ring main GPO ccts"?
    I am totally nontechnical.

    Regards
    Nagesh
     
  8. CJT

    CJT Guest

    That's why the fuses don't blow very often.
     
  9. ChipMIK

    ChipMIK Guest

    Probably due to India having Fault-current-relays? like rest of Europe,
    not the deadly dangerous anitique system as in UK. Detects if current is
    equal in & out of house (live & 0 wires)....if greater than treshold
    (like if you grap the live wire, mine´s 30 mA) it trips & saves your
    life.....not needing it to be a true shortcuirt.

    Normally dont reply on such a X-poster...but hey why not might save his
    life :))))))))

    Best regards

    ChipMIK, expecting some serious shouting from you UK-guys :)
     
  10. Neil

    Neil Guest

    Probably due to India having Fault-current-relays? like rest of Europe,
    Too true - my personal opinion is that the UK is an awful lot safer than the
    US.
    Current imbalance trips are pretty standard around here (south uk);
    individually fused plugs; plugs that make it diffcult to disconnect by just
    pulling the cable;
    man sized 240V instead of the wimpy 110v ... ;)))
    tee hee
    Neil
     
  11. J. Clarke

    J. Clarke Guest

    Don't look now but US building codes _require_ ground fault interrupters
    anywhere that there's a significant risk of a short to something other than
    the neutral.
    Hey, we've got all the 240 we want. We just don't waste it on clock radios
    and electric pencil sharpeners.

    Normal residential service in the US is 240. We split it to get two 120V
    phases, but the 240 is there any time we have a real use for it.

    The simple fact is that you Brits are going to defend your quaint way of
    life to the death, and that's as it should be.
     
  12. Here is some explanation of UK wiring (from www.epanorama.net):

    UK wiring is somewhat special case. The UK is unusual in having fused
    plugs as standard (according BS1363 parts 2 and 4). 13A max in
    eachplug, and 30A at the panel for each ring. Maximum current at wall
    outlet in the UK is for 13A. The plugs carry a fuse holder and the
    fuse should be rated to suit the appliance used (fuse rating from 1A
    up to 13A exist). The fuse in the plug is for protecting the cable to
    the appliance, not the appliance itself. For the latter, the appliance
    would have its own fuse (or other suitable protection means). Neutral
    is neither switched nor "protected". UK mains plugs are polarized. In
    the UK, a wiring system known as a ring mains is used. UK standard
    (for the last 30 years or so) has been the ring -main (domestic and
    commercial) rated at 30/32A @230V. A single cable runs all the way
    round part of a house interconnecting all of the wall outlets. This
    will be protected by one large fuse in the fuse box. A typical house
    will have three or four such rings. The power rings are normally
    protected by a 30 amp fuse and the lighting rings by 5 or 10 amp
    fuses. Those fuses protect the wiring, not the appliances so, every
    appliance carries its own fuse in the plug.


    The design philosophy of e.g. the German system (Schuko) is that a room
    (or a small number of rooms) has a 10 A or 16A fuse in the consumer
    unit, 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 a fault occurs, a circuit
    breaker is trivial to reset, The fuses are generally in the main
    distribution panel. The fuse inside equipment will provide the
    protection agains constant overload. This equipment fuse is rated
    based on the power the equipment might take, and the wire
    going to equipment must be thick enough to handle that load current
    that this fuse can pass before breaking.
     
  13. Arno Wagner

    Arno Wagner Guest

    That fuse would be in the fuse box on tha wall. 10A for light, 16A
    for power outlets and e.g. 3*25A for an electric stove.
    Actually there is no 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 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.

    For the british system in equipment without a fuse in the plug
    you would need something like 1.5mm^2 cables to all types of
    equipment. A 0.75mm^2 cable would likely have problems at 32A.
    Remember that power goes with the square of the current in
    cables, so the 0.75mm^2 cable would actually get heated up
    four times as trong as it would in germany with current that
    just about does not blow the fuse.

    As a result the british need additional fuses in thinner cables.
    I would guess that for 2.5mm^2 cables the british can do without
    the fuse in the plug.

    Arno
     
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