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Discuss How a big HRC Fuse is made.. in the Electrical Forum area at ElectrciansForums.co.uk.

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  1. Gavin John Hyde
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    Gavin John Hyde Regular EF Member

    Location:
    Somerset
    You aren't likely to see one of these everyday of the week but it is quite an interesting video i just saw, We are childminding tonight and my nephew is on a how its made binge on the youtube app on the tv... Didnt realise they had a firing pin in them mind!
     
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  2. UKMeterman
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    UKMeterman Electrician's Arms

    These are HV fuses for fitting into 11KV ring main units.
     
    • Informative Informative x 1
  3. sparkdog
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    sparkdog sparkdog Electrician's Arms

    Location:
    Sunny Sussex
    Business Name:
    C MacRae Electrical
    Be a struggle getting that into a 13A plug.
     
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  4. freddo
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    freddo Regular EF Member

    Location:
    Devon
    I have a similar one of those in my kitchen, it's not fitted with a striker. 63A 12KV. It's much heavier than it looks.
    upload_2017-12-8_0-8-53.jpeg
     
  5. PEG
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    PEG Trusted Advisor

    Location:
    Manchester
    All that would take,is a farmer,with a 240V compressor,a tractor with a flat tyre,and one blown standard fuse....and in it would go ;)
     
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  6. PEG
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    PEG Trusted Advisor

    Location:
    Manchester
    All that would take,is a farmer,with a 240V compressor,a tractor with a flat tyre,and one blown standard fuse....and in it would go ;)
     
  7. I2C
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    I2C Electrician

    Location:
    East Sussex
    Agree with previous comments, these are for use with HV (High-Voltage).

    Why do they contain an explosive-charge?
    Put simply, high-voltages can jump through the air (like a police taser for example) and higher-voltages will jump considerably further than lower-voltages; the result is referred to as an 'arc / arcing'.

    The problem is that arcing creates very-high temperatures, especially in the area that the arc starts & finishes, which can easily melt metal (basically how welding works). The heat is therefore perfectly capable of damaging electrical conductors during disconnection, and must be avoided.

    With this said, explosive-disconnection-fuses are made for use in HV conductors and designed to detonate a small charge during fault-conditions, causing the conductors to separate very-quickly in order to prevent damaging-arcs.
     
  8. I2C
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    I2C Electrician

    Location:
    East Sussex
    This is a three-phase fuse which is installed on each of the individual phases. It's imperative that all phases simultaneously disconnect, opposed to a singular phase. The "firing-pin" is used to trigger the disconnection of the other phases during a fault to ensure safety.
     
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  9. 1Justin
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    1Justin Electrician's Arms

    Location:
    Surrey
    Business Name:
    Circitas Ltd
    Likewise.. And I had no idea they would be wound on a spiral like that either. I can guess that compared to a straight element ( which I'd have expected), the spiral adds length so presumably reduces the relative heat-loss conducted out the ends in the event of a small overload.
     
  10. UKMeterman
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    UKMeterman Electrician's Arms

    Yes the firing pin hits the trip trigger for the contacts in the ring main unit so the other phases are also disconnected.
     
  11. Percyprod
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    Percyprod Regular EF Member

    Location:
    Cumbria
    It will only be about 25 amp
     
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