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Defective Bulb Tripping A Ckt Breaker: How Possible ?

Discussion in 'Electrical Engineering' started by Robert11, Oct 31, 2006.

  1. Robert11

    Robert11 Guest

    Hi,

    Boy, this is a funny one.

    Wife turned on a hall light switch last night, big flash by one of the hall
    lights, and the ckt breaker tripped.

    Was about 2 days since putting in a new bulb there.
    Was the el-cheapo brand picked up at CVS, and made in China.

    Replaced the bulb with a GE one, and so far everything seems O.K.

    Question: I can't imagine how anything, like e.g., a broken filament
    perhaps, can short out the circuit.
    But, perhaps ?

    Can anyone think of a bulb failure mechanism that might trip the breaker ?

    Or, do you think the bulb explanation might just be a coincidence ?
    All works fine, now, though.

    Thanks,
    Bob
     

  2. Is the breaker a Arc Fault interupter? They can trip on the arc intrernal
    to the lamp if the filament shorts out when it goes.
     
  3. Guest


    It doesn't have to be that complicated. The standoffs that hold the
    filiment on cheap bulbs can break and short out the bulb. I had
    several do it and after the first couple I broke the envelope to see
    WTF was going on. The stiff wire standoffs were welded together
     
  4. That's exactly right, except it doesn't even need the metal plasma;
    the low pressure gas fill can form the plasma. You effectively end
    up with an unballasted discharge tube, which will draw a very high
    current limited by the resistance of the supply wiring until a fuse
    or circuit breaker cuts out, or the bulb explodes.

    In the UK, filament lamps include fuses in the lead-in wires, but
    a fast acting circuit breaker can trip too.
     
  5. Roby

    Roby Guest

    Aliens. They can pass right through the glass, become entangled in the
    filament and ... you know.

    Roby
     
  6. Don Kelly

    Don Kelly Guest

    Others have given an explanation as to causes --- but GE vs Chinese is not
    necessarily the answer. How do you know that the GE bulb isn't made in
    China?. Probably in the same plant that makes Sylvania, Westinghouse, etc.
    etc where bulbs are run off on a common manufacturers line (as was done in
    the past in the US) and stamped with the appropriate logo as ordered.
     
  7. Don Kelly

    Don Kelly Guest

     
  8. Guest

    | Wife turned on a hall light switch last night, big flash by one of the hall
    | lights, and the ckt breaker tripped.

    I had this happen once on a 3 bulb mini-chandelier. It had these small
    socket bulbs of about 40 watts each.

    One bulb blew hard (very loud pop) and the circuit went out. After I
    reset the breaker, none of the bulbs lit up, so I was at first concerned
    about wiring damage or maybe the switch. I proceeded to change bulbs
    just to check and that when I started seeing just how bad this was.
    Fortunately there appeared to be no wiring or switch damage. But the
    bulb that initially blew also took out the other two bulbs with it.
    Usually I see a break in the filament in these clear bulbs. But in this
    case one bulb had no filament remaining. Piese of the glass stem and
    a couple loose pieces of support wires, along with a very blackened
    inside surface were all I could see. In addition to that, several spots
    on the screw-in shell were melted through. The other two bulbs showed
    significant filament destruction and some screw shell melting.


    | Was about 2 days since putting in a new bulb there.
    | Was the el-cheapo brand picked up at CVS, and made in China.
    |
    | Replaced the bulb with a GE one, and so far everything seems O.K.
    |
    | Question: I can't imagine how anything, like e.g., a broken filament
    | perhaps, can short out the circuit.
    | But, perhaps ?

    The arc itself is very high current and can trip the breaker if it
    stays long enough.


    | Can anyone think of a bulb failure mechanism that might trip the breaker ?

    Any that leads to an arc. Most do.


    | Or, do you think the bulb explanation might just be a coincidence ?
    | All works fine, now, though.

    All is fine mostly because you have a more reliable bulb, now.

    Maybe you got a batch of Chinese bulbs intended for Japan. Those would
    blow sooner, since Japan uses only 100 volts.
     
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