Hi Amp Interupt Capacity Circuit Breakers

Discussion in 'OnBoard Electronics & Controls' started by Willallison, Nov 20, 2011.

  1. Willallison
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    Willallison Senior Member

    I am having trouble finding a supplier of hi amperage (7,000 - 10,000 Amp) Interupt capacity circuit breakers... any suggestions...?
     
  2. jehardiman
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    jehardiman Senior Member

    Copper bus bar and an Ax, standard for the last 100 years.

    Really, that looks way too high. There may be some auto control breaker switches out there like on some old DC MPU systems, but just the sheer size of the thing works against you. Probably going to have to go to those who service the power industry, Westinghouse, GE, etc. for a bid.

    http://www.levydev.com/homewood/PDF...-DR/I.B.-210/Type-DR-Air-Circuit-Breakers.pdf
     
  3. Willallison
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    Willallison Senior Member

    I'm not looking for a 7000 Amp breaker, but a breaker with a 7000 Amp interupt capacity. The breaker(s) might only have trip capacities of 10 or 20 amps.
    It is for an installation in a 65ft pleasure boat that has a rather large house bank.
     
  4. DCockey
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    DCockey Senior Member

    Fuse? Disclaimer: I'm not an electrical engineer. Put a fuse with a sufficent interupt capacity and nominal rating ahead of the breakers?
     
    Last edited: Nov 21, 2011
  5. Whimsical
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    Whimsical Junior Member

    ANL, 6000, or T class, 20000, fuses feeding the board then just normal breakers
     
  6. CDK
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    CDK retired engineer

    There is confusion here.
    If the breaker trips at 20 Amps, when will it carry 7000 Amps ?
    Do you mean to say that you need ultra-slow breakers that can handle a 7000 Amps short spike but trip at a sustained 20 Amps ?

    Usually, if you cannot find the product you need on a planet with 7 billion people, sooner or later you will discover that you do not really need it.
     
  7. Whimsical
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    Whimsical Junior Member

    What he means is fuses and circuit breakers have a current interupting rating which has nothing to do with the trip current. With a high capacity bank of batteries it is possible the instantaneous current, during a short, can rise to huge levels before the breaker or fuse trips and if it happens the contacts in a breaker weld shut or if the distance between the terminals on a fuse is too close then the fuse can arc across and continue the current. So the regs dictate a minimum interupting current of 6,000 amps which is an ANL fuse or better. Very few circuit breakers can meet this requirement as most are only rated at about 2,000 amps. Thats why the batts should have an ANL or T type fuse close to the battery feeding the boat.

    Mike
     
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  8. Tim B
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    Tim B Senior Member

    MOSFET & current sensing circuit?

    Tim B.
     
  9. MechaNik
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    MechaNik Senior Member

    I use Merlin Gerin in part of the world and I think most others do too. Provided through Schieder electric.
    Normally for DC breakers I go for a c60-hc which gives 10000amps but the do special c32h-dc for DC circuits that I've never used.
    Most Classifications will still want to see some fuses in the battery and distributed buses.

    Hope this is what you where looking for.
     
  10. CDK
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    CDK retired engineer

    It would require a giant 24 V battery and .0035 ohms circuit resistance to create 7000 Amps. Even if the wiring was AWG #1 solid gold, the terminals and internal resistance of any 20 Amps circuit breaker prohibit such a current to flow.
    If there exist regulations dictating such current breaking capacities they were written by incompetent people and should be ignored.

    In any serious power circuit there must be a fuse or fusible link in close proximity to the power source, rated at or slightly above the maximum total current to be allowed through the circuit. It is good practice to use multiple circuits, each with their own fuse, if the total current reaches impractical values.
     
  11. Whimsical
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    Whimsical Junior Member

    maybe nuts but thats the regs
    1,000 A/h 12V battery 6,000 AIC. Most of the boat books such as Calder's have a little section about it. I am using some ANL's just to have have no arguements if **** ever hits the fan and they are cheap so why not.
    600 A/H of lifepo will easily deliver 6,000 into a short , but yes it would sure need a low impedence circuit.
     
  12. MechaNik
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    MechaNik Senior Member

    The use of too many fuses (ANL's) can lead to a cluttered and bulky distribution.

    On extreme over current some breakers may weld together, others obliterate themselves if not specified correctly. The price of breakers is not that high and reliability is good if selected correctly.
    They also make a really tidy job especially when used with tie/bus bars. DC 2-pole tie bars are great for a more professional job of isolating both positive and negative supplies to a consumer.
     
  13. Willallison
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    Willallison Senior Member

    Thanks... will check out the Merlin Gerin....

    That it is an unlikely occurance doesn't mean that it can't or doesn't happen. I draw your attention to a recent article by Steve D'Antonio in the October / November issue of Proffesional Boatbuilder where he discusses this very subject.
    The 12v battery bank in question here has a 1400 AH capacity. T fuses are an option, and that is likely the way we'll go, but I was just looking into the feasibility of putting in a breaker as an option....
     
  14. goboatingnow
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    goboatingnow Junior Member

    theres no problem getting 10000 amp interrupt. Most of CarlingSwitch standard circuit breakers have upto 100amp capacity, and 10000amp interrupt at 80v

    Dave
     

  15. jehardiman
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    jehardiman Senior Member

    If you are seriously worried about a short in the bank, and you have a large (10 or more cells) battery bank, you might consider an automatic battery cell monitoring system which will also help with charging. Combined with a auto cutout system based on the monitoring data, that is pretty standard for large battery installations.
     
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