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Ratings of Fuses for household applications?

  1. Jul 30, 2011 #1
    What is the rating of conventional rewirable fuse, MCB etc.

    What is the rating of polyfuse(resettable fuse or PPTC fuse). Polyfuse are normally used in electronic circuits.

    Can we replace conventional household power supply main rewirable fuse with these polyfuse. Is it available in such high power requirement?

    Pls help.
  2. jcsd
  3. Aug 1, 2011 #2


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    Staff: Mentor

    Welcome to the PF.

    What's an MCB?

    In general, I don't think you can replace a real fuse with a polyfuse. What is your application?
  4. Aug 1, 2011 #3
    MCB = miniature circuit breaker.
  5. Aug 2, 2011 #4
    Then, In which all places, we can use a polyfuse.

    What are its limitations?

    Why can't we replace a conventional rewirable fuse/MCB in electric circuits in our home by a Polyfuse?
  6. Aug 2, 2011 #5
    Hello jobinhere what is your normal working discipline?
    Is English your first language?

    Any competent electrical engineer or electrician would tell you that the correct term for what is popularly called a household fuse is actually a 'disconnection device'.

    The important part here is the word disconnection.

    The regulations in most countries require a device which actually disconnects the attached equipment from the electricity supply in the event of overcurrent.

    Polyfuses (again a popular misnomer) may not be used because they do not disconnect the apparatus.

    This is an extremely important safety matter which should not be taken lightly.
  7. Aug 2, 2011 #6


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    Staff: Mentor

    The polyfuse only increases in resistance when it is overloaded. When it cools down, the resistance returns to its regular low value.

    So it is useful for protecting some electronic circuits from overcurrent conditions, but only if the short-circuit condition that caused the overcurrent is of short duration. If the short circuit fault condition is permanent, the polyfuse will eventually fail...


  8. Aug 2, 2011 #7
    A fuse or breaker is there to protect the user and the building (wiring), not the connected electronic circuit.
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