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What is the difference between thermal fuse and MOV and polyfuse.Which is faster and also which companies produce polyfuse, especially in Asia.

I have to search for a component that can save my circuit which is connected via a TRIAC to a submersible motor. In it may happen that the live and gnd wires may touch due to rupturing of the overhead seal. This would send a surge that cant be handled by TRIAC. A fast fuse is a temporary solution which has to be changed everytime, so i wanted to ask if Polyfuse was viable in its place.

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Tell us a bit more about background and application. What is 'fast' or 'fast enough'? What sort of circuit are you using/designing, ... The more you tell us, the better answer we can give you. –  jippie Dec 25 '12 at 9:28

1 Answer 1

  • Thermal fuse:
    Goes open circuit when the temperature reaches a certain value. Comes in non-resettable and resettable varieties.

  • MOV (Metal-Oxide Varistor):
    This is not a fuse at all. It is a device that begins to conduct when the voltage across it exceeds a certain value. MOVs are used to absorb high-voltage pulses, hopefully for long enough to blow a upstream fuse or circuit breaker.

    If you don't have a fuse or circuit breaker upstream from the MOV, you usually get a fire.

  • Polyfuse:
    A Polyfuse is a self-resetting fuse. Basically, the way they work, when you have a certain amount of current flowing though a polyfuse, it goes open circuit for a period of time.

    Generally, they're thermal in mechanism. Once they heat up to a certain point, their resistance increases dramatically. Then, they stay high-impedance until their temperature decays back again.


Anything else, and we'll need more information about your application. It sounds like you're in a bit over your head.

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