How to test a Circuit breaker

Discussion in 'General Electronics Chat' started by harrison2015, May 6, 2015.

  1. harrison2015

    Thread Starter Member

    Apr 22, 2015
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    How do you test a circuit breaker? when I put my DVM meter on continuity mode my meter beeps having continuity with the circuit breaker button out or in so how do i know if the circuit breaker works if i'm always getting continuity with the circuit breakers button pressed or not pressed?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    There are all kinds of circuit breaker, adjustable, some have test button etc, a little more specific in type would help.
    Max.
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    You can test for continuity across line and load terminals with a meter.
    You can test its auxiliary contact functions if it has them with a meter too (assuming its not a breaker that only switches aux states with a true tripping of the breaker)
    You can test if the breaker actually functions in an overcurrent situation by running current through it in excess of its trip point with a power supply/load. Note the time curve of the breaker will effect how long it can sustain an overcurrent situation and how much over you may need to go before it actually trips..

    but yes as max stated there are many types.. shunt trip/adjustable,etc... so more details would allow a better answer
     
  4. tranzz4md

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    Apr 10, 2015
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    I'll bet you've got more than 1 of these breakers in your possession. Take one that you know works properly, and open it and close it while observing your VOM in either continuity or resistance mode. Then do that same observation on the questionable one.
    A circuit breaker must fully, truly open the circuit, no measurable resistance/ continuity. The terminal to terminal (or "stab") impedance should read the same as terminal to insulated case.
     
  5. Calton57

    Member

    May 4, 2015
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    Circuit breaker
    483-G533
    Jimi-B2S0Z
    MS 3320-1

    How can I test this circuit breaker without applying power, voltage or current? or what kind of test circuit can i build to test the circuit breaker?

    They call it a thermal circuit breaker, not sure what that means

    What is the difference between having auxiliary contacts and non auxiliary contact?
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    To test it I imagine you would need to use a circuit where the rated current can be increased to the point of trip.
    A thermal breaker is usually a time delay breaker, the current heats a bi-metal which mechanically trips the breaker, opening the circuit.
    In the case of the aux contacts these are generally low level dry contacts that open at the same time to advise a main system that the breaker has tripped and possibly used to take extra action in the controlling device.
    You can also get breaker that are tripped by an aux coil remote triggered from the controlling device
    Max.
     
    Last edited: May 6, 2015
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  7. tranzz4md

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    Apr 10, 2015
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    Aux contacts are not rated for the same voltage and current as the power contacts. Aux contacts are typically used for external alarms or interlocking. If it has more than 3 pairs of power contacts it is quite unusual, but some do exist.
     
  8. harrison2015

    Thread Starter Member

    Apr 22, 2015
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    So there is no way a DVM meter can test a thermal breaker or circuit breaker?

    What types of circuit breakers can i test with a DVM meter?
     
  9. MaxHeadRoom

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    Jul 18, 2013
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    Just to be clear, when you say test them, I assume you mean test if they trip at their rated current?
    Because of course a meter will give a simple continuity reading when they are manually tripped and then reset.
    Max.
     
  10. harrison2015

    Thread Starter Member

    Apr 22, 2015
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    How do I know if the circuit breaker or thermal breaker is tripping? what kind of test circuit do i need to build to test the trip point

    I can use an external power supply and turn up the current until the circuit breaker trips?
     
  11. MaxHeadRoom

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    One method is to use a Variac and place a suitable load, and increase the voltage to approach the trip point, meanwhile monitoring the load current.
    The majority of O/L's are thermal based (although some electronic), so there can be a delay before trip to avoid nuisance tripping on momentary peaks.
    Max.
     
  12. harrison2015

    Thread Starter Member

    Apr 22, 2015
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    what can i use breaker as a load? the wattage of the resistors would be 5 watts?

    Block diagram would be:
    AC variac to Circuit breaker to Resistor load?

    Does the datasheets tell what the trip point is?
     
  13. MrChips

    Moderator

    Oct 2, 2009
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    You cannot have multiple memberships:

    SamEricson
    Calton57
    harrison2015

    Which one do you want to retain?
     
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  14. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Why do you even feel the need to test it?
    If you are worried that its old or something then just buy a new one.
    Its not worth the time/effort to setup a power supply/load.

    And frankly if you have to ask how to test it you aren't capable/qualified of doing it safely anyways.
     
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  15. Alec_t

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    Sep 17, 2013
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    You can't.
     
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  16. blocco a spirale

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    I thought the same; another nonsense thread.
     
  17. dl324

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    Mar 30, 2015
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    Anyone asking this question should contact a qualified electrician. Clearly they don't know what they're doing and could get themselves or someone else killed.
     
  18. dl324

    Distinguished Member

    Mar 30, 2015
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    I thought it a bit peculiar when carlton57 responded to a thread started by harrison2015 as if he were the OP...
     
  19. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Nice and direct, just the way I like it...
    Another way that this question could've been formulated is: "How do I test if a match will burn without actually having to light it up?"
     
  20. MaxHeadRoom

    Expert

    Jul 18, 2013
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    ...didn't catch that one!:(
    Max.
     
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