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Unusual MCB

Sparkymania
Here's an interesting one.

Federal Electric 20A MCB. Had no type on it and was taking a long time to trip. Opened one up and discovered why it didn't have a type.

Others with it were ECC but virtually the same design. Only thermal. Both are plug in types called stab-lok and are bakerlite.


No instantaneous trip mechanism. Only a thermal one.



34200b5e07a12e120f5fc679b8b1b9aa-huge-mcb-with-no-instantanious-trip-mechanism-4.jpg
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    Thanks for the picture - I remembered the promise of opening it when it arrived. 


    Regarding comments about modern parts and bakelite-type housing: 


    *  US-type RCDs (GFCIs etc) have a long heritage of being electronic, partly because they have tended to demand levels such as 6 mA (based on let-go current) rather than the common European 30 mA (based mainly on hearts). There's (still) debate about whether passive or electronic ones are more reliable in terms of delicate parts to go wrong: this paper (Cohen ~1996?) gives a bit of background mainly from one side of the story. 


     * US breakers appear to like the bakelite "industrial history" look.  Even many modern GFCIs and AFCIs have this look, e.g. these. 


    We're seeing more and more electronic RCBOs (voltage-dependent for operation) due to the desire to fit into 1 module or to be cheaper. The current-transformer part can be very small if it only feeds an amplifier. 

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  • 0
    Thanks for the picture - I remembered the promise of opening it when it arrived. 


    Regarding comments about modern parts and bakelite-type housing: 


    *  US-type RCDs (GFCIs etc) have a long heritage of being electronic, partly because they have tended to demand levels such as 6 mA (based on let-go current) rather than the common European 30 mA (based mainly on hearts). There's (still) debate about whether passive or electronic ones are more reliable in terms of delicate parts to go wrong: this paper (Cohen ~1996?) gives a bit of background mainly from one side of the story. 


     * US breakers appear to like the bakelite "industrial history" look.  Even many modern GFCIs and AFCIs have this look, e.g. these. 


    We're seeing more and more electronic RCBOs (voltage-dependent for operation) due to the desire to fit into 1 module or to be cheaper. The current-transformer part can be very small if it only feeds an amplifier. 

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