November 2011
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The 80 Amp Circuit Breaker

Just because I can, here are a few pictures of the inside of a rather expensive 80 amp DC rated circuit breaker:

80 amp DC rated circuit breaker open

80 amp DC rated circuit breaker open

What is the difference between a DC rated breaker and an AC rated breaker? Good question. Because DC is, well DC, the current is continuous. Once an arc is struck, greater separation is needed between conductors to extinguish the arc.  Using an AC breaker in a DC application can lead to an internal arc and fire.  That would be a bad outcome.

Just how did the insides get exposed, one might ask? Well, there I was working on a solar installation with said breaker placed on a horizontal surface waiting for installation when somehow it was knocked to the floor, creating a large crack in the side of it.  Angry I was because this thing set me back some fifty dollars.

80 amp DC rated circuit breaker closed

80 amp DC rated circuit breaker closed

This picture shows the breaker closed, the contacts are still under cover to the left of the exposed parts. What is cool is one can get a good idea of how a circuit breaker works.  As the current flow increases, the magnetic field around the coil increases.  When it reaches the trip point the small steel piece is pulled down, causing the mechanical assembly to unlock and open the contacts.

Old tech stuff that is taken for granted, probably has saved millions of lives since electrical use became widespread.

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2 comments to The 80 Amp Circuit Breaker

  • Joe Farley

    I am reminded of something I read long ago in a trade magazine, possibly EDN. The blurb described an archaic power distribution switchpanel which used plugs and sockets for load switching. The panel had instructions for the technician on it which went something like:

    1. Grasp plug firmly and remove from socket quickly.
    2. Fan the arc with your hat.

    Guess we’ve come a long way…

  • Teresa

    That’s classic. Must why hats were so popular back in the day

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