Circuit breaker teardown

Here is teardown of 10 A DIN rail mounted miniature circuit breaker (Biltema brand)

What you see when you open the case

Turn around – circuit open/off/tripped

Device reseted to “on” position

On the left side of mechanism there is bimetallic overcurrent triggering mechanism – load current goes through bimetallic strip and heats it. 

On the center there is solenoid coil for quick tripping on short circuit. 

Contacts that make and break the current are on right. On bottom there are stack of metal plates that take part in breaking the high short circuit current quickly.

Related posting with more background information: 

Circuit breakers for mains panel


  1. Tomi Engdahl says:

    How a Circuit Breaker Works in Slow Motion – Warped Perception – 4K

  2. Tomi Engdahl says:

    32 Amp MCB explodes

    Cap bank charged up to 7000 Volts DC
    32 Amp 400 Volts MCB rated at 10kA is the test subject.
    No surprise that it blew apart.


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