Los Angeles, California


Parts of a Circuit Breaker

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Inside of a Miniature Circuit Breaker

Low Voltage Thermal-magnetic miniature ciruit breakers are a very common type of circuit breaker. They are commonly DIN rail mounted and are either mounted directly into equipment or arranged in circuit breaker panels. There are a variety of other types of low voltage circuit breakers such as solid state, magnetic, and magnetic-hydraulic.

  • 1. Actuator lever - used to manually trip and reset the circuit breaker. Also indicates the status of the circuit breaker (On or Off/tripped). Most breakers are designed so they can still trip even if the lever is held or locked in the "on" position. This is sometimes referred to as "free trip" or "positive trip" operation
  • 2. Actuator mechanism - forces the contacts together or apart.
  • 3. Contacts - allow current when touching and break the current when moved apart.
  • 4. Terminals
  • 5. Bimetallic strip - separates contacts in response to smaller, longer-term overcurrents
  • 6. Calibration screw - allows the manufacturer to precisely adjust the trip current of the device after assembly.
  • 7. Solenoid - separates contacts rapidly in response to high overcurrents
  • 8. Arc divider/extinguisher

circuit breaker inside view


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