Description

• A circuit breaker is an electromechanical device built into a sturdy, insulated housing. When the current flowing through the breaker exceeds its rating, it "trips," or opens the circuit.
  
  

Mechanism

• A circuit breaker has a spring-loaded mechanism that opens a switch. The switch is normally closed so current can flow. The mechanism can be triggered by heating a bimetal strip, by energizing an electromagnet or by other means.
  
  

Reset

• Circuit breakers, once tripped, can be reset. This should be done when the overload, if any, has been fixed. Breakers can be cycled hundreds of times before needing replacement.
  
  

Types

• Household breakers operate at 110, 220 and 240 volts, and are rated for a few to a few hundred amperes. Industrial breakers go to thousands of volts and tens of thousands of amps. Others are specialized for aircraft, custom electronics and flammable environments.
  
  

Size

• Some compact circuit breakers are less than an inch tall. Industrial substation breakers can be 15 feet high and 13 feet wide.