How do circuit breakers work?

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Circuit breakers are designed to interrupt current when there is too much load on a circuit. They are designed to stop the flow of electricity to prevent injury or the failure of other electrical components like the wiring, generator end or receptacles. Winco uses multiple types of over-current protection technologies based upon the application.


A thermal breaker, as it sounds, works with heat. Current (amps) creates heat as it passes through the breaker, if the breaker gets too warm, it opens a switch that is normally spring loaded to open the circuit and stop the electrical current.

  • Advantages: Less expensive and has a time delay as the breaker heats up.
  • Disadvantage: Slower reaction and is affected by ambient temperature.
Thermal Trip
Source: Schneider Electric


A magnetic breaker has a coil. When excess current passes through, it becomes a electromagnet which opens the breaker.

  • Advantages: Very fast to high current like dead shorts.
  • Disadvantages: Can’t handle the slow overload trip with time delay.
magnetic trip
Source: Schneider Electric


With an electric breaker, a computer chip controls the trip point and delay precisely. We use electronic breakers on our generators above 100kw so you can set the trip point and switch between voltages using the same breaker.

  • Advantages: Quick, precise trip
  • Disadvantages: More expensive
Electronic Trip
Source: Schneider Electric


A hydraulic breaker is similar to a thermal breaker, but instead of using heat, a viscous liquid control the trip point.

  • Advantages: Not affected by ambient temperature and a delayed trip is possible
  • Disadvantages: Not available in all sizes

In order to get the best combination of trip characteristics many circuit breakers combine technology. For example, a thermal/magnetic breaker has a slow reacting thermal trip mechanism and a fast reacting electromagnetic mechanism. Winco indicates which safety technology the main line circuit breaker is using on our spec sheets.

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