Trip Free Circuit Breaker

Introduction to Trip-Free Circuit Breakers

A trip-free circuit breaker is designed to trip (open) during an overcurrent or fault condition, even if an attempt is made to hold it in the "on" position.        

The purpose of the trip-free requirement is to ensure the safety of equipment and personnel by preventing the circuit breaker from remaining closed during a fault condition.

It is commonly used in electrical distribution systems to protect equipment and circuits from overcurrent or short-circuit conditions.

Operational Modes of Circuit Breakers

Trip Mode: The circuit breaker trips and interrupts the flow of electrical current during an overcurrent or short-circuit condition.

Reset Mode: After tripping, the circuit breaker can be manually reset to re-energize the circuit once the fault is cleared.

Trip-Free Functionality: Prevents resetting the circuit breaker while the fault condition persists, ensuring continuous protection.

Importance and Benefits of Trip-Free Circuit Breakers

Safety: Protects both equipment and personnel from electrical hazards by ensuring the circuit breaker trips under fault conditions.

Equipment protection: Prevents damage to electrical devices by not exposing them to overcurrent conditions.

Prevents Misuse: Avoids accidental or deliberate attempts to hold the circuit breaker in the "on" position during a fault.

Applications

The NFPA 70 in is article 240 states:

Trip-free is an important safety feature, as it assures that the decision to open a circuit breaker dominates over the command to close. Further, and probably most important, if there were no trip-free functional requirement, it would not be possible to lock a circuit breaker open (fundamental to lockout-tagout procedures) when performing maintenance.        

Conclusion

A trip-free circuit breaker is designed to trip and interrupt the electrical current during an overcurrent or fault condition, even if an attempt is made to hold it in the "on" position. This functionality ensures the safety of both equipment and personnel by preventing the circuit breaker from staying closed during a fault. Commonly used in electrical distribution systems, trip-free breakers protect against overcurrent conditions, prevent damage to electrical devices, and ensure proper lockout-tagout procedures during maintenance.

Reference

[1]: NFPA 70 2017

[2]: What is a trip-free circuit breaker?

[3]: Siemens TechTopics No. 94

[4]: Introduction to Circuit Protection Devices

Authors: Yves Zomebot, PE & Jixil Johnson

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