Q&A: Operational Observations and Considerations for Selecting Circuit Breakers

In today’s industrial electrical systems, the importance of effective protection and reliable operation cannot be overemphasized. Machine design We caught up with Klaus Tum, Product Director at Altech, to learn more about the basics of miniature circuit breakers (MCBs), components used to protect electrical circuits.

Tum offers valuable insight into the functionality and application of miniature circuit breakers, from the differences between MCBs and fuses, to the factors to consider when selecting MCBs, to the different tripping mechanisms used in circuit breakers.

Editor’s note: Questions and answers have been edited for clarity.

Machine design:What are the differences between circuit breakers and fuses in terms of operation and protection?

Klaus Tum: The main difference is that circuit breakers can be reset after a fault (scenario) that exceeds their tripping parameters. Their tripping mechanism consists of an electromechanical mechanism (solenoid, which consists of a magnetic coil, housing, and plunger/armature) that will respond to a rapidly increasing short circuit current. The magnetic field in the magnetic coil will accelerate the armature in such a way that it will immediately strike the moving contact of the circuit breaker to break the circuit.

For slower rising and smaller currents (overloads), the circuit breaker uses a bimetallic strip that bends according to the tripping parameters and eventually hits the moving contact on the other side of the pivot point to break the circuit. The arc (energy consisting mainly of fire) short circuit (especially in short circuits) will be directed to the so-called arc deionization chamber and the arc will be extinguished there.