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Function and operation of circuit breakers

By definition a circuit breaker is an electrical safety device, a switch that automatically interrupts the current of an overloaded electric circuit, ground faults, or short circuits. Circuit breakers "trip", shut off, current flow after protective relays detect a fault. Unlike fuses that were used previously, circuit breakers are not usually damaged so they can be reset as opposed to being replaced. Circuit breakers are used in residential and in industrial applications.


There are 5 basic components used in every circuit breaker:

4 categories of circuit breakers:

Molded Case Circuit breakers (MCCB)
ABB molded case circuit breakers

15-1200A Tmax XT Tested UL 489 and meets NEMA AB Standards

Residential to Industrial

single, two pole or three pole

Lighted panelboards

Insulated Case Circuit Breakers
ABB insulated case circuit breakers

Powerbreak II Tested UL 489 and meet NEMA AB Standards

Frame Sizes 800-4000A frames - mains and large

Electrically operated breaker

Commercial to Light Industrial - office buildings, schools, shopping malls

Somewhat maintainable but contacts not replaceable

Rugged design

Air power circuit breakers
ABB air power circuit breakers

(Emax 2)

Heavy industrial application - can involve switchgear

Optimal reliability - Hospitals, Data Centers

Serviceable in the field

Best choice for heavy switching (Contacts replaceable)

30 Cycle Withstand

Frame sizes 250-6000A built on ANSI rated

True switchgear breakers

Used in industrial environments where maintenance staff and customer needs high reliability

All electronic eKip Touch and eKip - Bluetooth standard

3 and 4 pole versions

Miniature Circuit Breakers (MCB)
ABB miniature circuit breakers

Used for low-energy requirements, like home wiring, offices, or small electronic circuits.

MCBs are equipped with two tripping mechanisms: the delayed thermal tripping mechanism for overload protection and the magnetic tripping mechanism for short circuit protection.

ABB Conversations Blog

ABB Conversations
15 JAN 2018
How does a miniature circuit breaker actually work?

Everyone knows what it is—but not everyone knows what it does.

Read more