Molded Case Circuit Breakers (MCCB)

Molded case circuit breakers (MCCBs) provide overcurrent and short-circuit protection for industrial power distribution systems, motor branch circuits, and feeder applications across a wide range of ampere ratings and fault-current interrupting capacities. Controls engineers, panel shops, and machine builders source MCCBs in several form factors: compact low-ampere frame breakers for branch-circuit protection, mid-range thermal-magnetic units with adjustable trip settings for motor circuit protection, and large-frame high-interrupting-capacity breakers rated for main feeder and service-entrance duty. Accessories commonly stocked alongside MCCBs include terminal shrouds and cover kits for finger-safe busbar protection, spacer modules for isolation assemblies, and step-down current transformers that extend trip unit sensing into higher ampere ranges. Typical selection criteria include frame size, continuous ampere rating, interrupting rating at system voltage (commonly 480V three-phase), trip characteristics (fixed or adjustable thermal-magnetic), and applicable certifications such as UL 489 or IEC 60947-2.