Eaton MC2-442-57CQB-1-2A Molded Case Circuit Breaker
The Eaton MC2-442-57CQB-1-2A is a three-pole thermal-magnetic molded case circuit breaker from the Eaton Moeller NZM series. This breaker is designed to provide reliable overload and short-circuit protection for electrical circuits in industrial, commercial and infrastructure applications. The comprehensive part number provides specific details about its frame size, interrupting capacity, current rating, trip unit type and auxiliary features.
Technical Specifications
The Eaton MC2-442-57CQB-1-2A is a three-pole breaker with a rated current of 57A. The C-curve tripping characteristic provides magnetic trip between 5 and 10 times the rated current, offering a balance between inrush tolerance and short-circuit sensitivity. The rated operational voltage is typically 415V or 480V AC at 50/60 Hz. The breaking capacity is determined by the 442 frame size, with typical values ranging from 42kA to 50kA depending on the specific configuration. The breaker includes 1 NO plus 1 NC auxiliary contacts as factory-installed options, simplifying panel design and wiring.
Design and Construction
As a member of the MC2 series, this circuit breaker features a robust molded case housing that contains the operating mechanism, main contacts, arc chute and trip unit. The molded case provides mechanical protection for internal components and ensures safe isolation of the operator from energized parts. The compact design offers high breaking capacity in a relatively small form factor, saving valuable panel space in electrical enclosures.
The breaker functions as both a manually operated disconnect switch and an automatic protection device. Under normal conditions, the operator can manually open or close the breaker to isolate circuits for maintenance. Under fault conditions, the breaker automatically interrupts fault currents safely, protecting downstream equipment from damage.
Thermal-Magnetic Protection Mechanism
The thermal-magnetic trip unit provides two distinct protection functions within a single device. The thermal element responds to sustained overload conditions, providing time-delayed protection that mimics the heating characteristics of conductors and equipment. This delay allows temporary inrush currents to pass while still clearing persistent overloads before damage occurs. The magnetic element responds instantaneously to short-circuit conditions, opening the breaker within milliseconds to limit fault current magnitude and duration.
C-Curve Tripping Characteristics
The C-curve tripping characteristic is selected for general-purpose applications where moderate inrush currents are expected. The magnetic trip threshold of 5 to 10 times the rated current accommodates the starting currents of small motors, transformers and other inductive loads while still providing adequate short-circuit protection. This characteristic makes the MC2-442-57CQB-1-2A suitable for circuits including small motors, lighting systems, general distribution panels and control circuits.
Applications
The Eaton MC2-442-57CQB-1-2A is deployed across a wide range of applications requiring reliable circuit protection. Industrial facilities use the breaker for motor protection in manufacturing equipment, conveyor systems and pumps. Commercial buildings employ the breaker for distribution panel protection in offices, retail spaces and data centers. Infrastructure applications include power distribution in water treatment plants, transportation facilities and telecommunications installations. The breaker also serves as a branch circuit protector in industrial control panels, providing coordinated protection with upstream and downstream devices.
When installed on 35mm top-hat rail, the MC2-442-57CQB-1-2A serves as an end-of-line distribution protection element. The integrated bimetal thermal trip mechanism and electromagnetic instantaneous mechanism precisely respond to motor starting currents of 5 to 10 times rated current. In industrial PLC cabinets or building distribution boxes, the breaker can control small power loads such as sensors and solenoid valves, preventing short-circuit cascading failures. The C-curve trip time is less than 100 milliseconds under short-circuit conditions, providing fast fault clearing.
