Introduction Of Molded Case Circuit Breaker

Molded case circuit breakers can automatically cut off the current after the current exceeds the trip setting. Molded case refers to the use of plastic insulators as the outer shell of the device to isolate the conductors and the grounded metal parts. Molded case circuit breakers usually contain thermal magnetic trip units, while large-sized molded case circuit breakers are equipped with solid-state trip sensors. Its trip units are divided into: thermal magnetic trip and electronic trip. Commonly used rated currents are as follows: 16, 25, 30, 40, 50, 63, 80, 100, 125, 160, 200, 225, 250, 315, 350, 400, 500, 630A.
Molded case circuit breakers are also called device-type circuit breakers. All parts are sealed in plastic shells. Auxiliary contacts, undervoltage releases, and shunt releases are mostly modular. Due to the very compact structure, molded case circuit breakers are basically impossible to repair. They are mostly manually operated, and large capacity can be selected for electric separation and closing. Due to the application of electronic overcurrent releases, molded case circuit breakers can also be divided into Class A and Class B. Class B has good three-stage protection characteristics, but due to price factors, Class A products using thermal-magnetic releases have a higher market share. Molded case circuit breakers are contacts, arc extinguishing chambers, releases and operating mechanisms all installed in a plastic casing. Generally, maintenance is not considered and they are suitable for branch circuit protection switches. Overcurrent releases are of two types: thermal-magnetic and electronic. Generally, thermal-magnetic molded case circuit breakers are non-selective circuit breakers with only two protection modes: overload long delay and short-circuit instantaneous. Electronic molded case circuit breakers have four protection functions: overload long delay, short-circuit short delay, short-circuit instantaneous and ground fault. Some newly launched electronic molded case circuit breakers also have regional selective interlocking functions. Most molded case circuit breakers are manually operated, and some are equipped with motor operating mechanisms.