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Main Functions of Molded Case Circuit Breaker

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Moulded Case Circuit Breaker is also known as device type circuit breaker. All parts are sealed in plastic case, auxiliary contacts, undervoltage trippers and shunt trippers are modular, and have strong breaking ability and isolation protection function. Today, Xiaobian will give you a detailed introduction of the main functions and functions of the Moulded Case Circuit Breaker.

Molded case circuit breaker function:

(1) rated limit short circuit breaking capacity Icu

There are two kinds of breaking capacity indexes of circuit breaker: rated limit short circuit breaking capacity 4U and rated operation short circuit breaking capacity Ics. As a characteristic parameter, ICs not only considers the breaking ability of circuit breaker, but also acts as a breaking index, that is, it can ensure its normal operation after several short-circuit breakdowns. For Moulded Case Circuit Breaker, there should be enough Icu to break short circuit current and make the switch trip. According to the regulations, the Ics of Moulded Case Circuit Breaker is qualified as long as it is more than 25% Icu. At present, most of the ICs of circuit breakers in the market are between (50% - 75%) Icu, so only Icu should be considered for distribution systems with low power supply requirements.

(2) Current Limiting and Breaking Capacity

Current-limiting interrupting capability refers to the ability to limit fault current when circuit breakers are short-circuit tripping. When the circuit breaker is short-circuited, the contact opens quickly to generate arc, which is equivalent to a rapidly increasing arc resistance in series in the circuit, thus limiting the increase of fault current. The shorter the breaking time of circuit breaker, the closer Ics is to Icu, the better the current limiting effect. It can also greatly reduce the adverse effects of electromagnetic, electric and thermal effects caused by short circuit current on circuit breakers and electrical equipment, and prolong the service life of circuit breaker.

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