Molded case 2 pole mcb enclosure circuit breaker has the following characteristics:
Rated limit short-circuit breaking capacity Jcu. The breaker's breaking capacity includes rated limit short-circuit breaking capacity Icu and rated operating short-circuit breaking capacity CCS.ICS, as a characteristic parameter, is not simply considered as the breaker's breaking capacity, but as a kind of breaking index, that is, after several short-circuit failures, it can still ensure its normal operation. For molded case circuit breakers, there should be sufficient Icu to break the short-circuit current to trip the switch. According to the regulation of molded case circuit breaker LCS as long as more than 25% Cu is qualified. The majority of Ics of circuit breakers currently on the market are in the (50%-75%) Icu range, so distribution systems with low power requirements need only consider the Icu.
2. Current limiting and breaking capacity refers to the ability of limiting fault current when a circuit breaker shorts and trips. When the circuit breaker is short-circuited, the contact is opened quickly to produce an arc, which is equivalent to a rapidly increasing arc resistance in the line, thus limiting the increase of fault current. The less the breaker disconnection time is, the closer the Ics is to the LCU, the better the current limiting effect is, it can also greatly reduce the electromagnetic effect, electric effect and thermal effect caused by the short circuit current on the circuit breaker and electrical equipment, prolong the service life of the circuit breaker.
3. The short 2 pole mcb enclosure circuit protection, that is, molded case circuit breaker short circuit instantaneous tripping, pay attention to changes in load after adjust protection setting value, prevent the setting value is too small frequent tripping, affect the quality of power supply or setting ambassador 4 lines and equipment can not get effective protection, overload delay protection, refers to the load current exceeds equipment limits are in danger of fire equipment, protective device can to a certain Time to cut off the power supply. There is a process of heat accumulation, and the protective action does not need to be too rapid. For short overcurrent, the guard should not operate. 5. The isolation function requires that the leakage current after the MCCB is disconnected will not cause harm to the human body and equipment. After several short circuit trips, the switch performance decreases and the leakage current increases. For the human body, the safe leakage current is below 30mA, and in the harsh environment, the leakage current of more than 300mA lasts for more than 2 hours, may cause the insulation damage phase short circuit and cause fire. 6 leakage protection, leakage has two kinds of thermomagnetic and electronic, compared with electronic leakage, has the advantages of small size, high precision, high sensitivity, but its anti-interference ability is poor. At present, the electronic leakage protector occupies the mainstream. When the leakage current reaches the setting value, the executive circuit receives the inductive voltage signal from the secondary side of the zero-sequence current transformer, drives the conversion contact to output the leakage protection signal, and makes the tripping device move to cut off the power supply.
The setting leakage trip current of the general terminal switch is 30mA, and the setting value of the upper branch switch is 300mA. The arc short circuit with high fire risk is difficult to be effectively cut off by short circuit protection, and the leakage plastic case circuit breaker can be disconnected grounding fault, to prevent the occurrence of personal electric shock and phase short circuit fault.
Automatic air switches, also known as low-voltage circuit breakers 2 Pole Mcb Enclosure, are used to switch on and off load circuits and to control motors that start infrequently. Its function is equivalent to the knife switch, over-current relay, voltage loss relay, thermal relay and leakage protector and other electrical parts or all of the total function, is an important protection of low-voltage distribution network.
Automatic air switch has a variety of protection functions (overload, short circuit, under-voltage protection, etc.) adjustable action value, high breaking ability, convenient operation, safety and other advantages, so it is widely used at present.
Low-voltage circuit breaker 2 Pole Mcb Enclosure as a low-voltage switchgear, the important switch appliances, almost every switchgear and distribution box will be used. Its main function is equivalent to the knife switch, fuse, thermal relay, the combination of overcurrent relay and under voltage relay, can be used to connect and breaking load circuit, also can be used to control not frequent start motor, is a manual switch function and can automatically and owe voltage switch electrical voltage, overload and short circuit protection. Is a distribution box, distribution cabinet can play a protective role in one of the important electrical appliances.
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