The molded case circuit breaker of Chint is installed in the switchgear

 Chint's molded case circuit breakers are widely used in switchgears. The following is some relevant introduction:

Common Models and Characteristics

- **NM1 Series**: It belongs to the upgraded molded case circuit breaker. The rated insulation voltage is up to 800V. It is suitable for the power distribution network circuits with an alternating current of 50Hz/60Hz, a rated operating voltage up to 690V (415V for 2P products and NM1-63), and a rated operating current ranging from 10A to 250A. It has the characteristics of small size, high breaking capacity, and short arcing distance. It can distribute electric energy and protect the circuits and power equipment from damage caused by overload, short circuit, undervoltage and other faults. It can also be used for the infrequent starting of motors and the protection against overload, short circuit and undervoltage. It complies with standards such as GB/T 14048.2 and IEC 60947 - 2, and has obtained CCC, KEMA, and CB certifications.

- **NXMNS Series**: It is an electronic molded case circuit breaker. It covers a current range of 32 - 1600A, is equipped with 11 frames, adopts a miniaturized, modular and universal design. It has a complete range of accessories and supports various manual operations, enabling one-stop flexible selection. With a compact design and small size, the height of some frames and key components is reduced by 23% - 26%. The terminals adopt a U-shaped terminal design, which can be connected in multiple directions, improving the installation efficiency and space utilization rate. It uses a high-strength environmentally friendly plastic double-layer cover composite technology, with high safety. The electronic controller has been comprehensively upgraded and can be equipped with a COMA communication module to achieve the "four remote" functions.

- **NM5 Series**: It includes various types of products such as thermomagnetic type, electronic type, direct current type, and isolating switch type. It is suitable for circuits with an alternating current of 50/60Hz, a rated voltage up to AC1140V/DC1500V, and a rated current of 800 - 1600A. It can provide reliable protection when the circuit and electrical equipment encounter overload, short circuit and undervoltage. It can also be used for the infrequent starting of motors and the protection against overload, short circuit and undervoltage. The whole series meets the requirement of free incoming wiring from top or bottom, with a flexible wiring method, universal accessories, and can expand a variety of additional functions.

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 Functions in the Switchgear

- **Circuit On-off Control**: During normal operation, the circuit can be turned on or off through a manual or electric operating mechanism to meet the needs of equipment maintenance, debugging or operation. For example, when maintaining other equipment in the switchgear, the molded case circuit breaker can be turned off first to cut off the power supply and ensure the safety of maintenance personnel.

- **Overload Protection**: When the current in the circuit exceeds the rated current of the molded case circuit breaker, the thermal release inside it will heat up and deform. After a certain period of time, it will push the tripping mechanism to act, making the circuit breaker trip and cut off the circuit, thus protecting the circuit and equipment from overload damage. For instance, when the electrical equipment connected behind the switchgear malfunctions and causes the current to be continuously too large, the molded case circuit breaker will act in a timely manner to prevent the equipment from being damaged due to overheating.

- **Short Circuit Protection**: Once a short circuit fault occurs in the circuit, the short circuit current will make the electromagnetic release of the molded case circuit breaker act quickly and cut off the circuit instantly to limit the damage of the short circuit current to the equipment and circuit. Short circuit faults may cause dangerous situations such as electric arcs and overheating, and the quick action of the molded case circuit breaker can effectively avoid the occurrence of these dangers.

- **Undervoltage Protection**: When the power supply voltage drops to a certain extent (generally 70% - 35% of the rated voltage), the undervoltage release of the molded case circuit breaker will act, making the circuit breaker trip and cut off the circuit. This can prevent the equipment from operating under undervoltage conditions and avoid equipment damage or abnormal operation caused by insufficient voltage.

Consideration Factors for Selection

- **Rated Current**: Select a molded case circuit breaker with an appropriate rated current according to the size of the load current connected to the switchgear. Generally, the rated current of the circuit breaker should be greater than or equal to the maximum operating current of the load. For example, if the switchgear mainly supplies power to some small motors and the total load current is 50A, then a molded case circuit breaker with a rated current of 63A or larger can be selected.

- **Rated Voltage**: It should match the operating voltage of the switchgear to ensure that the circuit breaker can work normally at the corresponding voltage and has sufficient insulation performance and withstand voltage capacity.

- **Breaking Capacity**: Select a molded case circuit breaker with sufficient breaking capacity according to the possible maximum short circuit current in the circuit where the switchgear is located to ensure that the circuit can be reliably cut off in case of a short circuit fault and avoid dangerous situations such as explosion of the circuit breaker due to its inability to withstand the short circuit current.

- **Tripping Characteristics**: Select appropriate tripping characteristics such as thermomagnetic tripping, electronic tripping, etc. according to the nature of the load and protection requirements. The thermomagnetic release is suitable for general power distribution and motor protection, while the electronic release has more accurate protection characteristics and more flexible setting functions, which is suitable for occasions with higher protection requirements.