Air circuit breaker has large capacity, high limit breaking capacity, good short-time withstand ability and good stability, but it is expensive. It is mostly used for main switch of low-voltage distribution system, trunk line with large load and protection of large motor. Compared with air circuit breaker, moulded case circuit breaker has the advantages of small volume, good contact protection, convenient installation and low price, but it has small capacity and poor short-time tolerance, so it is suitable for branch protection switch.
Molded case circuit breakers MCCBs automatically cut off current when the current exceeds the trip setting. Plastic housing refers to the housing of a device using a plastic insulator to isolate between conductors and the grounded metal part.
Molded case circuit breakers usually contain thermal magnetic trip units, while large moulded case circuit breakers are equipped with solid state trip sensors. Due to the very compact structure, the moulded case circuit breaker can hardly be serviced. Air circuit breaker ACB is a mechanical switching device which can turn on, carry and break current under normal circuit conditions, and also turn on and carry certain time and break current under specified abnormal circuit conditions.
Air circuit breakers are used to distribute electric energy and protect lines and power supply equipment from overloads, undervoltages, short circuits, etc. Air circuit breakers generally have a steel frame, and all parts are installed in the frame. It has a large capacity, can be installed with multiple functions of tripping devices and more auxiliary contacts, has a higher segmentation capacity and thermal stability, so it is often used in places that require high breaking capacity and selective protection.
From the appearance, the size of moulded case circuit breaker is different from that of and air circuit breaker.
Moreover, the current level and breaking capacity of air circuit breaker are greater than those of molded case circuit breaker. The intelligent release of air circuit breaker has protection function, measurement function, auxiliary function, special function and communication function. Measurement function: current measurement, voltage measurement, power measurement, frequency measurement, electric energy measurement, harmonic measurement. Auxiliary functions: pre alarm, self diagnosis function, fault history record function and test function.
The release of moulded case circuit breaker mainly has the functions of long time delay protection, short time delay protection i. It can be seen from here that the protection function of air circuit breaker is more powerful than that of moulded case circuit breaker.
The rated current range of air circuit breaker is usually A, which is mainly used in distribution network to distribute electric energy, protect lines and power equipment from overload, undervoltage, short circuit, single-phase grounding and other faults. The rated current range of moulded case circuit breaker is usually A, which is used to provide protection for lines and equipment in case of overload, short circuit and under voltage of lines and equipment in distribution lines.
It can also provide overload, short circuit, and undervoltage protection for scenes where the motor is not frequently started. The primary distribution equipment, collectively referred to as the power distribution center, is installed in the substation of the enterprise to distribute electric energy to the lower level distribution equipment in different locations.
This level of equipment is close to the step-down transformer, so the requirements for electrical parameters are high, and the output circuit capacity is also large. Generally, in the main distribution cabinet, the main component is the air circuit breaker.
Secondary power distribution equipment is the general name of power distribution cabinet and motor control center. The power distribution cabinet is used in the situation where the load is dispersed and the circuit is less; the motor control center is used for the occasion where the load is concentrated and the circuit is more. They distribute the electrical energy of a circuit of the upper power distribution equipment to the nearest load.
This class of equipment should provide protection, monitoring and control of the load. The circuit breakers commonly used are moulded case circuit breaker, micro break switch and dual power supply products. Moulded case circuit breakers are usually class A. When using MCCB for these types of applications, the protective characteristics can be attained easily by using an electronic MCCB that has variable long-delay tripping characteristics.
Instantaneous tripping characteristics of MCCB are fixed for compact models, adjustable for large models. ACBs are donated with more protection functions by using the advantage of advanced electronic releases. MCCB is used for general wiring protection. It is not suitable for applications requiring frequent switching. Its total breaking time is short, and transient energy is small, so MCCB is suitable for protecting wiring and load devices. ACB is used for generator and transformer protection in the main circuit.
Its rated short-time current is high, so easy to structure a selective breaking system. Components with low weight and volume make life easy for users of MCCBs. The short-time capacity of the ACB is high. It is easy to structure a selective breaking system and is suitable for applications as the main circuit breaker.
Load-side switching operations are more frequent than upstream. MCCB has a simple and safe structure that does not require maintenance or inspections. However, the ACB is designed with many updated parts and must be sufficiently serviced and inspected. Thus, MCCB is not suitable for applications intended for frequent short circuit interruption. Over Current can occur due to excess use of electricity, or because of a short circuit in the electrical circuit.
MCB is generally used for safety at home electrical installations, as a safety control circuit, lights and measuring instruments on an MCC panel, and as a safeguard on the LCC Lighting Control Centre panel. Most of the MCCB is used for industrial electrical systems that have considerable power and are usually used for 3-phase electricity, which requires a greater capacity for Breaking Capacity.
0コメント