The low-voltage circuit breaker (formerly known as the automatic switch) is a switching device that can not only turn on and off the normal load current and the overload current, but also can switch on and off the short-circuit current. In addition to the control function, the low-voltage circuit breaker has certain protection functions, such as overload, short circuit, under voltage and leakage protection. There are many types of low-voltage circuit breakers, which are classified according to the type of use, selective (protective device parameters are adjustable) and non-selective (protective device parameters are not adjustable), according to arc extinguishing media, air and vacuum (currently domestic Mostly air type). Low-voltage circuit breakers have a wide range of capacities, from a minimum of 4A to a maximum of 5000A. Low-voltage circuit breakers are widely used in the feeding lines of all levels of low-voltage power distribution systems, power control of various mechanical equipment and control and protection of power terminals. 1, rated voltage (1) rated working voltage The rated working voltage of the circuit breaker refers to the voltage value associated with the breaking capacity and the type of use. For a polyphase circuit, it refers to the voltage value between phases. (2) rated insulation voltage The rated insulation voltage of the circuit breaker refers to the voltage value of the designed circuit breaker. The clearance and creepage interval should be determined by referring to these values. Unless otherwise specified in the model product documentation, the rated insulation voltage is the maximum rated operating voltage of the circuit breaker. In any case, the maximum rated operating voltage does not exceed the insulation voltage. 2, rated current (1) The rated current of the circuit breaker frame is expressed by the rated current of the maximum trip unit that can be loaded in the frame or plastic case with the same size and structure. (2) rated current of circuit breaker The rated current of the circuit breaker is the rated continuous current. That is, the current that the trip unit can pass for a long time. A circuit breaker with an adjustable trip is the maximum current that can be passed for a long time. For example, the rated current of DZ10-100/330 low-voltage circuit breaker frame is 100A, and the rated current rating of the trip unit is 15A, 20A, 25A, 30A, 40A, 50A, 60A, 80A, 100A and so on. The maximum rated current of 100A is consistent with the rated current of the frame. 3, rated short circuit segmentation capability The maximum short-circuit current that the circuit breaker can break under specified conditions. 4, the meaning of the low-voltage circuit breaker model The meaning of the low-voltage circuit breaker model is shown in Figure 3. Figure 3 The meaning of the low-voltage circuit breaker model (1) It is divided into AC AC and DC DC according to the type of current. (2) Air according to arc extinguishing medium; vacuum; gas (very rarely used in low voltage circuit breakers) (3) by use category Class A: In the case of a short circuit, the circuit breaker does not explicitly indicate the selective protection of another short-circuit protection device used in series on the load side, that is, in the case of a short circuit, the artificial short-delay required for non-selective protection, and thus no Short-time withstand current requirements. Class B: In the case of a short circuit, the circuit breaker clearly indicates the selective protection of another short-circuit protection device used in series on the load side, that is, in the case of a short circuit, selective protection can be achieved, and a short delay (adjustable) is available. Therefore, there is a short-time withstand current requirement. (4) According to the structure type Universal type: ACB for short, all parts are mounted on an insulated or metal frame, with more structural changes, more types of trip units, a larger number of auxiliary contacts, and generally selective disconnection The device, especially the large-capacity circuit breaker, is designed to be versatile. Plastic housing type: simply referred to as molded case or MCCB, all parts are installed in an insulating case. The plastic case circuit breaker is compact, small in size, light in weight, low in price, and safe to use (the operator is less likely to contact conductive parts), and is suitable for independent installation. Due to its low rated current, non-selective circuit breakers are often designed in a plastic housing. (5) According to the protection device Thermal: mostly bi-metallic, also three-metal Electromagnetic type: core with coil, mostly used for instantaneous action release or backup protection Electronic: using electronic components to form a trip unit Intelligent: use the microprocessor to form a trip unit to achieve various protection characteristics Communicative intelligent: With intelligent trip unit, adding interface and field bus, it can support various communication protocols and achieve two-way communication. (6) According to the principle of action Current limiting type: The short-circuit current repulsion effect is used to make the contact open and break quickly, and the short-circuit current can be broken when the first peak maximum value has not appeared. Non-current limiting type: Generally used for industrial use, it can break the expected short-circuit current. (7) According to the breaking speed General type: The action time is above 20ms, generally for industrial use. Fast type: the action time is 10~20ms, mostly used for DC (8) by purpose Residual current protection circuit breaker; no overcurrent protection circuit breaker CBI; instantaneous action circuit breaker ICB; Distribution breaker: used for power circuits, protection circuits and electrical equipment from short circuits, overload hazards Special circuit breaker for motor protection: specially designed to protect the starter motor. Fiber Optic Splice Closure,Fiber Optic Splice Case,Fiber Splice Closures,Outdoor Fiber Optic Splice Closure Cixi Dani Plastic Products Co.,Ltd , https://www.danifiberoptic.com
Low voltage circuit breaker concept
March 08, 2023