Classification of low-voltage circuit breakers
1. According to structure
It can be divided into frame type and plastic shell type kind. All structural components of frame-type circuit breakers are installed on the same frame or base plate, and there can be more structural changes and more types of releases. Generally, large-capacity circuit breakers mostly use frame-type structures. All structural components of plastic case circuit breakers are installed in a plastic case, which is compact in structure and small in size. Generally, small capacity circuit breakers use plastic case structures.
2. According to the purpose
①The circuit breaker for wire protection. Mainly used for lighting circuits and protecting household appliances, with rated current in the range of 6-125 amps.
②The circuit breaker for power distribution. It is used for overload, short-circuit and under-voltage protection in low-voltage power distribution systems, and can also be used for infrequent operation of circuits. The rated current is generally 200-4000 amps.
③ Circuit breaker for motor protection. In occasions of infrequent operation, it is used to operate and protect the motor, and the rated current is generally 6 to 63 amps.
④ Earth leakage protection circuit breaker. Mainly used to prevent leakage and protect personal safety, the rated current is mostly below 63A.
3. According to performance
It is divided into two types: normal type and limited flow. Current-limiting circuit breakers generally have a contact system with a special structure. When the short-circuit current passes through, the contacts are repulsed under the action of electrodynamic force to present an arc in advance, and the arc resistance is used to limit the growth of the short-circuit current. Current-limiting circuit breakers have greater breaking capacity than ordinary circuit breakers, and can limit the effect of short-circuit current on the electrodynamic and thermal effects of the protected line. The low-voltage circuit breaker has a strong ability to break and connect short-circuit current. The plastic case circuit breaker with a rated current of 100 amps has a short-circuit on-off capacity of about 12 kA, while the current-limiting circuit breaker can reach 30 kA. .
Notes on low-voltage circuit breaker installation
1. Before installation, check whether the technical parameters listed on the nameplate of the low-voltage circuit breaker meet the requirements for use.
2. The low-voltage circuit breaker should be installed vertically. The low-voltage circuit breaker connected in front of the board is allowed to be installed on a metal bracket or metal base plate, but the low-voltage circuit breaker connected behind the board must be installed on the insulating base plate. The bracket or bottom plate for fixing the low-voltage circuit breaker must be flat to prevent the insulation base from being damaged by force when tightening the screws. In order to prevent accidents caused by arcing, the copper busbar of the low-voltage circuit breaker should be wrapped with 200mm insulation material from the insulating base or phase arc spacer.
3. The power supply should be connected to the incoming terminal of the static contact of the low-voltage circuit breaker, and one end of the release should be connected to the load. In order to ensure the protection characteristics of the overcurrent release, the section of the connecting wire should be selected according to the rated current of the release.
4. When the circuit breaker is used in conjunction with the fuse, the fuse should be installed before the circuit breaker to ensure safe use.
5. The thermal release and electromagnetic release of the low-voltage circuit breaker have been calibrated and sealed with red paint before leaving the factory. They should not be adjusted by themselves during installation, so as not to affect the action characteristics of the release. If the working current of the place of use does not match the rated working current of the release, the low-voltage circuit breaker suitable for the rated working current of the release should be replaced.
6. In order to prevent arcing, the arcing distance of the circuit breaker should be considered during installation, and it should be noted that the busbar should not be bridged above the arc-extinguishing chamber near the arcing distance.
7. When the low-voltage circuit breaker is used as the main circuit breaker or the control switch of the motor, an isolation switch, knife switch or fuse must be installed on the power inlet side of the circuit breaker as an obvious disconnection point . All products with grounding screws should be grounded reliably.
8. If the low-voltage circuit breaker uses an electric operating mechanism, you must pay attention to the power supply voltage of the operating mechanism, and do not connect it wrongly.
9. Before installing the low-voltage circuit breaker, the internal dust should be removed, and some lubricating oil should be added to each transmission part appropriately; The action value of the organization.
10. After installation, handle or other transmission device should be used to check the accuracy and reliability of the circuit breaker. For example, check whether the release can operate within the specified operating value range, whether the electromagnetic operating mechanism is reliably closed, and whether the movable parts are blocked.
