This part of GB/T 10963 is applicable to AC air circuit breakers with AC 50 Hz, 60 Hz, or 50/60 Hz, rated voltage not exceeding 440 V (phase to phase), rated current not exceeding 125A, and rated short circuit capacity not exceeding 25000 A. This section should be as consistent as possible with the technical requirements in GB/T14048.22008. These circuit breakers are used to protect building circuit facilities from overcurrent and similar purposes; They are designed for use by untrained personnel and do not require maintenance. The circuit breakers in this section are expected to be used in pollution level 2 environments. The circuit breakers in this section are suitable for isolation. Except for circuit breakers with a rated voltage of 120 V or 120/240 V (see Table 1), the circuit breakers in this section are suitable for use in IT systems. This section also applies to circuit breakers with several rated currents, as long as the appliance that changes from one rated value to another during normal operation is inaccessible and cannot change its rated value without tools. This section does not apply to: - circuit breakers for protecting motors- A circuit breaker whose setting current can be adjusted by a device that can be touched by the user. For circuit breakers with a protection level higher than TP20 in IEC 60529, as well as those commonly used in harsh environmental conditions (such as excessive humidity, overheating, overcooling, or dust deposition) and in hazardous locations (such as explosive prone areas), special structures may be required. The technical requirements for circuit breakers used for AC and DC applications can be found in GB/T 10963.2-2020. The technical requirements for circuit breakers equipped with residual current release devices can be found in IEC 61009-1, IEC 61009-2-1, and IEC 61009-2-2. Guidelines for the coordination between circuit breakers and other short-circuit protection devices (SCPDs) under short-circuit conditions can be found in Appendix D. For more severe overvoltage conditions, circuit breakers that meet other standards should be used (such as GB/T 14048.2-2008). For environments with higher pollution levels, it is advisable to use enclosures with appropriate protection levels. Note: Based on its tripping characteristics and device performance, circuit breakers within the scope of application of this section can also be used for electric shock protection in case of faults. The scope of application for electric shock protection is specified by the installation regulations. This section contains all necessary requirements to ensure compliance with the operational characteristics required by type tests for such devices. This section also includes relevant details necessary to ensure the repeatability of the test results. This section stipulates: a) Characteristics of circuit breakers: b) Conditions that circuit breakers should meet in the following aspects: 1) Operation and working conditions of circuit breakers under normal operation; 2) Operation and working conditions of circuit breakers under overload; 3) The operating and working conditions of the circuit breaker under rated short-circuit capacity and below; 4) The dielectric performance of the circuit breaker