A circuit breaker is a switching device capable of closing, carrying, and interrupting current under normal circuit conditions, and capable of closing, carrying, and interrupting current under abnormal circuit conditions within a specified time. Circuit breakers are classified into high-voltage circuit breakers and low-voltage circuit breakers according to their application range. The boundary between high and low voltage is somewhat blurred; generally, circuit breakers above 3kV are referred to as high-voltage electrical appliances.
Circuit breakers are used to distribute electrical energy, infrequently start asynchronous motors, and protect power lines and motors. They automatically disconnect the circuit when serious overloads, short circuits, or undervoltage faults occur, functioning similarly to a combination of a fuse switch and over/under-temperature relays. Furthermore, they generally do not require component replacement after interrupting a fault current. They have gained widespread application. Power distribution is a crucial link in the generation, transmission, and use of electricity. Power distribution systems include transformers and various high and low voltage electrical equipment, with low-voltage circuit breakers being a widely used type of electrical appliance.
A residual current circuit breaker (RCCB) is a switch that automatically trips when the leakage current in a circuit exceeds a predetermined value. Common RCCBs are classified into two types: voltage-type and current-type. Current-type RCCBs are further divided into electromagnetic and electronic types. RCCBs are used to prevent electric shock and should be selected based on the different requirements for protection against direct and indirect contact electric shock.
Commonly Used Circuit Breakers
DZ5 series molded case circuit breakers: Suitable for AC 50Hz, 380V circuits with rated current from 0.15 to 50A. Circuit breakers for motor protection are used to protect motors from overload and short circuits. Circuit breakers for power distribution are used in power distribution networks to distribute electrical energy and provide overload and short circuit protection for lines and power supply equipment. They can also be used for infrequent motor starting and infrequent line switching.
DZ12 series molded case circuit breakers: Compact size, novel structure, and excellent and reliable performance. Mainly installed in lighting distribution boxes, they are used in AC 50Hz single-phase 230V, 360V and below lighting circuits in hotels, apartments, high-rise buildings, squares, airports, railway stations, and industrial and commercial enterprises for overload and short-circuit protection, and for infrequent switching of circuits under normal conditions.
DZ15 series molded case circuit breakers: Suitable for AC 50Hz circuits with a rated voltage of 380V and a rated current up to 63A (100) for switching operations. They can also be used for overload and short-circuit protection of lines and motors, as well as for infrequent switching of lines and infrequent starting of motors.
DZ20 series molded case circuit breakers: Suitable for AC 50Hz, rated insulation voltage 660V, rated operating voltage 380V (400V) and below, with rated current up to 1250A. Generally used for power distribution, circuit breakers with rated currents of 200A and 400Y can also be used for motor protection. Under normal conditions, the circuit breakers can be used for infrequent switching of circuits and infrequent starting of motors.
Four-pole circuit breaker: Mainly used in three-phase five-wire systems with AC 50Hz, rated voltage of 400V and below, and rated current of 100 to 630A. It can ensure that the user and the power supply are completely disconnected, ensuring safety, thus solving the drawback of non-zero neutral current that cannot be overcome by any other circuit breaker.
Circuit breakers for power distribution: Used in power distribution networks to distribute electrical energy and provide overload, short circuit, and undervoltage protection for lines and power supply equipment. Circuit breakers for motor protection: Used in power distribution networks for starting and disconnecting squirrel-cage motors, as well as for overload, short circuit, and undervoltage protection of the motors.
DZ47 series miniature circuit breakers: mainly suitable for AC 50Hz/60Hz circuits with rated operating voltage of 240V/415V and below and rated current up to 60A. These circuit breakers are mainly used for overload and short circuit protection of electrical circuits and equipment in modern buildings, and are also suitable for infrequent operation and isolation of circuits.
SCM1(cm1) series circuit breakers: Suitable for infrequent switching and infrequent starting of motors in AC 50Hz, 60Hz, 500V and below circuits. The circuit breaker has overload, short circuit and undervoltage protection devices to protect lines and power supply equipment from damage. This circuit breaker can be installed vertically or horizontally.
DW15 series universal air circuit breakers: Suitable for AC 50Hz power distribution networks with rated current up to 4000A and rated operating voltage up to 1140V (frame class rated current below 630A) and 80V (frame class rated current 1000A and above). Used for power distribution and overload, undervoltage, and short-circuit protection of power lines and equipment. Circuit breakers with a frame class rated current of 630A and below can also be used for overload, undervoltage, and short-circuit protection of motors in AC 50Hz, 380V networks.
DW17(me) series universal air circuit breakers: Suitable for AC 50Hz, 380V, 660V or DC 440V, current up to 4000A power distribution networks. Used for power distribution and protection of lines and power equipment against overload, undervoltage, short circuit, etc. Under normal conditions, they can be used for infrequent line switching. Circuit breakers below 1250A can be used to protect motors from overload and short circuit in AC 50Hz, 380V networks. Under normal conditions, they can also be used for infrequent motor starting.
DZ20l series residual current circuit breaker: It is a current-operated electronic residual current protection device, mainly suitable for AC 50 Hz, rated voltage of 380 volts, and rated current up to 630A power distribution network. It is used for personal electric shock protection, and can also be used to prevent fire hazards caused by ground fault current due to equipment insulation damage. It can also be used to distribute electrical energy and protect lines and power equipment from overload and short circuit, and can be used for infrequent line switching.
DZL18-20 series: Household residual current circuit breakers are suitable for use in single-phase circuits with AC 50Hz, voltage of 220V, and rated current up to 20A for personal electric shock protection. They can also be used for overload and overvoltage protection of lines and equipment, and to prevent fire hazards caused by ground fault current due to equipment insulation damage. When connected in series with an RL1 fuse, they can be used for short circuit protection.
