A circuit breaker is an electrical appliance commonly used in AC circuits. The utility model is generally composed of a movable contact, a movable contact and a static contact. In a circuit, the utility model can cut off the power supply, connect the power supply and protect the electric equipment. According to its structure and working principle, it can be divided into single-phase circuit breaker, three-phase circuit breaker and air circuit breaker. Circuit breaker, as the interrupting device between control circuit and power supply, plays an important role in power grid. When the circuit overload, short circuit and other faults, the protection of electrical timely action will be cut off, so that circuit open to protect personal and property safety and other equipment from damage. So the circuit breaker widely used in power system is also called “over-undervoltage protector” or “fuse”. One of the important functions is to automatically cut off the power supply when there is a short circuit.
Principle of operation
When the AC current through the circuit breaker contacts, electromagnetic attraction, driving the action of the operating mechanism, so that the circuit breaker release tripping, thereby cutting the circuit.
In practice, a delay device can be added so that the circuit can be disconnected only after the switch operation is completed within the prescribed time.
When the short-circuit current passes through the circuit breaker, the metal near the contact is melted and pulled off by the thermal release due to the arc kinetic energy and intense heat generated by the melting of the contact, thus cutting off the current.
When the power switch is closed or the circuit connected to it fails, the circuit breaker can break the circuit in a short time.
According to the structural form is divided into fixed, mobile and suspended three.
According to the release mode is divided into manual and electric two forms.
According to the operating mechanism can be divided into belt transmission and no belt transmission two types;
Classification
(1) Circuit breakers can be divided into vacuum interrupter chamber (VHV), arc interrupter gate (AVR), vacuum release (VSD) and vacuum contactor according to the medium of arc interrupter.
(2) The circuit breakers can be divided into three types: single-phase circuit breaker, three-phase circuit breaker and air circuit breaker.
(3) Air circuit breakers can be divided into two types, AC and DC, according to the users and the different places of use.
(4) The circuit breaker may be combined with the air capacitor bank, air inductor and other electric equipment according to the installation method, and may be used as a protective electric appliance.
(5) They are classified into over-current protection type, short-circuit protection type and over-under-voltage protection type according to their protection characteristics.
(6) There are 100V series general-purpose air voltage and current grades according to their rated voltage and current values.
Specification parameter
The type of circuit breaker is similar to that of other electrical appliances, such as the code composed of the letters “P”, “Y” and digits for distribution switches, and the code composed of the letter “C” and digits for knife switches, etc., but their functions and structures are obviously different and generally can not be used for general purposes. Take ZF6 and ZF14 for example.
2) Rated voltage: refers to the rated value that the circuit breaker can bear under the rated frequency (50Hz) and the rated frequency (25Hz).
3) Rated current: refers to the maximum working current that the circuit breaker can withstand under specified conditions.
4. “Breaking capacity” means that the circuit breaker can reliably disconnect AC 50Hz or DC 1000V or below under the prescribed conditions, and the breaking time shall not exceed 5ms.
5) Performance characteristics
Principle of selection
1、 Divided into:
(1) Single-phase circuit breakers refer to those used for the protection of circuits, motors and other electrical equipment. The circuit breaker has the advantages of infrequent operation and convenience, but it is required to cut off the power supply in time when the line and motor are overloaded or short-circuited to prevent the accident from expanding. Therefore, the circuit breaker should meet the requirements of cutting off the power supply within the prescribed time, with short breaking time, good selectivity and so on.
(2) The term “three-phase AC low-voltage circuit breaker” refers to a circuit breaker used in motor protection and control circuits, which has the same function as a single-phase circuit breaker, but has added a disconnecting switch to the internal structure of the electric appliance so as to meet the requirements for protecting motors and control circuits in AC circuits. In addition, it also has overload relay, undervoltage relay and zero sequence current relay.
Post time: Feb-17-2023