Overview of circuit breakers in low-voltage distribution boxes and introduction of main technical parameters

The low-voltage circuit breaker is one of the important distribution electrical appliances used in the low-voltage distribution box/cabinet. Because of the different places and conditions used, low-voltage circuit breakers are divided into four categories: distribution protection type, motor protection type, over-current protection type for household and similar purposes, and residual current (leakage) protection type. Since the user's understanding of the protection characteristics and the range of use of the low-voltage circuit breaker is not deep or comprehensive, various errors or problems often occur in the actual use of the low-voltage circuit breaker. Next, the Taiyuan distribution box manufacturers will tell you about it. Definition, main technical performance and parameters of low voltage circuit breakers. In order to give users a deeper understanding of low voltage circuit breakers.

1 Overview

In modern society, the lives of all walks of life and people cannot leave electricity. After the generation of electricity, distribution is a very important part of transportation and use. Electrical equipment used in power distribution systems, including transformers and various high and low voltage electrical equipment, electrical equipment used in electrical equipment is a low voltage circuit breaker.

50hz frequency or 60 Hz, and the rated voltage 1200v, and 1500v DC rated voltage is called a voltage below the low-voltage circuit. Low-voltage electrical appliances (including low-voltage circuit breakers) are electrical products used for the above-mentioned grid voltages. Low-voltage electrical appliances can be divided into two major categories: distribution electrical appliances and control electrical appliances according to their relationship with the use system. The scope of distribution electrical appliances includes low-voltage circuit breakers and fuses, knife switches, transfer switches and so on.

The low-voltage circuit breaker is a switching device that can not only turn on and off the normal load current and the overload current, but also can turn 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. Low-voltage circuit breakers are classified in many ways and can be classified according to the structure, the functions they have, and the different protection objects. According to the structure and use, the functions can be divided into two categories: plastic shell type and universal type; according to different protection objects, it can be divided into four types: power distribution protection type, motor protection type, household and similar home protection type. Residual current (leakage) protection type.

2. Main technical parameters of low voltage circuit breaker

(1) Rated voltage: refers to the rms value of the normal working voltage rms value, which can be added to the electric appliance for a long time during normal operation without the adverse effect of the economic working voltage.

(2) Rated frequency: The rated frequency is 50 Hz and 60 Hz.

(3) Rated current: 1 circuit breaker frame rated current is expressed by the rated current of the maximum decouper that can be loaded in the frame or plastic casing of the same size and structure.

2 The rated current of the circuit breaker is the rated continuous current, which is the current that the trip unit can pass for a long time. The circuit breaker with adjustable trip unit is the maximum current that can be passed for a long time.

(4) Temperature rise: The operating temperature of each component of the circuit breaker must be less than one rated value.

(5) Power frequency withstand voltage: between the incoming and outgoing lines of the circuit breaker, between the phases of the circuit breaker, according to the level of the insulation voltage, after the electrodes are closed, the electrodes are connected in parallel with the metal casing to apply a power frequency. The voltage value does not allow flashover or breakdown.

(6) Protection characteristics of overload and short circuit: two-stage protection, three-stage protection, single-phase ground fault protection.

(7) Residual current: Under certain conditions, only the residual current is used to operate the residual current operated circuit breaker.

(8) Remaining non-operating current: Under certain conditions, only the residual current is used to make the residual current operated circuit breaker not operate.

(9) Life: It can be divided into mechanical life and electrical life.

(10) The ability to short-circuit segments: the ability to limit short-circuit segments and the ability to run short-circuit segments.

(11) Short-time withstand current I _cw : Under a certain test condition, the short-time withstand current value that the circuit breaker can withstand without being damaged, should also be specified in the design and development: rated short-time withstand current The minimum value. When the rated current I _n ≤ 2500A, the rated short-time withstand current I _cw is l2 I _n or 5kA, whichever is greater; when I _n >2500A, it is 30kA, the delay time should be not less than 0.05s, the preferred value It is 0.05-0.1-0.25-O.5-1s. The short-circuit withstand current I _{cw is} only applicable to circuit breakers with short-circuit short-delay characteristics.

(12) Power consumption of the circuit breaker itself: refers to the heating power loss generated by its own resistance when the circuit breaker passes the maximum current, which is generally expressed by the three-phase total power watt.

With the rapid development of China's national economy, the use of power distribution in the power grid is increasing, and the requirements for power consumption are getting higher and higher. The correct use of circuit breakers can effectively improve the operating performance of low-voltage power distribution systems. Therefore, it is especially important that the low-voltage circuit breakers are safe and economical. In the next section we describe the selection and installation conditions of low voltage circuit breakers in low voltage distribution boxes.