General knowledge of electrical materials - lighting and distribution system

2017-05-27  192

Components of lighting and distribution system (I) lighting distribution system is composed of lighting distribution box, fuse, leakage protector and miniature circuit breaker respectively.

1. Lighting distribution box is divided into three types: vertical distribution box, open distribution box and concealed distribution box. The size and specification of the distribution box have certain differentiation requirements: (1) vertical distribution box: it is generally used for the main distribution system of the community and is the power supply hub of the whole community. Due to the large power load, there must be a certain heat dissipation space in the design and placement. (2) The exposed distribution box is generally used to be installed on the wall that should not be changed, such as the concrete wall of high-rise residential buildings. (3) Concealed distribution box is generally suitable for offices and residential families. Because it does not occupy the ground space of the house and is relatively beautiful, it is an ideal product often used by families.

2. Leakage protector can be divided into electronic and electromagnetic protection forms. The installation form can also be divided into direct installation on the wall distribution board and guide rail modular panel. The difference between electronic leakage switch and electromagnetic leakage switch: the starting of electronic leakage switch uses the principle of potential difference between live line and zero line, that is, it starts the electronic induction coil with the help of the change of auxiliary voltage of (electronic circuit board) operational amplifier, so there are unsafe factors. The following five cases illustrate the relatively unsafe factors of the electronic leakage switch: (1) if the electronic leakage switch is installed in a wet place with high steam in the bathroom, the misoperation of the switch may often occur, mainly because the water molecules are electrically conductive. (2) In areas with unstable grid voltage (too high or too low), the switch does not act. (3) The phase line and protective line (PE line and pen) have short circuit faults, resulting in the reduction of grid voltage and affecting the switching action. (4) In case of lightning strike or switching overvoltage, the electronic components are sensitive to voltage, causing difficulties in switching action. (5) The occurrence of high-frequency electromagnetic wave causes the increase of tripping current, and the switch is prone to malfunction.

The advantage of the electromagnetic leakage switch is that the phase line and zero line of the electromagnetic leakage switch pass through the leakage induction coil at the same time. When there is no grounding leakage, the magnetic fields m2 and Mn generated by the phase line current L2 and the current ln passing through the zero line should be equal (that is, the inflow and outflow of current are usually equal). As long as there is no potential difference, the electromagnetic induction coil will not work, so it is a relatively safe form of leakage protection. Some electromagnetic leakage switches are equipped with micro filters, isolation capacitors and electromagnetic diaphragm, which can resist lightning strike, sudden change current and surge current impact at the same time.