Basic safety requirements for electrical structure

2022-08-11
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Basic safety requirements for the electrical structure of explosion-proof lamps

the electrical structure in the cavity of explosion-proof lamps must meet the requirements of two aspects: ① during normal or abnormal work, it will not cause unsafe factors to people and the surrounding environment. ② Provide excellent electrical parameters, ensure the photoelectric parameters of the light source, facilitate the start of the light source, do not affect the service life of the light source, and let the light source give full play to its maximum efficiency. The electrical structure in the explosion-proof lamp chamber mainly includes the following contents: 1. Electrical components electrical components should meet the requirements of relevant national standards, be able to withstand the working temperature of the lamp chamber for a long time, provide electrical parameters matching with the light source, and be able to meet the requirements of various specific explosion-proof types of explosion-proof lamps. 2. The design of the structure size of the wiring chamber must meet the specific explosion-proof performance requirements, and it should also be convenient for wiring, leaving a space suitable for the bending radius of the conductor to ensure that the electrical clearance and creepage distance after correct wiring meet the requirements of relevant standards. The inner wall of the wiring chamber and the inner wall of the metal shell that may produce sparks during normal operation must be coated with arc resistant paint. 3. Connectors and terminals ① connectors, insulating sleeves and terminals shall have sufficient mechanical strength to prevent damage during installation and wiring. The wiring shall be firm and reliable, and shall not be loosened due to vibration, heating, thermal expansion and cold contraction of conductors and insulating parts. ② The power connector shall be designed so that after the multi strand stranded conductor is wired, if the wire head comes out of the terminal, it will not touch the surrounding metal parts. ③ Measures shall be taken to prevent loosening of the terminal to prevent the wire at the root of the terminal from being broken. It is not allowed to directly press the connecting wire with the screw head, which is easy to damage the connector. ④ Insulating sleeve shall be made of materials with less hygroscopicity. For explosion-proof lamps with voltage higher than 127V, phenolic plastic products shall not be used. 4. Grounding ① connect accessible metal parts to the grounding terminal permanently and reliably to prevent these metal parts from becoming live parts when insulation problems occur, resulting in electric shock and sparks. ② The wiring cavity and shell of explosion-proof lamps must be equipped with internal and external grounding respectively, and the grounding terminal must be equipped with the grounding symbol "〨". Portable and movable lamps may not be equipped with external grounding to improve the effect of magnetic separation. Lamps with anti electric shock protection of class II and class III may not be equipped with grounding terminals. ③ The diameter of the inner grounding screw shall be the same as that of the connecting bolt, and the specification of the outer grounding screw shall not be less than m6-m8. The grounding screw shall be made of stainless metal or material with stainless surface, and the contact surface shall be bare metal surface. There are anti loosening measures after the screws are tightened. ④ The grounding connection should be low resistance. The grounding resistance from any accessible metal part to the grounding terminal shall not exceed 0.5 Ω. ⑤ The grounding wire must be a conductor with yellow and green insulation. 5. External and internal lines ① the external conductor of the lamp shall be copper core wire wrapped with insulating layer, and its nominal cross-sectional area shall not be less than 1mm2. ② The internal conductor shall be insulated copper core wire with a nominal cross-sectional area of not less than 0.5 mm2. ③ Wire connection 4 According to the stress state of the sample and the application speed of the experimental force, it can be divided into static force and dynamic force. The experimental machine and wiring are not allowed to bear mechanical stress and are allowed to be connected by any of the following methods; A. It can prevent loose bolt or screw connection; B. extrusion connection; C. wires shall be mechanically connected before soldering; D. hard welding connection; E fusion welding connection. ④ When the conductor passes through the hard material, the entrance should be chamfered to make it smooth, with a minimum radius of 0. But it does not mean that the equipment has the above characteristics of 5mm to prevent scratching the conductor insulation. ⑤ The insulation layer of the conductor shall be able to withstand the high voltage and maximum temperature that may be generated in normal use. Bushing can be used to protect the hot spot, so as to ensure that the safety of the lamp will not be affected due to damage after the lamp is correctly installed and connected to the power supply. ⑥ Current carrying parts of lamps shall be made of copper, alloys containing at least 50% copper or materials with at least the same performance. 6. Electrical clearance and creepage distance ① the electrical clearance between live parts of different polarity in the light source cavity shall not be less than 3mm, the creepage distance shall not be less than 3mm, the electrical clearance between live parts and adjacent conductive parts shall not be less than 3mm, and the creepage distance shall not be less than 4mm. ② The electrical clearance and creepage distance between live parts with different polarity in the wiring cavity and between live parts and adjacent conductive parts must be not less. 8. The lead screw and transmission part of the electro-hydraulic servo universal testing machine should be regularly lubricated as specified in the following table. Table minimum electrical clearance and creepage distance of wiring cavity (mm) rated voltage (V) electrical clearance creepage distance ABCD note: A, B, C and D in the table are the electric trace resistance levels of insulating materials. 7. Insulating material ① insulation. The insulating material used for explosion-proof lamps should have low hygroscopicity and good insulation performance. ② Heat resistant. The insulating material must be able to withstand the heat resistance test without softening and deformation. The temperature of the heat resistance test is 25 ℃ higher than the working temperature of the relevant parts measured during normal operation, and the test temperature of the insulating material of the parts in which the live parts are fixed in place is at least 125 ℃ for other parts

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