At present, the common LED fluorescent lamps are basically designed based on the fluorescent lamps of T8 and T10. The different places are mainly based on the different materials used for the light sources. The LED fluorescent lamps have built-in power supplies (does not exclude some of them as external power supplies) and the traditional double ends. Fluorescent lamps are excited by external ballasts. From an electrical point of view, the LED fluorescent lamp is both a light source and a lamp. It must meet the requirements for the size and heat-resistance and fire-resistance of the lamp head in the safety standard of double-end fluorescent lamp GB18774-2002. It must also meet the lighting standard GB7000.1-2007. Standards and GB19510.1-2009 standards for the entire light and built-in LED drive power on the structure, internal lines, creepage distances and clearances, insulation and electrical strength, heat resistance, fire resistance and other aspects.
This article will combine GB18774-2002 and GB7000.1-2007 content of the two standards, from the structure, internal wiring, protection against electric shock, insulation resistance and electrical strength, creepage distance and clearance, heat and fire resistance analysis of these aspects There may be safety issues with LED fluorescent lamps.
First, the structure
LED fluorescent lamps are prone to problems with the lamp, screws, basic insulation, and accessible metal parts. The lamp cap needs to meet the torque test specified in GB18774-2002 and the dimensional requirements specified in GB2799-2001. Among them, the torque test specified in GB18774-2002 must meet the requirements of Clause 2.3.1 before and after the high temperature test, that is, when the torque test is applied, the rotation between the parts of the lamp cap does not exceed 6°. The lamp head applies a high temperature condition of (125 ± 5) °C and a heating time of (2000 ± 50) h. If a G13 lamp is used and the lamp power is greater than 40W, the high temperature condition is: (140 ± 5) °C. High-temperature conditions and duration The inspection of LED fluorescent lamps using plastic materials for the lamp base is rather harsh. Using plastic lamp holders with poor heat resistance, after applying such a long period of high temperature conditions, the plastic parts are likely to have softened. If metal caps are used, it is relatively easy to meet this test condition, but the degree of connection between the metal caps and the body of the LED fluorescent lamp, as well as creepage distances and clearances, etc. must also be considered.
The screw of the LED fluorescent lamp head mainly plays the role of connection and fixation between the lamp head and the lamp body. At present, the screw diameter of the common LED fluorescent lamp head is less than 3mm, and according to the provisions of GB7000.1, such screws need to be screwed into the metal. At present, the common practice is that the LED fluorescent lamp uses an aluminum casing, and this screw is screwed directly into the metal casing, which can also meet the requirements. However, a common problem that arises is that, after the screw is screwed into the metal shell, the screw is too close to the charged metal parts of the lamp head, which easily leads to the failure of creepage distance and clearance.
The internal wiring of the LED fluorescent lamp is mainly used to connect the input and output of the lamp plug and the built-in power supply, and the built-in power supply is isolated from the aluminum casing by the bushing. According to the provisions of GB7000.1, insulation between internal live parts and accessible metal parts shall meet double insulation or reinforced insulation. This requires that the insulation of the bushing needs to meet the electrical strength requirements of the reinforced insulation class.
Second, internal wiring
According to the requirements of the GB7000.1 standard, the internal wiring used by LED fluorescent lamps needs to be assessed mainly in terms of wire diameter and insulation thickness, mechanical damage, insulation layer heating temperature, and whether the insulation meets the requirements in four aspects. In general, there is no problem with the protection of mechanical damage in internal lines. The main problems will be in the other three aspects. According to the requirements of GB7000.1 standard, when the normal current is lower than 2A (the working current of the general LED fluorescent lamp will not exceed 2A), the nominal cross-sectional area of ​​the internal conductor is not less than 0.4mm2, and the thickness of the insulation layer is not less than 0.5mm. Moreover, from the insulation point of view, because the aluminum shell is accessible metal parts, the internal basic insulation can not be in direct contact with the aluminum shell, which requires the internal wire to be double insulated wire, unless there is relevant certificate to prove that the wire insulation layer can meet the strengthening Insulation requirements, it is also possible to use a single-layered insulated wire for internal wiring. However, at present, the internal lines used in LED fluorescent lamps on the market rarely consider the requirements of the cross-sectional area, the thickness of the insulating layer and the level of the insulated wire.
In addition, when the internal wires are being routed, care must be taken to avoid direct contact between the wires and components that generate heat inside the power supply, such as transformers, filter inductors, bridge stacks, heat sinks, etc., because these components operate at LED fluorescent lamps and the temperature is very high. It is possible to exceed the heat-resistant temperature of the internal wire insulation. When the internal wires are routed, they do not contact the parts with large heat, which can prevent the insulation layer from being damaged due to the local overheating of the insulation layer, and cause safety problems such as leakage or short circuit.
Third, protection against electric shock
LED fluorescent lamps in the protection against electric shock, there may be two cases of unqualified circumstances, one is that the lamp head and the lamp body is not reliably connected so that the manpower can directly remove the lamp, which led to direct contact with the test and internal live parts; Internal insulation is not done, causing the casing to leak.
Fourth, insulation resistance and electric strength
From the perspective of electrical classification, the LED fluorescent lamp belongs to type II anti-shock type, which requires that the input of the LED fluorescent lamp between the accessible parts, as well as the need to meet the insulation resistance and electrical strength requirements of the reinforced insulation level between input to the mounting surface. At present, many LED fluorescent lamps can pass through during the insulation resistance test, but the resistance strength test fails. This is mainly due to the selection of the transformer with built-in power supply and the installation position of the LED module's aluminum substrate. Many companies choose to use non-isolated transformers for cost-saving or high-efficiency power supplies, which can result in the incompatibility between the input and output ends of the built-in power supply. At the same time, since the aluminum substrate of the LED module is in direct contact with the metal shell during installation, the insulation level between the input end and the accessible part cannot meet the electrical strength requirements of the reinforced insulation class.
In order to meet the requirement of strengthening the insulation strength of the insulation class, an isolation transformer may be used to electrically isolate the input and output of the built-in power supply, or instead of using a metal shell, the insulation material may be used instead. However, if an insulating material is used, the above-mentioned screw with a diameter of less than 3 mm needs to be screwed into the metal.
This article will combine GB18774-2002 and GB7000.1-2007 content of the two standards, from the structure, internal wiring, protection against electric shock, insulation resistance and electrical strength, creepage distance and clearance, heat and fire resistance analysis of these aspects There may be safety issues with LED fluorescent lamps.
First, the structure
LED fluorescent lamps are prone to problems with the lamp, screws, basic insulation, and accessible metal parts. The lamp cap needs to meet the torque test specified in GB18774-2002 and the dimensional requirements specified in GB2799-2001. Among them, the torque test specified in GB18774-2002 must meet the requirements of Clause 2.3.1 before and after the high temperature test, that is, when the torque test is applied, the rotation between the parts of the lamp cap does not exceed 6°. The lamp head applies a high temperature condition of (125 ± 5) °C and a heating time of (2000 ± 50) h. If a G13 lamp is used and the lamp power is greater than 40W, the high temperature condition is: (140 ± 5) °C. High-temperature conditions and duration The inspection of LED fluorescent lamps using plastic materials for the lamp base is rather harsh. Using plastic lamp holders with poor heat resistance, after applying such a long period of high temperature conditions, the plastic parts are likely to have softened. If metal caps are used, it is relatively easy to meet this test condition, but the degree of connection between the metal caps and the body of the LED fluorescent lamp, as well as creepage distances and clearances, etc. must also be considered.
The screw of the LED fluorescent lamp head mainly plays the role of connection and fixation between the lamp head and the lamp body. At present, the screw diameter of the common LED fluorescent lamp head is less than 3mm, and according to the provisions of GB7000.1, such screws need to be screwed into the metal. At present, the common practice is that the LED fluorescent lamp uses an aluminum casing, and this screw is screwed directly into the metal casing, which can also meet the requirements. However, a common problem that arises is that, after the screw is screwed into the metal shell, the screw is too close to the charged metal parts of the lamp head, which easily leads to the failure of creepage distance and clearance.
The internal wiring of the LED fluorescent lamp is mainly used to connect the input and output of the lamp plug and the built-in power supply, and the built-in power supply is isolated from the aluminum casing by the bushing. According to the provisions of GB7000.1, insulation between internal live parts and accessible metal parts shall meet double insulation or reinforced insulation. This requires that the insulation of the bushing needs to meet the electrical strength requirements of the reinforced insulation class.
Second, internal wiring
According to the requirements of the GB7000.1 standard, the internal wiring used by LED fluorescent lamps needs to be assessed mainly in terms of wire diameter and insulation thickness, mechanical damage, insulation layer heating temperature, and whether the insulation meets the requirements in four aspects. In general, there is no problem with the protection of mechanical damage in internal lines. The main problems will be in the other three aspects. According to the requirements of GB7000.1 standard, when the normal current is lower than 2A (the working current of the general LED fluorescent lamp will not exceed 2A), the nominal cross-sectional area of ​​the internal conductor is not less than 0.4mm2, and the thickness of the insulation layer is not less than 0.5mm. Moreover, from the insulation point of view, because the aluminum shell is accessible metal parts, the internal basic insulation can not be in direct contact with the aluminum shell, which requires the internal wire to be double insulated wire, unless there is relevant certificate to prove that the wire insulation layer can meet the strengthening Insulation requirements, it is also possible to use a single-layered insulated wire for internal wiring. However, at present, the internal lines used in LED fluorescent lamps on the market rarely consider the requirements of the cross-sectional area, the thickness of the insulating layer and the level of the insulated wire.
In addition, when the internal wires are being routed, care must be taken to avoid direct contact between the wires and components that generate heat inside the power supply, such as transformers, filter inductors, bridge stacks, heat sinks, etc., because these components operate at LED fluorescent lamps and the temperature is very high. It is possible to exceed the heat-resistant temperature of the internal wire insulation. When the internal wires are routed, they do not contact the parts with large heat, which can prevent the insulation layer from being damaged due to the local overheating of the insulation layer, and cause safety problems such as leakage or short circuit.
Third, protection against electric shock
LED fluorescent lamps in the protection against electric shock, there may be two cases of unqualified circumstances, one is that the lamp head and the lamp body is not reliably connected so that the manpower can directly remove the lamp, which led to direct contact with the test and internal live parts; Internal insulation is not done, causing the casing to leak.
Fourth, insulation resistance and electric strength
From the perspective of electrical classification, the LED fluorescent lamp belongs to type II anti-shock type, which requires that the input of the LED fluorescent lamp between the accessible parts, as well as the need to meet the insulation resistance and electrical strength requirements of the reinforced insulation level between input to the mounting surface. At present, many LED fluorescent lamps can pass through during the insulation resistance test, but the resistance strength test fails. This is mainly due to the selection of the transformer with built-in power supply and the installation position of the LED module's aluminum substrate. Many companies choose to use non-isolated transformers for cost-saving or high-efficiency power supplies, which can result in the incompatibility between the input and output ends of the built-in power supply. At the same time, since the aluminum substrate of the LED module is in direct contact with the metal shell during installation, the insulation level between the input end and the accessible part cannot meet the electrical strength requirements of the reinforced insulation class.
In order to meet the requirement of strengthening the insulation strength of the insulation class, an isolation transformer may be used to electrically isolate the input and output of the built-in power supply, or instead of using a metal shell, the insulation material may be used instead. However, if an insulating material is used, the above-mentioned screw with a diameter of less than 3 mm needs to be screwed into the metal.
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