LED fluorescent lamp safety requirements
From an electrical point of view, LED fluorescent lamps are not only light sources, but also very similar to lamps. It not only meets the requirements of the double-capped fluorescent lamp safety standard GB 18774-2002 for the size and heat resistance and fire resistance of the lamp holder, but also needs to meet the lamp standard GB7000.1- The 2007 standard and the GB19510.1-2009 standard have requirements for the structure, internal wiring, creepage distance and electrical clearance, insulation and electrical strength, heat resistance, fire resistance, etc. of the whole lamp and the built-in LED drive power supply.
At present, common LED fluorescent lamps are basically designed with reference to T8 and T10 fluorescent lamps in appearance and size. The main difference lies in the different materials used for the light source. LED fluorescent lamps have a built-in power supply (external power supply), while traditional double-capped fluorescent lamps rely on external ballasts.器动。 Excitation.
This article will combine the contents of the two standards GB18774-2002 and GB7000.1-2007 to analyze the structure, internal wiring, protection against electric shock, insulation resistance and electrical strength, creepage distance and electrical clearance, heat resistance and fire resistance. Safety issues of LED fluorescent lamps.
structure
LED fluorescent lamps are prone to problems in the three places where the lamp cap, the screw, the basic insulation and the contact of the accessible metal parts. The lamp holder needs to meet the torque test specified in GB18774-2002 and the size requirements specified in GB2799-2001.
The torque test specified in GB18774-2002 requires that both before and after the high temperature test meet the requirements of clause 2.3.1 of the standard, that is, when the torque test is applied, the rotation between the parts of the lamp cap should not exceed 6°.
The high temperature condition applied by the lamp cap is (125±5)℃, and the heating time is (2000±50)h.
If G13 lamp holder is used, and the lamp power is greater than 40W, the high temperature condition is: (140±5)℃. High-temperature conditions and duration are more stringent for the assessment of LED fluorescent lamps with plastic materials in the lamp cap. Using plastic lamp caps with low heat resistance, after applying such a long period of high-temperature conditions, the plastic parts are likely to have softened.
If a metal lamp holder is used, it is relatively easy to meet this test condition, but the connection between the metal lamp holder and the LED fluorescent lamp body, as well as the creepage distance and electrical clearance, should also be considered.
The screws at the lamp cap of the LED fluorescent lamp mainly play the role of connection and fixing between the lamp cap and the lamp body. The diameter of the screw at the base of the common LED fluorescent lamp is less than 3mm, and according to the provisions of GB 7000.1, this type of screw needs to be screwed into the metal. The current common practice is to use an aluminum shell for LED fluorescent lamps, and this screw is directly screwed into the metal shell, which can meet the requirements.
The internal wiring of the LED fluorescent lamp is mainly used to connect the lamp holder pin and the input and output of the built-in power supply, and the built-in power supply is isolated from the aluminum shell by a sleeve. According to GB7000.1, the insulation between internal live parts and accessible metal parts must meet double insulation or reinforced insulation. The insulation of the bushing is required to meet the electrical strength requirements of the reinforced insulation level. A common problem is that after the screw is screwed into the metal shell, the screw and the charged metal part of the lamp cap are too close, which easily leads to the unqualified creepage distance and electrical clearance.
Internal wiring
According to the requirements of the GB7000.1 standard, the internal wiring used by the LED fluorescent lamp needs to be evaluated in four aspects: wire diameter and insulation thickness, mechanical damage, the heating temperature of the insulation layer, and whether the insulation meets the requirements.
Since the aluminum shell is an accessible metal part, the internal basic insulation cannot directly contact the aluminum shell. This requires the internal wire to be a double insulated wire, unless the relevant certificate can prove that the insulation layer of the wire can meet the requirements of reinforced insulation. Layer insulated wires are also possible. At present, the internal wires used in LED fluorescent lamps on the market rarely take into account the requirements of cross-sectional area, insulation layer thickness and insulation wire level at the same time.
There will be no problems in the protection of mechanical damage to the internal wires, and the main problems will lie in the other three aspects.
According to the requirements of the GB7000.1 standard, when the normal current is less than 2A (generally the working current of LED fluorescent lamps does not exceed 2A), the nominal cross-sectional area of the internal wire is not less than 0.4mm2, and the thickness of the insulating layer is not less than 0.5mm.
When routing the internal wires, you also need to pay attention to avoid direct contact between the wires and the components of the internal power supply that heat up, such as transformers, filter inductors, bridge stacks, heat sinks, etc., because these components are likely to have a temperature when the LED fluorescent lamp is working. Will exceed the heat-resistant temperature value of the inner wire insulation material. When the internal wires are routed, do not touch the components that generate a lot of heat, which can avoid the insulation layer damage caused by the local overheating of the insulation layer, and the safety problems such as leakage or short circuit.
Protection against electric shock
In terms of protection against electric shock, there are generally two types of unqualified LED fluorescent lamps.
One is that the unreliable connection between the lamp cap and the lamp body causes the lamp cap to be directly removed by human hands, which leads to direct contact with the internal live parts in the test;
The second is that the internal insulation is not done well, resulting in leakage of the shell.
Insulation resistance and electric strength
From the perspective of electrical classification, LED fluorescent lamps belong to the II type of anti-shock type, requiring the input of LED fluorescent lamps to the touchable parts and the input to the installation surface to meet the insulation resistance and electric strength requirements of the reinforced insulation level.
At present, the LED fluorescent lamp can pass the insulation resistance test, but the dielectric strength test fails, mainly due to the selection of the transformer with the built-in power supply and the installation position of the aluminum substrate of the LED module. Many companies choose to use non-isolated transformers for the purpose of saving costs or high power supply efficiency, which will cause the built-in power supply's input and output terminals to fail to meet the electrical strength requirements of the reinforced insulation level. During installation, the aluminum substrate of the LED module is in direct contact with the metal shell, which causes the insulation level between the input terminal and the accessible parts to fail to meet the electrical strength requirements of the reinforced insulation level.
In order to meet the requirements of the electrical strength of the reinforced insulation level, choose to use an isolation transformer to electrically isolate the input and output of the built-in power supply, or use an insulating material instead of a metal casing. However, if an insulating material shell is used, it is also necessary to consider the aforementioned problem that screws with a diameter of less than 3mm need to be screwed into metal.
Creepage distance and electric clearance
In the design of LED fluorescent lamps, in addition to the creepage distance and electrical clearance between the live parts of the lamp cap and the accessible parts and the live parts of different polarities, the internal driving power supply also needs to meet the GB19510.14-2009 standard due to the built-in power supply. The requirements for creepage distances and electrical clearances specified in.
heat and fire resistance
There are certain differences between GB18774-2002 and GB7000.1-2007 for heat resistance and fire resistance tests. The differences are mainly concentrated on the insulating material base used in LED fluorescent lamps. The insulating material of the lamp holder is an electric shock-proof insulating part, and it is also an insulating material for fixing live parts.
The requirements of the GB7000.1-2007 standard for the heat resistance of the lamp holder insulating material are assessed by ball pressure test. The ball pressure test temperature is 25°C or 125°C higher than the maximum working temperature of the insulating component, whichever is the maximum. The test time is 1h, and whether the indentation diameter is greater than 2mm is used to determine whether it is qualified.
In terms of fire resistance, since the lamp holder insulating parts are both anti-shock insulating parts and fixed live parts, it is necessary to perform the 650℃ glow wire and needle flame tests at the same time.
GB18774-2002 standard heat resistance requirements are that the high temperature condition applied to the lamp cap is (125±5) ℃, and the heating time is 168h. If G13 lamp holder is used, and the lamp power is greater than 40W, the high temperature condition is: (140±5)℃. After the test, there should be no loosening, cracking, swelling and shrinking of the lamp holder pins, and the insulation resistance between the lamp holder pins and the accessible parts is not less than 2MΩ, and it can withstand the electric strength of 1500V (AC effective value) for 1 minute. In terms of fire resistance, it is required to withstand the glow wire test at 650°C.
The two standard assessment methods have their own harsh points. At present, there is no standard that stipulates which requirements are used to assess the insulation of LED lamp holders. But in the final analysis, manufacturers are still required to focus on evaluating the heat and fire resistance of the insulating material when choosing LED fluorescent lamp holder insulation.
From the perspective of product structure, LED fluorescent lamps combine the characteristics of double-capped fluorescent lamps and lamps. When performing electrical safety assessments on LED fluorescent lamps, it is necessary to integrate the safety standards of double-capped fluorescent lamps, the safety standards of lamps and the safety standards of LED driving power supplies, and the Products undergo a more comprehensive and detailed electrical safety assessment.
