At present, LED is becoming more and more popular in daily lighting. From outdoor lighting to indoor lighting, we can see the footprint of LED lighting products. With the decline of LED cost, LED lighting products are no longer limited to road lighting fixtures. In the market, more LED products such as self ballasted lights, , LED lamps and other LED products that are in line with the public's purchasing power have begun to appear. The design of this kind of product is based on the structure of the ballast fluorescent lamp and the double end fluorescent lamp, which can be conveniently installed on the traditional home lighting, and will not add extra cost for the purchase of lamps and lanterns. Because of the rapid development of LED products, many LED products have no corresponding safety standards up to now. It is neither comprehensive nor suitable to assess the safety standards of traditional lighting sources. This will lead to the failure of many LED products in safety design, which will affect the safety and quality of LED products. 

    At present, the common LED lamp tubes are designed with reference to T8 and T10 fluorescent lamps. Different places mainly depend on the different materials used by light sources. The LED lamp has a built-in power (nor does it exclude that some are designed for external power supply), while the traditional dual ended fluorescent lamps are activated by external ballasts.
 

      This article will combine the two standards of GB18774-2002 and GB7000.1-2007.  and analyze the possible safety problems of LED lamps from the aspects of structure, internal wiring, protection against electric shock, insulation resistance and electrical strength, creepage distance and electrical gap, heat resistance and fire resistance.

 

1. the Structural aspects

The three part of LED lamps are prone to problems are contact of lamp holder, screw, basic insulation and accessible metal parts. The lamp head needs to meet the GB18774-2002 requirements of torque test and the GB2799-2001 size requirements. Among them, GB18774-2002 specified the torque test are required to comply with the provisions of the 2.3.1 provisions of this standard for the high temperature test, When the torque test is applied, the rotation between the components of the lamp holder does not exceed 6 degrees. The high temperature condition of the lamp holder is (125 + 5) centigrade, and the heating time is (2000 + 50) H. If the G13 lamp holder is used and the lamp power is greater than 40W, the high temperature condition is: (140 + 5) centigrade. High temperature condition and duration are very harsh for the LED light tube with plastic material. It is likely that plastic parts will soften after applying such a long time high temperature condition with the use of a plastic lamp holder. If the metal lamp holder is used, it is easier to meet this test condition. However, it is also necessary to take into account the reliability of the connection between the metal lamp holder and the LED lamp body, as well as creepage distance and electrical clearance. If the metal lamp holder is used, it is easier to meet this test condition. But we should also consider the connection between metal lamp holder and LED lamp body, the reliability and creepage distance and electrical clearance.

The screw at the lamp head of the LED lamp is mainly connected and fixed between the lamp head and the lamp body. At present, the diameter of the screw at the common LED lamp head is less than 3mm. and according to GB 7000.1, this kind of screw needs to be rolled into the metal. So far the common way is the LED lamp tube uses an aluminum shell and the screw is swirled directly into the metal shell so that it can also meet the requirements. But a common problem is that, when The screw is screwed into the metal shell. It is too close between the bolt and the electrified metal piece of the lamp head, which can easily lead to the disqualification of the creepage distance and the electrical gap.
 

The internal wiring of the LED lamp tube is mainly used to connect the input and output of the lamp socket and the built-in power supply. And The built-in power supply and the aluminum shell are separated by the casing. According to the provisions of GB7000.1, Insulation between an electrically charged part and a palpable metal part it is necessary to meet double insulation or to strengthen insulation. This requires the insulation of the casing necessary to meet the requirement of strengthening the electrical strength of the insulation level.
 

2. Internal wiring
 

According to the requirements of the GB7000.1 standard, the main points to be evaluated for the internal wiring of LED lamp are mainly the following four aspects: wire diameter and insulation thickness, mechanical damage, insulation layer heating temperature, and whether or not the insulation meets the requirements. Generally speaking, the internal line will not have problems in the protection of mechanical damage; the main problem will be in the other three aspects. In accordance with the requirements of GB7000.1, when the normal current is less than 2A(n general, the working current of the LED lamp will not exceed 2A) the internal wire nominal cross-sectional area is not less than 0.4mm, the thickness of the insulating layer is not less than 0.5mm. And, from the perspective of insulation, because the aluminum shell is a palpable metal part, the internal basic insulation cannot contact with the aluminum shell directly. This requires the internal wire to be a double insulated wire. Unless the relevant certificate can prove that the insulating layer of the wire meets the requirement of strengthening insulation, it is also possible to use a single layer insulation line in the inner line. However, at present, the internal lines of LED lamps used in the market rarely take into consider the requirements of the sectional area, the thickness of the insulating layer and the grade of the insulation line at the same time.
 

In addition, when The inner wire is on the line, it is necessary to avoid the direct contact between the wire and the hot parts of the internal power supply. Such as transformer, inductance, bridge, radiator etc., Because when these parts work in the LED lamp tube, The temperature is might to exceed the heat - resistant temperature of the insulating material of the internal wire. The internal wire does not touch the larger heating component when the wire is on the line. It can avoid the insulation layer damage caused by the overheating of the insulation layer, and generate safety problems such as leakage or short circuit.
 

3. electric-shock safeguard
 

In the aspect of electric-shock safeguard of LED bulb, Xingyuan laboratory to remind you there are two general way might cause the failed situation, One is that there is no reliable connection between the lamp head and the lamp body leads to the direct removal of the lamp holder from the human hand, Two is the internal insulation is not done well, leading to the leakage of the shell.
 

4. Insulation resistance and electrical strength
 

From the electrical classification, the LED lamp tube belongs to the type of II anti electric shock. This requires the input of the LED lamp tube to the palpable parts, and input to the installation surface need to be satisfied Strengthening insulation resistance and be satisfied electrical strength requirements. At present, many LED lamps can pass through the insulation resistance test, but the test of resistance to electricity is fail. The main reason is the selection of the power source transformer and the installation location of the LED module aluminum substrate. Many enterprises choose to use non isolated transformers for the purpose of saving cost or high power efficiency. This will lead to a built-in power supply between the input and output terminals to fail to meet the requirements of strengthening the insulation level's electrical strength. At the same time, due to the direct contact between the aluminum substrate of the LED module and the metal shell when it is installed, this leads to the insulation level between the input and the palpable parts, which cannot meet the requirements of the strength of the insulation.
 

To meet the requirement of strengthening the electrical strength of the insulation level, you can choose to use the isolation transformer electrically isolated the input and output of the built-in power supply or do not use a metal shell to use the outer shell of the insulating material. However, if the insulating material is used, it is also necessary to consider the problem that a screw with a diameter of less than 3mm needs to be rolled into the metal.
 

5. Creepage distance and electrical gap
 

Xingyuan remind you when LED lamp at design time, In addition to the need to take into account the Creepage distance and the electrical gap between charged parts of the lamp head to the touch parts and the different polarity charged parts Because of the built-in power supply, the internal driving power needs to meet the requirements of the creepage distance and the electrical gap stipulated in the GB19510.14-2009 standard.

6. Heat resistance and fire resistance

 

 

There are differences in the heat-resistance test and fire-resistance tests regulation between GB18774-2002 and GB7000.1-2007. The major focus is on the insulation materials which are used on LED bulb holders. They are belong to against electric shock insulated part as well as a portion of insulation materials of fixed live parts.
 

The heat resistance of the GB18774-2002 standard is that the lamp head is applied at a high temperature (125 + 5), and the heating time is 168h. If the G13 lamp is used and the light power is greater than 40W, the high temperature condition is: (140 + 5). If the G13 lamp is used and the light power is greater than 40W, the high temperature condition is: (140 + 5). After the test, it cannot appear rupture, cap pin loosening, bulging and shrinkage, and the insulation resistance between the lamp head and the palpable part is not less than 2M Omega, can withstand the dielectric strength of 1500V (RMS) 1 minutes.
 

The requirement of GB7000.1-2007 standard for heat resistance of lamp insulation materials is checked by ball pressure test. The ball pressure test temperature is the highest working temperature of the insulation part, which is 25 or 125 ℃, and the two gets the maximum value. The test time was 1H, and it was determined whether the diameter of the indentation was greater than 2mm. for the Fire resistance, Because the lamp head insulation belongs to both the anti electric shock insulation and the insulated parts of the fixed charged parts, and it is necessary to carry out the 650 degree heating wire and needle flame test at the same time.

 

The two standard assessment methods have their own harsh areas. At present, there is no standard provision for the LED lamp head insulation assessment according to which requirements. But in the final analysis, it is necessary for the manufacturers to examine the heat and fire resistance of the insulating material when they choose the LED lamp head insulation.

In order to achieve this goal, China has revised the laws of energy conservation law and renewable energy law, etc. and has established the strict assessment index system for energy conservation. Local leaders who cannot finish tasks will face strict accountability.