LED tube light with Alu+PC housing has possible security problems?

LED tube light which is with half Alu and half PC housing has possible security problems?


Let's talk about it by its structure,internal wiring,electric shock protection,insulation resistance and electric strength,creepage distance and electrical gap,heat and fire resistant.

1. Structure
   
     Lamp holder,screw,basic insulation and accessible metal parts,these three places are prone to problems of LED tube light.

     Lamp holder needs to meet the requirement of the torque test specified in GB18774-2002 and the size requirement specified in GB2799-2001.Among them,the torque test specified in GB18774-2002 requires that the high temperature test must comply with the provisions of 2.3.1 of the standard, when torque test is imposed, the rotation between the various components of the lamp is not more than

6°. High temperature  conditions imposed by the lamp holder is (125±5)℃,heating time is (2000±50)h. If you are using a G13 lamp holder and lamp power larger than 40W,high temperature condition is as (140±5)℃.High temperature conditions and duration for LED tube light with plastic lamp holder is harsh assessment,plasic parts are likely to be softened to impose such a long time in high temperature conditions when a not good heat resistant lamp holder is used for LED tube light.If metal lamp holder is used,relatively speaking, it is easier to meet this test conditions, but also, there are things to be taken into account, such as solid connection level between the lamp holder and LED tube light, creepage distance and electrical gap,etc.

    Screw on the lamp holder plays a connection and fixation role between lamp holder and lamp body. At present,screw of the common LED tube light is with diameter less than 3mm.According to provisions of the GB7000.1,such screw must be screwed into the metal. The common practice is that LED tube light uses Alu housing,and the screw is srewed directly into the Alu housing, which would also meet the requirements. A common problem is happened by that. Scews and lamp charged metal parts are too close and it easily lead to creepage distance and electrical gap failed by screw screwed directly into the Alu housing.

    Internal wiring of LED tube light is for connecting the input and output of the lamp latch and built-in power supply. Built-in power supply and Alu housing are insulated by sleeve. According to the provisions of the GB7000.1,  internal charged parts and accessible metal parts shall meet the double insolation or reinforced insulation requirements.

2. The internal wiring

     According to provisions of the GB7000.1 standard requirements, LED tube light used internal wiring needs to meet assessment as following four aspects: the diameter of wiring and thickness of the insolating layer; mechanical damage;insulating layer heated temperature; whether insulation meets the requirements.

     In general, the internal cable protection from mechanical damage does not have a problem, the main problem will be out in the other three aspects. In accordance with the GB7000.1 requirments of the standard, normal current is less than 2A ( general LED tube light current does not exceed 2A), the nominal cross-secttional area of internal wiring  is not less than 0.4mm2,and the thickness of insulating layer is not less than 0.5mm. Also, from the insulation point of view, Alu shell and internal basic insulation can not contact directly ,coz the ALu shell belongs to the accessible metal parts,which requires internal wiring is with double insulation.Unless there is relevant certificates to prove that the wiring insulation to meet strengthen insulation requirements,then, it is also possible for internal wiring with single-layer insulation. However, LED tube light which is on the market today use internal wiring and rarely take into acccount for the cross-sectional area, the thickness of insulating layer and the insulated wire level requirments.

    In addition, the internal wiring trace also need to pay attention to avoid the wire and the large heating parts of  internal power supply in direct contact, such as transformers,filter inductors,bridge rectifiers,heat sinks,etc, coz temperature of these components may exceed the heat resistance temperature of internal wire insulation material. Internal wiring trace and large heat parts in not direct contact,which can avoid security problems, such as, insulation damage for insulating layer by local overheating,resulting in shell leakage or short circuit etc.

3. Protection against electric shock

    For unqualified case for LED tube light in the protection against electric  shock,there are two problems may happen in generally:

    a). manpower can remove lamp holder directly due to unreliable connection between lamp holder and lamp body.

    b). Internal wiring insulation does not do a good job,resulting in shell leakage.

4. Insulation resistance and electric strength

From electrcal classification,LED tube light is the type of Class II protection against electric shock.It is required to meet the enhanced insulation resistance and electric strength requirements,among the input of LED tube light to accessible metal parts,and among the input of LED tube light to the mounting surface.

At present, most of LED tube light can pass insulation resistance test, however, cant pass electric strength test.It is mainly caused by built-in power transformer selection and LED module installation position.

For cost savings or high power efficiency purposes, non-isolation transformer is choosen by most of manufacturers,as results,its insulation calss among the inputs and outputs of built-in power supply can not meet the electric strength of reinfored insulation class requirements.At the same time, due to dirct contact between Alu shell and LED module in installation, as results,its insulation class among the inputs of built-in power supply to accessible metal parts can not meet the electric strength of reinfored insulation class requirements.

In order to meet the electric strenght of reinforced insulation class requirements, isolation transformer can be choosen for built-in power supply input and output electrical isolation. Another way is that, using insulating material to instead of metal(Alu) shell.

If metal (Alu) shell is used, security problems for diameter less tan 3mm screws screwed into metal shell shall be taken into consideration as the previous mentioned standard.

Our plastic (ABS+PC) material LED tube light can completely solved the above security problems of LED tube light which is with  half Alu and half PC.
                

Wanna know more about our plastic(ABS+PC) material LED tube light?

Please refer to my another blog text,which topic is "LED with active heat dissipation?-As crazy as it sonds!"

Click link as following:
http://wanyu-led.blogspot.com/2012/06/led-with-active-heat-dissipation-as.html
Besides, you can contact Amber Zhu: amberzhu0915@gmail.com or call Amber Zhu: +86  18948177087  or add Amber Zhu's skype account: amber.zhu88