Technical application of tunnel light

In the new century, the country has increased the construction of transportation systems, such as railways, highways, expressways, high-speed railways and so on. Roads cannot be built around the tunnel, so tunnel lights must be installed, leading to a large-scale LED tunnel light industry. However, there are not many large-scale LED tunnel light manufacturers at present. Except for a few professional LED tunnel light manufacturers such as Shanghai Grand Canyon, Dongguan Qinshang Optoelectronics, Zhongshan Yueshen Lighting, others are not small-scale scattered small factories.

LED tunnel lights have incomparable advantages over traditional light source tunnel lights, such as energy saving and high efficiency, high brightness, high color rendering index, long life, small volume and easy installation, especially high-power LED tunnel lights, which are better than traditional sodium tunnel lights in terms of brightness and service life, and are currently the mainstream tunnel light products. Here's a comparison between LED tunnel lights and traditional tunnel lights.

1. Comparison and selection of functions between conventional tunnel lights and LED tunnel lights

At present, most of the traditional tunnel lighting uses high pressure sodium lamp as the light source, but there are many deficiencies in the radiation form, color rendering, visual sensitivity characteristics, power specifications, brightness control and other aspects of high pressure sodium lamp. However, the emerging LED tunnel lamps, especially the high-power LED tunnel lamps, are characterized by their excellent performance, especially the controllability of brightness. Overcoming many deficiencies of high pressure sodium lamp, it is becoming the mainstream tunnel lighting fixture in the world today. The state also introduced a new measure of "Ten cities ten thousand lights" semiconductor lighting project, bringing unprecedented opportunities for the development of LED tunnel lights. In order to actively respond to the "Ten cities ten thousand lights" plan, Zhongshan Moon God Lighting has invested heavily in the introduction of European advanced LED tunnel light production equipment, vigorously research and development and production of new LED tunnel lights, and currently occupies a significant market share in the domestic LED tunnel lights.

LED(LightEmittingDiode) is a semiconductor light emitting technology. The earliest leds, which emit only red light, are used for indicators in electronic devices. With the development of technology, LED lights can now emit a variety of colors, and is widely used in a variety of industries, the main application markets include the traditional display and signal light market, backlight market, LED street lights, LED tunnel lights, automotive lighting market, outdoor landscape lighting and interior decoration lighting market, special lighting market. LED as a tunnel light source has its unique advantages.

(1)LED tunnel lamp has low power consumption and energy saving, saving more than 60% energy compared with high pressure sodium lamp.

(2) Long service life of LED tunnel lamp. Taking Luna lighting high-power LED tunnel lamp as an example, the normal service life is more than 60,000 hours, which is more than 10 times the service life of sodium lamp.

(3)LED tunnel light has good working stability and is basically maintenance-free during use, while the maintenance cost of sodium lamp in the later stage is very high.

(4) reduce the construction cost of the distribution system (cable, transformer, distribution box, bridge, etc.). For the long tunnel and long distance power supply, the proportion of the cost of cable and distribution facilities is especially large. The use of LED tunnel lights can greatly reduce the investment of cable and distribution equipment due to power saving.

(5)LED tunnel light can realize instant start, easy to adjust the brightness, with zero strobe, wide starting voltage range and other advantages, can realize a variety of energy saving ways, such as according to the road, tunnel traffic flow intelligent regulation of illuminance. Luna Lighting's new LED tunnel light can also realize remote control, time - sharing control and other intelligent control.

(6) Chemical pollutants such as mercury and lead are contained in high-pressure sodium lamp, fluorescent lamp and electrode less lamp, while LED tunnel lighting source does not contain chemical polluting substances and is a green and low-carbon light source. Luna Lighting LED tunnel lights have passed the European standard ROHS certification, energy saving and high efficiency is a prerequisite for entering the European market.

2. Design requirements for high-power LED tunnel lights

(1) The tunnel should be equipped with basic lighting during the day or at night. When vehicles enter the tunnel during the day, the brightness of the road surface should gradually decrease, so that the driver's vision has an adaptation process, and the entrance section is divided into the introduction section, the adaptation section and the transition section.

(2) Determine the length (S) of the leading-in segment, adaptation segment and transition segment, which is usually determined by the adaptation time of T=2s according to the vehicle speed (V), and can be estimated by S=VT/3.6m; The exit section should also have transition lighting, which is the same as the entrance section in two-way traffic.

(3) There should be no enhanced lighting at the entrance and exit at night, and street lamps should be set outside the cave, with the brightness not less than 1/2 of the basic brightness inside the cave; Emergency lighting shall be provided in the tunnel, and its brightness shall not be less than 1/10 of the basic brightness.

(4) According to the provisions of China JTJ026-90 Code for Design of Highway Tunnel, the length of tunnel entrance lighting interval and the road surface low brightness standard are designed according to the requirements in Table 1.

3. Design scheme of high-power LED tunnel light

3.1 Selection of LED light source

LED single watt lumen output is the basic index to determine whether LED tunnel lights have practical value. According to the requirements, the single watt lumen number of LED tunnel lights should reach more than 100 lumens. After nearly three years of rapid development of LED luminous efficiency, At present, the LED lighting efficiency that can be supplied by Luna Lighting in large quantities has reached more than 120-130lm/W, and the brightness is still improving. Table 2 provides the main technical parameters of the mass-produced high-power 1W white LED from several leading manufacturers in the world. OSRAM manufacturer LUWW5AM can be used as the design light source. The LED light source has a variety of different color temperatures to choose from, and the LED light source with a color temperature of 4000~6000K similar to the sunlight can effectively reduce the "bright hole" and "black hole" effect.

3.2 Light distribution design

According to the tunnel lighting requirements, different light distribution lamps are used according to different lighting segments. According to the optical principle and the characteristics of high directivity of LED light source, reasonable light distribution is adopted to reduce the power of lamps when meeting the requirements of brightness or illumination, so as to achieve the purpose of energy saving. Luna's new LED tunnel lights adopt transverse light distribution, which is more suitable for the lighting needs of the narrow road inside the tunnel.

(1) The introduction section, adaptation section, transition section and exit section at the entrance of the tunnel adopt asymmetric lighting (backlight lighting). Under the same illumination condition, compared with ordinary lighting, it can improve the brightness of the road surface by 121%. At the same time, it takes advantage of high directivity to strictly control the light intensity of large Angle direction and eliminate most of the glare.

(2) In the basic section of the tunnel, the current common distribution types of light distribution include concentrating light distribution, side beam light distribution, Lambert light distribution, etc. Different types of light distribution are suitable for different applications. For example, bat-wing light distribution should be selected for road lighting and spotlights should be concentrated light distribution. Due to the particularity of tunnel lighting, the arrangement density of lamps in tunnel lighting is very high, so the secondary light distribution form of lamps in tunnel lighting is different from that of common road lighting. In tunnel lighting, both Bat-wing light distribution and Lambert light distribution can meet the requirements of illuminance uniformity, mainly because the light spacing in tunnel lighting is relatively small. Figure 1 shows the C0 direction light distribution diagram of two types of LED tunnel lights. On the left is the road lighting and the bat-wing light distribution commonly used in tunnel lighting, and on the right is the Lambert type light distribution. Using batwing light distribution, that is, wide light strip symmetrical lighting lighting, can improve the brightness of the road surface by 64% and improve the uniformity of the road surface brightness compared with ordinary lighting under the same illumination condition.

3.3 Heat Dissipation Design

LED is a photoelectric device. For the high-power LED that is currently at the forefront of the world, only 15%~20% of the electric energy is converted into light energy during the working process, and most of the remaining electric energy is converted into heat energy, which increases the temperature of LED. On the other hand, the lumen output of LED decreases with the increase of LED junction temperature, while the LED life is shortened with the increase of junction temperature. Therefore, the heat dissipation of LED will be directly related to the use effect and life of tunnel lamps.

At present, the heat dissipation of high-power LED is mainly divided into three ways: (1) natural heat dissipation, fan forced heat dissipation and heat pipe heat dissipation fin technology. Natural heat dissipation using natural convection and thermal radiation, reliable structure, easy to do waterproof, but the lamp body itself of the structure design requirements are high. (2) Installing a fan forced heat dissipation mainly uses forced convection to achieve heat dissipation, heat dissipation speed is fast, but the cost and noise are high, it is difficult to do waterproof. ③ Heat pipe heat fin technology mainly uses heat pipe to rapidly transmit the heat generated by the LED to the heat fin to achieve the purpose of heat dissipation, no moving parts, system stability, but the cost is relatively high.

Because the tunnel has its unique nature compared with the general road, we use the heat pipe and heat fin technology for heat dissipation treatment, the vertical design of the heat channel, to achieve modular heat dissipation, so that the LED junction temperature is kept below 70℃, to ensure the LED long-term low light decline under the stable work, improve the maintenance factor of lamps, save maintenance costs.

According to the flow characteristics of the air flow in the tunnel, the heat dissipation cavity is asymmetrical ventilation design, to ensure the air convection heat dissipation, and reduce the car generated soot and other pollutants into the heat dissipation cavity, adsorption in the heat dissipation structure resulting in reduced heat dissipation efficiency.

3.4 Structural Design

With lightweight aluminum alloy shell, the lamp weighs less than 10kg. The protection level of LED light source cavity and electrical cavity is designed according to IP65, and the cooling cavity is designed according to IP23. The light source cavity and the heat dissipation cavity are separated in a reasonable way to avoid the mutual influence of heat flow between the light source cavity and the heat dissipation cavity. Because the air in the tunnel is not circulating, and the automobile exhaust is doped among them, the composition is complex, so the LED tunnel lamps should have good corrosion resistance, exhaust gas, smoke and other chemicals contained in the atmosphere in the tunnel. The outer surface of each structural component is anti-corrosion treatment, so that it meets the anti-corrosion requirements of GB/T7000.5.

3.5 Circuit Design

The forward volt-ampere characteristics of LED and ordinary diode are similar, the external forward voltage changes slightly, the forward current will have a great change, resulting in LED internal loss and heating rapid rise, seriously affecting the normal work and life of LED. In order to prevent this from happening, high-power leds generally must be powered by constant current. In order to improve the efficiency of the current source and reduce heating as much as possible, the input voltage of the current source must be controlled reasonably, so that its larger value is the same as the current after deducting the internal voltage drop, and also matches the total voltage required by the LED. The internal loss is small, the reliability of the current source can be guaranteed.

Tunnel lighting generally requires a large number of lamps, power consumption is huge, in order to save energy and reduce the "pollution" to the power grid, LED tunnel light driver also requires its power factor and harmonic must meet the relevant standard requirements, and give due consideration to electromagnetic interference and electromagnetic compatibility.

(1) Adopt the power supply with high conversion efficiency and high stability, the conversion efficiency is greater than 87%, the power factor is greater than 95%, and the switching power supply (96~264V) with strong resistance to the voltage fluctuation of the external grid, with the constant current circuit design, to drive the LED light source in the constant current way, to ensure the service life of LED.

(2) The control circuit suitable for tunnel lighting is used to adjust the power of the lamps according to different lighting segments and different time periods of the tunnel, so as to achieve good lighting effect and energy saving. Different currents are used to drive the inlet section, the adaptation section, the transition section and the outlet section of the tunnel to make it as close as possible to the requirements of the tunnel lighting curve, so as to achieve a better lighting effect; The inlet and outlet sections of the tunnel use timing adjustment function, through PWM dimming to adjust the output current or use double power supply, at night with a single power supply, so that its power is reduced to 50% of the daytime lighting, both in the day and night, effectively reduce the "bright hole" and "black hole" phenomenon.

4. Conclusion

The production and development, design and application of LED light source of high-power tunnel lighting, add wider market expansion of national railway and highway tunnel lighting, it has not only filled the gap of the application of new light source in our country, but also a step forward on the road of low carbon energy-saving and high efficiency, it is worth the popularization and application. Grand Canyon, Qinshang, Moon God Lighting and other LED tunnel light enterprises will show their skills in this market, continue to develop and produce more advanced LED tunnel lights, benefit the country and the people, and benefit the society.