Using lightweight aluminum casing can keep the weight of the entire lamp body under 10kg. LED lighting chamber and electrical cavity can be designed in the IP level of 65 and IP 23 design for the cooling sections. Lighting chambers and cooling sections should utilize reasonable isolations, preventing the interference between these two parts. Due to the poor ventilation inside the tunnel, air composition is relatively complex, abundant vehicle exhaust, waste gases and other toxic chemical gases mixed up within it. It is necessary for high-power LED tunnel lights to be more reliable and corrosion-resisted. Normally, before leaving factories, anticorrosion treatments should be carried out on these LED tunnel lights.

 

 

Circuit design:

LEDs’ voltage-current characteristics are similar to ordinary diodes. The tiny vibrations of external forwards bias voltage will cause huge changes on input current, increasing the internal working temperature dramatically and consequently reduce the service life of LED lighting products. In order to prevent this from happening, high-power LED lights must be supplied by constant current (including high-power LED tunnel lights). On other hand, in order to increase the efficiency of power suppliers, the input voltage should be under strict controls, limiting the peak value of input voltage to match up with LEDs after a certain potential drop.

 

Generally, LED tunnel lighting fixtures consumed more power than other lamps. In order to reduce the power grid pollution, many countries have strict regulations for the power factor (PF) and harmonic content of high-power LED tunnel lights.

1)       Use high conversion, reliable power suppliers. Normally, only power suppliers with a converting efficiency larger than 87% and a PF lager than 95% (powerful in resisting external fluctuations from the power grid) are competent for these high-power LED lighting appliances. These power suppliers are usually equipped with constant-current circuit design, using constant-current to drive LED lighting sources.

2)       Adopt suitable control circuits for tunnel lighting, arranging different lighting modes for different sections. Experienced designers should choose different LED tunnels lights (different power consumption) for different sections. For example, in order to effectively reduce the glare, tunnel lights that used in entering/leaving sections should have a lower brightness (power consumption). Therefore, lamps in different sections should be powered by different drives, make them as close to the tunnel lighting curve requirements to achieve the best lighting effects. Timing adjustment on the tunnel entrance and outlet is suggested. Adjust output current through PWM or use double power supplies. Use single power supply during the night, reducing the power consumption by 50% compared with daytime.

LED is a type of photoelectric devices. Take the existing most advanced high-power LED chips for instance, the conversion from electrical energy to optical energy is only 15%-20%, far less than the requirements of most industrial applications and commercial applications. The rest 85%-80% energy will be transformed into heat, keeping LEDs in an over-heated state. That is the reason why most high-power LED lighting products have relatively short service lives. On the other hands, the luminous flux (lumen output) of LED lights will be reduced with the increase of PN junction temperatures. Thus an incompetent cooling design may dramatically cut down the lighting effect and working time of high-power LED tunnel lights.

 

 

Currently, there are three major solutions for cooling technology of high-power LED tunnel lights: 1) natural cooling. Adding fans/ventilators and heat pipes/sinks to assist cooling. Natural heat dissipation is base on natural convection and thermal radiation, reliable structure, waterproof, but strict in the structure design, cannot be easily handled. Normally, the practical effects are far less than the theoretical results. 2) Mandatory cooling through fans/ventilators on the base of forced convection. This method can provide a much faster cooling effect, but generate more noise and cost a lot, hard for waterproof. 3) Mandatory cooling through heat pipes/sinks. This technology takes the use of heat pipes to conduct unwanted thermal energy to heat sinks/pins to realize a rapid thermal dissipation. There are no other motion compartments and the entire system is more stable, but correspondingly cost a lot.

 

Different from ordinary roads, tunnels have many special properties. Mandatory cooling with the help of heat pipes and heat sinks would be the most suitable cooling technology for high-power LED tunnel lights among three. The vertical design of heat dissipation channel can realize the modularization of cooling section. Normally, high-power LED lamps using this cooling method can maintain a working temperature below 70℃, keeping LED chips working in a stable low-light-attenuation state, improving the maintenance factor to save more maintenance costs.

 

According to the airflow characteristics within tunnels, scientists usually made asymmetry ventilation designs, ensuring the air convection cooling. Meanwhile these asymmetry designs also can reduce the mass of soot and other pollutions generated by vehicles to enter the cooling chamber. These dusts may probably absorbed by cooling devices and reduce heat dissipation effects.