Light Emitting Diode (LED), compared with traditional light sources such as incandescent lamps, has the characteristics of low power consumption, long life, small size, light weight, low operating voltage, short response time, and pure color. As a new light source, LED light source is rapidly entering the field of illumination. It has the characteristics of high luminous efficiency, low energy consumption and long life. It has obvious advantages in green low carbon and energy saving. At present, the rapid development of urban underground rail transit has become an important way to alleviate the pressure on urban pavement traffic. With the rapid development of the LED industry and the development strategy of green and low carbon in the corresponding countries, LED lamps and light sources will be rapidly applied to the lighting of underground rail transit, and the replacement of traditional light sources and lamps will be gradually completed.
Advantages of LED light sources for subway car lighting
First, LED light sources have an advantage in the optical design of the interior lighting fixtures. In lighting optics engineering, light and human life must be perfectly integrated, and the lighting method is transformed into space lighting. Through different designs, the environment or space atmosphere is created and formed to form system lighting. It combines science and artistry, and in visual art, people can understand, understand and express the theme of light from a new perspective. The LED light source belongs to the Lambertian light source, and the light has a certain directivity. The light can be easily controlled, and the light can be distributed according to specific optical requirements. Since the light emitting area is small, the lens or the reflector can be used to properly distribute the light, and Diversification of the functions and appearance of the luminaire enables the LED to be well applied to the various lighting environments in the cabin.
Secondly, LED luminaires are easier to implement intelligent control of compartment lighting. As a semiconductor electronic device, LEDs are easily integrated into intelligent control systems for intelligent dimming, color grading, and remote control. Intelligent lighting methods can provide different lighting solutions at any time according to different optical, aesthetic, human psychology and physiology needs; intelligent lighting methods can also control lighting energy consumption in an optimized way in terms of energy saving. Improve the energy saving and emission reduction effect of LED. Future semiconductor lighting devices will also be developed in the direction of environmental and optical adaptation, and meet the needs of different lighting through the intelligent adjustment of the light-emitting devices or the lamps themselves. Furthermore, the use of LED luminaires will make it easier to maintain the interior lighting. LED light sources have a longer life and lower light decay than conventional light sources, significantly extending the life cycle of the fixture and reducing maintenance. At the same time, when the LED light source exceeds its own life limit, the LED light source will not be extinguished immediately and cause illumination failure, which provides safety and time guarantee for the lighting maintenance of the place. With the continuous advancement of LED chips and packaging technology, its performance will be greatly improved, which will be more conducive to the lighting maintenance of places and facilities.
Basic requirements for LED light sources used in subway car lighting
First of all, the LED light source used for subway rail transit lighting should have high security features. Metro vehicles are important means of transportation for urban residents. Safety should be improved. When selecting LED light sources, safety should be evaluated. In the compartment lighting, low-voltage and low-current driving, high temperature resistance and low thermal resistance should be used. A bio-safe light source to avoid potential safety hazards and damage to the human body during use. Secondly, the LED light source used for subway rail transit lighting should have high optical quality. The luminous efficacy of the light source is always an important evaluation parameter. The long-term operation of the subway vehicle consumes a large amount of energy. The LED light source with higher luminous efficiency can more clearly reflect the advantages of energy saving and emission reduction. In addition, the LED light source also has good performance in terms of color temperature stability, color rendering, and color tolerance. The stability of optical parameters such as color temperature and color rendering, in addition to ensuring the stability of the interior lighting effect of the car, can keep the passengers in a comfortable state of mind; the color tolerance of the LED light source will directly determine the effect of the interior lighting of the car, and a reasonable selection of the light source The range of color tolerances will ensure the color consistency of the lighting fixtures and maintain good lighting. Finally, the LED light source used for subway rail transit lighting should have high reliability. Due to the long working hours and high frequency of subway vehicles, the workload of vehicle maintenance is large. Therefore, the internal equipment requirements are good maintainability, and even the maintenance requirements of the lamps are required. The lamps of subway vehicles are always in strong vibration. Working under conditions of high sealing and low heat dissipation, the reliability requirements are naturally different from those of ordinary lighting fixtures. Therefore, the bracket material, package structure and production process of the LED light source itself are also very high requirements. In order to ensure the reliability meets the requirements, the LED light source must be fully evaluated for reliability to ensure normal operation under harsh conditions.
Optical design of subway train lighting fixtures using LED light sources
Due to its small light-emitting area, LEDs can be designed with a secondary lens. In the design, the size structure of the luminaire will affect how the lens is lighted. The advantages and disadvantages of the light distribution will directly determine the lighting appearance and effect of the luminaire. In this design case, the optical space of the luminaire is low, the illuminating surface is large, and the light source needs to form a wing. The type of light distribution meets the requirements, as shown in Figure 1.
Through the light distribution of the lens, the light of the LED is evenly distributed to the light-emitting surface of the lamp, and the light trace is shown in FIG. 2 .
Figure 3 is the surface brightness curve of the same lamp using LED light source and fluorescent tube respectively. It can be seen from comparison that the surface of the lamp using fluorescent tube has obvious brightness peak, while the edge part has darker brightness and poor uniformity, and the LED light source After the lens is lighted, the transition of the surface brightness of the lamp is relatively smooth, and the uniformity is obviously improved, which not only improves the aesthetics of the lamp, but also reduces the glare value.
Lighting design of subway cars
In the lighting design of the interior of the subway car, the appropriate illumination and uniformity of illumination can improve the visual comfort of the passengers and avoid visual fatigue; the appropriate environmental contrast and brightness can effectively improve the visual sensitivity of the passengers; the soft lighting of the lamps and the lower The spatial glare value enables the human eye to quickly complete the visual adaptation; the high color rendering index can restore the color of the object and improve the color resolution of the human eye. In the design case design of actual lighting, it is necessary to take into account the functionality and aesthetics. Under the premise of keeping the train style consistent, the parameters and arrangement of the lamps are reasonably adjusted to ensure the best lighting effect. In ordinary trains, in order to provide a good visual environment, the color temperature of the light source should be selected from 4000K natural white light, the color rendering index is above 80, and the average horizontal illumination of the car floor should be 400lx or more, in order to satisfy passengers reading, reading newspapers and information. For the visual requirements of browsing, the vertical illumination of the work surface must reach 300lx, and the glare value should be controlled below 25.
Figure 4 is a pseudo color diagram of the interior lighting of the subway car in this case. The luminaire is assembled on both sides of the top of the car, extending linearly in the length direction, and is well integrated with the structure of the car. Through illumination analysis, the illuminance distribution of the ground is as shown in Fig. 5. It shows that the average illumination of the subway car floor can reach 402lx, the minimum illumination/maximum illumination value is 0.833, and the illumination level and uniformity have good performance. The glare value evaluation points are set at different positions in the subway car to evaluate the glare value of the passenger's eyes. The result is shown in Fig. 6. The maximum is 19, the minimum value is less than 10, and the glare is good.
Actual lighting effects and analysis
summary
In terms of optical design, lighting quality and intelligent control, LED light source has inherent advantages compared with traditional light sources, and can be optically designed according to the needs of lighting to provide passengers with high-quality lighting environment. The high reliability, high safety, high optical utilization and long life of the LED light source can greatly reduce the maintenance and operating costs of the cabin lighting system, and have great social effects in energy saving, low carbon and environmental protection.
Advantages of LED light sources for subway car lighting
First, LED light sources have an advantage in the optical design of the interior lighting fixtures. In lighting optics engineering, light and human life must be perfectly integrated, and the lighting method is transformed into space lighting. Through different designs, the environment or space atmosphere is created and formed to form system lighting. It combines science and artistry, and in visual art, people can understand, understand and express the theme of light from a new perspective. The LED light source belongs to the Lambertian light source, and the light has a certain directivity. The light can be easily controlled, and the light can be distributed according to specific optical requirements. Since the light emitting area is small, the lens or the reflector can be used to properly distribute the light, and Diversification of the functions and appearance of the luminaire enables the LED to be well applied to the various lighting environments in the cabin.
Secondly, LED luminaires are easier to implement intelligent control of compartment lighting. As a semiconductor electronic device, LEDs are easily integrated into intelligent control systems for intelligent dimming, color grading, and remote control. Intelligent lighting methods can provide different lighting solutions at any time according to different optical, aesthetic, human psychology and physiology needs; intelligent lighting methods can also control lighting energy consumption in an optimized way in terms of energy saving. Improve the energy saving and emission reduction effect of LED. Future semiconductor lighting devices will also be developed in the direction of environmental and optical adaptation, and meet the needs of different lighting through the intelligent adjustment of the light-emitting devices or the lamps themselves. Furthermore, the use of LED luminaires will make it easier to maintain the interior lighting. LED light sources have a longer life and lower light decay than conventional light sources, significantly extending the life cycle of the fixture and reducing maintenance. At the same time, when the LED light source exceeds its own life limit, the LED light source will not be extinguished immediately and cause illumination failure, which provides safety and time guarantee for the lighting maintenance of the place. With the continuous advancement of LED chips and packaging technology, its performance will be greatly improved, which will be more conducive to the lighting maintenance of places and facilities.
Basic requirements for LED light sources used in subway car lighting
First of all, the LED light source used for subway rail transit lighting should have high security features. Metro vehicles are important means of transportation for urban residents. Safety should be improved. When selecting LED light sources, safety should be evaluated. In the compartment lighting, low-voltage and low-current driving, high temperature resistance and low thermal resistance should be used. A bio-safe light source to avoid potential safety hazards and damage to the human body during use. Secondly, the LED light source used for subway rail transit lighting should have high optical quality. The luminous efficacy of the light source is always an important evaluation parameter. The long-term operation of the subway vehicle consumes a large amount of energy. The LED light source with higher luminous efficiency can more clearly reflect the advantages of energy saving and emission reduction. In addition, the LED light source also has good performance in terms of color temperature stability, color rendering, and color tolerance. The stability of optical parameters such as color temperature and color rendering, in addition to ensuring the stability of the interior lighting effect of the car, can keep the passengers in a comfortable state of mind; the color tolerance of the LED light source will directly determine the effect of the interior lighting of the car, and a reasonable selection of the light source The range of color tolerances will ensure the color consistency of the lighting fixtures and maintain good lighting. Finally, the LED light source used for subway rail transit lighting should have high reliability. Due to the long working hours and high frequency of subway vehicles, the workload of vehicle maintenance is large. Therefore, the internal equipment requirements are good maintainability, and even the maintenance requirements of the lamps are required. The lamps of subway vehicles are always in strong vibration. Working under conditions of high sealing and low heat dissipation, the reliability requirements are naturally different from those of ordinary lighting fixtures. Therefore, the bracket material, package structure and production process of the LED light source itself are also very high requirements. In order to ensure the reliability meets the requirements, the LED light source must be fully evaluated for reliability to ensure normal operation under harsh conditions.
Optical design of subway train lighting fixtures using LED light sources
Due to its small light-emitting area, LEDs can be designed with a secondary lens. In the design, the size structure of the luminaire will affect how the lens is lighted. The advantages and disadvantages of the light distribution will directly determine the lighting appearance and effect of the luminaire. In this design case, the optical space of the luminaire is low, the illuminating surface is large, and the light source needs to form a wing. The type of light distribution meets the requirements, as shown in Figure 1.
Through the light distribution of the lens, the light of the LED is evenly distributed to the light-emitting surface of the lamp, and the light trace is shown in FIG. 2 .
Figure 3 is the surface brightness curve of the same lamp using LED light source and fluorescent tube respectively. It can be seen from comparison that the surface of the lamp using fluorescent tube has obvious brightness peak, while the edge part has darker brightness and poor uniformity, and the LED light source After the lens is lighted, the transition of the surface brightness of the lamp is relatively smooth, and the uniformity is obviously improved, which not only improves the aesthetics of the lamp, but also reduces the glare value.
Lighting design of subway cars
In the lighting design of the interior of the subway car, the appropriate illumination and uniformity of illumination can improve the visual comfort of the passengers and avoid visual fatigue; the appropriate environmental contrast and brightness can effectively improve the visual sensitivity of the passengers; the soft lighting of the lamps and the lower The spatial glare value enables the human eye to quickly complete the visual adaptation; the high color rendering index can restore the color of the object and improve the color resolution of the human eye. In the design case design of actual lighting, it is necessary to take into account the functionality and aesthetics. Under the premise of keeping the train style consistent, the parameters and arrangement of the lamps are reasonably adjusted to ensure the best lighting effect. In ordinary trains, in order to provide a good visual environment, the color temperature of the light source should be selected from 4000K natural white light, the color rendering index is above 80, and the average horizontal illumination of the car floor should be 400lx or more, in order to satisfy passengers reading, reading newspapers and information. For the visual requirements of browsing, the vertical illumination of the work surface must reach 300lx, and the glare value should be controlled below 25.
Figure 4 is a pseudo color diagram of the interior lighting of the subway car in this case. The luminaire is assembled on both sides of the top of the car, extending linearly in the length direction, and is well integrated with the structure of the car. Through illumination analysis, the illuminance distribution of the ground is as shown in Fig. 5. It shows that the average illumination of the subway car floor can reach 402lx, the minimum illumination/maximum illumination value is 0.833, and the illumination level and uniformity have good performance. The glare value evaluation points are set at different positions in the subway car to evaluate the glare value of the passenger's eyes. The result is shown in Fig. 6. The maximum is 19, the minimum value is less than 10, and the glare is good.
Actual lighting effects and analysis
Figure 7 shows the actual lighting effect of this case. The surface brightness of the luminaire is uniform and the light is soft. The illumination and brightness distribution of the whole illumination space is even and the visual comfort is good. Through actual tests, for the same train compartment, when using LED lamps for illumination, the average illumination on the ground in the compartment is 410lx, and the power consumption is 960W. When the lamps using fluorescent tubes are illuminated, the average illumination on the ground in the compartment is 350lx, and the power consumption is At 1730W, LED lamps can exceed the lighting level of fluorescent tube lamps with nearly half of the power loss, and the lighting quality has been greatly improved, which is enough to reflect the advantages of LED lamps in train compartment lighting.
summary
In terms of optical design, lighting quality and intelligent control, LED light source has inherent advantages compared with traditional light sources, and can be optically designed according to the needs of lighting to provide passengers with high-quality lighting environment. The high reliability, high safety, high optical utilization and long life of the LED light source can greatly reduce the maintenance and operating costs of the cabin lighting system, and have great social effects in energy saving, low carbon and environmental protection.
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