1 luminous efficiency
Luminous efficiency refers to the ability of an electric light source to convert electrical energy into light energy, defined as the ratio of the luminous flux emitted by the lamp to the electrical power consumed, in lm/W. At present, the luminous efficiency of LED light sources is about 75 lm/W in the United States and Japan, and about 65 lm/W in domestically produced LEDs. The luminous efficiency of the high-pressure sodium lamp source is about 100 lm/W, which is 25 to 35 lm/W higher than that of the LED. The luminous efficiency of the 400W high pressure sodium lamp is as high as 120lm/W.
2 average life expectancy
The average life is the number of hours when a batch of light sources are lit to a total of 50% of the damage, in h. The average life of LED light source is more than 50 000h, but there are many factors affecting its life in practical applications. In addition to the materials, manufacturing processes and technologies of LED devices, the combination of LED particles, the design of lamps, the components of control circuits, Factors such as heat dissipation, water resistance, and dust resistance all affect the life of the LED light source. Therefore, the lifetime is more than 50 000h, and currently can only refer to the theoretical life of the LED light source. The average life of the high-pressure sodium lamp source is more than 24 000 h, and the high-pressure sodium lamp is a very mature product. The life of the supporting energy-saving magnetic ballast is greater than 50 000 h, and the ballast of the sodium lamp source can still be used after the end.
3 luminaire utilization factor
The luminaire utilization factor refers to the utilization efficiency of the light flux emitted by the light source through the illuminator to distribute the light twice. The urban road lighting design standard stipulates that the lamp utilization factor is 70%. The single power of the LED is small, and the single 1W is considered to be high power. In addition, the LED light source has a small emission angle and a strong directivity of the light source. In combination, hundreds of LEDs can be used in combination in a single lamp to replace the high-pressure sodium lamp, which brings the matching problem between the LED combination light source and the LED lamp. Some common LED lamps, some simply flatten the LEDs on the reflector and fold it into an angle to increase the illumination surface; some combine several high-power LEDs, use the convex lens to refract the illumination angle, but the use of lamps The coefficients are all low. The high-pressure sodium lamp source is a line and column type illuminating source, that is, omnidirectional radiation in the entire space, and the secondary distribution of light can be better performed by the refracting of the luminaire reflector, so the utilization coefficient is high.
4 Light distribution curve of the luminaire
The luminaire must have a batwing-shaped light distribution performance, because the distance between the two lamps in the longitudinal direction of the road is generally about 40m, and the luminaire must illuminate the light to more than 20m, forming a cross between the two lamps to avoid darkness between the two lamps. Area.
LED road luminaires are limited by the directionality of the illuminating source, and the illuminating source is too small and numerous. It is difficult to achieve the ideal batwing light distribution requirement. Its maximum light intensity is within 15°, and most of the light is directed to the light. The lower end of the road surface cannot cover the dark area between the two lights, as shown in Figure 1.
The light source of the high-pressure sodium lamp is not limited by the directionality, and the batwing shape is formed by the secondary distribution of light, and its maximum light intensity is about 60°~65°. It can illuminate the light in a farther direction, covering the dark area between the two lights, as shown in Figure 2.
5 Shield's degree of protection
The degree of protection of the luminaire is indicated by IP, which is the degree of dustproof and waterproof sealing of the luminaire. General luminaires are required to be IP55~IP65, and both types of luminaires can meet this requirement.