1. Luminous efficiency If an incandescent lamp works at […]
1. Luminous efficiency
If an incandescent lamp works at the melting point of tungsten (3 653K), if there is no loss of thermal conductivity and convection, the theoretical luminous efficiency can reach 53lm.W-1. What are the operating characteristics of incandescent lamps? The luminous efficiency of the actual incandescent lamp is much lower than this value. Take the current general lighting incandescent lamp with a rated life of 1000h as an example, and its luminous efficiency is 8~21.5lm.W-1.
What are the operating characteristics of incandescent lamps? The reason why the light efficiency of the incandescent lamp is so low is mainly because most of its energy becomes infrared radiation, and the proportion of visible radiation is very small, generally less than 10%.
2. Color table and color rendering
Ordinary incandescent lamps have a low color temperature, about 2800 K, and have a good color table. Compared with 6000 K sunlight, the light of incandescent lamp is yellowish and warm. The radiation of the incandescent lamp covers the entire visible light region, and its color rendering is second to none in the artificial light source, the general color rendering index Ra = 100.
3. Light switch
Under normal conditions, the light switch does not affect the life of the light. Only when the filament becomes quite thin after ignition, the mechanical stress caused by the rapid temperature change caused by the switch will damage the filament. But there is one thing to pay attention to when switching the lights, that is, the current of the light is very large at the moment the light is started.
This is due to the positive resistance characteristics of tungsten, and its resistance at operating temperature is much greater than that in the cold state (20 ℃). Generally, the thermal resistance of the filament of an incandescent lamp is 12-16 times the cold resistance. Therefore, when using large quantities of incandescent lamps, the lamps should be started in batches. What are the operating characteristics of incandescent lamps?
Ordinary incandescent lamps can be dimmed without limitation. The working temperature of the filament of the dimming lamp is reduced, so that the color temperature of the lamp is lowered, and the luminous efficiency of the lamp is reduced, but the service life is extended. Therefore, the advantage of long life comes at the expense of light efficiency. When the lamp is almost continuously dimmed, it is generally better to use an incandescent lamp with a lower power.
When the incandescent lamp works below 50% of the nominal voltage, the lamp hardly emits light. However, the energy loss at this time is still not small. What are the operating characteristics of incandescent lamps? Therefore, we suggest that when dimming to this depth, it is better to turn off the light instantly.
5. Influence of power supply voltage changes
When the power supply voltage changes, the operating characteristics of the incandescent lamp will change. For example, when the power supply voltage increases, the working current and power of the lamp increase, the working temperature of the filament increases, the luminous efficiency and luminous flux increase, and the life is shortened.