Due to their low cost and ease of use, incandescent lamps continue to be common sources of lighting. But they have low efficiency, low reliability, so they are increasingly being replaced by more efficient fluorescent or LED models. In order to correctly make a replacement without losing the quality of lighting, it is important to analyze the technical characteristics of incandescent lamps.
Light bulb options:
- light flow;
- power consumption;
- light output;
- color rendering index and color temperature;
- life time;
- ripple factor;
- Operating temperature range.
In addition, additional design characteristics of the lamps are important, such as the type of base, degree of protection, dimensions.
Consider all these indicators in relation to incandescent lamps.
Efficiency
An incandescent lamp uses the phenomenon of light emission by a heated material (tungsten filament). If the body is heated to 570 ° C (red color), then light will come out in the visible range of electromagnetic waves. In order for the emission spectrum to fill the entire range of visible light (from red to violet), the temperature of the emitter must be much higher. The choice of tungsten is just due to the fact that it has the highest melting point (3410 ° C) among metals. It can withstand 2000-2800°C without breaking down.
Taking into account the relative spectral sensitivity curve of human vision, the most suitable for illumination is sunlight, which is characterized by a temperature of the upper layer of the Sun of 5770 K.
Since the temperature of the filament in the light bulb is lower, the maximum radiation is shifted towards the violet color. Therefore, most of the luminous flux of such a lamp lies in the UV radiation region, and no more than 5% is emitted in the visible part of the range. Therefore, the value of light output, which characterizes the efficiency of converting the power supplied to the lamp into light, is small and amounts to 10-15 lm / W.
light quality
The light quality of a light bulb is determined by the color temperature and color transfer coefficient.
The color temperature indicates the temperature of a black body, which has the same color as the radiation of a given heated object. This indicator characterizes the shades of light. For an incandescent lamp, the color temperature is usually 2200-2900K. Such a light bulb emits a yellowish light, different from daylight. It has been proven that such light in the evening suppresses the release of melatonin, a regulator of circadian biorhythms, in humans, which makes such light more comfortable.
The color rendering index characterizes the proximity of the color illuminated by a given bulb of an object to its true color when illuminated by a standard source. For an incandescent lamp, the value of this coefficient is equal to the maximum value of 100, since it is the standard for comparing this indicator.
Life time
Compared with analogues, incandescent lamps have a short service life. Those. they burn out faster and faster. This is due to the evaporation of the tungsten layer during the operation (heating) of the light bulb. The thread thins and breaks.
In addition, when the lamp is turned on, the resistance of the tungsten filament is less than the resistance of a working light bulb, which leads to the formation of a current surge. And this degrades the quality of the thread.
The lamp life is 1000 hours. After working for 750 hours, its light output is reduced by 15%. Even a small increase in the supply voltage can greatly reduce the service life.
To assess this effect, you can use the empirical formula:
(T 0 /T)=(U 0 /U) 13
where: U 0 – operating voltage, V;
U is the mains voltage, V;
T 0 – passport service life, hour;
T is the service life at mains voltage U.
If U 0 \u003d 220 V, and U \u003d 230 V, then the lamp life will be almost halved and will be equal to only 0.56 of the nominal.
This is confirmed by the frequent burnout of light bulbs in the entrances and on the stairs. This is due to the fact that such bulbs are on at night when the load on the network decreases and the voltage in the network rises.
To increase the reliability of such lamps in non-residential premises or on stairs, they can be used at reduced voltage or with a diode connected in series. A more expensive option is to turn on the soft start device. Such a device gradually increases the voltage and eliminates the occurrence of current surges.
Ripple factor and operating temperature
Incandescent lamps are powered by a network with a frequency of 50 Hz. When the lamp is operating, its filament either heats up or cools down. Accordingly, the brightness either increases or decreases. Since these oscillations occur with a high frequency, the human eye does not notice these oscillations. However, these pulsations affect human fatigue. Therefore, workplace lighting standards contain requirements for light pulsations. For small work, these ripples should not exceed 10%, and for low-responsibility work -25%.
Studies have shown that the pulsation of lamps depends on their power and ranges from 1 to 4%. The largest ripple was found in lamps with a power of 40 watts.
Since the efficiency of incandescent lamps is small, they emit a lot of heat. Experiments have shown that after 15 minutes of continuous operation, the bulbs of the light bulb become very hot. The temperature of a lamp with a power of 40 W reaches +120 ° C, and 95 W – up to + 210 ° C.
Volt-ampere characteristics
The current-voltage characteristic of an incandescent lamp is non-linear. This is due to an increase in the resistance of the tungsten filament with an increase in the current flowing through it and the temperature. This automatically stabilizes the operating point of the lamp. Therefore, it does not require any additional ballast devices.
Design
The incandescent lamp consists of 11 structural elements.
Various types of plinths are used for connection to the power supply . There are several standards for the types of socles; European ones are used in our region. The most common Edison threaded bases are E14 (minion), E27, E40. There are also 2-pin bases and bayonet bases.
The bulb of an incandescent lamp can be of different sizes, which is affected by the power of the light bulb. By color, it can be transparent, matte, mirror, painted.
Some characteristics of incandescent lamps are incorporated in their designations:
- B – vacuum;
- B – bispiral;
- ZK – mirror;
- Ш – ball;
- C – candle.
New Generation
The main tasks in the design of new generation incandescent lamps:
- increase in efficiency;
- improved reliability;
- security enhancement.
To reduce the evaporation of tungsten, the lamp is filled with gas. For example, iodine vapor is used in a halogen lamp. This allows you to increase reliability and light output. A mixture of argon with nitrogen, krypton, xenon is also used. These models are more expensive, as their gas has a low thermal conductivity, thereby increasing the brightness.
The quality of light is also increased constructively. The flask is made of glass with the addition of neodymium.
Minuses
- Low efficiency. Light output is only 10 lm/W. For fluorescent lamps, this parameter is 50 lm / W, and for LED – 80 lm / W.
- Low reliability. The service life is 1000 hours. For fluorescent lamps, this parameter is 8,000 hours, and for LED – 50,000 hours.
- High operating temperature. For powerful lamps, the temperature can reach + 210 ° C. For luminescent and LED lamps this value is +60°С…+70°С.
- Compared to LED lamps, incandescent lamps are fragile and do not tolerate vibration well.
pros
- Relative cheapness. The cost of an incandescent lamp is 30-40 rubles. The cost of luminescent – 150 rubles. The cost of LED – 500 rubles.
- High level of color rendering. The color rendering coefficient is 100. For fluorescent and conventional LED lamps, this coefficient is much lower. The lamp emits a comfortable light that does not disturb human biorhythms.
- There is no need to connect control gear. A choke and a starter are needed to start a fluorescent lamp, and a power supply is needed for stable operation of an LED lamp.