What does service life of glow lamps depend on?
Glow lamps from the moment of their invention traditionally apply not only to lighting of dwellings, but also in cars, the cinematographic equipment, different type pocket small lamps and other devices.
The normal household glow lamp consists of the exaggerated glass cylinder in which thread from high-melting metal is placed, is normal from tungsten. In order that thread of the lamp worked the long time, from its cylinder air is extorted and replaced with inert gas. In the cylinder thread is strengthened on special delays - holders.
The end of one of delays is removed through the lower reinforced part of the cylinder and soldered to contact in the center of the lower part of the socle, and the end of other delay is soldered to screw cutting on the socle. These soldered ends of delays are isolated from each other by vitreous insulating weight. The cylinder is pasted to the socle by special fire-resistant glue.
The lamp by means of screw cutting on the socle is screwed in the electrocartridge connected by wires to the room power supply network. At turning on of the switch which is in the lamp chain, electric current passes through thread and warms it up to the temperature of 2600...2700 °C therefore there is light radiation. In household lighting instruments glow lamps with power from 15 to 300 W are used.
Service life of the glow lamp fluctuates over a wide range because depends on very many factors: from quality of connections in the electrical wiring and the lamp, from stability of rated voltage, from availability or lack of mechanical impacts on the lamp, pushes, concussions, vibrations, from ambient temperature, from type of the used switch and rise speed of size of current when giving the power supply on the lamp.
During the long operation of the glow lamp its filament under the influence of high temperature of heating gradually evaporates, decreasing in the diameter, is torn (fuses). The filament heating temperature is higher, the more light is radiated by the lamp. At the same time process of evaporation of thread proceeds more intensively and lamp service life is reduced. Therefore for glow lamps such temperature of heat of thread at which the necessary luminous efficiency of the lamp and the certain duration of its service is provided is established.
The average duration of burning of the glow lamp at design stress does not exceed 1000 hours. After 750 hours of burning the luminous flux decreases on average by 15%. Glow lamps are very sensitive even to rather small increases in tension: at increase in tension service life decreases by only 6% twice. For this reason of the glow lamp, the lighting staircases, quite often fuse as at night the power supply network is a little loaded and tension is increased.
In one of the German cities there is the lamp in which one of the first glow lamps is twisted. She is more than 100 years old. But it is made with the huge safety margin therefore burns still. Presently bulbs of incandescence are issued in large quantities, but with very small safety margin.
The current throw arising at lighting inclusion often puts the bulb out of action because of small resistance in the cold state. Therefore at lighting inclusion the bulb should be warmed small current, and then to include at full capacity. The glow lamp fails, as a rule, at inclusion because of the small resistance of cold filament.
Let's consider small cunnings on extension of life to glow lamps.
Accounting of rated voltage
Now the industry makes glow lamps on which not one tension (127 or 220 V), and voltage range is specified (125...135, 215...225, 220...230, 230...240 V). Within each range the glow lamp gives the good luminous flux and is rather durable. Availability of several ranges is explained by the fact that operating voltage in network differs from rated: at the power source (substation) it is higher, and far from the power source is lower. In this regard, that lamps long served and well shone, it is necessary to choose necessary range correctly.
It is obvious that if tension is equal in your room network to 230 V, then it does not make sense to buy and install glow lamps on which the range 215...225 B is specified. Such lamps work with overheating and long will not serve as fuse prematurely.
- Influence of vibration on service life of lamps. Glow lamps which work in the conditions of vibration and are exposed to pushes, fail more often than working in the quiet state. If there is the need to use carrying, then it is better to carry out its movement in the switched-off state.
- Prevention of the cartridge in which lamps often fuse. Sometimes happens that in the chandelier the same lamp fuses, and during the work of the lamp the boss very hot. In this case it is necessary to clean and turn in central and side contacts, to tighten contact connections of the wires suitable to the boss. It is desirable to establish all lamps in the chandelier to identical power.
- Use of the diode for protection of the lamp. Very favourably on landings of houses to turn on glow lamps via the diode as the quality of lighting in this case has no essential value, and the lamp as shows operating experience, serve at the same time for years. And if you manage consistently with the attach diode the resistor, then it is possible to forget in general about the lamp for a long time. Council: for the 25 W glow lamp it is enough to use the resistor of the MLT with a resistance of 50 Ohms type.