Fluorescent fluorescent lamps: characteristics, types, principle of operation

Fluorescent lamps are a gas-discharge light source where an electrical charge in mercury vapor creates ultraviolet radiation. It is converted into visible radiation by means of a phosphor. Its role is played by calcium halophosphate and other elements. The luminous efficiency of fluorescent lighting is several times higher than that of an incandescent lamp with exactly the same power.

Classification of fluorescent lamps

Fluorescent bulbs last approximately 5 years, provided the number of starts is limited to 2000. That is, during the warranty period of 2 years, there are no more than 5 inclusions per day. The most common are high and low pressure gas discharge mercury lamps. The characteristics of fluorescent lamps are as follows:

1. High pressure models are used for street lighting and high power lighting fixtures;
2. Low pressure modifications are used for residential and industrial premises.

The low pressure mercury discharge lamp is a phosphor coated glass tube. The product is filled with argon and amalgam at a pressure of 400 Pa. Plasma displays are another modification of fluorescent lamps.

Scope of lamps

Fluorescent lamps are widely used to illuminate public buildings. Since then, as modifications of the contact type appeared, equipped with electronic ballast, they began to be actively used instead of the usual lighting devices.

It makes sense to use these devices for general lighting, especially if you have to work with a large area. Thanks to this, it is possible to improve lighting conditions and reduce energy consumption by 80%.. This extends the life of the lamps.. They are used to:

• local lighting of the working space;
• illumination of facades;
• illuminated advertising.

Such lighting devices acted as the sole source of illumination for LCD screens until the advent of LEDs.

Pros and cons of lighting equipment

These devices are popular, as they have a whole set of advantages. What is their advantage over incandescent lamps:

• high luminous efficiency and good efficiency indicators;
• diffused light;
• a wide range of shades of light;
• long service life.

They also have some disadvantages.. These include:

• potential health hazard due to mercury content;
• flicker with double the frequency;
• a change in the spectrum that occurs over time, caused by negative transformations in the phosphor;
• the presence of an additional device for the lamp trigger;
• reduced power indicator, which creates a load on the power grid.

How the device works

When the device is turned on, an arc discharge is formed. It is located at opposite ends of the lamp between two electrodes. The device is filled with mercury vapor and inert gas. After the passage of an electric current, ultraviolet radiation is formed, which is invisible for the human eye.

From the inside, the walls of the device are covered with a phosphor. This is a special substance that can absorb ultraviolet radiation. Visible light emanates from it. By changing the composition of the phosphor, it is possible to change the shade of the lamp glow. Phosphor function performed mainly by orthophosphates and calcium halophosphates.

Features of marking

The perception of color by the human eye directly depends on the level of illumination. If it is small, then red is perceived as the worst. At the same time, a person is quite well able to discern a blue tint. The average illumination of residential buildings is 75 Lux. In workrooms and offices, it is equal to 400 Lux.

If daylight is in the 5,000 to 6,500 Kelvin range, it will appear blue in low light. Light with a color temperature of 3000 Kelvin looks the most natural at illumination from 50 to 75 Lux. If the illumination is 400 Lux, the resulting light appears yellow. The most natural is light with a temperature of 4 to 6 thousand. Kelvin.

The industry produces various modifications of lamps. Marking allows you to figure out for which zone a particular model is suitable. Digital code indicates parameters such as light quality, color temperature, and color rendering index. The first digit indicates the color rendering index.

For fluorescent lighting devices, this characteristic varies from 60 to 98 Ra. Accordingly, the higher the index, the more reliable the color rendition can be considered. The second and third digits indicate the color temperature of the model. For example, if there is a marking of 827, this indicates that the color temperature here is 2700 Kelvin, and the color rendition is 80 Ra. These parameters correspond to those of an incandescent lamp.

Electrical connection

Discharge lamps of all types are not directly connected to the mains. This is their main difference from incandescent lamps. There are two reasons for this:

1. High resistance when cold. Due to this, a high voltage pulse is required to ignite the discharge.
2. After the discharge occurs, the lighting device forms a negative resistance. Therefore, if you turn on the resistance in the circuit, a short circuit will occur, and the lighting device will fail.

To solve these problems, ballasts are used. These are ballasts of a special type. The most common connection methods today are:

1. the use of electronic ballast;
2. use of an electromagnetic ballast in combination with a neon starter.

Description of electromagnetic ballast

The device is an electromagnetic type choke. It has an inductive reactance. It is connected to the lamps in a certain sequence. A starter, which is a neon lamp, is connected to the filament. Its design includes a capacitor and bimetallic electrodes. Today, the advantages of electromagnetic balance are long service life, ease of use and reliability. At the same time, some drawbacks are also revealed, for example, a long start-up. It varies from 1 to 3 seconds depending on how worn out the device is.

The electromagnetic balance consumes a large amount of energy due to its choke. Sometimes there may be a low-frequency hum of the magnetic wire plates. Does not add advantages and flicker with twice the frequency of the network. This can adversely affect human vision. These lighting fixtures, including ballast, must not be used to illuminate mechanisms and moving parts of locks. It is also important to point out the impressive dimensions of the device. The mass of such ballast is several kilograms. If temperatures are below zero, the device may not start.

Starting with electromagnetic ballast and starter

The classic scheme provides for the connection of an electromagnetic balance together with a starter. The latter is a neon lamp with a capacitor connected in parallel, hidden in the case. The electrodes are initially in the open state. The starter is connected parallel to the lamp so that an electric current passes through the lamp spiral. This happens after the electrodes are closed.

A large capacitor is connected in parallel. It is necessary to create a resonant circuit that forms a pulse of long duration. Due to this, it is possible to light the lamp. When the starter is opened, the lamp spirals are in a hot state. A sufficient surge voltage must be provided to ignite the discharge.

The operating voltage of the lighting fixture is low as it drops across the choke. That is why a higher extinction voltage level is set in the starter lamp initially. As a result, the starter does not operate again.

The operating voltage of the lighting device gradually increases, when the end of its life is approaching, the voltage may increase. Due to this, a characteristic continuous flashing of a failed lamp is formed. As soon as it goes out, you can see the glowing cathodes installed over the entire area of ​​the starter.

Electronic ballast and its properties

This element is responsible for powering the lamp with electric current. In this case, a voltage of the off-network frequency is formed, which varies from 50 to 60 Hertz. High frequency levels from 25 to 133 kilohertz are provided here, so blinking, irritating to the eyes, is eliminated.

It is possible to distinguish cold and hot start of the model. In the first case, the lighting device is closed after switching on. This method is used when the lamp is rarely used. Frequent use of this technique is not recommended, as it damages the electrodes.

The second type of start involves preheating the electrodes. The lamp lights up after 1 second, but it also has a longer service life, especially when regular use of the device is expected.

Factors predisposing to breakage

The electrodes in the design of the lighting device are a spiral of a tungsten filament. They are covered with a layer of alkaline earth metals. It is necessary to ensure the stability of the discharge. During operation, this layer continuously crumbles and evaporates.

This happens especially intensively during launch. This is why all fluorescent lighting fixtures have a specific lifespan. It depends on the ignition speed and the quality of the electrodes. It exceeds the life of the incandescent lamp. Darkening forms at the ends of the product, which intensifies as the time of failure approaches. After complete burnout of the metal paste, the voltage rises abruptly. For this reason, the circuit in which the lamp operates is not capable of providing high voltage for combustion.

Electromagnetically balanced lamps have an increased voltage when the end of their life is approaching. By this time, the paste has completely burned out on one of the electrodes. As a result, the starter starts to work constantly.

When the starter fails, a shunting of the lamp along the circuit is formed, so the ignition of the discharge becomes impossible. Only the filaments are left to work, and for this reason the electricity consumed by the lighting device becomes higher.

When it comes to devices with electronic ballast, the mass of electrodes involved in the work is actively burned out. The threads overheat and fail. In high-quality models, auto-shutdown of a burned-out device is provided. In low-quality modifications, such protection is absent. Also, in such devices, a capacitor is installed, designed for a voltage close to the voltage of the new lamp. As the product ages, the pressure rises and a breakdown forms in the condenser. For this reason, the ballast transistors also fail.

Phosphor emission spectrum

Cheap lamps use a halophosphate phosphor. It produces blue and yellow colors. Much less red and green tones are emitted. This mixture appears to be white, but an incomplete spectrum can be seen when reflected. On the other hand, such devices have a high level of light output. There are also special fluorescent lamps. with different spectral parameters:

1. Fluorescent lamps. Most closely matched to natural color in daylight 5400 Kelvin. Most often, such devices are used in museums, printing houses, laboratories and dental offices.
2. Fluorescent lamps that are as close to sunlight as possible. If there is not enough light in the room, or if there are any important working operations, the use of these models is recommended. More often you can see these devices in banks, offices and shops. The lighting level is 6500 Kelvin.
3. Models for plants and aquariums. The spectral range here displays blue and red. The illumination level is from 5400 to 6700 Kelvin.
4. Models for the inhabitants of the aquarium. Radiation varies in the range of blue and ultraviolet light. Illumination also ranges from 5400 to 6700 Kelvin.
5. Decorative patterns. They form blue, red, green, yellow and crimson colors. Recommended for sterile production, shops for the manufacture of microcircuits.

There are also special models for tanning salons and beauty salons, counters in supermarkets, rooms where poultry are kept. Allocate ultraviolet modifications with black glass flasks. They are able to convert invisible radiation into light, creating the so-called fluorescence effect. Used in food and textile industries.