Technical features of using LEDs

LED lampsModern have sufficient brightness, which could not be said about the LEDs of the previous generation, whose low brightness significantly limited their use. Currently,..

Efficiency. Coefficient useful action modern LED lamps is 22%. In addition to high efficiency, LED lamps also boast great durability, up to 50,000 hours, which in turn is equivalent to 17 years of operation, 8 hours a day. Modern have sufficient brightness, which could not be said about the LEDs of the previous generation, whose low brightness significantly limited their use. Currently, after the issue of LED brightness, their popularity has increased dramatically. Despite the high cost, but thanks to their high efficiency, service life and significant savings on electricity and installation work, LEDs are gaining more and more popularity. In addition, the long service life of LED lamps allows them to be installed in hard-to-reach places, this is especially true when using LEDs V . For more than 130 years of history, incandescent lamps, which have dominated the world of lighting technology all this time, have had big amount disadvantages: it is a fragile thread that can fail during shaking, and high percentage heat output, which significantly reduces the ratio useful power To luminous flux. The efficiency of conventional incandescent lamps is only 2.6%. A more technologically advanced fluorescent lamp has a slightly higher efficiency of 8.7% and has also made a significant contribution to energy savings. The use of fluorescent lamps has revealed several significant disadvantages: this and short term operation in real conditions, possible flickering, and possible refusal to turn on when low temperatures, as well as blinking when there is a lack of voltage. In addition, burnt out fluorescent lamps require special disposal. Fluorescent lamps They have an extremely negative attitude towards the intermittent cycle of operation, on and off.

have high efficiency, low power consumption and long service life, bright light, excellent illumination and no flicker. Due to their high performance characteristics they are becoming more and more widespread, they are especially often used in. Company Professional Light and Sound offers you a wide range of modernLED lamps And high quality reasonable price, based on qualityLED lamps(Cm:) .

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Recently I saw a payback calculator on one website LED lamps. I immediately became interested in how many years would it take for an LED lamp to pay for itself, since this moment Not every customer wants to install LED lamps.

According to the calculator, an office LED lamp should pay for itself in just 3.68 years. Now let’s check whether we actually get such a figure.

For the office, a CERTAIN manufacturer of LED lamps produces a recessed lamp with a power of 42 W, with a luminous flux of 3500 lm, efficiency = 94%, color rendering index 80. Such a lamp costs $ 175. This lamp completely replaces the lamp with fluorescent lamps LVO 4×18, which costs only $25. As you can see, the LED lamp for office premises 7 times more expensive than a lamp with fluorescent lamps.

First, let's compare the two lamps.

Now, based on these data, we will calculate the annual energy consumption and how many years will it take for the LED lamp to pay for itself. We have 2000 working hours a year (for an office worker). We will change fluorescent lamps after 10,000 hours, because... the luminous flux will begin to decrease.

The result was quite disastrous.

Why then did this happen?

Everything is very simple. The payback time of an LED lamp depends on the price of electricity and operating time. The higher the cost of kWh and the number of operating hours, the shorter the payback period.

After doing some reverse calculations, I realized that the manufacturers of LED lamps do not spare us at all (including designers, since we are also office workers), they force us to work seven days a week and set us the maximum estimated tariff for electricity. In general, they charged everything to the maximum to get minimum term payback.

In this case we will have the following result.

To be honest, I'm a little upset. I expected the payback period for the LED lamp to be at least 5 years. The manufacturer promises 3.68 years, but in reality it is about 10 years. Moreover, for 10 years, provided that the office operates seven days a week and at the maximum calculated rate.

The declared 70,000 hours for an LED lamp is just a theory, but in practice, who knows how it will behave in 5-10 years.

I think that by the time it pays for itself, and according to my calculations this is 10 years, this lamp will already be obsolete, although it will be in working condition.

IN current conditions manufacturers of LED lamps will only be FOR an increase in electricity prices, since the use of LED lamps directly depends on the price of electricity.

It is advantageous to install LED lamps in areas where the cost of electricity is high. I think this is more relevant for European countries.

Maybe I didn’t take everything into account or you have more accurate information on this topic?

P.S. I'm not against LED lights at all. I just love numbers. In my opinion, the cost of an LED lamp needs to be further reduced so that it can be used everywhere. An LED lamp has many advantages compared to a fluorescent lamp, but it also has one big drawback - the price.

Technical and economic indicators of lamps

The TEP of a lamp is significantly influenced by the type and quality of the optical systems of the lamp. The level of efficiency depends on the power factor of the ballast and the optical efficiency of the device, as well as the condition of the optics. A number of domestic equipment and most foreign samples have high coefficients. However, no matter how good these indicators are, the optics (transparent cover, diverging or converging lens and reflectors) become dirty during operation and undergo significant changes in surface structures, which leads to deterioration of parameters. This statement applies to all types of luminaires, regardless of whether ballasts are used or not.

In new lamps, optical efficiency ranges from 60 to 95%. As a result of practical observations and special laboratory examinations, it turned out that during the period of 1 year of operation, the optical efficiency decreases to 35% of its original value (and the main level of losses occurs in the very first days of operation). Within 2 years, optics lose from 50 to 65% of their original efficiency level.

The observed devices were operated outdoors (street lighting) on ​​the territory of the Republic of Tatarstan, under normal, non-extreme conditions. It is clear that if operating conditions require the operation of lighting equipment in conditions of increased dust or gas pollution, then the optical efficiency decreases at a faster rate.

*Measurements of optical and electrical properties were carried out by specialists from the TATLED Group of Companies at their own base.

(Luminous flux, Ф; Distribution of the total luminous flux over any 2 levels of luminous intensity or radiation angles within the radiation pattern, Ф(Ω),

Data on measuring equipment in Appendix 1.

As a rule, the task of protecting lamps (especially their internal volume) from unfavorable factors impact external environment is solved by manufacturers of lighting equipment by sealing between the housings of closed lighting devices and protective glass, as well as seals for wire entry points.

However, with more detailed study problems, it turned out that this was not enough to ensure proper insulation of the internal volume of the lamp. According to the laws of thermodynamics, in closed lighting devices there is a “breathing” effect associated with a change in air pressure enclosed in the internal isolated volume of the lighting device. When the light source of the device is turned on and the air trapped inside the device is heated, the pressure increases, and when it is turned off, the pressure drops. As a result of even an imperceptible defect in the seal, contaminated air is sucked into the internal cavity of the lamp. This phenomenon presents the possibility of dust, fibers and corrosive particles settling on the lamp bulb, reflector, inner surface, protective glass, diffuser and cartridge contact units. As a result, the lighting capacity of the devices decreases and they themselves fail within a short period of operation (for example, in some areas of metallurgical production, lighting devices are replaced annually, significantly increasing the cost of operating the lighting system).

LED lamps do not have the above disadvantage. The fact is that the LEDs used in such lamps do not require reflective reflectors.

In lighting devices using conventional light sources, a reflective reflector is built in, the shape of which cannot always be adjusted in accordance with the requirements of light distribution. Unlike conventional lamps LED devices use light sources that emit light energy not in all directions, but in one. The direction and intensity of the light flux is regulated by the location of the axes of the light emitter in a given direction and their number. The opening angle of the emitted radiation is adjusted using secondary optics (microlens).

Thus, the LED lamp is free from the disadvantages caused by losses in optical systems using omnidirectional light sources. That is, the Lumen/Watt ratio for LED lamps is more attractive.

Lumens measure the flow in all directions, i.e. in a solid angle of 4pi. One lumen is equal to the luminous flux emitted by a point isotropic source, with a luminous intensity equal to one candela, into a solid angle of one steradian (1 lm = 1 cd × sr)

A steradian is equal to a solid angle with its vertex at the center of a sphere of radius R, cutting out on the surface of the sphere an area equal to the area of ​​a square with side R (that is, R²). If such a solid angle has the form of a circular cone, then its opening angle will be approximately 65.541° or 65°32′28″).

If we assume that the calculated cone is directed directly at the illuminated object, then the rest of the light energy hits the illuminated surface through a reflector or optical lenses.
Candela (from Latin candela - candle), unit of luminous intensity International system units. Designation: Russian CD, international CD. Candela (unit of luminous intensity) - the intensity of light emitted from an area of ​​1/600,000 m2 of the cross-section of a full emitter in a direction perpendicular to this cross-section at an emitter temperature equal to the solidification temperature of platinum (2042 K) at a pressure of 101,325 n/m2.

Based on the above, to compare TEC lamps with a conventional light source and an LED lamp, it is necessary to introduce a correction for the difference in the efficiency of optical systems.

Consider as concrete example widely used lighting device RKU15-250 using DRL lamps and LED lamp.

To determine real lighting performance indicators, we make the following calculations:

According to the manufacturer, the efficiency of the RKU15 lamp is 65%. The light source (DRL-250 (V) lamp) has a luminous flux level of 13,200 Lumens. We get the level of luminous flux actually emitted by the device: 65% of 13,200 lm = 8,580 Lumens.

It is also necessary to take into account the accelerated loss of the DRL luminous flux level in the first 1000 hours of operation. From the graph below (according to VNISI data) it is clear that during the first 1000 hours of operation, the level of emitted luminous flux decreases by 15-20% of the initial value. From here we get Фv = 6,864 Lumens. During the further period of operation, degradation occurs less intensively.

The luminous flux level curve of LEDs used in LED luminaires also has an uneven characteristic. However, as you can see from the graph below (courtesy of OSRAM Opto Semiconductors), after a short dip the level gradually increases (Golden Dragon plus diodes).

Chart of device ownership costs over 5 years

The data is given taking into account the constant cost of electricity. Taking into account the growth of tariffs predicted by the Ministry of Economic Development, the point of intersection of the cost level curves will occur earlier than the period obtained by calculations (presumably 4 years).

An example of the use of DRL lamps and LED lamps for road lighting. Thanks to a more rationally distributed light energy, the road surface illuminated by LED lamps (picture on the left) is flooded more evenly.

Conclusion: the optical properties of luminaires using LEDs are noticeably superior in lighting parameters to luminaires with conventional light sources.

CONTROL EQUIPMENT (CONTROL EQUIPMENT).

Ballasts (ballasts) are a special product that is used to start and maintain the operation of a light source.

Structurally, the ballast can be made in the form of a single block or several separate ones.

Depending on the type of light source, ballasts are divided into:

• Ballasts for gas discharge lamps
• ballasts for halogen lamps(transformers)
• Ballasts for LEDs (LED drivers)

Depending on the type of device and operation of ballasts, there are:

• electromagnetic (EMPRA)
• electronic (electronic ballasts)

In addition to the optical parameters, the efficiency of a lighting device is significantly affected by the power factor parameter of the ballast.

For discharge lamp ballasts, this parameter (according to manufacturers) ranges from 0.6 to 0.9. The most effective today are electronic ballasts, since with the help of electronics the ability to ignite and control the glow can be done much more efficiently compared to inductive chokes. Ballasts for discharge lamps have been produced for a long time and, despite ongoing improvement, are well known to consumers, so they are not discussed in detail in this work.

In LED lamps, the ballast (LED driver) performs the function of a stabilizer direct current, voltage stabilizers and dimming (specialized).

Drivers can be divided into two main groups:

1. LED power supplies with constant stabilized output current (LED drivers) - designed to power LEDs (or LED lamps) connected in series.

2. Power supplies with stabilized constant voltage (LED transformers) - designed to power groups of LEDs that are already equipped with a current-limiting resistor, usually LED strips, rulers or panels.

In addition, since the industry produces LEDs designed for different meanings rated current, LED drivers are also divided according to this parameter.

The most common current values ​​are 350 and 700 milliamps.

The power factor of LED drivers from most manufacturers is 0.95. Separate LED required DC voltage 2-4V and several tens of mA current. A daisy chain array of LEDs requires more high voltage. The LED driver is the source of this voltage. It transforms 110-240V AC household power supply into low voltage DC to power LED systems.

There are increased requirements for the quality of LED control gear, since LEDs, being a semiconductor device, are extremely demanding on the quality of the power supply. Deviations from given parameters within 2-5% sharply affects the lighting and electrical properties of LEDs, and can lead to a significant reduction in the life of the crystal or phosphor.

Based on the foregoing, it is clear that the quality of LED control gear is initially high, and accordingly it is a product with high efficiency.

The vast majority of manufacturers' stated values ​​range from 0.90 to 0.95. Simple measurements confirm these values.

For dimming (changing the brightness of LEDs), the principle is usually used pulse width modulation(PWM).

In terms of efficiency and degree of reliability, ballasts for discharge lamps and ballasts for LED lamps differ only in the quality of the circuitry and the used element base, which ultimately implies a difference in the cost of the product. High-quality and expensive ballasts various types lamps are approaching a single indicator (close to 1).

Appendix 2 and Appendix 3 contain reviews from organizations that have implemented LED lamps as prototypes.

Conclusion: influence of efficiency Ballasts for overall efficiency lighting fixture for discharge lamps and for LED lamps there is no noticeable difference, and is determined only by the price of the product.

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When using LEDs as the main light source, the question arises - what power of lamps is needed for this. To answer this, you need to know what the efficiency of LEDs depends on.

LED element efficiency

In an ideal LED with 100% efficiency, each electron delivered emits a photon of light. Such efficiency is unattainable. In real devices, it is estimated by the ratio of the luminous flux to the supplied (consumed) power.

This indicator is influenced by several factors:

• Radiation efficiency. This is the number of photons emitted at the pn junction. The voltage drop across it is 1.5-3V. With a further increase in the supply voltage, it does not increase, but the current through the device and the brightness of the light increase. Unlike an incandescent lamp, it has linear dependence from the flowing current only up to a certain value. With a further increase in current, additional electric power is spent only on heating, which leads to a drop in efficiency.
• Optical output. All selected photons must be emitted into the surrounding space. This is the main limiting factor for increasing the efficiency of LEDs.
• Some LEDs for best transmission colors are covered with a layer of phosphor. In this case, the efficiency of the device is additionally affected light conversion efficiency.

At the beginning of the 21st century, an efficiency of 4% was considered the norm, but now a record has been set at 60%, which is 10 times more than that of an incandescent lamp.

The “hospital average” efficiency for top manufacturers such as Philips or Cree ranges from 35-45%. The exact parameters can be seen in the datasheet specific model. Efficiency for budget Chinese LEDs- it’s always roulette with a spread of 10-45%.

But these are theoretical indicators that we cannot influence. On practice key role play the current supplied to the diode and temperature regime. An excellent job was done by a YouTube user under the nickname berimor76, showing in practice the dependence of the luminous flux on the supplied current and temperature. Let's watch the video.

Power supply efficiency

In addition to the efficiency of the LEDs themselves, the energy efficiency of LED lamps and luminaires is influenced by the power source. They are of two types:

• Power unit. It supplies the LEDs with a constant, predetermined voltage, regardless of the current consumed.
• Driver. Provides a constant current value. The voltage doesn't matter.

power unit

The power supply supplies the LED with a voltage that exceeds what is required for opening p-n transition. But the resistance of an open diode is very small. Therefore, to limit the current, a resistor is installed in series with the light source. The power released by it is completely converted into heat, which reduces the efficiency of the LED lamp. For example, in an LED strip the losses are about 25%.

A more advanced and economical device is an electronic driver.

Driver

The driver for powering the LEDs provides them with a constant current. Diodes are connected to the device in series in an amount that depends on the operating voltage of the LEDs and maximum voltage devices.

LED lamps use a current-limiting capacitor instead of a driver. When passing through it electric current the so-called reactive power. It does not turn into heat, but the electric meter still takes it into account. The efficiency of such a “driver” depends on the number of diodes connected in series with it.

Electronic driver installed in luminaires high power or in portable devices, where saving electricity or battery capacity is more important than the price of the device.

Lamp efficiency

When organizing lighting, including LED lighting, the efficiency of the form factor of the lamp is important. This is the ratio of all the light coming out of the lamp to the luminous flux emitted by the lamp itself.

Any lamp design, even one made of mirrors or transparent glass, absorbs light. The ideal lossless option is a socket with a light bulb suspended on wires.

But this is a rare case when ideal does not mean best. The light flux from the light bulb on the wire is directed in all directions, and not just in the desired direction. Of course, the light that hits the ceiling or walls is reflected from them, but not all of it, especially under open air or in a room with dark wallpaper.

Has the same disadvantage LED lamp with a versatile arrangement of elements (“corn”) or with matte dispersion. In the latter case, the diffuser additionally absorbs light.

Unlike such lamps, an LED lamp with a one-way arrangement of diodes directs light in one direction. The efficiency of a lamp with such a lamp is close to 100%. The illumination created by it is higher than that of another, with the same luminous flux, but directed towards different sides.

It's connected with design features LEDs - unlike incandescent and fluorescent (energy-saving) lamps, which have a circular radiation pattern, they emit light in the range of 90-120 degrees. LED strips and spotlights have the same properties, emitting light in only one direction.

Thus, the maximum luminous flux per watt of power is emitted by LEDs in spotlights with a built-in electronic driver.

The traditional approach to LED lamps often leads to a misunderstanding of fundamental circumstances. It's about about the efficiency of lamps and the influence of the design of LED and conventional lamps on the efficiency.

The efficiency of a luminaire is the ratio of the luminous flux coming out of the luminaire to the entire luminous flux created by the light source. For example, a lamp in the form of a light bulb without lighting fixtures, primarily without a reflector, has an efficiency of 100%. This does not mean at all that this is an ideal to which we must strive; for lamps - less efficiency, this does not mean worse. Any attempts to concentrate (direct) light leads to a decrease in efficiency. But the method of concentration and the quality of the reflector may be different, and the lamps will have different efficiency. You can compare luminaires by efficiency only those that have a similar light distribution(KSS), in this case the efficiency will be determined by the quality optical system lamp (reflector, glass). It makes no sense to compare luminaires with different KSS in terms of efficiency!

The fundamental difference between LEDs and lamps is that they shine only in one half-plane. That is, an LED lamp without lighting fixtures (100% efficiency) will be directed! The emission angle of LEDs without secondary optics is 90-120 degrees. For example, if we compare two “lamps” in the form of a light bulb and an LED (100% efficiency) with the same luminous flux, then on the axis of the lamp at the same distance the illumination will be approximately 2 times less than on the axis of the LED. If you try to collect the luminous flux of the lamp using a reflector (to achieve the same angle of radiation), then in any case you will not be able to obtain the same illumination that the LED provides due to reflection losses. In this regard, replacing the light source in the form of a light bulb with LED source in directional luminaires will make sense even if these sources have the same luminous efficiency (lm/W).

If a luminaire with a lamp has flat glass, that is, the entire light source is “immersed” inside the lamp, The efficiency of the lamp will decrease significantly due to the fact that the main part of the light coming out of the lamp will be reflected, that is, with reflection losses. For an LED lamp of this design, there is practically no decrease in efficiency(only losses in glass are about 5%), although intuitively it seems that, by analogy with lamp efficiency lamps should decrease.

A tube lamp with flat glass will have an efficiency of about 50-60%.

An LED lamp with flat glass will have an efficiency of about 95%.

This is the main thing fundamental difference LED lamps from lamp lamps. Directional LED lights are much more efficient than directional tube lights. This is related to to a large extent with the design features of LEDs, and not just with their high luminous efficiency.

Understanding this circumstance should lead to a revision of approaches to the calculation of lighting installations using LED lamps.