Theoretical foundations of indicators and types of lighting. Industrial lighting, its quantitative and qualitative characteristics. requirements for industrial lighting Quantitative indicators characterizing lighting

Professional lighting technicians and specialists working in the field of lighting constantly use different terms and definitions that mean little to the average layman.

To make it easier to understand what we are talking about and what these words mean, we have prepared a list explaining the main lighting terms and characteristics. It does not need to be learned by heart, you can simply go to the desired page and refresh the forgotten parameter in your memory. Speaking "in the same language" is always easier.

Lighting parameters and concepts.

1 - Visible and optical radiation

The entire world around us is formed by visible radiation concentrated in the band of electromagnetic waves from 380 to 760 nm. Ultraviolet radiation (UV) is added to it on one side, and infrared (IR) on the other.

UV rays have a biological effect and are used to kill bacteria. Dosed they are used for therapeutic and healing effects.

IR rays are used for heating and drying in installations, as they mainly produce a thermal effect.

2 - Luminous flux (F)

The luminous flux characterizes the power of visible radiation by its effect on human vision. measured in lumens(lm). The value is independent of direction. Luminous flux is the most important characteristic.

For example, an E27 75 W incandescent lamp has a luminous flux of 935 lm, a 75 W halogen G9 - 1100 lm, a 35 W T5 fluorescent lamp - 3300 lm, a 70 W metal halide G12 (warm) - 5300 lm, an E27 LED 9.5 W ( warm) - 800 lm.

3 - Lumen

Lumen (lm) is the luminous flux from a light source (lamp) at an ambient temperature of 25°, measured under reference conditions.

4 - Illumination (E)

Illumination is the ratio of the luminous flux supplied to a surface element to the area of ​​this element. E \u003d F / A, where, A is the area. Illumination unit - luxury(OK).

Most often, horizontal illumination is normalized (on a horizontal plane).

Average illumination ranges: outdoors under artificial lighting from 0 to 20 lux, indoors from 20 to 5000 lux, 0.2 lux during the full moon in natural conditions, 5000 -10000 lux during the day with clouds and up to 100,000 lux on a clear day.

The picture shows: a - the average illumination on the area A, b - the general formula for calculating the illumination.

5 - Strength of light (I)

The intensity of light is the spatial density of the luminous flux limited by a solid angle. That is, the ratio of the light flux emanating from a light source and propagating inside a small solid angle containing the direction under consideration.

I \u003d F / ω The unit of measurement of luminous intensity is candela (cd).

The average luminous intensity of a 100 W incandescent lamp is about 100 cd.

KSS ( light intensity curve) - the distribution of light intensity in space, this is one of the most important characteristics lighting fixtures, necessary for the calculation of lighting.

6 - Brightness (L)

Brightness (light density) is the ratio of the luminous flux carried in an elementary beam of rays and propagating in a solid angle to the cross-sectional area of ​​​​a given beam.

L=I/A (L=I/Cosα) Luminance unit - cd/m2.

Brightness is related to the level of visual sensation; The distribution of brightness in the field of view (indoors/interiors) characterizes the quality (visual comfort) of lighting.

In complete darkness, a person reacts to a brightness of one millionth of a cd / m2.

A fully luminous ceiling with a brightness of more than 500 cd / m2 causes discomfort in a person.

The brightness of the sun is about a billion cd/m2, and that of a fluorescent lamp is 5000-11000 cd/m2.

7 - Light output (H)

The luminous efficacy of a light source is the ratio of the luminous flux of a lamp to its power.

Η=F/R The unit of measure for light output is lm/W.

This is a characteristic of the energy efficiency of the light source. Lamps with high luminous efficiency provide energy savings. Replacing an incandescent lamp with a light output of 7–22 lm/W with fluorescent ones (50–90 lm/W), the power consumption will decrease by 5–6 times, and the illumination level will remain the same.

8 - Color temperature (TC)

Color temperature determines the color of light sources and the color tone of the illuminated space. The color temperature is equal to the temperature of a heated body (Planck emitter, black body), the same color as a given light source.

The unit of measurement is Kelvin (K) on the Kelvin scale: T - (degrees Celsius + 273) K.

Candle flame - 1900 K

Incandescent lamp - 2500–3000 K

Fluorescent lamps - 2700 - 6500 K

Sun - 5000–6000 K

Cloudy sky - 6000–7000 K

Clear day - 10,000 - 20,000 K.

The color rendering index characterizes the degree of reproduction of the colors of various materials when illuminated by a light source (lamp) when compared with a reference source.

The maximum value of the color rendering index is Ra =100.

Color Rendering Ratings:

Ra = 90 or more - very good (color rendering 1A)

Ra = 80–89 - very good (color rendering 1B)

Ra \u003d 70–79 - good (color rendering degree 2A)

Ra \u003d 60–69 - satisfactory (color rendering degree 2B)

Ra \u003d 40–59 - sufficient (color rendering degree 3)

Ra = less than 39 - low (color rendering 3)

Ra he is CRI- The color rendering index was designed to compare continuous spectrum light sources whose color rendering index was greater than 90, since below 90 it is possible to have two light sources with the same color rendering index but with very different color rendering.

Comfortable for the human eye CRI value = 80–100 Ra

What is light? What is it "eaten" with?

Insufficient lighting for a long time can also lead to poor vision.

There are three types of industrial lighting: natural, artificial and combined.

• natural- illumination of premises with sky light (direct or diffused), penetrating through light openings in the external structures of buildings;
• artificial- lighting with electric light sources;
• combined- lighting, in which natural lighting, which is insufficient according to the norms, is supplemented by artificial lighting.

Visible radiation (light) - radiation that, falling on the retina of the eye, can cause a visual sensation. Light is a part of electromagnetic radiation with a wavelength from 0.38 to 0.78 microns.

Lighting quantities that determine the performance of industrial lighting are based on an assessment of how they feel to the human eye. There are quantitative and qualitative indicators of lighting.

1.1. Quantitative indicators

To quantitative indicators include: luminous flux, luminous intensity, illumination, brightness, reflection coefficient.

Luminous flux (F)- the power of the luminous flux of radiation, estimated by visual sensation by the human eye. The dimension of the luminous flux is lumen (lm).

Light intensity (J) is the spatial density of the light flux in a given direction, i.e. luminous flux per solid angle ω in which it is emitted

Candela (cd),
Where ω is the solid angle in steradians (sr).

Illumination (E)- the density of the light flux on the surface illuminated by it - the light flux, referred to the area of ​​the illuminated surface S, measured in m2, provided that it is uniformly distributed over the surface, when the source light falls on it perpendicularly

Brightness (V) is a light quantity directly perceived by the eye. It is determined by the ratio of the luminous intensity in a given direction to the projection area of ​​the radiating surface onto a plane perpendicular to the direction of radiation

The values ​​of the maximum brightness values ​​on the working surface are given in Table 1, page 14.

Reflection coefficient surface r characterizes its ability to reflect the light flux incident on it. It is determined by the ratio of the reflected light flux to the incident

Coefficient (r) values ​​for surfaces different nature are given in table. 12., adj. 1.

1.2. Qualitative indicators

To quality indicators illumination include: background, contrast of the object of distinction with the background, glare index, illumination pulsation coefficient, discomfort index.

Background- the surface adjacent directly to the object of distinction on which it is viewed. The background is considered light if the reflection coefficient P is greater than 0.4; medium at P = 0.2...0.4 and dark if P is less than 0.2.

Object contrast with background К – photometrically measured brightness difference between two zones. It is determined by the ratio of the absolute value of the difference between the brightness of the object and the background to the brightness of the background:

The contrast is considered large when K is more than 0.5 (the object and background differ sharply in brightness), medium at K = 0.2 ... 0.5 (noticeably different) and small if K is less than 0.2 (slightly different).

Blindness score2 (P)- criterion for assessing the blinding effect of the lighting installation, determined by the expression

P \u003d (S - 1) 1000,

where S is the glare coefficient equal to the ratio of the threshold brightness differences in the presence and absence of glare sources in the field of view.

The normalized values ​​of the coefficient P are given in App. 1, tab. 1.

Illumination ripple factor (Kp)- a criterion for estimating the relative depth of fluctuations in illumination as a result of a change in time of the luminous flux of gas-discharge lamps when they are powered alternating current, expressed by the formula

where Еmax, Еmin, and Еср are, respectively, the maximum, minimum and average values ​​of illumination for the period of its fluctuation, lx.

The normalized values ​​of Kp are given in App. 1, table 1.

Discomfort score (M) is a criterion for assessing uncomfortable glare1, which causes discomfort with an uneven distribution of brightness in the field of view. It determines the degree of additional intensity of visual work caused by the presence of a sharp difference in brightness in an illuminated room.

This indicator for industrial premises is not standardized, its standardized values ​​for residential, public and administrative premises are given in, table. 2, pp. 7–8. In the same place on page 25 there is a formula for determining the indicator of discomfort M.

Of the listed lighting indicators, the following are directly measured (names of devices are indicated in brackets):

– illumination (luxmeters);
– brightness (photometers subjective and objective).

With the help of these instruments, it is possible to determine the values ​​of the reflection coefficients P and ripples Kp of the contrast of the object of distinction with the background K and the blindness index R.

Illumination standards When choosing the type of luminaires, their number and power, it is necessary to take into account the illumination standards. In the norms, three values ​​​​of the degree of illumination are given: low, normal and high. Usually the normal degree is used, but in some cases it is advisable to choose a small or high degree illumination. The degree of protection of electrical equipment The degree of protection is indicated by the combination IP XX. The first digit is the degree of protection against dust and fur. impacts. The second is the degree of protection against moisture. As outdoor luminaires at a height of up to 0.5 m, luminaires of protection class IP 44 can be used. For installation on high masts (above human reach), the minimum protection class is IP 23. Luminaires mounted at ground level must be waterproof (IP 67), and luminaires immersed in water (for example, to illuminate a pond) must have an IP 68 protection class (protection against the ingress of water under pressure). Protection class 0 class - there is no complete double and reinforced insulation, there is no possibility of grounding. I class - there is full insulation, and there is the possibility of grounding. Class II - equipped with double and reinforced insulation, without the possibility of grounding. Class III - a luminaire designed to be connected only to a protective voltage network. Units of measurement Here are some physical quantities that characterize the light source. They can be used when choosing fixtures, their location. Light intensity (I). The unit of measure is the candela (cd).

Illumination (E)- luminous flux per unit of illuminated surface. The unit of measure is lux (lx). 1 lx = 1cd*sr/m2, where sr is the solid angle (in steradians). Brightness (L) characterizes the glow of the light source in a given direction.

The brightness of an element of a luminous surface in any direction is determined by the ratio of the luminous intensity of this element to the projection area of ​​the element on a plane perpendicular to this direction.

Color temperature (T). It is measured in degrees Kelvin (K). Characterizes the spectral composition of radiation.

Illumination: Moonlight 0.25 lx Sun through clouds 10,000 lx sunlight 100 000 lx Office lighting 300-2000 lx Road lighting 10-50 lx

Luminosity: Fluorescent lamp 0.8 cd/m2 Well lit street 2 cd/m2 Midday sun 150,000 cd/m2 Candle power is about 1 cd, and beacon light can reach 2,000,000 cd.

Measurement of lighting parameters. The main parameter used in assessing lighting is illuminance e, measured in lux.

Various types of light meters are used to measure illumination.

An example of an analog light meter is the device Yu - 116, the principle of operation of which is based on the phenomenon of the photoelectric effect.

Under the influence of the light flux incident on the selenium photocell, a current arises in a closed circuit, the magnitude of which is proportional to the light flux. The instrument is calibrated in lux. A significant advantage of the selenium photocell compared to other types of photocells is that its spectral sensitivity curve most closely matches the relative visibility curve of the human eye. When measuring illumination, the photocell is installed in the working plane (horizontal or vertical) at some distance from the operator conducting the measurements so that the shadow does not fall on the photocell.

At present, analog-digital devices are widely used, which allow measuring not only illumination, but also other parameters that characterize illumination, for example, pulsation coefficient or brightness.

An example of an analog-digital device is the Argus-07 pulsemeter-luxmeter, which is used to measure illumination and pulsation coefficient. The principle of the device is based on the conversion of the luminous flux created by extended objects into a continuous electrical signal proportional to the illumination, which is then converted by an analog-digital converter into a digital code displayed on the digital display of the indicator unit. A primary radiation converter is installed in the measuring head - a semiconductor silicon photodiode with a system of light filters that form the spectral sensitivity corresponding to the visibility curve. The ripple factor readings are displayed as a percentage, while the device determines the maximum, minimum and average value of the illumination of the pulsating radiation and calculates the value of the ripple factor using the above formula.

Qualitative and quantitative indicators of lighting are a set of parameters that together provide high-quality lighting in any room. In our article, we will get acquainted with all of them in detail, and evaluate their impact on various lighting systems.

But before talking about the parameters, let's briefly get acquainted with the types of lighting. After all, each of them is characterized by its own characteristics, which can differ quite significantly.

Qualitative and quantitative parameters of lighting

The concept of "High quality lighting" is formed based on a number of qualitative and quantitative indicators. Let's understand these indicators and evaluate their impact. At the same time, we will try to make it as accessible as possible.

Quantitative indicators of lighting

Each type of lighting has its own quantitative indicators. Let's look at all of them, and determine what they depend on and what they affect.

• The first of these indicators is usually indicated by the luminous flux. This is a value that estimates the amount of light energy according to its perception by the eye. It is measured in lumens. Simply put, this is the amount of light entering through a window or emitted by a lamp.
• From the luminous flux on a straight line depends usually set norm of illumination of the room. After all, it is its derivative. The illumination of a room is equal to the luminous flux divided by the area of ​​the room.

• The next quality indicator is the intensity of light. It characterizes the density of the light flux in a given direction. That is, let's say we have a lamp, all the light emitted by it is its luminous flux. But only part of the light travels to a certain point. It is called the power of light. This indicator is often used in the calculation of luminous stripes and local illumination.

• Another quantitative indicator that depends on the angle of perception is the brightness of the light. This indicator is defined as the intensity of light emitted by a surface located perpendicular to the radiation source. This value is measured in cd / m 2.

• The reflection coefficient of the surface is also referred to the quantitative indicators of illumination. After all, any surface has the ability to reflect light. This ability is determined by a special coefficient, which is defined as the ratio of the light flux falling on the surface to the reflected light flux.

• But the norms are usually based on such an indicator as the illumination of a room or object. It is a kind of total component of all quantitative indicators, but primarily of the luminous flux, luminous intensity and surface reflectance. This parameter indicates the amount of light that a person needs to orient himself in space and perform a certain type of work.

Note! The norms give the minimum illumination for an object or room. Therefore, in real conditions, it should be higher. Taking into account the safety factor, operating factors and other variables, this indicator becomes 20-50% higher.

Quality lighting indicators

But to determine whether lamps provide high-quality lighting or not, the amount of light alone is not enough. An important aspect is the quality of such lighting, and in this regard, the indicators are no less, if not more. And it is quite difficult to determine the priority of one or another parameter.

• Let's start our conversation with such a parameter as the pulsation coefficient of the fixtures. As you probably know, many types of lamps, such as diode, fluorescent, sodium and some others, do not give an even light, like incandescent lamps, but pulsate. Sometimes this pulsation can be seen even with the naked eye. But in most cases, the eye does not perceive it on a conscious level.
• In this regard, the lighting instruction strictly normalizes this indicator and even introduced the so-called pulsation coefficient. It is the ratio of the difference between the maximum and minimum luminous flux of a luminaire to its average value.

• The next important parameter is the glare indicator. This indicator depends on many parameters. But first of all, this is the brightness of the lamp and the angle of incidence of light on the iris of the human eye.
• This indicator is important in the context of the fact that it is more economical to put one luminaire with a large luminous flux to illuminate the entire room.. But in terms of comfort, it is not very convenient. Therefore, SNiP 23-05-95 introduces such a norm as a glare indicator, which normalizes this indicator and fixes the protective angles of incidence of light.

• Another qualitative indicator is the indicator of discomfort. It is the ratio of the brightness of the illumination of objects in the field of view. Simply put, the illumination of objects in the field of view should not have significant differences in illumination, otherwise it causes eye fatigue.

Note! The indicator of discomfort is applicable only for residential, public and administrative buildings. For industrial facilities, this indicator is not standardized.

• Sometimes quantitative and qualitative factors intersect. This applies to the so-called cylindrical illumination factor - this is the illumination of the side wall of a vertical cylinder, which has dimensions tending to zero.
• Speaking more plain language is the volume of light. After all, one of the main factors of this indicator is the reflectivity of light from the walls and floor. This factor is very important for showrooms, trading floors and other similar premises.

• Another important factor is color rendering. It's no secret that different types lamps emit light, the color range of which is far from the sun. As a result, not all colors are distinguishable, or their brightness is incorrectly transmitted. Therefore, for rooms where color reproduction is important, this factor should be taken into account, although the cost of lighting from this may increase.

• The next quality indicator of light is its temperature. It is measured in "K" and usually ranges from 2000 to 7000K. A reading of 2000K is considered warm light, while readings above 5000K are considered cool white light.
• Another factor is the uniformity of illumination. This factor is very similar to the indicator of discomfort, only it does not take into account the brightness of objects in the field of view, but the difference in illumination.

• The uniformity of lighting is standardized for almost all premises, and even street lighting has its own norms for the difference. To achieve maximum uniformity, regulatory documents have even developed special layouts for lighting fixtures for different rooms. It is important to note that it is not the ratio of the maximum illumination to the minimum that is normalized, but the average to the minimum.

• Another indicator that we, by the way, select with our own hands is the contrast of the object of distinction and the background. It is characterized as the ratio of the brightness of the object and the background. Great contrast a value of 0.5 or higher is considered, and a value of 0.2 or less is considered low contrast. This factor is especially important for exhibition halls, public and residential buildings, street lighting of facades and some other objects.

• We will end our conversation with one of the most important parameters for natural lighting - KEO. It stands for natural light coefficient and is characterized as the ratio of natural light inside the building to the light in an open area outside the building. Moreover, this ratio is calculated at a strictly defined point in the room. For example, with side lighting a meter from the wall opposite the window.
• SNiP 23-05-95 strictly standardizes this indicator and, starting from it, it is concluded that it is necessary to expand the light openings or, depending on the feasibility studies, install combined lighting.

Conclusion

The standards for indoor and outdoor lighting are quite strict. They contain a lot of indicators that should make the lighting not only sufficient, but also comfortable.

At the same time, in our article we have disclosed only the main ones, but there are also derivatives and other indicators on which lighting depends, but which do not characterize it. Therefore, if you set out to create really high-quality lighting, then we advise you to look at other articles on our website that reveal each of these indicators in more detail.

Lighting is characterized quantitative And quality indicators . quantitative are luminous flux, luminous intensity, illuminance, luminosity, surface reflectance, brightness, luminous efficacy of the light source, daylight ratio.

Luminous flux F- this is the energy of light electromagnetic waves, transferred per unit time through a certain surface area and estimated by visual sensation. The unit of luminous flux is lumen (lm).

Light Force I is the spatial density of the luminous flux, numerically equal to the luminous flux emitted by a point light source into a solid unit angle w (ster):

therefore, the total luminous flux emitted by a point source with luminous intensity I is equal to:

The unit of luminous intensity I is the candela (cd).

Illumination E, lux, is the surface density of the light flux, which is characterized by the luminous flux per unit area of ​​the illuminated surface S, m 2:

Illumination, lx, created by a point source, at a distance r from it is equal to:

(4)

where a is the angle between the incident ray and the normal to the surface at the point of incidence of the ray.

A light source, the linear dimensions of which differ slightly from the distance to it from the observation point, is not a point. To characterize it, the value of luminosity and brightness is used.

Luminosity R, lx, is determined by the value of the luminous flux emitted from the unit area of ​​the luminous surface S pov:

If the luminosity of a body is due to its illumination, then R = r × E, where r is the reflection coefficient.

Surface reflectance r characterizes the ability of the surface to reflect the light flux incident on it:

where Ф otr and Ф pad are the light flux reflected and incident on the surface, respectively, lm.

At r > 0.4, the surface is light; at r = 0.4…0.2 the surface is average; if r< 0,2, то поверхность темная.

Brightness B, cd / m 2, characterizes the radiation of the projection area of ​​the luminous surface S pov in a given direction a:

(7)

where I a is the luminous intensity of the luminous surface in the direction a, cd;

a is the angle between the normal to the surface element and the direction of the observer, degrees.

The maximum brightness value is set by SNiP 23-05-95 "Natural and artificial lighting» depending on the area of ​​the illuminated working surface. If the working surface area S is less than 10 -4 m2, the value B max = 2000 cd/m 2 is acceptable, if S > 1×10 -1, then B max = 500 cd/m 2.

Light output of the light source y, lm / W, is determined by the ratio of the luminous flux Ф, lm, of the source to its power P, W:

The characteristic of natural light is daylight ratio e in percent: the ratio of illumination E ext at a given point in the room to the simultaneous external horizontal illumination E nar, created by the light of the entire sky:

(9)

TO quality indicators illumination include: spectral composition of light, background, object contrast with the background, visibility of the object, pulsation coefficient of illumination, glare index. The last two indicators are normalized taking into account the characteristics of visual work according to SNiP 23-05-95.

Contrast of the object with the background K characterized by the ratio of the brightness of the object under consideration and the background:

(10)

where B o and B F are the brightness of the object and background, respectively, cd / m 2.

If the object of distinction stands out strongly against the background, then the contrast is large (K > 0.5); if the difference in brightness is noticeable (K = 0.2 ... 0.5), then the contrast is average; with a small difference in brightness (K< 0,2) контраст малый.

Object Visibility V characterizes the ability of the eye to perceive an object. It depends on the illumination, brightness, size of the object and is determined by the number of threshold contrasts in the contrast of the object with the background:

where Kthr is the smallest contrast distinguishable by the eye, with a slight decrease in which the object becomes indistinguishable against the background.

Lighting ripple factor K P , in percent - the criterion for assessing the relative magnitude of fluctuations in illumination as a result of a change in time of the luminous flux of light sources when they are powered by alternating current:

, (12)

where E max and E min are the maximum and minimum illumination for the period of its fluctuation, lx;

E cf is the average illumination for the same period, lx.

The pulsation coefficient for I ... III categories of visual work should not exceed 10%.

Blinding index P- criterion for assessing the glare of the lighting installation:

, (13)

where W is the glare coefficient equal to the ratio of visibility when shielding sources V e to visibility in the presence of bright sources in the field of view V.

One of the lighting characteristics of lamps is luminaire efficiency hSt. characterizing the loss of part of the light flux in the reflector (diffuser):

(14)

where Ф sv - the luminous flux that came out of the lamp, lm;

F l - luminous flux of the lamp, lm.

If there are several lamps in the lamp, then the luminous flux F l is determined as the sum of the flux of all lamps installed in the lamp.

Examples of problem solving

Example 1.1. Determine the luminous flux, lm, incident on a surface with an area S \u003d 0.2 m 2, located at a distance
r = 2 m from a source whose luminous intensity is I = 400 cd.

Let us assume that the light source is located in the center of a sphere with a radius
2 m. The illuminated surface S is part of the surface area of ​​the sphere, the angle of incidence a = 0.

From expressions (3) and (4) we find I / r 2 \u003d Ф / S, from where:

Answer: luminous flux Ф = 20 lm.

Example 1.2. An incandescent lamp with a luminous intensity of I = 200 cd is located in a matte spherical lamp with a diameter of D = 0.2 m.

Find the luminosity of the lamp, neglecting the absorption of light by the lamp.

Full solid angle w = 4p, luminous surface area S = pD 2 . Then from expressions (5) and (2) the luminosity, lx, is determined by the formula:

Example 1.3. Above a round table with a diameter D = 1.6 m at a height h = 0.6 m hangs a lamp that emits light evenly in all directions. The luminous flux incident on the table is
F = 200 lm. Normalized illumination in the workplace
E H \u003d 200 lux. Determine the luminous intensity of the lamp, its total luminous flux, compliance with the illumination standards in the center and at the edge of the table.

The solid angle at which the table surface is visible from the source (Fig. 1) is equal to:

,

where a is the beam incidence angle.

h

Rice. 1. Scheme for example 3

From figure 1 it follows:

From formula (1), the luminous intensity I, cd, is equal to:

The total luminous flux, lm, emitted by a point light source according to formula (2) is:

The illumination of the center of the table E c, lx, is determined by the formula (4):

.

Illumination of the edge of the table E kr, lux, calculated by the formula (4):

.

Therefore, the illumination of the center of the table meets the requirements of the standards (E H = 200 lux). It is unacceptable to perform work of this degree of accuracy on the edge of the table.

Example 1.4. A lamp hangs in the center of a square room of 25 m2. Assuming it to be a point source, find how high the lamp should be from the floor so that the illumination in the corners of the room is the greatest.

The distance from the lamp to the corner of the room r, the value a (half the diagonal of the square floor of the room), the side of the square floor b and the height of the lamp above the floor h are related by the equation:

Then, taking into account formula (4), the expression for illumination can be written as follows:

To find the maximum E, we take the derivative dE/da and equate it to zero:

hence tg 2 a = 2. Then the desired height h, m, will be equal to:

.

Tasks for independent solution

Task 1.1. An incandescent lamp with light intensity I \u003d 100 cd hangs above the center round table with a diameter of 2 m. Considering the lamp as a point light source, calculate the change in the illumination of the edge of the table when the lamp is gradually raised to a height h from 0.5 to 1.0 m every 0.1 m. Plot the dependence E \u003d f (h).

Task 1.2. At a height of 0.4 m from the surface of a round table with a diameter of 1.2 m, an incandescent lamp is installed in the local lighting fixture. Above the center of the table at a height of 2 m from its surface hangs a chandelier with four of the same lamps. In which case will the illumination at the edge of the table be greater and by how many times: with local or general lighting?

Task 1.3. Find the illumination of the Earth's surface created by normally incident sunbeams. The brightness of the Sun is 1.2×10 9 cd/m 2 .

Task 1.4. Determine the luminosity and brightness of an incandescent lamp with a frosted spherical bulb with a diameter of 0.05 m and 0.1 m. The luminous intensity generated by the lamp is 100 cd. Ignore the loss of light in the flask.

Task 1.5. A luminous flux of 120 lm falls normal to the surface on a sheet of white paper measuring 0.2x0.3 m. Find the illumination, luminosity and brightness of a paper sheet if its reflectance is r = 0.75. What should be the illumination of the sheet so that its brightness does not exceed allowable value 2000 cd/m2?

Problem 1.6. A sheet of paper measuring 0.1 x 0.3 m is illuminated by a lamp with a light intensity of 100 cd. The luminaire efficiency is 50%. Determine the illumination of a sheet of paper.

Problem 1.7. An electric lamp with a light intensity of 100 cd radiates 122 J of light energy every minute in all directions. Find the light output if the lamp power consumption is 100 W.

Problem 1.8. At a height h 1 \u003d 2 m above the middle of a round table with a diameter D \u003d 3 m, a lamp hangs with a light intensity of I 1 \u003d 100 cd. It was replaced by a lamp with light intensity I 2 = 25 cd, changing the distance from the table so that the illumination of the middle of the table did not change. How will the illumination of the edge of the table change?

Problem 1.9. Three identical point light sources are located at the vertices of an equilateral triangle. In the center of the triangle, perpendicular to its plane and parallel to one of the sides, there is a small plate. Determine the illumination of both sides of the plate, if the luminous intensity of each of the sources
I \u003d 10 cd, and the length of the side of the triangle l \u003d 1 m.

Problem 1.10. At what height above the drawing board should a lamp with a power of P = 200 W be hung in order to obtain an illumination of the board under the lamp E = 50 lux? The luminous efficiency of the lamp is
y = 12 lm/W. Board slope a = 30 0 .

Problem 1.11. The luminous flux of a lamp with a power of R l \u003d 200 W at a voltage of U \u003d 120 V is equal to F l \u003d 3050 lm. Determine the luminous flux of the lamp, if its efficiency is
h sv = 78%.

TASK 1.12. Determine the luminous efficiency of an incandescent lamp with a power of R l \u003d 60 W, voltage U \u003d 127 V, if its luminous flux is F l \u003d 6000 lm.

CLASSIFICATION OF INDUSTRIAL LIGHTING

Depending on the light source, industrial lighting can be of two types: natural, created directly by the solar disk and diffuse light of celestial radiation, and artificial, carried out by electric lamps.
By design features natural lighting is divided into:
lateral, carried out through windows in the outer walls;
the upper one, carried out through aeration and rooflights, openings in the coatings, as well as through light openings in places of height differences in adjacent spans of buildings;
combined, when side lighting is added to the top lighting.
Artificial lighting is provided in rooms where there is not enough natural light or to illuminate the room during those hours of the day when there is no natural light.
According to the design, artificial lighting can be of two types - general and combined, when local lighting is added to the general lighting, concentrating the luminous flux directly at the workplace.
General lighting is divided into general uniform lighting (with a uniform distribution of the luminous flux, excluding the location of the equipment) and general localized lighting (with the distribution of the luminous flux, taking into account the location of the workplaces).
The use of one local lighting inside buildings is not allowed.
According to the functional purpose, artificial lighting is divided into the following types: working, emergency, special.
Working lighting is mandatory for all premises and in illuminated areas to ensure normal operation, the passage of people and traffic. Emergency lighting is provided to ensure minimum illumination in the production area in the event of a sudden shutdown of working lighting.
Emergency lighting to continue work should be arranged in cases where the sudden shutdown of working lighting (in the event of an accident) and the associated disruption of normal maintenance can cause an explosion, fire, poisoning of people, prolonged disruption of the technological process, disruption of facilities such as power plants, control rooms, water supply pumping units and other industrial premises where work stoppage is unacceptable.
The lowest illumination of working surfaces that require maintenance during emergency operation should be 5% of the illumination normalized for working lighting with a general lighting system, but not less than 2 lux inside buildings.
Emergency lighting for evacuation should be arranged in places dangerous for passage, on stairwells, in industrial premises with more than 50 employees. It should provide the least illumination in the premises, on the floor of the main passages and on the steps of at least 0.5 lux, and in open areas - at least 0.2 lux. Exit doors of public premises, in which more than 100 people can be located at a time, must be marked with light signals-indicators.
To continue working, emergency lighting fixtures are connected to an independent power source, and fixtures for people evacuation are connected to a network independent of working lighting, starting from the substation switchboard.
For emergency lighting, only incandescent and fluorescent lamps should be used.
Special types of lighting include: security, duty. For security lighting of sites of enterprises and emergency lighting of premises, if possible, a part of the lamps for working or emergency lighting should be allocated.

1. Main lighting characteristics

1.1. Quantitative indicators

The sensation of vision occurs under the influence of visible radiation (light), which is electromagnetic radiation with a wavelength of 0.38 ... 0.76 microns. The sensitivity of vision is maximum to electromagnetic radiation with a wavelength of 0.555 microns (yellow-green color) and decreases towards the boundaries of the visible spectrum.

Lighting is characterized by quantitative and qualitative indicators. Quantitative indicators include:

- light flowФ - part of the radiant flux, perceived by a person as light; characterizes the power of light radiation, measured in lumens (lm);

- luminous intensity J - spatial density of light flux; is defined as the ratio of the light flux df, emanating from the source and uniformly propagating inside the elementary solid angle dШ, to the value of this angle; J \u003d df / dSch; measured in candelas (cd);

- illumination E - surface density of light flux; is defined as the ratio of the luminous flux df uniformly incident on the illuminated surface dS(m 2), to its area: E \u003d df / dS, measured in lux (lx);

- brightness L surface at an angle b to the normal is the ratio of the luminous intensity dJb emitted, illuminated or luminous surface in this direction, to the area dS projections of this surface onto a plane perpendicular to this direction: L\u003d df / (dScosb), measured in cd * m -2.

1.2. Qualitative indicators

For a qualitative assessment of the conditions of visual work, indicators such as background are used. , contrast of the object with the background, pulsation coefficient of illumination, index of illumination, spectral composition of light.

Background - it is the surface on which the discrimination of the object takes place. The background is characterized by the ability of the surface to reflect the light flux incident on it. This ability (reflection coefficient p) is defined as the ratio of the light flux reflected from the surface F neg to the luminous flux Fpad incident on it; p == Phot/Fpad. Depending on the color and texture of the surface, the values ​​of the reflection coefficient are in the range of 0.02 ... 0.95; at p>0.4, the background is considered light; at p = 0.2...0.4-average and at p<0,2-темным.

The contrast of the object with the background k - the degree of distinction between the object and the background is characterized by the ratio of the brightness of the object under consideration (points, lines, signs, spots, cracks, risks or other elements) and the background; k = (Lop-L o)/L op considered large if k>0.5 (the object stands out sharply against the background), medium at k==0.2...0.5 (the object and the background differ noticeably in brightness) and small at k<0,2 (объект слабо заметен на фоне).

Illumination ripple coefficient kE- this is a criterion for the depth of fluctuations in illumination as a result of a change in the luminous flux over time

KE=100(E max -E min)/(2E cf);

where E max, E min E cp - maximum, minimum and average illumination values ​​for the oscillation period; for discharge lamps ke= 25...65%, for conventional incandescent lamps kE? 7%, for halogen incandescent lamps K E = 1%.

Blindness Rho - criterion for assessing the blinding effect created by the lighting installation,

Po=1000(V 1 /V 2 -1),

where V 1 and V 2 are the visibility of the object of distinction, respectively, with screening and the presence of bright light sources in the field of view.

Shielding of light sources is carried out using shields, visors, etc.

Visibility V characterizes the ability of the eye to perceive an object. It depends on the illumination, the size of the object, its brightness, the contrast of the object with the background, the duration of the exposure. Visibility is determined by the number of threshold contrasts in the contrast of the object with the background, i.e. V=k/k pop , where k pore - the threshold or smallest contrast distinguishable by the eye, with a slight decrease in which the object becomes indistinguishable against this background.