PHOTOMETRY

Measured in the range between 0 and 100, this is a quantitative measure of the ability of a light source to reveal the colours of various objects faithfully in comparison with an ideal or natural light source. Numerically, the highest possible CRI value is 100 and would only be given to a source identical to standardised daylight (sunlight with a colour temperature of 6670K). The higher the CRI value, the better the colours of illuminated object/surface are revealed. Ra is the average value of 8 colour samples, whereas CRI uses a palette of 15 colours (R1 – R15) and tends to be more accurate.

Position of the coordinates on the chromaticity diagram in relation to the Planck curve. The parameter determines the distance from the Planck curve.

MacAdam’s ellipses show the areas shown in the chromaticity diagram. They are defined in MacAdam steps, indicating colour temperature differences. It is assumed that the differences in colour temperature of LED sources falling within step 3 are indistinguishable by most people.

These represent the light distribution produced by a luminaire or light source after measuring its light intensity in different directions. A curve (diagram) of the luminaire’s light intensity can be created after converting the results into values, which would be obtained using light sources with a total luminous flux of 1000lm.

The graph shows light distribution in two planes:

  • In the vertical plane passing through the longitudinal axis of the luminaire, planes C90-C270;
  • In a plane perpendicular to the axis of the luminaire, plane C0-C180.

These are defined as shown in the figure below. If the luminaire is rotationally symmetrical, the light distribution is given in one plane C only. However, in the case of an unsymmetrical luminaire, the luminous values are given in planes C in angles of 30° or even 15°. The light distribution diagram provides basic information about the shape of the luminaire’s light distribution.

 

This is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls within a given solid angle. The SI unit of luminance is ‘candela per square metre’ (cd/m2).

This shall not be confused with Luminance. Illuminance is a measure of how much the incident light illuminates the surface: 1m2 (lm/m2), wavelength-weighted by the luminosity function to correlate with human brightness perception. The SI unit is Lux.

A batch file dedicated for the design software (e.g. Dialux, Relux) – these files are necessary for the creation of lighting design.  It describes the intensity of light in the individual points of a sphere grid. These files also contain information on the geometry of the light output to the outside of a luminaire. The files are featured by the *.ies extension defined by IESNA LM-63-2001 and *.ldt defined as EULUMDAT.

Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power, measured in lumens per watt (lm/W) in the International System of Units (SI).

This is the ratio of luminous flux (a percentage of light output) emitted by the luminaire to the light output emitted by its lamps (sources of light) η = Φ opr./Φ.

 

This is the measure of the perceived power of light. The SI unit of luminous flux is Lumen (lm).

This is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The SI unit of luminous intensity is the candela (cd), an SI base unit.

Expressed in Kelvins [K], it is a measure of the colour impression of a given light source. Lower [K] values are perceived by the human eye as warmer colours.

PHOTOBIOLOGICAL SAFETY

Flickering can be defined as: the perception of visual instability/unsteadiness caused by lighting variations in brightness. The Illuminating Engineering Society (IES) developed two flicker metrics.

Percent Flicker - A relative measure of the cyclic variation in the amplitude of a light in one on/off cycle (index range: 0%-100%). 100% flicker would indicate that, at some point in the cycle, there is no illumination provided at all. In a properly stabilised light source, the Percent Flicker parameter will be 0%.

Flicker Index - This includes the flicker percentage and two other variables: the shape of light intensity waveform or output light distribution curve. In another words, it is a measure of the cyclic variation taking into account the shape of the waveform.. The lower the flicker percentage and flicker rate, the better the stability of a light source.

The SVM is a method used to quantify the stroboscopic effect visibility in general illumination application. SVM is defined by  measuring  the visibility  threshold  of  light  waveforms  modulated  at  several  frequencies and uses Fourier analysis to convert the wavelength shape of the light intensity. The stroboscopic effect can cause an impression of slowness, stopping or even reversal of the direction of movement of an object, which can lead to various accidents.

An uncomfortable and undesirable state of the vision, defined as the sensation of dazzling light caused by excessive brightness level in the field of vision. UGR is not a stand-alone technical parameter of a luminaire, it only indicates which UGR rating can be achieved in a lighting design with a given luminaire.

This is the electromagnetic spectrum with wavelength from 100nm to 400nm, shorter than that of visible light but longer than X-rays. By reason of the extent (scale) or effects of the UV presence, the UV is divided into the following:

UV-C 100nm - 280nm

UV-B 280nm - 315nm

UV-A 315nm - 400nm

Over 95% of the UV radiation reaching the earth is UV-A, the rest of the radiation is retained by the earth's atmosphere.

LEDs do not emit UV radiation so the technology is safe not only for living organisms but also for various elements, such as paints, colorful plastics, museum exhibits.

ELECTRICAL PARAMETERS

In alternating current circuits, reactive power is a quantity describing the fluctuations of electric energy between the elements of an electric circuit. This oscillating energy is not converted into usable/effective energy or heat, but is necessary for the functioning of electrical equipment. The energy is taken from the source in one part of the alternating waveform period, stored by the receiver and returned to the source in the other part of the period, which is related to the disappearance of the magnetic field in the receiver. For sinusoidal waveforms, reactive power is defined as the multiplication (product) of induced voltage and current values, and the phase shift angle sinus between voltage and current. The reactive power SI unit is var (var).

Q=U*I*sin

In AC systems, this is the part of the power that the receiver takes from the source and changes to effective energy or heat. In DC systems, all power is active power. The SI unit of active power is watt (W)

P=U*I*cosᶲ    in AC systems

P=U*I       in DC systems

 

Apparent power is the product (multiplication) of the RMS (root mean square) values of the current and voltage in AC circuits.

S=U*I 

The apparent power SI unit (S) is the Volt-Amp (VA). Apparent power is closely related to reactive and active power.
This relationship is represented by the formula and the power triangle.

 

The power factor of an AC electrical power system is defined as the ratio of the active power absorbed by the load to the apparent power flowing in the circuit. In simple terms, it determines what part of the energy taken from the electrical network will be used effectively by the device. A power factor of less than one indicates that the power was consumed from the electrical network but not used (reactive power). This causes undesirable heat emission.

The table shows the permitted PF values depending on the electrical power of the LED lamps

Functionality parameter

Requirement as from stage 1, except where indicated otherwise

Lamp power factor (PF) for lamps with integrated control gear

  • P ≤ 2 W: no requirement
  • 2 W < P ≤ 5 W: PF > 0,4
  • 5 W < P ≤ 25 W: PF > 0,5
  • P > 25 W: PF > 0,9

COMMISSION REGULATION(UE) NR 1194/2012 

LIGHTING CONTROL

This is a system in which by controlling input voltage the user adjusts the output power level of the device. The control voltage is independent of the device power supply voltage. The value of 10V corresponds to 100% of the output power. The value of 1V corresponds to 5-10% of the output power.

This is a digital addressable interface dedicated for lighting control devices. The DALI interface’s technical standards are set out in IEC 60929 E4 document. This is a widely available standard for lighting control devices created by the leading lighting manufacturers.  It is a two-way dimming interface with a master-slave structure. Information flows from the controller, which acts as a master, to the control units (DALI controllers), which only act as slaves. The digital signals are transmitted via a standard two-wire cable. These control wires can be negative and positive polarised, although most DALI controllers are designed to be neutral.  The DALI system is configurable by using dedicated software. With the use of DALI system, the user may create up to 16 configurations addressing up to 64 devices without the need for rewiring.

This is a digital interface for lighting control devices, in particular – this is a dedicated solution for dynamic lighting. The system can be addressed with 512 channels in one signal line with up to 32 devices. The DMX technical standards are set out by USITT organisation and has become a widely used system within the music/movie stage industry or for the professional illumination of various buildings. Signal receivers are controlled by a shielded two-wire cable with an impedance of 110 ohm. The control is performed with the use of DMX standard controllers.

This is a method of controlling and regulating electric current or voltage signal of constant amplitude and frequency by changing the value of the current or voltage fed to the load. The average value of voltage (and current) fed to the load is controlled by turning the switch between supply and load on and off at a fast rate. The longer the switch is on compared to the off periods, the higher the total power supplied to the load.

Phase control dimming systems alter the light intensity by altering the supply voltage. The power supply voltage is altered by cutting off the leading or trailing edge. This means of control is performed without an additional control wire. The user shall simply connect the dimmer in series between one of the mains wires and the receiver (equipment). We must remember about the compatibility of light sources (driver, LED module) with this analog dimmer.

For LED receivers it is more appropriate to use RC type of dimmers dimming the trailing edge. Impact current is small and grows relatively slowly.

For RL loads it is generally more appropriate to use dimmers cutting off the leading edge.

 

DESIGN/CONSTRUCTION PARAMETERS

The IK rating is an international numeric classification to indicate the degrees of protec-tion provided by light fixtures against external mechanical impacts. It provides a means of specifying the capacity of a fixture (luminaire) to protect its parts (components) from external impacts. The range of protection is measured on the scale from 00 (no protection) up to 10 (impact resistance against 20J). The higher the numerical value of the IK parameter, the greater the mechanical protection of the given device.

IK rate

Impact energy

Impact equivalent

000J

no protection

010,15J

impact of a 200g mass dropping from 7.5cm height

020,20J

impact of a 200 g mass dropping from 10cm height

030,35J

impact of a 200 g mass dropping from 17,5cm height

040,50J

impact of a 200 g mass dropping from 25cm height

050,70J

impact of a 200 g mass dropping from 35cm height

061J

impact of a 500g mass dropping from 20cm height

072J

impact of a 500g mass dropping from 40cm height

085J

impact of a 1700g mass dropping from 29.5cm height

0910J

impact of a 5000g mass dropping from 20cm height

1020J

impact of a 5000g mass dropping from 40cm height

 

IP protection class classifies and rates the degree of protection provided against ingress of body parts, solid objects, dust, water or other liquids to the inside of the luminaire. Depending on the degree of protection, the device may be dedicated to work in various conditions. This table below shows what each digit or part of the IP code represents. 

First digit: protection against the ingress of solid objects (according to PN-EN 60529: 2003)

Protection level
0  - no protection
1  - protection against contact with hazardous parts with a back of a hand protection against solid objects with a diameter of 50mm or more
2  - protection against contact with hazardous parts with a finger protection against solid objects with a diameter of 12.5mm or more
3  - protection against contact with hazardous parts with tools, tick wires, etc. protection against solid objects with a diameter of 2.5mm or more
4  - protection against contact with hazardous parts with most wires, slender screws, etc. protection against solid objects with a diameter of 1mm or more
5  - protection against contact with hazardous parts with wires dust protected – ingress of dust not entirely prevented (some ingress shall not have a harmful effect on the operation of the luminaire)
6  - protection against contact with hazardous parts with wires dust tight – full protection against ingress of dust

Second digit: protection against the ingress of liquids (according to PN-EN 60529: 2003)

Protection level
0  - no protection
1  - protection against water drops
2  - protection against water drops when tilted at 15° (vertical dropping shall have no harmful effect on the operation of the luminaire)
3  - protection against spraying water at any angle up to 60° from the vertical
4  - protection against splashes of water from any direction
5  - protection against a water jet (12.5 litre per minute) poured onto the housing from any direction
6  - protection against a powerful water jet (100 litre per minute) poured into the housing from any direction
7  - protection against the short immersion in water (30 minutes up to 1m of submersion)
8  - protection against the continuous immersion in water (housing permanently submerged in water as per the conditions agreed between the producer and the user, but the depth should be greater than at IP7 above)
9  - protection against powerful high temperature and high pressure water jets (80-100 bar and temperature + 80° C) in accordance with DIN 40050

Additional letters (according to PN-EN 60529: 2003)

Letter Degree of protection
A - protection against access to dangerous parts with the front of hand
B - protection against access to dangerous parts with a finger
C - protection against access to dangerous parts with a tool
D - protection against access to dangerous parts with a wire

Supplementary letters (according to PN-EN 60529: 2003)

Letter  Meaning
H - high voltage equipment
M - device moving during water test
S - device standing still during water test
W - Device is suitable for use under certain weather condition

 

This is an international standard set up by the International Electrotechnical Commission defining the protective-earth connection requirements for electronic devices. In other words, the protection class defines the means that should be adopted to ensure protection against electric shock. However, it is not in any extent a measure relating to the safety of the given product. The classification is set out in the PN-EN 61140: 2005 regulations. In summary, there are four classes of protection: 0, I, II, III. Protection classes are illustrated with symbols, except for protection class 0, which has no symbol and therefore no protective earth connection whatsoever. The symbols are shown in the below picture.

Amount of Cu (copper) used in the production of PCB laminate. Copper is a very good conductor of heat and electricity. The greater amount of copper used on the laminate guarantees higher voltage and current stability as well as thermal resistance, which allows for the longer life span of LED light sources.

This is also known as acrylic glass - material used for the production of lamps’ covers and diffusers. This material is highly resistant to UV radiation which prevents the diffusor from yellowing (the diffusor remains pure white for many years of use) . It also has a very good visible light transmission of 92%. The material is also easily recyclable.

Material used in the construction of LED luminaires. It has an excellent mechanical properties and is particu-larly resistant to mechanical impact. Compressive strength is similar to aluminium. Visible light transmission is at 90%.

Type of safety glass processed by controlled thermal or chemical treatments to increase its strength compared with normal glass. It is used in the production of lampshades and diaphragms in LED fittings. It has three times greater resistance to mechanical damage compared to ordinary glass. Tempered glass has much higher thermal resistance than standard glass and, when broken, the glass crumble into small granular chunks instead of splintering into jagged shards as plate glass.