Three-phase alternating current consists of four electrical conductors, of which 3 are phase conductors and 1 is the protective conductor. Each of the three phases can be switched separately, which makes it easy to change the lighting. This allows a functional system to be created that is suitable both for accent lighting and for illuminating billboards and decorative materials.

A spotlight belongs to the category of directional lighting and is ideal for supplementary and accent lighting. Its applications are highly versatile: it can be used to illuminate individual areas of a room or sales areas, and it is also excellent for highlighting certain objects and products. The beam angle of the spotlight (the angle illuminated by the spotlight) depends on the size of the object and the distance of the light source.

The common feature of different types of floodlights is that they can illuminate large areas, making them ideal for the general lighting of rooms, larger areas and objects.

Illuminance, i.e. the amount of luminous flux falling on a certain surface (lx = lm/m²), is measured in lux (lx). One lux is equal to one lumen of luminous flux per square metre. Illuminance cannot be measured in luminous intensity, because the illumination can be perceived differently depending on the reflectance of the illuminated area. This is why dark/light walls, furniture or objects require different lighting methods.

The colour rendering index describes the effect of a lamp’s light on coloured objects. The higher this value, the better it is from the user’s point of view, because the original colours appear more lifelike under the light produced by the lamp. Natural light (daylight) has a colour rendering index of 100 Ra, so the best achievable value is 100 Ra. Colour rendering values of different lamp types depending on the colour of the light:
Halogen lamps: 95–100 Ra
Energy-saving lamps: 80–90 Ra
Fluorescent lamps: 80–90 Ra
LED lamps: 70–92 Ra

In enclosed indoor spaces, e.g. offices, the Ra value must not fall below 80.

Example:
The value 830 indicates the combination of Ra and light colour.
The first digit, 8(0), indicates Ra > 80. The 2nd and 3rd digits, 30(00), indicate the light colour, which in the example above is 3000 K.

Classification:

Class 1A
Lamps and luminaires with an Ra/CRI value of 90 or higher are classified as Class 1A. These products have an excellent colour rendering index, close to daylight. These light sources can also be used in areas where colour rendering is particularly important. E.g. sales areas, workplaces, or for designers and graphic designers.

Class 1B
Lamps with an Ra/CRI value between 80 and 89 are classified here. These lamps have a good colour rendering index. They are suitable for use in living rooms and offices.

Class 2A
Lamps and luminaires with an Ra/CRI value between 70 and 79 are classified as Class 2A. Their colour rendering is medium or good. They can be used in areas where colour rendering is of secondary importance. E.g. warehouses or offices.

Class 2B/3/4
Lamps and luminaires with an Ra/CRI value below 70 are classified as Class 2B/3/4. Their colour rendering is inaccurate, so they are not suitable for places where people spend long periods of time. Their use is recommended only in places where lighting is necessary but colour rendering is not required.

When determining luminance, the luminous intensity of an element of a luminous or illuminated surface is divided by the area of that surface element. Unit: candela per square metre.

Luminance = candela / area (cd / m²)

The ratio between the luminous flux emitted by the luminaire and the “rated” luminous flux emitted by the light sources used in the luminaire. Efficiency is influenced by the luminous surface of the lamp as well as thermal conditions. The measured initial luminous flux (lm) must be divided by the measured initial input power (W) of the same luminaire. Lighting efficiency is expressed in lumens per watt (lm/W), which can also be used to measure energy efficiency.

Luminous efficacy is a measure of the economic efficiency of a light source. Calculation: the luminous flux generated by the luminaire (lumen – lm) is divided by the energy consumption (watt – W). The higher the lumen/watt ratio, the more efficiently the lamp converts energy into light.

People experience their surroundings through colours as well. The colour of lighting is determined by the spectral composition of the light, whether it comes directly from a light source or from the reflection of an object.

The flame of a candle (1500 K) and the blue sky (>10,000 K) serve as reference values for colour temperature.
The higher the colour temperature (Kelvin – K), the whiter the colour of the lighting. The lower this value, the warmer and cosier the colour of the light becomes.

Classification of colour temperatures:

Warm white (WW): <3,000 K. This colour temperature is pleasant to the eye. It is recommended for places where comfort is of outstanding importance, e.g. living rooms, restaurants or bars.

Neutral white (NW): 3,300–5,300 K. There are no additional tones besides white, so this lighting provides colour-faithful colour rendering and is therefore highly suitable for lighting almost any room. It is an ideal choice for workplaces and offices.

Cool white (CW): >5,300 K. In addition to white, there is a slight bluish tone, creating an elegant, icy effect; it is therefore characterised by stronger brightness and clearer illumination. It is highly suitable for public spaces, offices, workplaces and hospitals.

An additional number such as 830 is often found alongside the colour temperature. What does it mean?
As shown below, it is a combination of the colour rendering index and the colour temperature.

Thus, 830 means:
1st digit: 8 (0) = Ra > 80
2nd and 3rd digits: 30 (00) = colour temperature 3000 K

Luminous intensity is measured in candelas (cd), indicating the luminous intensity emitted by a light source in a given direction.

The spatial distribution of the luminous intensity of a light source results in a three-dimensional representation. A cross-section of this representation forms the light distribution curve. Light intensity is generally specified in a polar coordinate system as a function of the beam angle. Depending on the shape and symmetry properties of the luminaire’s luminous-intensity distribution, a distinction must be made between deep, wide, symmetrical and asymmetrical light distribution.

Luminous flux is measured in lumens (lm). Luminous flux describes the total “amount” of visible light emitted by the light source. By definition, luminous flux is a power-type quantity, so its unit of measurement should be watt. The purpose of introducing the lumen is that luminous flux refers to the visible-light range, unlike radiant power, which applies to the entire electromagnetic spectrum.

The protection rating of a luminaire indicates how well it is protected against contact, foreign objects and water. It is identified by the IP code system, which is used for many different electrical devices. The IP marking is followed by two digits: the first refers to protection against the ingress of foreign objects, e.g. dust, and the second refers to protection against moisture, e.g. water.

First digit: protection against contact and foreign objects
0: No protection
1: Protection against solid foreign objects ≥ 50 mm
2: Protection against solid foreign objects ≥ 12.5 mm
3: Protection against solid foreign objects ≥ 2.5 mm
4: Protection against solid foreign objects ≥ 1 mm
5: Dust-protected
6: Dust-tight

Second digit: protection against moisture
0: No protection
1: Protection against vertically falling water drops
2: Protection against dripping water when tilted up to a maximum of 15°
3: Protection against water spray up to a maximum of 60°
4: Protection against splashing water
5: Protection against water jets
6: Protection against powerful water jets
7: Protected against the second immersion
8: Protected against continuous immersion
9: Protection against high-pressure water jets

Additional markings:
A: Hazardous parts cannot be reached by hand.
B: Hazardous parts cannot be reached by finger.
C: Hazardous parts cannot be reached with a tool.
D: Hazardous parts cannot be reached with a wire.
F: Oil-resistant.
H: High-voltage device (>1 kV).
M: Water test while in motion.
S: Water test while stationary.
W: Suitable for use under specified weather conditions.
K: Pressure-resistant, i.e. can be cleaned with a high-pressure/steam cleaner (IP69 only).

Common combinations / examples:
IP20 minimum requirement for indoor lighting
IP44 protected against water drops, e.g. house-number lighting
IP54 e.g. light fitting (outdoor)
IP65 e.g. moisture-resistant diffuser luminaire, recessed luminaires in bathrooms

The protection class indicates the measures taken in the design of the luminaire to prevent electric shock. The construction and operating method determine the protection class. A fault or short circuit can create a life-threatening situation, especially in products with a metal housing. According to DIN VDE 0711, three protection classes are distinguished, describing the scope of protective measures against electric shock:

Protection Class I:
All electrically conductive housing parts of the lamp or device are securely connected to the protective conductor system. The protective conductor connection of the housing is dimensioned so that no permanent hazardous touch voltage can occur on the housing and so that the fuse or residual-current device (RCD) trips and disconnects the circuit.

Protection Class II:
Luminaires or devices in Protection Class II must have double or reinforced insulation. If the devices have an electrically conductive surface or accessible part, these are separated from live parts by double or reinforced insulation. Most of these devices are not connected to the protective conductor.

Protection Class III:
Luminaires or devices in Protection Class III use safety extra-low voltage (SELV – unearthed protective extra-low voltage) or functional extra-low voltage with electrically safe separation (PELV – earthed protective extra-low voltage), and may therefore only be connected to suitable SELV or PELV power sources (<42 volts). These include safety transformers or batteries. Luminaires or devices with PELV have double or reinforced insulation between the mains connection and conductive parts.

UGR is an abbreviation of the English term ‘Unified Glare Rating’. The UGR value is a dimensionless number indicating the degree of glare sensation caused by indoor lighting. UGR values must be determined step by step within the range from 10 to 30. The levels 13, 16, 19, 22, 25 and 28 defined in DIN EN 12464-1 express the statistical glare sensation of a large number of observers. The lower the UGR value, the fewer observers experience unpleasant, dazzling glare. Different activities have different glare requirements:
Technical drawing: UGR ≤ 16
Reading, writing, classrooms, computer work, inspection work: UGR ≤ 19
Industrial and craft work, reception: UGR ≤ 22
Work, stairs: UGR ≤ 25
Corridors: UGR ≤ 28