LED lamps differ in length, diameter and width. The lamp must be selected to match the luminaire used.
The electrical power in watts is given in accordance with the manufacturer's specifications.
Luminous flux [lm]
The luminous flux describes the total light output of a light source. The luminous flux is expressed in lumens. This is the target value specified by the manufacturer.
Luminous efficacy [Luminous/Watt]
The ratio of luminous flux in lumens to power consumption in watts provides information about the efficiency of the lamp.
Life time [h]
The service life is usually stated as the period after which the LEDs still have a luminous flux of 70 % of the initial luminous flux. Top products must have a service life of at least 15,000 hours.
Colour rendering index
The quality of the colour rendering is indicated by the colour rendering index "Ra" or Color Rendering Index "CRI". The Ra is determined from the mean value of the colour fastness of 8 different colours. The best value is 100. Good LED lamps have a Ra of 80 to 95.
Colour temperature [K]
The colour temperature indicates the blue or red component of the light. Reddish light is called warm white, bluish light cold white. Neutral white lies between them. The colour temperature is decisive for the perception of light quality. With regard to compact fluorescent lamps and fluorescent tubes, there is often the prejudice that they produce only cold light, which is particularly unsuitable for living areas compared with classic incandescent lamps. This light quality is determined by the colour temperature (expressed in degrees Kelvin, K). Colour temperatures in the range of 3,000 Kelvin or slightly below (often 2,700 Kelvin) correspond to warm white light comparable to classic light bulbs. Lamps with a colour temperature above 4,000 Kelvin increasingly have the character of cold white. The colour temperature is indicated in Kelvin on the packaging.
- Warm white: 2700 to 3500 Kelvin (light bulb)
- Neutral white: 3500 to 5000 Kelvin
- Cold white: 5000 to 10.000 Kelvin (daylight)
The base establishes the mechanical and electrical contact to the socket. The lamp socket fixes the light source in the lamp base.
- E27: Edison screw with 27 mm diameter
- E14: Edison screw with 14 mm diameter
- GU10: Bayonet base, pin spacing: 10 mm
- GX53: Bayonet base, pin spacing: 53 mm
Energy saving lamp
Energy-saving lamps or compact fluorescent lamps are particularly small fluorescent lamps. The tube containing the gas discharge and the fluorescent material is smaller, curved or folded several times compared to other fluorescent lamps of the same wattage. They are equipped with an Edison base (screw base) and a ballast so that they are interchangeable with incandescent bulbs.
A conventional incandescent lamp ("bulb") has an average service life of approximately 1,000 operating hours and is inexpensive to purchase. A compact fluorescent lamp, on the other hand, lasts between 5,000 and 15,000 operating hours, depending on the make and type, but is considerably more expensive to purchase. However, if one considers their considerably longer service life, they are cheaper than correspondingly many incandescent lamps. In addition, the energy-saving lamp consumes 75-80 % less electricity.
The halogen lamp is a further development of the incandescent lamp in which a tungsten filament is used and the filling gas has a halogen additive (usually bromomethane). The glass bulb is very small and consists of quartz or hard glass. The tungsten atoms that evaporate from the filament during operation combine in the cooler zones near the bulb with the bromine that is released from the bromine compound at this temperature. At the high piston temperatures of over 250 °C, the tungsten bromide does not settle on the wall but remains gaseous. For this reason, the glass bulb is kept small. Close to the helix, the tungsten compound decomposes again into atomic tungsten, which attaches itself to the hottest (and thus thinnest) points of the tungsten wire, and into bromine, which again decomposes into bromomethane. The result is a circulation process that prevents piston blackening caused by tungsten deposits and regenerates the filament at its weak points. It is therefore possible to work with higher temperatures of the filament than with normal incandescent lamps, which results in high luminous efficacy. Halogen lamps have a long service life, constant luminous flux throughout their service life and very small dimensions.
Light emitting diodes (LEDs) are based on semiconductor compounds that convert electricity directly into light. When current flows through the diode in the forward direction, it emits light.
The service life of LEDs is defined as the time after which the luminous efficacy has fallen to half of its initial value. LEDs become weaker and weaker over time, but do not fail suddenly. The service life depends on the semiconductor material and the operating conditions (heat, current).
The properties of the generated light can be changed by the semiconductor materials and the doping. Especially the spectral range and the efficiency can be influenced. In order to produce white light with light emitting diodes, an ultraviolet or blue light emitting diode is usually combined with fluorescent dyes (phosphors).
The advantages of LEDs over incandescent lamps are their low energy consumption, hardly any heat is generated, they are resistant to vibrations, have shorter switching times and a long service life. The efficiency (luminous efficacy) of LEDs is constantly being improved and more powerful LEDs are constantly being further developed.
LED lamps in bulb or candle shape shine all around the room, their light is called "undirected". The brightness of lamps with non-directional light is measured in lumens (luminous flux).
LED spots are used for the targeted illumination of objects or surfaces; their light is called "directed". The brightness of spots is not easy to describe, because different properties are important depending on the application.
Energy efficiency class
The energy efficiency class is still indicated by means of the well-known A-G scale. However, the efficiency classes below C will in future only be available for discontinued incandescent and halogen bulb models. In the case of halogen lamps in particular, care should be taken to ensure that no discontinued models with lower efficiency than the C-Class are purchased. The efficiency value in lumen per watt is not always stated by manufacturers, but it is easy to calculate:
Luminous efficacy [Luminous/Watt] = Luminous flux [Lumen] / Power [Watt]
indicates whether the lamp is dimmable or not is indicated as text and/or symbol (see figure Packaging *4).
The average service life is given in hours and possibly years, although it is not so easy to determine the service life according to the standard. For example, the L70 value describes a 30% decrease in luminous flux from the output value of the LED module. The B-value, on the other hand, describes the number of affected LEDs that no longer function over time. Thus, the LED life is dependent on several factors, including the maximum number of switching cycles, which must also be taken into account.
Halogen lamp 2.000 - 4.000h
Energy saving lamp 10.000h
LED lamp 20.000 - 50.000h