Glossary

Dimensions

LED lamps differ in length, diameter and width. Depending on the type of luminaire, choose the appropriate lamp.

Electrical power

This is quoted in watts according to the manufacturer’s specifications.

Luminous flux [lm]

This describes the total light power emitted by a light source. The luminous flux is specified in lumens and is a target value set by the manufacturer.

Luminous efficiency [Lumen/Watt]

The ratio of luminous flux (lumens) to power consumption (watts) provides information about the efficiency of the lamp.

Service life [h]

This is usually specified as a time period. After this period, LEDs still exhibit a luminous flux of 70% of the initial value. Top products must have a service life of at least 50 000 hours.

Color rendering index [Ra]

This indicates the quality of color rendering (CRI). The Ra is determined from an average value of the color fastness of eight different colors. The best value is 100. Good LED lamps have an Ra between 80 and 95.

Color temperature [K]

It indicates the blue or red component of the light and is determined in degrees Kelvin (K). The color temperature is crucial for the perception of light quality. There are

• Warm white: reddish light, 2 700 to 3 500 Kelvin (incandescent lamp)
• Cold white: bluish light, 5 000 to 10 000 Kelvin (daylight)
• Neutral white: between reddish and bluish light, 3,500 to 5,000 Kelvin

Socket type

This provides the mechanical and electrical contact to the socket. The lamp socket fixes the bulb in the lamp base. There are the following types:

• E27: Edison screw thread with Ø 27 mm
• E14: Edison screw thread with Ø 14 mm
• GU10: bayott socket, pin spacing: 10 mm
• GX53: bayott socket, pin spacing: 53 mm

Technology Overview

Energy saving lamp

Energy-saving or compact fluorescent lamps are particularly small. Compared to other fluorescent lamps of the same power, the tube containing the gas discharge and the fluorescent material is smaller, curved or folded several times. Since they are equipped with an Edison base and ballast, they can be used instead of incandescent bulbs.

Advantages and disadvantages: A conventional incandescent lamp is inexpensive to purchase and has a service life of approx. Ø 1,000 operating hours. Compact fluorescent lamps can be used for between 5,000 and 15,000 operating hours, depending on the make and type. However, these are considerably more expensive to purchase.

In the long run, however, energy-saving lamps are cheaper. This results from electricity savings of 70 to 80% and their much longer life compared to conventional incandescent lamps.

LED

Light emitting diodes or LEDs are based on semiconductor compounds that convert electricity directly into light. It emits light when current flows through the diode in the forward direction.

Unlike other light sources, LEDs do not suddenly fail, but become weaker and weaker. If the luminous efficacy is reduced by half compared to the initial value, it has reached the end of its service life. The total lifetime depends on the semiconductor material and the operating conditions.

Advantages over incandescent lamps:

• low energy consumption,
• hardly any heat is generated,
• resistant to shocks,
• shorter switching times,
• high durability.

Energy efficiency class

This is currently still specified using A-G scaling. Efficiency classes below C are hardly ever used anymore due to the high power consumption. The efficiency value in lumens/watt is not always specified by the manufacturers. You can calculate this with the following formula:

Luminous efficacy [Lumen pro Watt] = Luminous flux [Lumen] / Power [Watt]

Dimmability

Whether a lamp is dimmable is indicated either as text or as a corresponding symbol on the packaging.

Lifetime
The average service life is usually given in hours, in rare cases also in years. It is difficult to determine according to the standard. Here are two examples: The L70 value describes a 30% drop in luminous flux from the output value of the LED module. The B value, on the other hand, describes the number of LEDs that no longer function over time. The service life of LEDs depends on various factors as well as the maximum number of switching cycles.

The average service life of light sources known to date is at: