Electrodeless lamp

An induction lamp is a special fluorescent light or neon tube that couples the electromagnetic energy and the gas vessel therefore has no electrodes.


Induction lamps differ in their structure fundamentally different from conventional fluorescent lamps. While fluorescent electrodes protrude into the interior of a gas-filled glass tube and the high voltage between them to an ionization of the gas leads, no live parts are used in induction lamps with the gas filling into contact. The energy is transferred to the gas filling in accordance with the electromagnetic induction principle.

The low-pressure gas discharge in the interior is not powered as in conventional fluorescent lamps by means of electrodes, but maintained through inductive coupling. The discharge vessel for this purpose forms the secondary winding of a transformer. The windings of the excitation coils (better: Operating device) with a special ballast fed with a high-frequency AC voltage that produces it from the mains or from a DC voltage (eg for emergency lighting ).

The operating frequency of the open shapes, in contrast to excitation by microwaves ( for example, sulfur lamps) with relatively low 250 kHz. Therefore, and due to the most symmetrical structure a lesser Abschirmaufwand against spurious emissions than with microwave excitation is required.

Compact induction lamps with operating frequencies by 2.65 MHz possess a rod-shaped, so-called power coupler ( coil ) inside. They sometimes wear on their outer shell, a thin, electrically conductive layer or wire rings to keep the radiated interference low.

Induction lamps have external or at low power in the lamp integrated RF generators and are offered with output of 23 to 500 watts.

The light yields are 60 to 90 lumens per watt, based on the actually perceived by the human eye light there are up to 150 pupil lumens per watt (so-called VEL value).

Induction lamps have been used because of the high purchase price primarily in areas where high reliability is required and the lamp replacement requires a very high effort or is impossible. It will be partially guaranteed lifetimes of 100,000 hours and maintenance of over 10 years.

Induction lamps are similar to conventional fluorescent lamps available by selecting the phosphors in various color temperatures and excellent color rendering indices.


Open design

The dining winding in this design consists of two narrow wound toroidal cores which are placed around the tube self-contained. The basic structure is similar to that of a tokamak. The discharge vessel has the shape of a self-contained fluorescent lamp with two parallel tubes. The length of a 150 -watt unit is approximately 500 mm.

Compact design

There are induction lamps for E27 and E40 screw sockets, which can thus be used as a replacement to conventional lamps. The inductive excitation occurs in these lamps by a cylindrical coil in the center of the discharge vessel. The coil is supplied by an integrated electronic system or by an external radiofrequency generator.

Advantages and Disadvantages

Advantages over fluorescent lamps are:

  • Flicker-free instant start
  • Switching stability, therefore, with motion detectors or similar. application - even for security areas
  • High luminous flux over a wider temperature range ( amalgam mercury reservoir )
  • Lower potential ignition temperature (with suitable ballasts to -40 ° C)
  • High luminous efficacy up to 120 lm / W at a very good color rendering index
  • 100,000 hours and more possible
  • Tolerated by largely natural light spectrum for nocturnal insects

After 60,000 or 70,000 hours or 75% or 60% of the light intensity can be achieved according to the manufacturer's instructions.


  • Often special lamp with ballast required, often no more compatible with other light sources, base
  • High purchase price ( now available at moderate prices, including also as retrofit for existing lamps )
  • Lamp contains mercury - problematic in mechanical destruction ( vehicle collision, vandalism ) and recycling