Operating Principles continued...
- System Components
The induction lighting system consists of three main components (Figure 3.), each of which can be replaced separately if service is required:
Fig. 3.
Fig. 4.
Fig. 5.
Fig. 6. - The lamp bulb or discharge vessel (Figure 4.) is a closed glass bulb containing a low-pressure insert gas filling with a small amount of mercury vapor. The walls of the vessel are coated on the inside with a fluorescent powder of any of the modern three-line phosphor types, providing a choice of color temperatures (3500K, 4100K, 4700k and 5000K). The discharge vessel is fixed to the power coupler by the lamp cap with a “click system”. These two components normally never need to be disassembled due to the long lifetime of the system.
- The power coupler transfers energy from the HF generator to the discharge inside the glass bulb, using an antenna that comprises the primary induction coil and its ferrite core (Figure 5.). Other parts of the power coupler are a plastic support for the antenna, a 40 cm coaxial connecting cable carrying the current from the HF generator, and a heat conduction rod with mounting flange. The mounting flange allows the lamp system to be mechanically attached to the luminaire, and removes waste heat to a heat sink that forms part of the luminaire. The maximum permissible mounting flange temperature is one of the determining factors that contribute to the system’s long lifetime.
- The HF generator (Figure 6.) produces the 2.65 MHz alternating current supply to the antenna. It contains an oscillator that is tuned to the characteristics of the primary coil in the antenna and the 40 cm coaxial connecting cable. The HF generator also includes preconditioning and filtering circuits to correct fluctuations in the voltage and frequency of the main power supply, and to prevent distortion from feeding back into the mains. All the generator electronics are housed in a metal box that provides screening against radio frequency interference and serves as a heat sink. The maximum permissible testpoint temperature is the other determining factor that contributes to the system’s long lifetime.
