INTRODUCTION TO MAGNETIC INDUCTION LAMPS


Almost all of the light sources currently in use have one thing in common, metal electrodes sealed into the walls of the bulb or tube to bring the electrical current inside the lamp chamber/envelope. Unsurprisingly, the main failure mechanisms in these typical lamps [other than breakage] is:

  • Failure of the filament due to depletion of the filament material over time as atoms are stripped off by the electrical current;
  • Vibration which breaks the filament, especially when it is hot;
  • Failure of the seal integrity of the lamp; typically caused by thermal stresses in the area where the electrodes go through the glass walls.  The failure of the seal can either be sudden and complete, or a “slow leak” over time allowing the entry of atmospheric gasses which contaminates the interior.

The dream of lighting inventors has been to produce a lamp with no internal electrodes so as to eliminate these common failure modes.  In an electrodeless lamp the envelope [bulb] is completely sealed and thus there is no chance of atmospheric contamination due to seal failure and no electrodes/filaments to wear out over time.  On 23 June 1891, Nicholas Tesla was granted US patent 454,622 to cover a very early form of Induction lamp.

In an electrodeless lamp, the main failure mechanisms [other than breakage] are:

  • Depletion of the mercury amalgam inside the envelope [bulb].  When the mercury ions are excited and bombard the phosphors [which then emit the light we see], a small percentage of them are absorbed by the phosphor coating over time.  Once the mercury ions inside the envelope are depleted, the lamp emits only a very dim light and has to be replaced.
  • Failure of the electronics [ballast] used to drive the lamp.  This is not a catastrophic failure mode as typically the electronics [ballast] are external to the lamp and can be replaced.

So how do you get an electrical current inside the bulb (glass envelope) of a lamp to excite the mercury ions within?

Magnetic induction lamps are basically a type of fluorescent lamp with (one or two) electromagnets wrapped around a part of the tube (an external inductor lamp), or inserted inside the lamp (an internal inductor lamp).

Light is produced by an up-conversion process within the tube where UV light generated within the lamp by excited mercury atoms, is up-converted to visible light, by a coating of phosphors on the inside wall of the tube.  By adjusting the type and composition of the phosphors in the coating, various color temperatures (E.G.: Warm White, Cool White, etc.) can be produced.

The advantages of Induction


  • Magnetic Induction Lamps have an exceptionally long lifespan due to the lack of electrodes – between 65,000 and 100,000 hours depending on the lamp type and model (see chart below).
  • Very high energy conversion efficiency of between 62 and 85 Lumens/watt [higher wattage lamps are more energy efficient].
  • High power factor due to the high frequency electronic ballasts which are 99% to 95% efficient (depending on model and manufacturer) – less wasted energy in the ballast.
  • Minimal Lumen depreciation (declining light output with age) compared to other lamp types (see graph below).
  • Low glare as Induction lamps are a “broad source” rather then a “point source” like HID or LED lamps.
  • Instant-on and hot re-strike, unlike most conventional lamps used in commercial/industrial lighting which need to ‘warm up’ before reaching full output, and usually need to cool before they can be re-lit.
  • Environmentally friendly as the mercury is in a sold form and can be easily recovered if the lamp is broken, or for recycling at end-of-life.  The glass and metal components of the lamps can also be recycled.
  • These benefits offer a considerable cost savings of between 35% and 75% in energy and maintenance costs (depending on application) compared to other types of HID lamps which our Magnetic Induction Lamps can replace.