»When the wizard Gandolf walked into the caves in Lord of the Rings, he turned the globe atop his scepter into a glowing source of light. So far, lighting engineers can only perform this trick in the movies, but they are always working on new ways to create light. One relatively new source type is the induction light, which makes phosphors glow without the usual electrodes.

The main attraction of induction lighting is incredibly long lifetime. In a fluorescent lamp, the electrodes at either end are the weakest link, and the lamp usually fails when the cathode coating on one of the electrodes is depleted after 15,000–20,000 hours. Induction lamps have no such electrodes, so their rated lifetimes are as long as 100,000 (that's over 11 years, running 24/7!). They also have good vibration resistance and low starting temperatures, making them a good choice for rugged operating environments.

Induction lamps are discharge lamps, where the idea is to get mercury or other atoms to elevate their energy level, then discharge a photon as they fall back to normal. Induction lamps differ from fluorescents-their closest relative in the lighting family-in the way they energize the mercury atoms. Instead of striking an arc between electrodes in a tube, an electromagnetic field is generated by a carefully shaped coil. The field created by the coil induces a current flow in the gas/mercury blend within the lamp. This current excites the mercury atoms and starts the flow of photons. Mercury atoms emit UV photons; phosphors lining the lamp wall absorb the UV photons and in turn emit visible photons.

Like high-quality fluorescents, induction lamps offer instant strike, instant restrike, color stability, 80+ CRI, high power factor and low THD. A ballast-in this case called a field generator-is required to provide the power electronics that drive the induced current in the lamp. Finally, induction lamps have a coupling device that wraps the induction coils around some part of the lamp itself. Induction technology is not dimmable at this time, but it could be in the future.


THE LAMPS

The first lighting product to use induction technology was the Philips QL lamp, originally introduced in Europe in 1990 and in the U.S. in 1992. The QL is a globe-shaped lamp available in three sizes at 55W, 85W and 165W, and two color temperatures at 3000K and 4000K. With the coupling device at its base, it looks a bit like an overgrown A-lamp. The separate 2.65MHz field generator is rated for operation at or below 75 degree Celsius; its lifetime is cut in half for each 10-degree Celsius rise above that temperature. Lumen maintenance is 70 percent at 60,000 hours and 55 percent at 100,000 hours. Philips product specialist, Austin Cahill, says that the QL is primarily an OEM product and that the market is growing, particularly for outdoor installations such as tunnel and freeway sign illumination.

GE Lighting's Genura lamp was the next on the scene, although its emergence in the U.S. market was fitful. This 23W lamp is a self-contained induction lamp with a standard Edison screwbase. With its relatively low light output (1100 lumens) and 15,000-hour lifetime, the Genura is really more akin to a screw-in compact fluorescent. The Genura is available in color temperatures of 2700K and 3000K and is not dimmable. Gary Crawford of GE Lighting says that although the lamp is available in some retail stores, it is mostly a commercial product sold through distributors. Applications include downlights in hotel lobbies and hallways and retail fixtures where they can sometimes replace halogen PAR lamps. Crawford says that the Genura actually handles hot environments better than compact fluorescent alternatives.

Although it is now a forgotten chapter in history, in 1992, a media campaign blanketed the country, touting the 'lamp of the future'-the so-called E-lamp from Intersource Technologies. The E-lamp was an induction lamp that was first targeted at the downlight market. Unfortunately, the company seemed to have spent more of its funds on marketing than on engineering, and the product never made it to shelves.

The next induction lamp to reach the market was the Osram Sylvania Icetron, introduced in 1996. The Icetron lamp has two cylindrical field sources at opposite ends of a rectangular tube and is available in 100W and 150W models; a 75W version is due for release. Color temperatures are 3500K and 4100K, and lumen maintenance is 70 percent at 60,000 hours and about 64 percent at 100,000 hours. Like the QL, Icetron has a separate field generator; its rated maximum temperature is 70 degrees Celsius.

'The product's acceptance rate was slow at first, but now we're finding applications that go beyond our initial focus,' said Dwight Kitchen, manager of commercial engineering at Osram Sylvania. One such application is the Jefferson Memorial in Washington, D.C. where Icetron is used to light the portico area of the structure. Added Kitchen, 'This increased demand for Icetron has resulted in our decision to launch a 75W version later this quarter.'


THE FIXTURES

Jacques LeFevre, president of Indy Lighting, remembers the introduction of induction sources in the early '90s. 'The first applications were outdoors and the lamps were quite expensive, so we didn't get too excited,' said LeFevre. (Indy specializes in specification-grade fixtures for retail and commercial environments.) 'But a couple of years ago, our customer base started to show an interest in induction lighting because of the long life, so we began working on fixtures for places like escalator wells and ceilings over open mall areas.' Their first product was an induction downlight using the Icetron lamp that was installed above escalators and outside entrances to several Dillard's department stores. Indy now offers standard fixtures using both the 100W Icetron and the 85W QL lamps. Although LeFevre is enthusiastic about induction technology, he wants to be sure that limitations such as temperature control of the generators are addressed. He added, 'Premature failures are always bad, but in the places we're putting these fixtures, they would be very costly to replace.'

Bob Fiermuga is the owner of Eclipse Lighting, a company that specializes in decorative outdoor luminaires. He said, 'We are fascinated by induction technology-we think some of the bigger manufacturers may be overlooking this market.' Eclipse offers the 55W and 85W QL lamp in its Galileo outdoor wall sconce, as well as in several institutional and vandal-resistant fixtures. 'Induction lighting is a premium system, but the maintenance benefits are worth it,' said Fiermuga. 'The public sector in particular is always looking for ways to trim their maintenance budgets.' He also thinks that induction lighting makes sense for parking garage illumination. Although maintenance access is not difficult for these fixtures, they usually burn 24 hours a day, making the long lifetime an attractive feature. Eclipse offers four different garage fixtures that use either the 165W QL and the 150W Icetron lamp.

Another good place for induction lighting is in bollards. 'We've been amazed at the interest in induction-lit bollards,' said Kathleen Romfoe, product manager for Phoenix Products Co., an outdoor luminaire OEM. 'Owners like the fact that you can put them out there and forget about them. We're selling them to municipal governments.' Phoenix offers the 55W and 85W QL lamps in most of their bollards and in some shaded pendants and gooseneck fixtures.

Some of the key applications for induction lighting are roadway environments, particularly in tunnels and underpasses where maintenance is a real challenge. Robert Small, an engineering specialist with the Texas Department of Transportation (TxDOT), says that to change some lamps over roadways requires a small battalion of workers, including bucket trucks equipped with crash cushions, flashing arrow vehicles, cone placement and retrieval, and even police cars. TxDOT is now installing three different types of induction fixtures on a testing basis in the Spring Valley Tunnel in Dallas. 'If we get the expected lifetime out of these lamps, we won't be going out there to touch them for 20 years,' said Small, noting that test installations are also underway or planned in El Paso, Austin and Ft. Worth.

The Texas installations demonstrate an additional benefit of induction technology: luminaire positioning. Typically, sodium fixtures are mounted to the side of the roadway for maintenance access, so they must throw light across the road. The induction fixtures can be mounted right over the road where they can more effectively and evenly illuminate the road surface.


LINGERING CONCERNS

Induction sources pose technical challenges, most of which have been addressed by vendors now that the technology is nearly a decade old. Early systems faced concerns about electromagnetic interference from the field generators, but today's products meet FCC 47CFR Part 18 Non-Consumer certification, and complaints are just about non-existent.

LeFevre points out that the relatively small lumen package of the induction sources poses a challenge for luminaire designers. He said, 'We want to put these things in high-ceiling areas to get the maintenance benefits, but you need a lot of light to reach the floor from up there.' The larger 165W Philips QL lamps have helped address this problem. Another consideration is that the induction sources are essentially big blobs of light, so it's more difficult to design an effective reflector for them than the small arc tube of HID sources. Eclipse's Bob Fiermuga notes that the shape of the QL lamp makes it more applicable for refractor-type downlights, while the flat profile of the Icetron makes it more appropriate for cutoff-type floodlights.

A final concern is the temperature sensitivity of the generator, which is a solid-state electronic device that can fail prematurely if it gets too hot. While HID systems can operate at temperatures of 90-105 degrees Celsius, induction systems are limited to the 70-75-degree Celsius range. Danny Lambeth, president of Infinity Lighting, explains that his engineers have been working for the past four years to solve the temperature limitations associated with induction technology. 'If you exceed the rated temperature, the warranty is out the window,' he said. Still, with careful design and testing, Lambeth thinks induction technology can do the job. He noted, 'If you can design an induction fixture that can handle the heat, is watertight and explosion proof, it's a home run.'


January/February 2002 Architectural Lighting Magazine