A technology that has made little improvement over the years, Induction Lighting is being tried in many retrofits.  Induction bulbs have no electrodes; the bulb is energized from an RF (radio frequency) electromagnetic field induced from a nearby induction coil of wire.  Light is produced when gas inside the bulb is ionized to produce UV radiation, which excites the phosphor coating inside a glass envelope.  The Induction bulbs do contain Mercury.

Induction Lifetime:
See the sample lumen maintenance graph below.  You need the graph for your Induction product in order to properly size it to the application over time.  IMPORTANT to note that many Induction suppliers provide you another supplier’s graph.  When there are lighting standards to meet, Induction may be acceptable if you over light the space in the beginning, or you relamp before 60,000 hours.  Many specifiers often say the Induction lasts twice as long as the LED.  Note the LED end of life is considered at 70% of its lumen output, and the Induction end of life is considered when it is burned out.  LEDs can glow well into 100,000 hours when illuminance or lumen maintenance is not important.

Induction is similar to Fluorescent technology except it has no electrodes into the glass envelope.  It can tolerate vibration, condensation, glass and metal expansion/contraction; it’s immune to most things that cause electrical contacts to fail.  The integrity of the glass envelope is maintained; it can’t leak.

Retrofit Problems:
Induction lighting is sometimes suggested as a better alternative than LED technology.  Its Luminous efficacy is similar to Fluorescent, less than HID, and common shapes may appear like a bulb, or a rectangularly shaped tube.  HID directional luminaires such as cobrahead, shoebox, high-bay, downlight, etc., may have typical efficiencies of about 75%.  Induction lights have a light emitting area larger than the HID, and are often larger than the HID bulbs they replace.  This form factor has a considerable impact by blocking the light emittance aperture of the fixture even more. 

One issue is that HID bulbs mentioned above have a very small light emitting element inside a clear envelope, to which the fixture reflector is tuned.  This allows the reflector to be fairly close to the HID bulb. 

The Induction lamp has a large emission surface area covered with phosphor, therefore when retrofitting a common fixture, the output pattern is not similar to the original fixture and cannot simulate the lighting Standard originally achieved.  Diagram to right shows an Induction lamp blocking 16 square inches of the fixture's output coming from any reflectors.  Clearly, any reflector of the HID is miss-applied with the Induction lamp.

It is not possible for an Induction bulb to improve the fixture efficiency of an HID optical system; the source size is not matched to the reflectors, and the reflector output area is blocked considerably.  Since luminous efficacy is considerably lower than that of the HID they attempt to replace, they must be oversized in wattage to achieve an equivalent luminous output.  Lumen depreciation past about 60,000 hours would be considered EOL (end of life) if Lumen maintenance was tested.

The graph to the left compares the output/time relationships of a couple Induction products. Luminance can vary considerably over this long period, and the graph shows that not all brands perform alike.  An aged lighting system should be re-lamped when its luminous output no longer satisfies the application.  To realize the long life of Induction Lighting requires that its new lamp luminance allows enough to diminish and still have adequate output up to the time for relamping.

Proper Sizing for Lamp:
Start with an IESNA photometric file and layout program to determine lamp size for your application.
For example, if your photometric layout determines that 5,000 lumens provides the minimum lighting for your application, and if you choose 80,000 hours for re-lamping, the following process will define the new Induction lamp lumens for the lamps shown above to last 80,000 hours.

At 80K hours, output level is:              Lumens of NEW fixture:
The black line shows        66%;       5,000 ÷ 0.66 = 7,576
The red line shows           73%;       5,000 ÷ 0.73 = 6,849

The CRI (color rendering index) will sometimes be in the range of 80-90, depending upon the system you specify, and CCT (Correlated Color Temperature) can be specified from warm white through cool white.  However efficacy of the cool white model is used to compare with most other technologies to catch up with their lumen per watt values.

The Induction bulb is about equal to Fluorescent, and its luminous output deteriorates considerably for more than the last third of its life cycle.  The owner continues to pay the electricity price for full luminous output.  This is a misnomer in the Induction lamp marketing scheme, as it is called "life span" meaning it is still producing some light. 

Dimming is available with Induction lighting down to about 50% output with a dimmable external RF driver.  Remember that Fluorescent lighting can't go down that low because it requires electrical conduction through the gas in order to turn on.

Self-Ballasted, or not? One lamp that has enjoyed great market share is the Compact Fluorescent Lamp (CFL).  This is usually a narrow Fluorescent tube wrapped tightly around in a small package, attached directly to a ballast mounted atop a medium-base to screw directly into an incandescent socket.  The Induction light counterpart is known as Self Ballasted and has the bulb or rectangular tube attached directly to a ballast, sitting atop a medium screw base.  This is presumed ready to replace incandescent and CFL. 

The self ballasted Induction is available in a wide range of sizes, sometimes up to 80-Watts, and such sizes have made them attractive to replace HID; this is where problems may arise.  The maximum allowed ballast case temperature is typically around 70°C.  Actual testing has shown that placing a 60-Watt or higher self-ballasted device inside a sealed lighting fixture (such as a streetlight globe) will produce temperatures exceeding 80°C; this will surely lead to early failure.  Using sufficient power to achieve the necessary lighting levels, applications of this type should use a remote ballast type, placing the ballast in a position where it can properly cool.  Allowable distance between ballast and bulb is usually several feet, so this should pose no problem, other than inconvenient mounting.