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A Little Light on Induction Lamps

A Little Light on Induction Lamps

As a gas discharge lamp similar to metal halide, high pressure sodium, or mercury vapor lamps, induction lamps (also known as electrodeless lamps) generate light through an electromagnetic field that activates mercury in gases such as krypton and argon. Let’s take a closer look at these unique lamps, and their advantages and disadvantages as a light source.

Induction lamps are broken down into three different parts: a frequency generator (ballast), an electromagnet inductor, and a discharge tube. Current is produced inside the lamp via induction through an electromagnetic field. Energy is transferred and the mercury vapor inside the lamp’s envelope begins to create a UV light which reacts with the internal phosphor coating to generate light (similar to how a fluorescent lamp functions). Because of the strong magnetic field and the use of UV light, some induction lamps are coated in electrically conductive materials to reduce electromagnetic interference.

Courtesy of L. Michael Roberts.
Courtesy of L. Michael Roberts.

Internal and External Induction Lamps and HEP

Interestingly, induction lamps are actually a rather old technology. Nikola Tesla showed them off in the late 1890’s within a few decades of the first commercially-successful incandescent bulbs.  Despite being an energy efficient light source, induction lamps are not widely used.  You will find them primarily in industrial settings, though internal induction lamps can be used in the home as well. Some suggested areas to use these lamps include street lighting, outdoor lighting and replacements for common indoor lighting applications.

There are three different types of magnetic induction lamps. They are classified as external core lamps, internal core lamps and high efficiency plasma (HEP) lamps. External core lamps are fluorescent lamps where a portion of the magnetic core is enveloped around the discharge tube (pictured). Its distinctive design allows heat to escape directly through the discharge tube or coil, which creates a longer lamp life that is estimated at 85,000-100,000 hours.  Internal induction lamps are made differently; the coil is placed within the lamp or glass envelope of the light bulb, although the induction coil is not in direct contact with the gases inside the envelope (pictured). Unfortunately, because of this internalization, the heat within the bulb is harder to dissipate, causing a shorter lamp life (around 60,000-75,000 hours).

Image courtesy of Fred the Oyster.
Image courtesy of Fred the Oyster.

HEP lamps are unique in that they use very little energy and have the capability of providing 90 lumens per watt.  The principle

is very similar to other induction lamps; however, instead of inducing current into a mercury vapor using a magnetic field, HEPs use microwaves to generate a plasma out of a mixture of noble gases and halides, sodium, mercury, or sulfur. The concentrated microwaves ionize the gas and excite the electrons.  Once these electrons return to their normal state, they emit photons which provide a very bright light. HEP is still a very new lighting technology, but can be used for commercial and industrial lighting systems due to its high efficiency.

Advantages 

There are several advantages to using induction lamps. As stated earlier, one of these advantages is their long lumen life. Because of the absence of electrodes in the lamp, induction lamps don’t suffer from blackening or electrode degradation.  Flickering, strobing and noise are also not issues.  Induction lamps are extremely energy efficient and actually increase in efficiency the more their output increases. They exhibit incredibly high energy adaptation efficiency, around 62 and 90 LPW (or higher as the output increases).  The high frequency ballasts associated with induction lamps help to offset power factor issues typically present in traditional fluorescent or HID ballasts.  Another major plus is these lamps are instant on, meaning there is no start up time and they reach their full lumen output upon being powered on.

Disadvantages

With their long lumen life and energy-efficiency you would assume that induction lamps would be used more often. One of the biggest drawbacks of these lamps, mainly the internal inductor lamps, is that the ballasts used for these lamps can cause radio frequency interference or RFI. Radio frequency interference is a type of electrical disturbance that occurs when an object creates a powerful electromagnetic field.  However, newer external inductor lamps which mitigate this problem, as they are must meet certain standards placed by the Federal Communications Commission (FCC) so that this interference is either limited or will not occur.  As explained earlier, inductor lamps use mercury. Because mercury is considered to be a toxic substance and can be harmful when released into the environment this presents a drawback for the lamp, but is no different from a traditional fluorescent lamp. External inductor lamps tend to be used only in industrial settings because they are quite large.  The magnetic transformer requires a large space, especially at higher wattages, which is a huge disadvantage when space is at a premium. Another drawback to note is induction lamp cost.  One lamp can run you $60 or more.

It seems that internal and external induction lamps are energy efficient with a twist.  With their unique makeup, long lumen life and bright light, maybe things will finally turn around for these lamps. Have any questions or comments? Go ahead and leave us a comment in the section below, also feel free to drop us a line on Facebook, Twitter, Google Plus, LinkedIn, Pinterest, or Instagram.

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