Tips to Choosing Magnetic, Electronic Ballast Fluorescent, Germicidal Lamp for Industry, Application

The long history of fluorescent lamps has resulted in an equally long ballast industry history.  Fluorescent and germicidal lamps may operate on both magnetic and electronic ballast types but what are the differences and which ballast type is the better choice?

For many years, the magnetic ballast fluorescent lamp was the standard. Magnetic ballast fluorescent lamps contain either transformers or autotransformers that generate sufficient open circuit voltage to start the lamp. They are designed with high internal impedances that limit lamp current. Some ballasts may embody extra windings to heat the lamp electrodes. While actual designs differ, the internal construction is generally composed of copper coils on cores made out of stacked iron lamiae. The entire assembly is potted in a steel case filled with pitch. The resistance of the copper wire and power loss in the magnetic circuit limit the electrical efficiency of the lamp-ballast system.  In many regions, the magnetic ballast is being phased out by legislation due to inherent inefficiency.

More recently, research has shown that low-pressure mercury-vapor lamps operate more efficiently at high frequency. For example, a lamp operated at 60 Hz extinguishes once per cycle.  During this off time, the cloud of electrons that surrounds the anodes dissipates and must be replaced for the next cycle. This contributes to energy loss in the lamp. Lamps operated at high frequency stay conductive throughout the operating cycle eliminating the anode loss. Modern electronic ballasts operate at frequencies of tens or hundreds of Kilohertz, accommodating lamps from sub-miniature (2mm-5mm) to large-diameter (6mm-38mm). The electronic ballast is primarily a high frequency power supply capable of providing the required lamp power. There is included in the circuitry either a capacitor or a small inductor that sets the effective impedance of the power supply: this is the actual ballast.  Electronic ballasts may have electrical efficiencies of up to 95%, far outperforming the magnetic ballast.  Many electronic ballast types have special features that enable the user to program a soft lamp start, shut down if a lamp shows a fault (open circuit or ground fault) and/or turn off at end of lamp life.

Electronic ballasts are sometimes difficult to match to lamps since electronic ballast fluorescent lamps are rated on what is essentially an “equivalent light output” basis when compared to operating on the older magnetic ballast. For example, magnetic ballast operating a lamp at 425mA may operate the same lamp at 350mA on a replacement electronic ballast (to obtain the same light output).  This situation is acceptable for general lighting since the electronic ballast fluorescent lamp becomes more efficient resulting in power reduction.  This may not work for germicidal lamps that often need the full power to produce the rated UV output. The situation is even more complicated (worse) with so-called high output ballasts.

LightSources, together with our affiliated companies, represent the foremost high-tech designers and manufacturers in the lamp industry today.  LCD Lighting, our leading affiliate in fluorescent lamps has designed and manufactured thousands of custom fluorescent lamps for virtually every type of OEM lighting application. Contact us to learn more about our exclusive fluorescent light technology.