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Mercury vapor ballasts are designed to drive tubular ultraviolet lamps. There are two types of mercury vapor lamps. The most common is the medium pressure lamp. This lamp series has been standardized and is available in arc lengths of 1 inch to 120 inches. The other type of lamp is a mercury vapor lamp with metal additives. The additives used in the lamp create changes in the spectral output.

Ballasts are used to initiate and control the arc in mercury and metal additive curing lamps. Ballasts provide an instantaneous high voltage to strike the elements within a mercury vapor lamp, creating a plasma that, once initiated, is sustained by the ballast. Total wattages up to 50 kilowatts can be designed. Our constant wattage ballast consists of a transformer, capacitors and ignitor.

The advantage of a constant wattage ballast is that it allows for wide variations in input voltage to affect output wattage by only a few percent. These ranges can be customized to meet your applications requirements. Typical designs have an output variation of only +/- 3% with an input voltage varying over a range of -15% to +10%. Constant wattage is accomplished by a resonant tank circuit in which the lamp winding is in a controlled magnetic saturation with AC capacitors, such that voltage swings on the input side have a very small impact on lamp current. An interesting feature is that these current limiting capacitors can be switched (see schematic) in and out of the circuit to provide various lamp power levels.

Standard Ballast

Ballasts are available in sizes from 400 watts to 40KW in 50, 60, or 50/60Hz. Typically, input power factor is better than ninety (90%) percent at nominal input voltage. Ballasts are constructed using silicon grain oriented steel, UL rated copper wire, UL Class H insulation system and impregnated with a unique epoxy varnish for maximum thermal transfer.


This ballast offers a linear variation of output power from 40 to 100% as opposed to capacitor switching which changes lamp power as a step function. This is accomplished by varying the conduction time on an inductor which negates capacitance in the circuit allowing enhanced control of lamp current. Lamp current is sensed in a closed feedback loop circuit which can instantaneously respond to changes making the necessary adjustments.
A PLC interface is available to communicate with the ballast in order to vary lamp output. In order to protect all of the control circuitry from power problems typically found on the primary the control circuits are all located on the secondary of the ballast.


Saturable Reactors

If your application requires an accurate variation of lamp output power over a range of 30% power to full power, saturable reactors are available to provide a smooth, linear variation of lamp power