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In the 1970s, 34-watt energy-saving F40T12 fluorescent lamps were intoroduced in the United States. In the 1980s, T8 32-watt lamps were introduced, [8] but unlike the T8 tubes introduced in Europe, these T8s are not retrofits and require new matching ballasts to drive them. These ballasts were originally magnetic, but most today are electronic.
Ballasts for sign lighting in the United States, are heavier duty than other ballasts because the cooler outdoor temperatures increase the energy required to start a fluorescent tube. They are sized based on the total tube length used. Typical European 230V series choke ballast 40W T12 or 36W T8 fluorescent lamps.
This type of ballast is common in 220–240V countries (And in North America, up to 30W lamps). Ballasts are rated for the size of lamp and power frequency. In North America, the AC voltage is insufficient to start long fluorescent lamps, so the ballast is often a step-up autotransformer with substantial leakage inductance (to limit current flow).
A 230-volt LED filament lamp, with an E27 base. The filaments are visible as the eight yellow vertical lines. An assortment of LED lamps commercially available in 2010: floodlight fixtures (left), reading light (center), household lamps (center right and bottom), and low-power accent light (right) applications An 80W Chips on board (COB) LED module from an industrial light luminaire, thermally ...
Like other gas-discharge lamps such as the very-similar mercury-vapor lamps, metal-halide lamps produce light by ionizing a mixture of gases in an electric arc.In a metal-halide lamp, the compact arc tube contains a mixture of argon or xenon, mercury, and a variety of metal halides, such as sodium iodide and scandium iodide. [7]
A ballast regulator at work in Spain. A ballast regulator (also known as a ballast spreader or ballast sweeper) is a piece of railway maintenance equipment used to shape and distribute the gravel track ballast that supports the ties in rail tracks. They are often used in conjunction with ballast tampers when maintaining track.
The appropriate thickness of a layer of track ballast depends on the size and spacing of the ties, the amount of traffic on the line, and various other factors. [1] Track ballast should never be laid down less than 150 mm (6 inches) thick, [5] and high-speed railway lines may require ballast up to 0.5 metres (20 inches) thick. [6]
Pumps can also be used to empty the leeward ballast tank and fill the windward tank as the boat tacks, and the quantity of ballast can be varied to keep the boat at the optimum angle of heel. A disadvantage of water ballast is that water is not very dense and therefore the tanks required take up more space than other forms of ballast.