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Electrical System Optimization
Published in Albert Thumann, Scott Dunning, Plant Engineers and Managers Guide to Energy Conservation, 2020
High intensity discharge lamps are electric discharge sources. The basic difference from fluorescent lamps is that HID lamps operate at a much higher arc pressure. Spectral characteristics differ from those of fluorescent lamps because the higher pressure arc emits a large portion of its visible light. HID lamps produce full light output only at full operating pressure, usually several minutes after starting. Most HID lamps contain both an inner and an outer bulb. The inner bulb is made of quartz or polycrystalline aluminum; the outer bulb is generally made of thermal shock-resistant glass. HID lamps require current-limiting devices, which consume 10% to 20% additional watts. HID lamps include mercury, metal halide, high-pressure sodium, and low-pressure sodium lamps as described below.
Lighting
Published in Sue Reed, Dino Pisaniello, Geza Benke, Kerrie Burton, Principles of Occupational Health & Hygiene, 2020
An alternative and more efficient form of lighting is achieved by passing an electric current through a gas, exciting its atoms and molecules to emit radiation whose spectral distribution is characteristic of the gas present. The most commonly used metals are mercury and sodium vapour, as they emit useful visible radiation. Discharge lamps are often classified as high and low pressure. In a low-pressure lamp with mercury or sodium vapour as an active ingredient, the metal vapour is mixed with an inert gas, often neon or argon. The vapour pressure of the metal is usually well under 1 × 10–3 atmospheric pressure. High-pressure lamps are often referred to as high-intensity discharge lamps, or HID lamps. They include mercury vapour, metal halide, high-pressure sodium, and xenon short-arc lamps. Compared with fluorescent and incandescent lamps, HID lamps are highly efficient in that they produce a large quantity of light in a small package. They generate light by striking an electrical arc across tungsten electrodes housed inside a specially designed inner fused quartz or fused alumina tube. This tube is filled with both gas and metal halides. The gas aids in the starting of the lamps; the metals produce the light once they are heated to a point of evaporation.
Lighting
Published in Sue Reed, Dino Pisaniello, Geza Benke, Principles of Occupational Health & Hygiene, 2020
An alternative and more efficient form of lighting is achieved by passing an electric current through a gas. This excites the atoms and molecules of the gas, causing it to emit radiation, with the spectral distribution characteristic of the specific gas used. The most commonly used metals are mercury and sodium vapour, as they emit useful visible radiation. Discharge lamps are often classified as either high-or low-pressure lamps. In a low-pressure lamp with mercury or sodium vapour as an active ingredient the metal vapour is mixed with an inert gas—often neon or argon. High-pressure lamps are referred to as high-intensity discharge (HID) lamps. They include mercury vapour, metal halide, high-pressure sodium and xenon short-arc lamps. Compared with fluorescent and incandescent lamps, HID lamps are highly efficient because they produce a large quantity of light in a small package. They generate light by striking an electrical arc across tungsten electrodes housed inside a specially designed inner fused quartz or fused alumina tube. This tube is filled with both gas and metal halides. The gas aids in the starting of the lamps; the metals produce the light once they are heated to a point of evaporation.
Wide-range dimmable LED lighting based on QL-SEPIC converter
Published in EPE Journal, 2019
Chien-Nen Liao, Huang-Jen Chiu, Yao-Ching Hsieh
Light emitting diodes (LEDs) are widely applied as indicating signals and traffic lights. In 1996, the first white-light LED, which was realized by a blue LED die coated with a yellow phosphor, was commercialized by Nichia Corporation. The white light is emitted by mixing the spectra of the broad-band yellow light from phosphor coating and the narrow-band blue light from InGaN chips [1]. Nowadays, the white-light LEDs have made significant progress in terms of spectrum purity, luminous efficacy, colour rendering, power dissipation and lifetime. These improvements facilitate the competitiveness of the white-light LEDs compared with existing lighting sources, such as incandescent, fluorescent and high-intensity-discharge (HID) lamps [2,3]. White-light LEDs have solved the serious flaws of limited spectrum and poor colour rendering problems; colour rendering index (CRI) can be higher than 80 for indoor lighting products [4,5]. Regarding luminous efficacy, LEDs are better now than HID and can be two times more than fluorescent lamps and 10 times more than incandescent lamps. Some products are announced by the leading manufacturers such as Cree, Philips Lumileds and Osram; products of >150 lm/W are also announced [6–8]. In addition, the lumen maintenance lifetime of 35,000 h at high-temperature test condition 105°C are reported [6,7]. The LED module was constructed by mounting multiple LED dies to form a high power LED module for enhancing the total luminous flux. In addition, the fast response and proportional light output over power facilitate LEDs with better dimming flexibility. LEDs quickly overtake and replace the traditional light sources, becoming an important light source in various applications.