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Metal Halide Ballasts

Like other discharge light sources, high-intensity discharge (HID) metal halide lamps require a ballast to limit current to the electrodes. Ballasts also provide the correct voltage for starting and restarting, and they adjust current to maintain light color and intensity over time. All ballasts suffer internal losses—ranging from 5 to 90 percent of the lamp wattage—that should be included in any calculation of potential savings, especially when switching from nonballasted sources such as incandescent lamps. Two main types of ballasts are now available: the newer electronic ballasts and the more common magnetic ones

What Are the Options? Magnetic Ballasts Up until a few years ago, magnetic ballasts were the only option for HID light sources, and they are still the type that is most often used. The most common type of magnetic ballast sold today is the constant-wattage autotransformer, which effectively regulates lamp power to minimize flicker and unexpected shutoffs if the line voltage varies. Composed mainly of magnetic coils, these ballasts often include a capacitor in the circuitry to improve power factor. Magnetic ballasts generally have internal losses of at least 10 percent of the lamp wattage—and the percentage is even higher for lower-wattage lamps. Manufacturers produce magnetic ballasts capable of working with lamps of up to 1,500 watts (W). Electronic Ballasts Electronic ballasts are a relatively new offering, and they are now available for lamps of up to 450 W. They use switching electronics and small high-frequency inductors, rather than large line-frequency ones, to control current and voltage to the lamp. Though costly, electronic ballasts offer a host of benefits over their magnetic counterparts, including higher efficiency, better dimming capabilities, better light quality, and shorter warm-up times. Efficiency. Electronic ballasts for HID lamps consume about 60 percent less power than their magnetic equivalents—a typical electronic ballast for a 400-W lamp uses 15 to 30 W, compared with 50 to 60 W for a magnetic unit. Light output. Metal halide lamps are notorious for the color variability of their light output, but lamps operated by electronic metal halide ballasts provide more stable output than lamps operated by magnetic ballasts. That's because the electronic ballasts reduce the variability of the voltage supplied to the lamp. The light output of lamps driven by electronic ballasts also degrades more slowly over time, resulting in greater light output at the mean and end of the lamp's life (see Figure 1). This in turn enables systems with electronic ballasts to use fewer fixtures, or lower-wattage lamps, to provide the same output as systems with magnetic ballasts. Figure 1: Electronic ballasts improve lumen maintenance Lamp output degrades more slowly with electronic ballasts than with magnetic ballasts. Output declines more rapidly on probe-start metal halide lamps operating on magnetic ballasts. Source: Platts; data from Advance Transformer Dimming capability. Electronic ballasts can be made continuously dimmable, down to about 50 percent of full output power. This characteristic makes them more amenable to daylight harvesting than magnetic ballasts, which, at best, offer step-dimming down to one or two lower levels. Step-dimming to 50 percent of maximum light output is common in warehouses and other irregularly occupied building spaces. Electronic ballasts also have greater dimming efficiency than magnetic ones. A magnetic ballast step-dimmed to 50 percent of maximum light output typically consumes 65 percent of full power, whereas the ratio of light output to power input for an electronic ballast is nearly one-to-one. However, dimming any HID lamp, even with an electronic ballast, may lead to significant color-shifting, seriously limiting this capability in areas where color is of concern. Warm-up and restrike times. Metal halide lamps take several minutes to warm up to full output and several minutes to cool down and restart once they go out (either intentionally or due to a power failure). With electronic ballasts, warm-up times are significantly shortened for both quartz and ceramic lamps, but restrike times (the time it takes for a lamp to cool down and restart after a momentary outage) are only shortened for quartz lamps (see Table 1). None of the times is shortened to the point where metal halide lamps can be used with on/off controls. Table 1: Warm-up and restrike times for metal halide lamps Electronic ballasts have shortened warm-up and restrike times for pulse-start metal halide lamps. The ranges of values account for differences in ballast starting techniques, fixture heat dissipation, lamp type (coated or clear, open or enclosed rating), lamp age, and whether or not there is a hot restrike capability. Source: Platts; data from Stan Walerczyk Noise. Magnetic ballasts produce noise because the metal laminations within them vibrate as the magnetic field changes at the line frequency of 60 times per second. Electronic ballast products are available that operate at both high and low frequencies, but operation is silent because the ballasts don't have laminations to vibrate. This quality is important in areas such as libraries, concert halls, and retail shops. Light flicker. Some electronic ballasts for metal halide lamps operate at much higher frequencies than the 60 hertz (Hz) of magnetic ballasts. This high-frequency operation eliminates the flicker that can accompany line-frequency operation and can cause headaches or otherwise affect a room's occupants. High-frequency electronic ballasts also eliminate the stroboscopic effect. Although other types of lamp flicker are just annoying, the stroboscopic effect can be dangerous. When circular saws, drill presses, and other machinery operate at a certain speed, the stroboscopic effect from magnetic ballasts can cause the machines to appear as if they are not operating. Other electronic ballasts operate at lower frequencies (75 Hz for one product), but they have a square wave design that also eliminates flicker. Reduced stock variety. The use of dimming electronic ballasts allows a facility to minimize the different types of lamps and ballasts it must keep on hand—making inventory tracking easier and eliminating the risk that the wrong lamp would be installed. For example, instead of having to purchase, stock, and replace 250-, 320-, and 400-W pulse-start metal halide lamps and ballasts, a facility can stock just 400-W lamps and use dimming electronic ballasts to get the right light levels. This also enables the facility to take advantage of the 400-W lamps' longer life—20,000 hours versus just 15,000 hours for 250-W lamps. Longer lamp life. Ballast manufacturers report that pulse-start metal halide lamp life may be increased by about 25 percent through the use of electronic ballasts. This effect is plausible, because electronic ballasts provide more-precise control of current and therefore place less stress on electrodes when a lamp is started. But as of yet, no independent confirmations of increased lamp life have been made, and it may take some time for manufacturers to verify longer lamp life. Meanwhile, when trying to estimate the life of a lamp operating with a particular electronic ballast, use data from a lamp manufacturer rather than from a ballast manufacturer. Cost. Incremental costs for electronic ballasts have been running $60 to $150 above the $30 cost of magnetic pulse-start metal halide ballasts. However, electronic ballasts have reasonable simple-payback periods over magnetic ballasts based on efficiency and lumen depreciation alone (see Table 2). Table 2: Cost comparison—electronic versus magnetic ballasts Systems with electronic ballasts currently cost significantly more than those with magnetic ballasts. However, energy savings can lead to a reasonable payback, depending on the application. Source: Platts

How to Make the Best Choice? Electronic ballasts for HID light sources offer various benefits over magnetic ballasts: greater efficiency, greater light and color stability, lower lumen depreciation, better dimming options, faster warm-up and restrike times, less noise, elimination of flicker, and longer lamp life. However, they do carry a higher cost. To determine if electronic ballasts are a cost-effective solution, conduct a cost analysis that considers these five ballast/lamp parameters: ballast power, lumen maintenance (a measure of lamp light depreciation over time), lamp life, and end-of-life output. Other factors include the operational hours in a year, the cost of electricity, and the cost of the ballasts. When choosing a particular electronic ballast, make sure that it is compatible with the lamp and that the ballast's rated operating temperature falls into a range in which the ballast is expected to operate. Also, because electronic ballasts are a relatively new technology, there have been some reliability questions—look for manufacturers with a good track record.

What's on the Horizon? Although electronic ballasts are more expensive than magnetic ballasts, the incremental cost of electronic ballasts should drop and reliability should improve as sales volumes increase and manufacturers introduce new products and gain more experience. Newer, more-capable wireless systems, some of which are available today, may broaden the wireless lighting market considerably if costs can be reduced. Due to their enhanced dimming properties, electronic ballasts may one day be controlled via wireless controllers, providing an opportunity to enhance an existing electronic ballast system with daylighting capabilities. These newer wireless systems should begin to appear on the market in 2006.

Taken from: http://www.reliant.com/en_US/Page/Generic/Public/esc_purchasing_advisor_metal_halide_ballasts_bus_gen.jsp.

Referred to as a microalgae, brown or golden algae is actually not an algae at all, but diatoms. What you are actually seeing in your tank are diatom skeletons, all linked together. It can appear as a simple dusting on the tank walls and substrate surfaces, or it can turn into a massive growth that covers just about everything in the tank. This type of algae outbreak typically occurs when a tank is just completing or has finished the nitrogen cycling process, new live rock is introduced, as the curing process can add nutrients when some organisms on the rock dies off, or tank maintenance has been neglected.

What is Color Rendering Index – CRI

Color rendering describes how a light source makes the color of an object appear to human eyes and how well subtle variations in color shades are revealed. The Color Rendering Index (CRI) is a scale from 0 to 100 percent indicating how accurate a "given" light source is at rendering color when compared to a "reference" light source.

The higher the CRI, the better the color rendering ability. Light sources with a CRI of 85 to 90 are considered good at color rendering. Light sources with a CRI of 90 or higher are excellent at color rendering and should be used for tasks requiring the most accurate color discrimination.

It is important to note that CRI is independent of color temperature (see discussion of color temperature). Examples: A 2700K ("warm") color temperature incandescent light source has a CRI of 100. One 5000K ("daylight") color temperature fluorescent light source has a CRI of 75 and another with the same color temperature has a CRI of 90.

To further understand the physics of color rendering, we need to look at spectral power distribution.

What is spectral power distribution?
The visible part of the electromagnetic spectrum is composed of radiation with wavelengths from approximately 400 to 750 nanometers. The blue part of the visible spectrum is the shorter wavelength and the red part is the longer wavelength with all color gradations in between.

Spectral power distribution graphs show the relative power of wavelengths across the visible spectrum for a given light source. These graphs also reveal the ability of a light source to render all, or, selected colors.

Below see how a typical spectral power distribution graph for daylight.

Notice the strong presence (high relative power) of ALL wavelengths (or the "full color spectrum"). Daylight provides the highest level of color rendering across the spectrum.

Compare the daylight spectral power distribution with that for a particular fluorescent lamp.

The most obvious difference is the generally lower level of relative power compared to daylight – - except for a few spikes. All wavelengths (the "full spectrum) are again present but only certain wavelengths (the spikes) are strongly present. These spikes indicate which parts of the color spectrum will be emphasized in the rendering of color for objects illuminated by the light source. This lamp has a 3000K color temperature and a CRI of 82. It produces a light that is perceived as "warmer" than daylight (3000K vs. 5000K). It's ability to render color across the spectrum is not bad, but certainly much worse than daylight. Notice the deep troughs where the curve almost reaches zero relative power at certain wavelengths.

Here is another fluorescent lamp.

This spectral power distribution looks generally similar to the one above except it shows more power at the blue end of the spectrum and less at the red end. Also, there are no low points in the curve that come close to zero power. This lamp has a 5000K color temperature and a CRI of 98. It produces light that is perceived as bluish white (similar to daylight) and it does an excellent job of rendering colors across the spectrum.

Above are links to linear and compact fluorescent light bulbs from Topbulb that have a CRI of 90 or higher. If you want a high color rendering bulb to produce light perceived as warm white, choose a bulb with a color temperature of 3000K or 3500K. If you want a high color rendering bulb to produce light perceived as white, choose a bulb with a color temperature of 4000K. For a bulb that simulates daylight, choose a color temperature of 5000K or higher.

Note: all incandescent and halogen light bulbs, by definition, have a CRI close to 100. They are excellent at rendering color. However, except for some halogen bulbs, most incandescents produce a warm 2800K color temperature. The only way to achieve the bluish white appearance of daylight with incandescent bulbs is to use bulbs coated with neodymium. However, these bulbs have a CRI much lower than 90. They are not good for accurate color rendering across the spectrum. See neodymium light bulbs available from Topbulb.

Taken from – http://www.topbulb.com/find/cri.asp

תמונות שצולמו בתאריך 08.08.2009 בדיוק ביום שבו עברו שלושה חודשים מרגע הקמתו של האקוריום.

התמונות צולמו על ידי ועל ידי חיים Oz (תודה ילד) תהנו

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Amino Acids And Their Benefit In A Reef Tank

Written by Richard Gilliland Thursday, 19 March 2009 19:13

Amino Acids are quickly becoming one of the most popular additives to any serious reef keeper’s arsenal. There are many different reasons why they are being used and many why I suggest everyone should use them.  Many vitamins and proteins are including in one easy dosing supplement to provide your corals with much needed elements they would not otherwise get in a closed aquarium environment.

In Nature corals will receive these proteins via plankton, micro plankton or even bacterial plankton. However in a close aquarium environment these are normally absent.  Zooxanthellae which live symbiotically in many corals “excrete” these acids which in turn feed the coral along with many other substances. In most aquariums the activity of these symbiotic algaes are greatly reduced in which the corals are only “Surviving” and not “Thriving”.

Indirect and Direct feeding’s are generally not the best method to approach feeding your corals as it generally results in increased nutrient levels such as phosphates and nitrates. This is where the Amino acids come in handy. By dosing high quality products such as Zeovit Amino acid concentrates you are introducing the correct proportions of amino acids found in coral skeletons. This is helping to create the natural living conditions found in a wild living coral reef.

Higher end amino acids on the market are supplying up to 17 important amino acids essential to stony coral growth. These supplements also help coral utilize the absorption of calcium seen in their natural environment and increasing your coral growth in the aquarium. From our experience you will also notice increased polyp extension during their “daylight” hours.

There are many options on the market for amino acids but really there are only a few that aren’t using preservatives which decrease the quality of the product. Some are Zeovit Amino Acid Concentrate, Zeovit Amino Acid Concentrate for LPS. Elos OMGEA and Selcon.

Richard Gilliland is the President and CEO for Salty Supply. Specializing in high end aquarium supplies and equipment, they are a leader in online sales of only the best saltwater aquarium equipment.