Читать книгу Maintaining Mission Critical Systems in a 24/7 Environment - Peter M. Curtis - Страница 60

Besides all of the electronic equipment that is found in the data center, another significant consumer of electricity is the lighting system. Fluorescent lighting was the defacto standard for many, many years, and is typically fed with 277VAC in larger commercial buildings or data centers. Since fluorescent lamps vary by type and length, they operate on varying voltages and currents. A fluorescent ballast is used to adjust the supplied voltage and regulate current accordingly. In an effort to improve fluorescent lighting efficiency, the electronic ballast was invented in the 1970s. Besides adjusting the supplied voltage, electronic ballasts also changed the frequency from 60 Hz to 20,000 Hz or higher, which substantially eliminates flicker while also providing higher system efficiency.

LED lighting retrofits are available to replace fluorescent bulbs in existing fixtures, or the fixtures can be modified to bypass the ballasts. The LED bulb emits the same amount of lumens and can be produced to match any temperature (color) level. It is taking over the lighting industry in today’s environment to conserve energy since it is a simple alternative. It uses a fraction of the power fluorescents require and also gives off a fraction of the heat, which relieves some stress on the HVAC system.

Almost all new lighting installations are LEDs other than specialty lighting for stages or displays. In fact, most municipalities around the country have adopted LED lights or retrofits for all of their street and roadway lighting. Another benefit is fewer circuits are required since the load per light is a fraction of an amp. LED lights have also brought about better controls or wireless controls. The fixture can have an IP address associated with a wireless wall switch or ceiling occupancy sensor to operate a single or battery of fixtures

By supplying the lighting system with DC, we eliminate another power conversion and improve data center efficiency even further.

Figure 3.6 Electronic Ballast

(Courtesy of Antron Electronics Co., Ltd)