tailieunhanh - EC&M’s Electrical Calculations Handbook - Chapter 8

Phương pháp Lumen Nó luôn luôn có giá trị ghi nhớ định nghĩa của một footcandle: Đây là số lượng lumens mỗi foot vuông của bề mặt làm việc được chiếu sáng. Định nghĩa này một mình cung cấp cho các nhà thiết kế chiếu sáng một ước tính thô nhanh chóng của số lượng lumens cần thiết để thắp sáng (rơi vào) một khu vực nhất định: Lấy giá trị footcandle và nhân nó bằng các khu vực trong feet vuông: số lượng lumen ước tính rơi vào khu vực footcandles khu vực feet vuông . | Chapter 8 Lighting The Lumen Method It is always valuable to keep in mind the definition of a footcandle It is the quantity of lumens per square foot of illuminated work surface. This definition alone provides the lighting designer a quick rough estimate of the quantity of lumens required to illuminate fall on a certain area Take the footcandle value and multiply it by the area in square feet Approximate lumen quantity falling on the area footcandles X area in square feet A more accurate and easy approximation of the actual lamp lumen requirement how many lumens must be emitted by the lamps within the luminaires is also possible. Note that some of the lamp lumens are trapped within the fixture and do not reach the area to be illuminated. To provide for this inaccuracy a determination is made of the rough approximate total quantity of lumens required to illuminate the area dividing the total lumen requirement by the lumen output from each luminaire typically one-half the lamp lumens provides a good estimate of the quantity 22 Copyright 2001 by The McGraw-Hill Companies Inc. Click here for Terms of Use. 222 Chapter Eight of luminaires required to illuminate the area. One-half the lamp lumens is a good estimate of the light emitted by each fixture after the combination of luminaire coefficient of use CU and light losses is considered Approximate lumen quantity emitted by lamps _ footcandles X area in square feet - or stated in another way Approximate lumen quantity emitted by lamps 2 X footcandles X area in square feet This quick calculation method is also a good method of checking intensive manual calculations or computer calculations to see if their results are reasonable. From this basic logic the following lumen method of calculation formulas are derived footcandles X area in square feet Luminaire quantity ------7T--- lumens lamp lamps fixture fixture CU maintenance factor The footcandle illuminance determination can be made from a known .