objectives finish commercial electrical systems learn about lighting system in buildings terminology...
TRANSCRIPT
Objectives
• Finish commercial electrical systems
• Learn about lighting system in buildings• Terminology• Lamp types
• Duplexes (receptacles)• 3 Phase total 60 kVA, 14kVA (neutral)• 30 poles• 60 kVA / (208V √3 ) = 167A• Select: 200 A panel and same size conductors for all three phases • Neutral same like a phase 200 A
• Hot wires should be 250 MCM, Neutral #2/0 aluminum
• 2½ inch conduit
Panel D
Transformer capacity
• P = I V ∙√3 =200∙208∙√3 = 72 kVA ~ 75 kVA
SD switch selection: • For transformer: I1E1=I2E2 • I2 = I1E1/E2 = 200∙208 / 480 = 86 A
• Select switch rated for 100 A
• For 100 A rated switch select: Three #1 (aluminum)
and one #1 for neutral (aluminum)• 90A fuse for phases
Lighting Panel
• 100A - 20 poles
• Hot: 65kVA/(480V∙√3) = 78 A - #2 Aluminum
• Neutral: 22 kVA /277V = 79 A - #2 Aluminum
• Select 100 A three pole fused switch
• 1½ inch conduit
Power Panel
• No neutral? – all three phase circuits• 33 poles required – chose 42 standard size and allows
for expansion
• 165kVA/(480 √3) = 198 A
• Choose 225A switch (could use 200 A, but you count on expansion)
• 3 300 MCM aluminum wires – 2 inch conduit(in the book table you don’t have MCM 300, however it exist)
Wireway
• 198A + 86 A + 78 A = 362A
• 400A would allow for some expansion, some would probably go to 600A
• 400A three-pole switch
• Six 250 MCM (unlikely to find conductors big enough to just have 3) and one #2/0 aluminum
• Neutral current: maximum = 117 A, you can expand neutral too (130 A)
Summary Panel Sizing
• Find panel power usage and neutral usage
• Size panel conductors and associated conduit and switches
Summary of Electrical Systems
• Power generation transport and voltage transformation
• AC/DC Fundamentals
• Equipment
• Residential Buildings
• Commercial Buildings
• NEC code
Motivation
• Lighting represents a third of commercial building energy use
• Lighting has been measured to influence:• Worker productivity• Retail sales• Mood/emotion/comfort• Accident avoidance/safety
Vision and light
• Brightness, pattern, motion, and color
• Which is more sensitive – eye or camera?
• Which is more important, brightness or contrast?
Color
• Does color change the apparent size of rooms?
• Does color change perception of temperature, noise, elapsed time?
Want is light ?
• Light – electromagnetic radiation
• Radiation wavelength • Visible light 0.4 – 0.7 μm
Photometrics
• Luminous intensity [candela, cd] • Define the ability of light source to generate light (illumination) in
given direction
• Power – luminous flux [lumen, lm] • Quantity of light
• Illuminance – light power density [foot-candela, fc] [lux, lx] SI units
• Density of light (illumination) incident on a surface
• Luminance - surface brightness [foot-lambert, lm/ft2] • directional emission of visible light
Units and conversion• 1 cd = Area of unit sphere = 4·π = 12.57 lumens
Luminous flux [lumen]= Luminous intensity [cd] · (4·π)
• Illuminance [foot-candle, lux] = Luminous flux [lumen]/Area [ft2,m2]
• Luminance [Foot-lambert] = lumen/ft2 from surface in the direction of view
– define the brightness of surface – important for contrast
r=1
1cd
Ref: Tao and Janis (2001)
1
Important quantities
Chapter 14.2 (Tao and Janis)
• Sections: 14.2.3, 14.2.4, 14.2.5, 14.2.6
Major design parameters
• Lighting systems (lamps):• Define Luminous flux [lumen]
• Required level of light at design spot (table spot on the wall etc.) • Defined by Illuminance level (E)
Illuminance (E) depends on angle
Example:• Spot light with luminous
intensity I= 5000cd is aimed at painting at the wall 5 ft from the light and the angle φ=45°.
• What is the illuminance level (E) at the center of the painting?
Solution• Distance:
• Illuminance orthogonal to the beam
E=I/L2=5000/
Ebeam= 100 fc
• Illuminance orthogonal to the painting
Epainting= Ebeam/
Epainting=71 fc
25' L
2' )25(
25' L
2
Surface color rendering
Depending on the light type the surface colors can be different
Depends on spectral energy distribution
Terms for Lamps
• What is luminous efficacy?
• What does a lifetime of 1000 hours mean?• What affects lifetime?
• Does color rendering index (CRI) indicate if a lamp source will cause a color shift?
Incandescent
• Thomas Edison first incandescent lamp• Efficacy of 1.4 lumens/watt
• Life – 750 to 1000 hours
• 10 – 20 % decay in output
Fluorescent Lamps
• Electrodes arc through mercury vapor
• Phosphors fluoresce in visible range
• Efficacy of 60 to 100 lumens/watt (after burn-in)