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Thursday, 16 May 2013

Energy calculation

Single-Phase Calculations
 Basic electrical theory tells us that for a single-phase system,
KW = (V × I × PF) ÷ 1,000.
 For the sake of simplicity, let's assume the power factor (PF) is unity. Therefore, the above equation becomes
kW = (V × I) ÷ 1,000.
 Solving for I, the equation becomes
I = 1,000kW ÷ V (Equation 1)
 Now, if we look at the “1,000 ÷ V” portion of this equation, you can see that by inserting the respective single-phase voltage for “V” and dividing it into the “1, 000,” you get a specific number (or constant) you can use to multiply “kW” to get the current draw of that load at the respective voltage.

 3-Phase Calculations
 For 3-phase systems, we use the following equation:
KW = (V × I × PF × 1.732) ÷ 1,000.
 Again, assuming unity PF and solving this equation for “I,” you get:
I = 1,000kW ÷ 1.732V.

Symbol            Prefix               factor              Example
pico                 p                      10-12                 1pF = 10-12F
nano                n                      10-9                  1nF = 10-9F
micro               μ                      10-6                  1μA = 10-6A
milli                 m                     10-3                  1mA = 10-3A
kilo                  K                     10 3                  1KΩ = 1000Ω
mega                M                     10 6                  1MHz = 106Hz
giga                 G                     10 9                  1GHz = 109Hz



·         Common Appliances
Appliance
Est. Watts
Appliance
Est. Watts
Coffee pot (10 cup)
1200
VCR
40-60
Coffee pot (4 cup)
650
CD or DVD Player
35
Toaster
800-1500
Stereo
30-100
Cappuccino Maker
1250
Clock Radio
50
Coffee Grinder
100
AM/FM car cassette
8+
Blender
300
Satellite dish
30+
Microwave (600 to 1000 W cooking power)
1100-2000W (elec. consumption)
Vacuum cleaner
300-1100
Waffle iron
1200
Mini Christmas lights (50)
25
Hot plate
1200
Space Heater
1000-1500
Frying pan
1200
Iron
1000
Toaster Oven
1200
Washing machine
920
Blow dryer
900-1500
12" 3 speed table fan
230
Computer
- laptop
- pc & monitor
- printer-inkjet

50-75
200-400
60-75
TV - 25" color
- 19" color TV or monitor
- 12" b&w
13" color TV/VCR Combo
300
160
30
230
*Refrigerator/Freezer
600
Game Console (X-Box)
100
*Freezer
500-800
*Furnace Fan (1/3hp)
1200

·         Common Tools
Tool
Est. Watts
Appliance
Est. Watts
Jig Saw
300
1/4" drill
250
Band Saw
1200
3/8" drill
500
Table Saw
1800
1/2" drill
750
6 1/2" circ. saw
1000
Shop Vac 5 hp
1000
7 1/4" circ. saw
1200+
*Sabre Saw
500
8 1/4" circ. saw
1800
*Portable Grinder
1380
Disc Sander
1200
*Electric Chain Saw 14"
1200
Makita Chop Saw
1550
*Airless Sprayer 1/2 hp
600
Makita Cut Off Saw
1000
*Air Compressor 1 hp
2000


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