QUICK ESTIMATE
FORMULAS
• Horsepower
Formulas
• Torque Formulas
• AC Motor Formulas
• 3-Phase Electrical Formulas
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| HORSEPOWER
FORMULAS |
| For
Rotating Objects |
HP =
|
|
| Where |
T
= Torque (lbft)
N = Speed (rpm) |
| |
|
| Objects
in Linear Motion |
HP
= |
|
| Where |
F
= Force (lbs)
V = Velocity (ft/min) |
| |
|
| For
Pumps |
HP
= |
|
| |
|
| |
HP = |
|
| |
Where |
GPM = Gallons per
Minute
Head = Height of Water (ft)
Efficiency of Pump = %/100
PSI = Pounds per Inch
Specific Gravity
of Water = 1.0
1 CuFt per Sec. = 448 GPM
1 PSI = A Head of 2.309 ft (water weight)
62.36 lbs per CuFt at 62°F
|
| |
|
| For
Fans and Blowers |
HP = |
|
| |
|
| |
HP = |
|
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|
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HP = |
|
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Where |
CFM =
Cubic Feet per Minute
PSF = Pounds per Square Foot
PIW = Inches of Water Gauge
PSI = Pounds per Square Inch
Efficiency of Fan = %/100 |
| |
|
| For
Conveyors |
HP (verticle) |
 |
| |
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HP (horizontal) |
 |
| |
Where |
F = Force (lbs)
V = Velocity (ft/min)
Coef. of Friction
• Ball or Roller Slide = 0.02
• Dovetail Slide = 0.20
• Hydrostatic Ways = 0.01
• Rectangle Ways with Gib = 0.01 to 0.25
|
|
| TORQUE
FORMULAS |
| |
T = |
HP
x 5252 |
| |
|
N
|
| |
Where |
T = Torque
(LbFt)
HP = Horsepower
N = Speed (rpm) |
| |
|
| |
T = |
F x R |
| |
Where |
T = Torque
(LbFt)
F = Force (Lbs)
R = Radius (Ft) |
| |
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Ta (accelerating) |
WK2
x Change in RPM |
| |
|
308 x t (Sec)
|
| |
Where |
Ta = Torque (LbFt)
WK2 = Inertia at Motor Shaft (LbFt)2
t = Time to Accelerate (Sec)
Note:
To change LbFt2 to InLbSec2, Divide by 2.68
To change InLbSec2 to LbFt2, Mult. by 2.68
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|
| AC
MOTOR FORMULAS |
| |
Sync Speed
= |
Freq
x 120 |
| |
|
Number
of Poles |
| |
Where |
Sync Speed
= Synchronous Speed (Rpm)
Freq = Frequency (Hz) |
| |
|
| |
% Slip
= |
(Sync
Speed - FL Speed) x 100 |
| |
|
Sync Speed
|
| |
Where |
FL Speed
= Full Load Speed (Rpm)
Sync Speed = Synchronous Speed (Rpm) |
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|
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Reflected
WK2 = |
WK2
of Load
|
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|
(Reduction
Ratio)2 |
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