Power: DC Circuits                                                                                   Go to top of page

Watts = Volts x Amperes (W = EI)

Amperes = Watts   (I = W/E)
                  Volts

Horsepower = Volts x Amperes x Efficiency
                                    746

Speed: AC Machinery                                                                                                   Go to top of page

Synchronous RPM = Hertz x 120
                                  Poles

Percent Slip = Synchronous RPM - Full-Load RPM   x 100
                                 Synchronous RPM

Motor Application: Torque and/or Horsepower                                                             Go to top of page

Torque (lb.-ft.) = Horsepower x 5250
                               RPM

Horsepower = Torque (lb.-ft.) x RPM
                               5250

Operating Speed: Motors                                                                                              Go to top of page

Seconds =        WK² x Speed Change      
                 308 x Avg. Accelerating Torque

WK² = Inertia of Rotor + Inertia of Load (lb.-ft.²)

Average Accelerating Torque = [(FLT + BDT)/2] + BDT + LRT
                                                                  3

FLT = Full-Load Torque             BDT = Breakdown Torque

LRT = Locked Rotor Torque

Load WK² (at motor shaft) = WK² (Load) x Load RPM²
                                                   Motor RPM²

Shaft Stress (P.S.I.) =    HP x 321,000   
                                 RPM x Shaft Diam.³

Centrifugal Applications: Affinity Laws                                                                         Go to top of page

Flow₁ = RPM₁
Flow₂    RPM₂

Pres₁ = (RPM₁)²
Pres₂   (RPM₂)²

BHP₁ = (RPM₁)³
BHP₂   (RPM₂)³

Centrifugal Applications: Pumps:                                                                                  Go to top of page

BHP = GPM x FT x Specific Gravity
                  3960 x Efficiency of Pump

BHP = GPM x PSI x Specific Gravity
              1713 x Efficiency of Pump

Head in Feet = 2.31 PSIG

Centrifugal Applications: Fans and/or Blowers:                                                            Go to top of page

BHP =           CFM x PSF         
           33000 x Efficiency of Fan

BHP =           CFM x PSW       
           6344 x Efficiency of Fan

BHP =         CFM x PSI       
         229 x Efficiency of Fan

Centrifugal Applications: Abbreviations                                                                        Go to top of page

BHP  = Brake Horsepower
CFM  = Cubic Feet per Minute
FT   = Feet
GPM  = Gallons per minute
PSI  = Pounds per square inch
PSIG = Pounds per square inch gravity
PSF  = Pounds per square foot
PIW  = Inches of water gauge
Specific Gravity of Water = 1.0

Length Measurements: Standard                                                                                 Go to top of page

Common Usage

Reciprocal Value

1 ft. = 12 in..

1 in. = 0.0833 ft.

1 yd. = 3 ft.

1 ft. = 0.3333 yd.

1 rod = 5.5000 yd.

1 yd. = 0.1818 rods

1 furlong = 40 rods

1 rod = 0.0250 furlongs

1 mile = 8 furlongs

1 furlong = 0.1250 mi.

1 mi. = 5,280 ft.

1 ft. = 0.000189 mi.

1 mi. = 1,760 yd.

1 yd. = 0.000568 mi.

1 fathom = 6 ft.

1 ft. = 0.1667 fathom

120 fathoms = 1 cable

1 cable = 0.00833 fathoms

1 league = 3 mi.

1 mi. = 0.3333 leagues

1 nautical mi. = 6076.11 ft.

1 ft. = 0.000165 natical mi.

1 hand = 5 in. (equestrian)

1 in. = 0.2000 hands

Length Measurements: Metric                                                                                     Go to top of page

1 in. = 2.54 cm.

1 cm. = 0.3937 in.

1 ft. = 30.48 cm.

1 cm. = 0.0328 ft.

1 m. = 3.2808 ft.

1 ft. = 0.3048 m.

1 m. = 39.37 in.

1 in. = 0.0254 m.

1 m. = 1.0936 yd.

1 yd. = 0.9144 m.

1 rod = 5.029 m.

1 m. = 0.1988 rod

1 km = 1000 m.

1 m. = 0.001 km.

1 km = 0.621 mi.

1 mi. = 1.6103 km.

Wire Conversion: AWG to Metric                                                                                  Go to top of page

  American Wire Gauge Conversion Chart