Ohm's Law:

Ohms=Volts/Amperes (R=E/I)
Amperes=Volts/Ohms (I=E/R)
Volts=Amperes x Ohms (E=IR)

Power AC Circuits:

Efficiency=(746 x Output Horsepower)/Input Watts
Three-Phase Kilowatts=(Volts x Amperes x Power Factor x 1.732)/1000
Three-Phase Volt-Amperes=Volts x Amperes x 1.732
Three-Phase Amperes=(746 x Horsepower)/(1.732 x Volts x Efficiency x Power Factor)
Three-Phase Efficiency=(746 x Horsepower)/(Volts x Amperes x Power Factor x 1.732)
Three-Phase Power Factor=(Input Watts)/(Volts x Amperes x 1.732)
Single-Phase Kilowatts=(Volts x Amperes x Power Factor)/1000
Single-Phase Amperes=(746 x Horsepower)/(Volts x Efficiency x Power Factor)
Single-Phase Efficiency=(746 x Horsepower)/(Volts x Amperes x Power Factor)
Single-Phase Power Factor=(Input Watts)/(Volts x Amperes)
Horsepower (3 Phase)=(Volts x Amperes x 1.732 x Efficiency x Power Factor)/746
Horsepower (1 Phase)=(Volts x Amperes x Efficiency x Power Factor)/746

Power DC Circuits:

Watts=Volts x Amperes (W=EI)
Amperes=Watts/Volts (I=W/E)
Horsepower=(Volts x Amperes x Efficiency)/746

Speed AC Machinery:

Synchronous RPM=(Hertz x 120)/Poles)
Percent Slip=((Synchronous RPM - Full-Load RPM)/Synchronous RPM)) x 100

Motor Application:

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

Time For Motor To Reach Operating Speed:

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
LRT=Locked Rotor Torque
BDT=Breakdown Torque Load WK² (at motor shaft)=(WK² (Load) x Load RPM²)/Motor RPM²

Shaft Stress (P.S.I):

Shaft Stress=(HP x 321,000)/(RPM x Shaft Diam.³)

Resistance = Temperature

R_C=R_H x (K + T_C)/(K + T_H)
R_H=R_C x (K +T_H)/(K + T_C)

K= 234.5 - Copper
K= 236 - Aluminum
K= 180 - Iron
K= 218 - Steel
R_C= Cold Resistance (ºC)
R_H=Hot Resistance (ºC)
T_C=Cold Temperature (ºC)
T_H=Hot Temperature (ºC)

Vibration:

D=.318 (V/Hz)
V=pi(Hz) (D)
A=.051 (Hz)² (D)
A=.016 (Hz) (V)
D= Displacement (Inches Peak-peak)
V=Velocity (Inches per Second Peak)
A=Acceleration (g's Peak)
Hz=Cycles per Second

Volume of Liquid in a Tank:

Gallons=5.875 x D² x H
D= Tank Diameter (ft.)
H=Height of Liquid (ft.)

Centrifugal Applications

Affinity Laws for Centrifugal Applications:

Flow₁/Flow₂ = RPM₁/RPM₂
Pres₁/Pres₂ = (RPM₁)²/(RPM₂)²
BHP₁/BHP₂ = (RPM₁)³/(RPM₂)³

For Pumps:

BHP= (CFM x PSF)/(33000 x Efficiency of Fan)
BHP= (CFM x PIW)/(6344 x Efficiency of Fan)
BHP= (CFM x PSI)/(229 x Efficiency of Fan)
Head in Feet= 2.31 PSIG

Where:

BHP = Brake Horsepower
GPM = Gallons per Minute
FT = Feet
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

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