 Formula

# Basic Electrical Formulas

Volts (E):

Volts  =  square root of (watts x ohms)

Volts  =  watts  /  amperes

Volts  =  amperes x ohms

Ohms (R):

Ohms  =  volts  /  amperes

Ohms  =  volts²  /  watts

Ohms  =  watts  /  amperes²

Watts (W):

Watts  =  volts²  /  ohms

Watts  =  amperes² x ohms

Watts  =  volts x amperes

Amperes (I):

Amps  =  volts  /  ohms

Amps  =  watts  /  volts

Amps  =  square root of (watts  /  ohms)

AC Motor Formulas:

E = voltage / I = amps / W = watts / PF = power factor / Eff = efficiency / HP = horsepower

Single Phase:

 Current (amps) I = HP x 746 (where hp is known) E x Eff x PF Current (amps) I = KW x 1000 (where KW is known) E x PF Current (amps) I = Kva x 1000 (where Kva is known) E Horsepower (hp) (hp) = I x E x Eff x PF 746 Kilowatts (KW) (KW) = I x E x PF 1000 Kilovolt-Amps (Kva) Kva = I x E 1000

Three Phase:

 Current (amps) I = HP x 746 (where hp is known) 1.73 x E x Eff x PF Current (amps) I = KW x 1000 (where KW is known) 1.73 x E x PF Current (amps) I = Kva x 1000 (where Kva is known) 1.73 x E Horsepower (hp) HP = 1.73 x I x E x Eff x PF (where hp is known) 746 Kilowatts (KW) WK = 1.73 x I x E x PF (where hp is known) 1000 Kilovolt-Amps (Kva) Kva = 1.73 x I x E (where hp is known) 1000

AC Efficiency and Power Factor Formulas:

 Single Phase Efficiency: 746 x HP E x I x PF Single Phase Power Factor: Input Watts V x A Three Phase Efficiency: 746 x HP E x I x PF x 1.732 Three Phase Power Factor: Input Watts E x I x 1.732

Electrical Rules of Thumb:

 Sync Speed Approx. Torque rpm lb-ft per hp 3600 1.4 1800 3 1200 4.5 900 5.8

 Rated Approximate Amps / hp Voltage Single Phase Three Phase 115 10 230 5 2.5 460 1.25 575 1

Note:  This information is provided as a quick reference resource and is not intended to serve as a substitute for qualified engineering assistance.  While every effort has been made to ensure the accuracy of this information, errors can occur.  As such, neither Flodraulic, any of its affiliated companies nor its employees will assume any liability for damage, injury or misapplication as result of using this reference guide.

Top