E = Voltage / I = Amps /W = Watts / PF = Power Factor / Eff = Efficiency / HP = Horsepower
AC/DC Formulas
To Find
Direct Current
AC / 1phase 115v or 120v
AC / 1phase 208,230, or 240v
AC 3 phase All Voltages
Amps when Horsepower is Known
HP x 746 E x Eff
HP x 746 E x Eff X PF
HP x 746 E x Eff x PF
HP x 746 1.73 x E x Eff x PF
Amps when Kilowatts is known
kW x 1000 E
kW x 1000 E x PF
kW x 1000 E x PF
kW x 1000 1.73 x E x PF
Amps when kVA is known
kVA x 1000 E
kVA x 1000 E
kVA x 1000 1.73 x E
Kilowatts
I x E 1000
I x E x PF 1000
I x E x PF 1000
I x E x 1.73 PF 1000
Kilovolt-Amps
I x E 1000
I x E 1000
I x E x 1.73 1000
Horsepower (output)
I x E x Eff 746
I x E x Eff x PF 746
I x E x Eff x PF 746
I x E x Eff x 1.73 x PF 746
Three Phase Values
For 208 volts x 1.732, use 360 For 230 volts x 1.732, use 398 For 240 volts x 1.732, use 416 For 440 volts x 1.732, use 762 For 460 volts x 1.732, use 797 For 480 Volts x 1.732, use 831
E = Voltage / I = Amps /W = Watts / PF = Power Factor / Eff = Efficiency / HP = Horsepower
AC Efficiency and Power Factor Formulas
To Find
Single Phase
Three Phase
Efficiency
746 x HP E x I x PF
746 x HP E x I x PF x 1.732
Power Factor
Input Watts V x A
Input Watts E x I x 1.732
Power - DC Circuits
Watts =E xI
Amps =W / E
Ohm's Law / Power Formulas
P = watts
I = amps
R = ohms
E = Volts
Voltage Drop Formulas
Single Phase (2 or 3 wire)
VD =
2 x K x I x L CM
K = ohms per mil foot
(Copper = 12.9 at 75°)
(Alum = 21.2 at 75°)
Note:
K value changes with temperature. See Code chapter 9, Table 8
