Options:
- Motor Formulas
- Transformer Formulas


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

L = Length of conductor in feet

I  = Current in conductor (amperes)

CM
= Circular mil area of conductor

CM= 2K x L x I
VD
Three Phase VD= 1.73 x K x I x L
CM
CM= 1.73 x K x L x I
VD

If there is anything you would like to add or if you have any comments please feel free to email the Webmaster at webmaster@keystone-electric.com.


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