Electrical Formulas: How to Calculate Amps, Horsepower, Kilowatts, and kVA for DC and AC Motors
Use formulas in this chart to calculate amperes (amps), horsepower (HP), kilowatts (kW), and kilovolt-amps (kVA) for Direct Current (DC), Single Phase AC, and Three Phase AC Motors.
| To Find: |
Direct Current |
Alternating Current(AC):
Single Phase |
Alternating Current(AC):
Three Phase |
Amperes when HP
is known |
_HP x 746_
E x %EEF |
___HP x 746___
E x %EEF x PF |
_____HP x 746_____
E x %EEF x PF x √3 |
Amperes when kW
is known |
kW x 1000
E |
kW x 1000
E x PF |
kW x 1000
E x PF x √3 |
Amperes when kVA
is known |
|
kVA x 1000
E |
kVA x 1000
E x √3 |
| Horsepower (HP) |
E x I x %EEF
746 |
E x I x %EEF x PF
746 |
E x I x %EEF x PF x √3
746 |
| Kilowatts (kW) |
E x I
1000 |
E x I x PF
1000 |
E x I x PF x √3
1000 |
| Kilovolt-Amperes (kVA) |
|
E x I
1000 |
E x I x √3
1000 |
| E = Voltage | %EFF = Percent Efficiency | PF = Power Factor of Motor | I = Amps |
Equations for DC Motors
| To Find: |
|
Amperes when
HP is known |
_HP x 746_
E x %EEF |
Amperes when
kW is known |
kW x 1000
E |
Amperes when
kVA is known |
|
| Horsepower (HP) |
E x I x %EEF
746 |
| Kilowatts (kW) |
E x I
1000 |
| Kilovolt-Amperes (kVA) |
|
| E = Voltage | EFF = Percent Efficiency | PF = Power Factor of Motor | I = Amps |
Equations for Single Phase AC Motors
| To Find: |
|
Amperes when
HP is known |
___HP x 746___
E x %EEF x PF |
Amperes when
kW is known |
kW x 1000
E x PF |
Amperes when
kVA is known |
sVA x 1000
E |
| Horsepower (HP) |
E x I x %EEF x PF
746 |
| Kilowatts (kW) |
E x I x PF
1000 |
| Kilovolt-Amperes (kVA) |
E x I
1000 |
| E = Voltage | EFF = Percent Efficiency | PF = Power Factor of Motor | I = Amps |
Equations for 3 Phase AC Motors
| To Find:
|
|
| Amperes when HP is known |
_____HP x 746_____
E x %EEF x PF x √3 |
| Amperes when kW is known |
kW x 1000
E x PF x √3 |
| Amperes when kVA is known |
kVA x 1000
E x √3 |
| Horsepower (HP) |
E x I x %EEF x PF x √3
746 |
| Kilowatts (kW) |
E x I x PF x √3
1000 |
| Kilovolt-Amperes (kVA) |
E x I x √3
1000 |
| E = Voltage | EFF = Percent Efficiency | PF = Power Factor of Motor | I = Amps |
Warning: When using this information to perform electrical work, call a licensed electrician or consult the NEC® for safety.
All licensed electricians have passed examinations covering the National Electric Code®, know state and local building codes, and may carry insurance to cover damages.