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.