USEFUL FORMULAS

 

OHMS LAW     Ohms = Volts ÷ Amperes  Amperes = Volts ÷ Ohms  Volts = Amperes x Ohms     POWER - AC CIRCUITS     Power Factor = Watts ÷ (Volts x Amperes)  Three Phase Kilowatts = (Volts x Amperes x Power Factor x 1.732) ÷ 1000  Three Phase Volt-Amperes = Volts x Amperes x 1.732  Three Phase Amperes = (746 x Horsepower) ÷ (1.732 x Volts x Efficiency x Power Factor)  Single Phase Kilowatts = (Volts x Amperes x Power Factor) ÷ 1000  Single Phase Amperes = (746 x Horsepower) ÷ (Volts x Efficiency x Power Factor)     POWER - DC CIRCUITS     Watts = Volts x Amperes  Amperes = Watts ÷ Volts  Horsepower = (Volts x Amperes x Efficiency) ÷ 746     MOTOR APPLICATION FORMULAS     Torque (lbs.-ft.) = (Horsepower x 5250) ÷ RPM  Shaft Stress (lbs. per sq. inch) = (Horsepower x 321,000) ÷ (RPM x Shaft Diameter3)     FOR PUMPS     Horsepower = (GPM x Head in Feet x Specific Gravity) ÷ (3960 x Efficiency of Pump)     FOR FANS & BLOWERS     Horsepower = (CFM x Pressure (lbs. per sq. ft.)) ÷ (33,000 x Efficiency)     SPEED     Synchronous RPM = (Hertz x 120) ÷ Poles  Percent Slip = (Synchronous RPM - Full Load RPM) ÷ Synchronous RPM x 100