Single phase and Three phase useful formula's

Rules Of Thumb (Approximation)

At 1800 rpm, a motor develops a 3 lb.ft. per hp

At 1200 rpm, a motor develops a 4.5 lb.ft. per hp

At 575 volts, a 3-phase motor draws 1 amp per hp

At 460 volts, a 3-phase motor draws 1.25 amp per hp

At 230 volts a 3-phase motor draws 2.5 amp per hp

At 230 volts, a single-phase motor draws 5 amp per hp

At 115 volts, a single-phase motor draws 10 amp per hp

Mechanical Formulas

Torque in lb.ft. =

HP x 5250 rpm

HP =

Torque x rpm 5250

rpm =

120 x Frequency No. of Poles

Temperature Conversion

Deg C = (Deg F - 32) x 5/9
Deg F = (Deg C x 9/5) + 32