**Basic Motor Formulas**

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

High Inertia Loads

t = WK2 x rpm

308 x T av. WK2 = inertia in lb.ft.2

t = accelerating time in sec.

T = Av. accelerating torque lb.ft…

T = WK2 x rpm

308 x t

inertia reflected to motor = Load Inertia Load rpm

Motor rpm 2

Synchronous Speed, Frequency And Number Of Poles Of AC Motors

ns = 120 x f

Where Ns = Synchronous Speed

f = Frequency

P f = P x ns

120 P = 120 x f

ns

Relation Between Horsepower, Torque, And Speed

HP = T x n

5250 T = 5250 HP

n n = 5250 HP

T

Motor Slip

% Slip = ns - n

ns x 100