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