Rockwell Automation 150 MNL/SMC DIALOG+/APP-PROD GUIDE - Manual (Page 174)

10-12 Reference
Calculating Torque
(Acceleration Torque
Required for Rotating Motion)
(cont.) The same formula can be used to determine the minimum
acceleration time of a given drive, or it can be used to establish
whether a drive can accomplish the desired change in speed within
the required time period.
Transposed formula:
General Rule:
If the running torque is greater than the accelerating torque, use the
running torque as the full-load torque required to determine the motor
horsepower.
Calculating Horsepower Note: The following equations for calculating horsepower are
meant to be used for estimating purposes only. These
equations do not include any allowance for machine friction,
winding or other factors that must be considered when
selecting a device for a machine application.
After the machine torque is determined, the required horsepower is
calculated using the formula:
Where:
HP = Horsepower
T = Torque (ft.-lb.)
N = Speed of motor at rated load (RPM)
If the calculated horsepower falls between standard available motor
ratings, select the higher available horsepower rating. It is good
practice to allow some margin when selecting the motor horsepower.
Inertia Inertia is a measure of the body’s resistance to changes in velocity,
whether the body is at rest or moving at a constant velocity. The
velocity can be either linear or rotational.
The moment of inertia (WK
2
) is the product of the weight (W) of an
object and the square of the radius of gyration (K
2
). The radius of
gyration is a measure of how the mass of the object is distributed
about the axis of rotation. Because of this distribution of mass, a
small diameter cylindrical part has a much lower inertia than a large
diameter part.
T
WK
2
∆
N
( ) ×
30 8t
×
--------------------------- =
HP
T N
Ч
5,25
----------- =