Siemens SIMOTICS T-1FW68, Configuration Manual

Page: 86 / 194

Configuring
5.1 Configuring workflow
1FW68 radial segment motors
84
Configuration Manual, 08/2021, A5E51132930B AA
5.1.2 General mechanical conditions
Moment of inertia
The kinetic energy of a rotating body is directly proportional to its moment of inertia J in
kgm
2
. The moment of inertia takes into account the rotating mass and its spatial
distribution across the entire volume of the body with respect to the rotary axis. The
rotating mass comprises the mass of the rotating mechanical structure (e.g. tool and
holder) and the intrinsic mass of the moving part of the motor (stator or rotor).
Torque due to gravity
Every mass is subject to gravity. This means that the motor must compensate for the
gravitational torque M
g
that acts on the moved mass. M
g
for a horizontal axis, depends
on the position (angle α ) of the moved mass m along the circular path, radius r of the
circular path, the mass itself, force due to gravity g and possibly any torque
compensation being applied.
Figure 5-1 Calculating the gravitational torque to be compensated by the motor for a horizontal
axis
When using torque compensation, you must consider that the compensation does not
automatically amount to 100% and is linked to additional friction forces and inert
masses.