Siemens SIMODRIVE 611 Configuration Manual page 40

Configuration
3.3 Dimensioning
Load duty cycle
A load duty cycle defines the characteristics of the motor speed and the torque with respect
to time.
Figure 3-6
A load torque is specified for each time period. In addition to the load torque, the average
load moment of inertia and motor moment of inertia must be taken into account for
acceleration. It may be necessary to take into account a frictional torque that opposes the
direction of motion.
The gear ratio and gear efficiency must be taken into account when calculating the load
and/or accelerating torque to be provided by the motor. A higher gear ratio increases
positioning accuracy in terms of encoder resolution. For any given motor encoder resolution,
as the gear ratio increases, so does the resolution of the machine position to be detected.
For more information about gear units, see the motor descriptions.
For the motor torque in a time slice Δ
M
The motor speed is:
n
The rms torque is obtained as follows:
M
3-10
Example of a load duty cycle
2
( ) n
= + • • •
J J
60
t
= •
n i
∑
2
• Δ
M t
=
T
t
the following applies:
k
2
n
(
+ • • +
i J M
60
t
Configuration Manual, (PJAL), 11.2005 Edition, 6SN1 197-0AD07-0BP4
1
)
+ •
M
•
i
General Section for Synchronous Motors