Selecting Motors; Uneven Current Load - Siemens SIMOTICS T-1FW6 Configuration Manual

5.2.4

Selecting motors

Select a suitable torque motor using the values determined for the peak torque M
rms torque M
You must take the following factors into account when selecting a motor
● Avoid undesirable limiting effects when control loops overshoot. For the maximum torque
M
M
● The rated torque M
determined for the duty cycle.
● If certain general conditions (e.g. machining torque or frictional torque) are not known,
then you are advised to include an even higher reserve.
● In addition to the requirements resulting from the duty cycle, mechanical installation
conditions may influence your choice of motor. For instance, the same motor torque can
often be generated in a long motor with a smaller diameter as well as in a short motor
with a larger diameter.
● If more than one torque motor generates a torque for a specific axis, the values of the
peak torques and rms torques of the duty cycle of the individual motors must be added.
● If the motor is to be operated over a longer period of time at minimum speed, then select
a motor with an appropriately higher rated torque, see the subsequent Chapter "Uneven
current load (Page 103)".
5.2.5

Uneven current load

If the current load of the three phases is continuously uneven, the motor must only be
operated at no more than approx. 70 % of its rated torque, see also M
"Technical data and characteristics".
For exact configurations, contact your local Siemens office.
Note
Uneven current load
Not all of the three phases are necessarily evenly loaded in all motor operating modes!
Examples of uneven current load:
• Standstill with current fed to the motor, e.g. for:
– Compensation of a weight force
– Start-up against a brake system (damping and impact absorption elements)
• Low speeds over a longer period (n << 1 rpm)
• Very small oscillating rotary movements (path on rotor circumference < pole width)
1FW6 Built-in torque motors
Configuration Manual, 07/2017, 6SN1197-0AE00-0BP9
of the duty cycle.
eff
include approximately 10 % control reserve with reference to the required value
MAX
.
mMAX
of the motor must be at least as high as the rms torque M
N
Configuration
5.2 Configuring workflow
and
mMAX
eff
* in Chapter
0
103