Siemens SIMOTICS T-1FW68, Configuration Manual

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Configuring
5.1 Configuring workflow
1FW68 radial segment motors
86
Configuration Manual, 08/2021, A5E51132930B AA
Short-time duty S2
For short-time duty S2 the load duration is so short that the final thermal state is not
reached. The subsequent zero-current break is so long that the motor practically cools
down completely.
NOTICE
Motor overload
An excessively high load can lead to shutdown, or if the temperature sensors are not
correctly evaluated, then the motor could be destroyed.
• Ensure that the load does not exceed the value I
MAX
specified in the data sheets!
• Ensure that the temperature sensors are correctly connected and evaluated.
The motor may only be operated for a limited time t < t
MAX
with a current I
N
< I
M
≤ I
MAX
.
The time t
MAX
can be calculated using the following logarithmic formula:
with ν = (I
M
/ I
N
) 2 and thermal time constants t
TH
.
The thermal time constants, the maximum currents and the rated currents of the motors
can be taken from the data sheets.
The above equation is valid under the precondition that the initial temperature of the
motor - the intake temperature of the water cooling T
VORL
corresponds to what is
specified in the data sheet.
Significance of the duty cycle
In addition to the frictional torque, you must also take into account the duty cycle when
selecting the motor. The duty cycle contains information regarding the sequence of
motion of the drive axes and the machining forces that occur in the process.
Motional sequence
The motional sequence can be specified as a rotation angle-time diagram, angular
velocity-time diagram, speed-time diagram, or angular acceleration-time diagram. The
torques resulting from the motional sequence (accelerating torque M
a
) are proportional
with respect to the angular acceleration α and moment of inertia J, and are in opposition
to the acceleration.
Angle-time diagrams and speed-time diagrams can be converted to angular
acceleration-time diagrams α (t) in accordance with the following correlations: