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5 Description of the Functions
5.5 SIMODRIVE POSMO A functions
S (J
N
Shaft
Δt =
M
max_perm
2
M
1
max_perm
S
k
=
rot
S i
2
(J
)
N
Mot
Shaft
5-174
The following must also be observed:
The function "travel to fixed stop" causes an externally forced rotation
delay and therefore an externally forced torque that must be below the
permissible torques indicated in Chapter 2.5.1 for POSMO A
and 2.5.2 for POSMO A
fective here!
The torque must therefore be limited with mechanical measures for
forced braking. The endstop therefore cannot be designed to be per-
manently fixed; rather, it must be flexible enough that the forced brak-
ing process is extended over a specific minimum time Δt. The minimum
time results from:
S
The translated moment of inertia of the motor = J
S
The speed at the gearbox output (N
approached. The speed must be entered in rad/s for computational
inspection.
S
The maximum permissible gearbox torque
–
For the POSMO A
responds to a motor speed of 2916 rpm) yields, for example
S
18 rpm
S i
2
60 smin
)
Mot
=
The mechanical system of the fixed stop according to
the diagrams in Table 5-7 must therefore be designed to be flexible
enough that the motion is not braked abruptly, but is extended over at
least 65 ms. The centrifugal masses that are braked to a standstill by
the mechanical endstop comprise not only the moment of inertia of the
motor (as in the above example), but all moments of inertia and linearly
moved masses participating in the motion. For the event that the me-
chanical forced braking takes place unevenly, a corresponding safety
factor must be accounted for in the brake time calculation.
As an alternative to a carefully soft design of the endstop, the mechani-
cal limitation of the torque during forced braking can also be imple-
mented with a coupling on the gearbox output. The coupling then ex-
hibits the required flexibility k
the translated motor moment of inertia need then be considered as
centrifugal mass.
(48 N S m)
2
=
2
(0.00006 kg S m
S 162
2
Upon transfer of the maximum permissible torque for this gearbox, the
coupling twists by approx. 1/10 rad, in other words about 6 degrees.
The user must check whether this much twisting can be accepted.
SIMODRIVE POSMO A User Manual (POS1) – 08/2013 Edition
–
300 W. The electrical torque limiter is inef-
,) at which the endstop is
Shaft
75 W with i = 162 : 1 and a speed of 18 rpm (cor-
2 S π
S (0.00006 kg S m
–1
48 N S m
in the direction of rotation, whereby only
rot
1
S
2
2 S π
)
S
18 rpm
60 smin
E Siemens AG 2013 All Rights Reserved
05.13
08.04
02.99
–
75 W
S i@
Mot
S 162
2
2
)
= 65 ms
S
–1
= 410 N
m rad
–1
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