SIEMENS
7/5
Siemens CR 1 · 2015
7
■
Configuration
(continued)
SIMOTICS motors for cranes
General technical specifications
Continuous duty (S1)
Definition
Operation with a constant load state, the duration of which is suf-
ficient to attain thermal equilibrium.
Explanation
The operating time
t
e
of the motor must be greater than 3 ×
T
L
to
ensure that thermal equilibrium is attained. The rated motor out-
put for continuous duty must be designed such that the final
temperature
ϑ
e
matches the permissible winding temperature.
Start-up is deliberately discounted under the assumption that a
single high-inertia start will not achieve the final temperature.
The length of the subsequent idle time is insignificant. Caution is
advised, however, when high-inertia starting is carried out on a
warm machine or when a machine is started up several times in
succession. Certain restrictions may apply or advice from a third
party should be sought.
Short-time duty (S2)
Definition
Operation with a constant load state that, however, does not last
long enough to attain thermal equilibrium, followed by idle time
that lasts until the machine temperature differs from the coolant
temperature by no more than 2 K.
Explanation
The operating time
t
e
must be less than 3 ×
T
L
to ensure that the
theoretical final temperature is not reached. The rated motor out-
put and the operating time are harmonized in such a way that
the maximum winding temperature
ϑ
max
does not exceed the
permissible values. Here, too, start-up is deliberately discounted
because it is assumed that the machine starts up cold and the
start-up procedure is short with respect to the operating time
t
e
.
The rated motor output for short-time duty can be higher than for
continuous duty, although the permissible operating time must
also be specified. The shorter the operating time, the higher the
rated output of the machine. Operating times of 10, 30, 60, and
90 minutes are recommended.
The subsequent idle time must be sufficiently long to ensure that
the machine can cool back down to the ambient temperature
(i.e.
t
P
is greater than or equal to 3 ×
T
St
) because otherwise the
maximum temperature will be exceeded the next time a similar
duty cycle is carried out.
P
t
P
V
t
t
T
L
e
max.
=
≥
t
e
3
T
.
L
G_CR01_EN_00012
G_CR01_EN_00013
t
P
e
P
V
P
t
t
t
t
max.
e
<
t
e
3
T
.
L
≥
t
P
3
T
.
St
© Siemens AG 2015