SIEMENS
7/7
Siemens CR 1 · 2015
7
■
Configuration
(continued)
SIMOTICS motors for cranes
General technical specifications
Intermittent duty with effect of the start-up process (S4)
Intermittent duty with effect of the start-up process and
electrical braking (S5)
Definition
Operation that involves a sequence of similar duty cycles, each
with a noticeable start-up time, a constant-load period, a period
of rapid electrical braking (with S5), and idle time.
Intermittent duty S4
Intermittent duty S5
Explanation
These operating modes closely resemble S3 duty, except that
the temperature rise caused by start-up and, in some cases,
electrical braking are also included. This additional power loss
depends on the acceleration torque and the time in which this
occurs; in other words, it depends on the linear and rotating
masses to be accelerated (kinetic energy). The masses that are
moved, therefore, must be known. These are based on the mo-
ment of inertia referred to the motor shaft. How often and over
what period of time the masses are subject to acceleration and
braking procedures must also be known.
The more duty cycles performed by the crane drives every hour
(e.g. short traveling distances or low hoisting heights), the grea-
ter the importance of the acceleration work for motor dimensio-
ning purposes.
To accurately dimension a motor for duty cycles S4 and S5,
therefore, the following information is required in addition to the
steady-state output:
•
Cyclic duration factor (CDF)
•
External moment of inertia
•
Acceleration or acceleration torque
•
Accelerating time
•
Number of working cycles per hour
General performance specifications for motors in S4/S5 duty are
not possible because they always vary depending on the speci-
fic conditions under which the driven machine is operating (ex-
ternal moment of inertia) and the operating mode (working cyc-
les, ON duration). Crane drives do not have a constant load
across several working cycles but instead have a collective
load.
G_CR01_EN_00016
mean
max.
t
t
t
e
P
P
V
t
S
t
e
t
P
t
A
G_CR01_EN_00017
mean
max.
t
t
t
e
P
P
V
t
S
t
e
t
P
© Siemens AG 2015