Fig. A-1: Load Diagram For Switching Frequency; Fig. A-2: Maximum Switching Frequency When Ia = 4 X Ie (With Example); Maximum Switching Frequency When I - Siemens Ecofast 3RK1 323-2AS54-1AA0 Manual

Motor starter
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Switching Frequency
If motors are switched too frequently, the thermal motor model is activated.
The maximum permissible switching frequency depends on the following
operating data:
I
a
I
e
t
a
t
ED

Fig. A-1: Load diagram for switching frequency

The following diagrams can be used to determine the maximum switching
frequency.

Maximum switching frequency when I

Maximum switching frequency when I
0.1
Example: Cyclic duration factor: 1 s, starting time: t
switching
Determined switching frequency: approx. 1300 switching cycles/h,
Limit when I
Note: No limit with electronic switching
(dotted line, approx. 3000 switching cycles/h)

Fig. A-2: Maximum switching frequency when Ia = 4 x Ie (with example)

ECOFAST Motor Starters
GWA 4NEB 950 5221-12 DS 01
t
b
t
p
t
s
Class
1
10
Cyclic duration factor t
= 6 A for mechanical switching
e
Technical data
Load diagram
I
Direct motor starting current
a
I
Rated motor operational current
e
t
Motor starting time
a
t
Operating time
b
t
Idle time
p
t
Cyclic duration factor
ED
t
Operating cycle
s
t
ED
x 100%
ED[%] =
t
s
= 4 x I
(with example)
a
e
= 4 x I
a
e
Thermal
motor model
100
1000
in [s]
ED
= 0.1 s, I
: 6 A, mechanical
a
e
10000
A-3

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