Functions
6.6 Calculating switching cycles
Motor
starter (3RK1308‑0**00‑0CP0)
Equipment Manual, 11/2019, A5E34821005002A/RS-AC/003
83
6.6
Calculating switching cycles
The switching cycles attainable by the ET200 SP motor starter are determined by the
root-mean-square of the motor current l
rms_motor
. The switching cycle considered is admissible
if the following criterion is met:
I
rms_motor
≤
I
e
* 1.05
I
rms_motor
is determined on the basis of the root-mean-squares of the motor currents during the
startup time and the motor operation time taking the motor OFF time into account. In the
following formula, I
e
corresponds to the rated current of the connected motor.
x = starting current factor I
Startup
/I
e
Table 6- 3
Switching frequency per hour of the 3RK1308 motor starter for the switch-on duration of 0.5 s:
Current setting [A]
0.4
1
3
9
10
12
x = starting current
factor I
Startup
/I
e
Startup
time [s]
Number of starting operations per h
2.5
0.1
4131
4131
4131
4131
4131
4131
2.5
0.3
1377
1377
1377
1377
1377
1377
2.5
0.5
826
826
826
826
826
826
2.5
0.7
590
590
590
590
590
590
2.5
2
207
207
207
207
207
207
4
0.1
1446
1446
1446
1446
1446
1446
4
0.3
482
482
482
482
482
482
4
0.5
289
289
289
289
289
289
4
0.7
207
207
207
207
207
207
4
2
72
72
72
72
72
72
6
0.1
620
620
620
620
620
620
6
0.3
207
207
207
207
207
207
6
0.5
124
124
124
124
124
123
6
0.7
89
89
89
89
89
86
6
2
31
31
31
31
31
25
8
0.1
344
344
344
339
292
75
8
0.3
115
115
115
108
93
20
8
0.5
69
69
69
62
53
8
8
0.7
49
49
49
43
36
0
8
2
17
17
17
9
6
0
10
0.1
219
219
219
51
54
0
10
0.3
73
73
73
12
13
0
10
0.5
44
44
44
0
0
0
10
0.7
31
31
31
0
0
0
10
2
11
11
11
0
0
0
