Operate Curve for Symmetric Load
Tripping Times
The following table shows the tripping times for 3-pole symmetric load without preload for tripping class 2 to
50.
Table 3-1
Tripping Times for 3-Pole Symmetric Load without Preload at the Ambient Temperature of
25 °C
Tripping
Class
(_:110)
Thermal
time
constant
Coefficient
1.5
2
2.5
3
4
5
6
7.2
8
9
9.8
10
Tripping Time (s)
Class 2
1.0 min
46.3 21.6 12.9 8.7
4.7
3.0
2.1
1.4
1.1
0.9
0.8
0.7
Class 3
1.5 min
69.5 32.4 19.4 13.0 7.1
4.5
3.1
2.1
1.7
1.4
1.1
1.1
Class 5
2.5 min
115.8 54.0 32.3 21.7 11.8 7.4
5.1
3.5
2.9
2.3
1.9
1.8
Class 10a 4.5 min
208.4 97.3 58.1 39.0 21.2 13.4 9.2
6.4
5.2
4.1
3.4
3.3
Class 10 5.2 min
240.8 112.4 67.1 45.0 24.5 15.5 10.7 7.4
6.0
4.7
4.0
3.8
Class 20 9.7 min
449.1 209.7 125.2 84.0 45.8 28.9 19.9 13.7 11.1 8.8
7.4
7.1
Class 30 14.5 min
671.4 313.4 187.2 125.6 68.4 43.2 29.7 20.5 16.6 13.1 11.0 10.6
Class 40 19.3 min
893.6 417.2 249.2 167.2 91.1 57.4 39.6 27.3 22.1 17.4 14.7 14.1
Class 50 23.6 min
1093 510.1 304.7 204.4 111.4 70.2 48.4 33.4 27.0 21.3 18.0 17.2
The deviations of the tripping times are lower than 10 % for the tripping classes 5 to 50 without preload over
the permitted temperature range of -10 °C to +55 °C and considering all tolerances. According to the standard
EN 60079-7, the permitted deviations of the tripping times are lower than 20 %.
You can find the tolerances for the classes 2 to 5 in the device manual, in the chapter Technical Data.
Operate Curve
If the ambient temperature is not measured and is set to 40 °C, you can get the operate curve through the
following formula:
[foauslos-211010-01.tif, 1, en_US]
t
Tripping time
τ
th
Time constant
I
Measured load current
I
preload
Preload current
k
Setting factor according to VDE 0435 part 3011 or IEC 60255-149 (K factor)
I
rated, obj
Rated current of the protected object
According to the standard EN 60079-7, you must select an operate curve such that the tripping time for 3-pole
symmetric load does not exceed the locked-rotor time indicated on the name plate. The tripping time for 3-
pole symmetric load can be derived from the curve for the ratio I/I
rated
of the protected object. The character-
istic for starting without the preload applies. The characteristic includes the most unfavorable case of a short
operational break during which the motor does not cool down virtually.
3.1
Operate Curve
3.1 Operate Curve for Symmetric Load
20
SIPROTEC 5, Additional Information on the Protection of Explosion-Proof Motors with Type of Protection Increased Safety e,
Manual
C53000-H5050-C078-1, Edition 03.2019
