7SR11 & 7SR12 Commissioning and Maintenance Guide
©2017 Siemens Protection Devices Limited Chapter 6 Page 45 of 72
Time Constant (mins) Operate Time (sec)
1 17.3
2 34.5
3 51.8
4 69
5 86.3
10 173
15 259
20 345
25 432
30 51.8
50 863
100 1726
The Thermal State must be in the fully reset condition in order to measure the operate time correctly. This can be
achieved by setting change in the Thermal protection settings menu or by pressing the Test/Reset button when
the Thermal Meter is shown in the Instruments Mode.
Reset the thermal State then apply 2x the Overload Setting current.
Calculated Operate Time (s)
Measured Operate Time (s)
If the Thermal Overload Capacity Alarm is used, this can be tested by monitoring the Thermal Capacity in the
instruments menu. If the Thermal time constant is longer than a few minutes, this can be assessed during the
timing test above. If the Time Constant is less than a few minutes, a lower multiple of current will be required such
that the rate of capacity increase is slowed to allow monitoring of the instrument to be accurate.
2.13.1.1 Element Blocking
The Thermal element can be blocked by Binary Input Inhibit. This functionality should be checked.
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