Thermal Overload (49); Figure 2-13 Thermal Overload - Siemens 7SR21 Manual

2.12 Thermal Overload (49)

Voltage Inputs:
Current Inputs:
Disable:
Map Pickup LED:
The current can be applied from a 3P balanced supply or phase by phase from a 1P supply. Alternatively the 3
phase current inputs can be connected in series and injected simultaneously from a single 1P source.
The Thermal Overload Setting and Time Constant Setting can be considered together to calculate the operating
time for a particular applied current.
The following table lists operate times for a range of Time Constant Settings for an applied current of 2x the
Thermal Overload setting. Ensure that the thermal rating of the relay is not exceeded during this test.
©2010 Siemens Protection Devices Limited
7SR21 & 7SR22 Argus Commissioning and Maintenance

Figure 2-13 Thermal Overload

n/a
I (I ), I (I ), I (I ),
L1 A L2 B L3 C
51, 50, 37, 50CBF
49Alarm
Chapter 6 Page 44 of 69