Siemens 7SR242 Duobias - 2.8 Thermal Overload (49)

7SR242 Duobias Commissioning & Maintenance Guide
©2010 Siemens Protection Devices Limited Chapter 6 Page 36 of 57
2.8 Thermal Overload (49)
Figure 2-10 Thermal Overload
Voltage Inputs: n/a
Current Inputs: W1-I
L1
(I
A
), W1-I
L2
(I
B
), W1-I
L3
(I
C
), or W2-I
L1
(I
A
), W2-I
L2
(I
B
), W2-I
L3
(I
C
),
Disable: 51, 50, 37, 46NPS, 50CBF, 87BD
Map Pickup LED: 49 Alarm
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.
This elements can be allocated to W1 or W2 current inputs by relay settings, ensure that current is injected on the
correct input.
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.