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Settings Calculation Examples BE1-11m
Set the 49RTD-1 protection element as shown in Figure 84-44 to protect the stator winding insulation.
Voting is set to 2, meaning at least 2 RTDs must be at 155°C or higher to result in a trip. A delay is not
required for the reason that temperatures change slowly because of the large motor thermal mass.
Figure 84-44. Protection, Thermal, Resistance Temperature Detector (49RTD-1) Screen
Set the 49RTD-2 protection element as shown in Figure 84-45 to protect the motor bearings. The
maximum bearing temperature of 95°C is supplied in the motor manufacturer data. Voting is set to 1,
which provides a sensitive bearing overtemperature trip. Only 1 RTD must be 95°C or higher to result in a
trip.
Figure 84-45. Protection, Thermal, Resistance Temperature Detector (49RTD-2) Screen
Protection - Current
Five instantaneous overcurrent elements, one current differential element, and one instantaneous
undercurrent element are used in this settings example.
Instantaneous Overcurrent (50-1) - Short-Circuit Protection
Use the 50-1 protection element to protect the motor stator windings for a short circuit. Set the pickup as
low as possible without causing a trip to occur during motor starting. The pickup setting is derived using a
dc offset of 1.7, 125 percent of LRA, and a BE1-11m pickup tolerance of 2 percent. CTR is the CT ratio.
See Equation 84-26.
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