2 PROTECTION FUNCTIONS
2.1 Motor Starting and Running (stall protection) (48/51LR/50S/14)
2.1.1 Stall Protection Description
Comprehensive features are available to protect the motor during the critical starting sequence.
Measurements and diagnostics are also available to help the user in the maintenance of the electrical
process. For example, last start time and last start current can be displayed on the HMI of the relay.
2.1.2 Prolonged Start
The following criteria can be used to detect a motor start.
Single criteria: a change in the interrupting device position is detected. This is from open to close or
detection of a starting current of more than the starting current threshold. The start criteria is set to 52a
or I in the STALL DETECTION menu settings.
Extended criteria: a change in the interrupting device position is detected, along with the detection of
a starting current of more than the starting current threshold, 52a+I. Both criteria have to be present
within a 90 ms time period.
Once a start has been detected, using one of these methods, and the current fails to fall below the
current threshold before the normal starting time threshold, a trip is initialized.
The following diagram shows detection of a successful start with the use of the extended criteria.
Figure 1: Start Successful
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