Application Guide - NP900 Series
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)
A996A
Figure 3.3.3-125 Normal start of the motor.
The LRC function should be set so that in the normal motor start the application required
starting time is taken into account in the setting of the function. There should be setting
margin in the expected starting time and the setting of the LRC function. If the motor
starting is dependent of the process status e.g. the motor drive may be in full load or in no
load when started, this may affect to the starting time of the motor and the setting should
be according to the longest possible starting time. If the startup situation should always be
the same then this expected starting time + 10% margin should be sufficient setting for the
LRC starting monitor. During the start up the LRC function monitors the accumulated I
2
t
value and when it is below the calculated set I
2
t value, the function lets the starting
situation continue.
If the starting of the motor takes longer time than the set value is the function shall trip the
breaker and halt the starting since there is something wrong in the application if the motor
cannot start normally.
