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82
Protection Function Interlocked by Motor Start
By ticking the relative box, the Motor Start can block all the other protection functions, to avoid a
protection trip during the motor start phase.
The Block signal becomes active when the current exceeds 10% motor nominal current value IMn
(condition a). The block signal is removed if condition b is not fulfilled or when the Motor start
protection exits the START condition.
14.7.3.3.1 Operation criteria
Motor start protection function evaluates the current at the fundamental frequency.
The maximum measured motor current
A motor start is detected if:
a) the maximum measured motor current exceeds 10% of the setting threshold value nominal
motor current (i.e. Nominal Motor Current IMn)
AND
b) within a time of 100 ms the measured motor current exceeds the setting motor start detection
(Motor Start IMs).
When a motor start is detected, the protection is started, the start signal is activated and the
current-time integral is calculated:
The protection function will return to passive status and the start signal will be cleared if the
maximum motor current falls below the End of Start setting threshold value (Ieos). At that time,
calculation of current-time integral is stopped.
After the protection has entered the start status and the calculated current-time integration exceeds
⋅
2
I
T
the default
value, where:
s
I
is the Start current parameter (Start Value Is).
s
is the Time parameter (Time).
T
The function goes into TRIP status and the trip signal is generated.
The protection function will exit the TRIP status and the trip signal will be cleared when the measured
current value falls below the End of Start setting threshold value (Ieos).
I
is used to detect Start and Trip conditions.
RMS_max
∫
2
t i
) (
dt
(
)
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