Eurotherm 584SV Series, Product Manual

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This function block is designed to protect
the motor and the Inverter from damage that
may be caused by continuous operation
beyond specification.
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The I*t UPPER LIMIT, I*t THRESHOLD and I*t TIME parameters effectively define how long
the output current may exceed the I*t THRESHOLD . For example, if the output current equals
the I*t UPPER LIMIT then the trip will occur after I*t TIME . Alternatively, if the output current
exceeds the I*t THRESHOLD by only half as much as the I*t UPPER LIMIT then the trip will
occur after twice the I*t TIME .
As the output current is constantly monitored by the Inverter the I*t TRIP block constantly
updates the time at which a trip might occur, taking into account not only the present output level
but also the recent history. For an output current that moves around the I*t THRESHOLD level,
the time for which the current is below the level is used to balance the time for which the current
is above the level. This avoids spurious trips while maintaining the monitoring function.
Refer to Chapter 7 for a description of the trips supported by the Inverter.
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4
SETUP PARAMETERS
5
FUNCTION BLOCKS
6
TRIPS
7
I*T TRIP
I*T THRESHOLD
I*T TIME
I*T UPPER LIMIT
I*t TRIP
105.00 % – [237] I*t THRESHOLD –
60 s – [238] I*t TIME –
150.00 % – [239] I*t UPPER LIMIT –
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I*t THRESHOLD Range: 50.00 to 105.00 %
If the magnitude of the current delivered by the Inverter is greater than this threshold then the
Inverter will trip after a time determined by I*t TIME and I*t UPPER LIMIT .
This parameter must be less than the I*t UPPER LIMIT .
I*t TIME Range: 5 to 60 s
The trip delay time for a constant output current equivalent toI*t UPPER LIMIT .
I*t UPPER LIMIT
Range: 50.00 to 150.00 %
The output current level used to determine the trip delay. Used in conjunction with I*t TIME .
This parameter must be greater than I*t THRESHOLD .
Time
Current
Area that defines how
long the output may
exceed the threshold.
Example of current
output that causes
a trip.
Upper limit
Threshold
I*t TIME