Description of parameters
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5
5.6
Limit settings
5.6.1
Current limits
2.6.1.1 Current
Limit
The parameter sets the current limit for the Grid Converter unit. Set the value to
correspond to the maximum peak overload for the unit or if needed, to required short
circuit current (I
SC
).
The maximum value for air cooled unit is I
s
and liquid cooled unit I
th
. For air cooled units
I
s
is available when short circuit functionality is activated. See available current values
from “GTC Product compatibility note” column I
s
.
The drive can operate against the current limit if P2.6.1.3 Short Circuit time has been set
to zero, and P2.6.1.4 High Frequency Current limit has been enabled. Otherwise the drive
will trip to a short circuit fault immediately, or after a set time delay.
NOTE! The internal protections of the drive can trip the drive before the time limit or the
current level is reached.
NOTE! Set the current limit high enough so that limit is not reached in normal operation.
2.6.1.2
Short Circuit Level
This parameter defines the current level when the drive will start to feed reactive
current to the short circuit, i.e. this is short circuit current detection level.
This is instantaneous value, related to P2.1.3 System Rated Current. (
2.1.3 ∗ √2
)
This value should be above the set current limit of the drive but below the (F1) over
current trip limit (3,2-4 * I
h
, depending on unit).
The recommendation is to set Short Circuit Level about 25 % higher than the value of the
current limit. This will eliminate short circuit operation while already operating against
current limit due current spikes that goes to short circuit detection level.
Example LC AFE unit 730 A 500 Vac :
System Rated Current: 487 A (I
h
)
Current Limit: 730 A (I
th
)
Short Circuit Level:
∗ √2 ∗ 1,25
256 %
In this case Short Circuit Level 212% would be equal to Current Limit in rms. The
recommended value for the Short Circuit Level in the case above is 265 %. The function
will be disabled if a value above 499% is given. If it is possible, adjust System Rated
current to have values below 499%.
NOTE! The function requires a uGrid Licence (P3.2 uGrid Licence)
NOTE! During the short circuit grid voltage will be low; it may require that UPS is used
for auxiliary voltage that MCB is kept closed during short circuit.
