4.4.2.4 OL2 protection
Protection against the error OL2 can be activated via object is14 overload protect
mode for current controlled operation. There are two different modes:
No protection against OL2 tripping, but overload reserves can be fully usable
The permissible total current is limited according to the OL2 limiting characteristic.
The permissible percentage of the OL2 current, to which the current setpoint is
limited, must be adjusted in is21 OL2 safety fact.
The most stable OL2 protection is achieved with this function, provided the safety
distance to OL2 is selected not too small. No short-term overload reserves are
available in the lower frequency range. In the whole frequency range the current
is limited to
Imax = (de29 inverter maximum current * is21 OL2 safety fact).
The current is not limited initially if there is sufficient distance between OL2 coun-
ter and is21 OL2 safety fact..
The current limit is reduced to the OL2 limit characteristic value only when the
OL2 counter reaches the value of is21.
An OL2 error can rather occur in this mode caused by too high factor is20 OL2
prot. gain or too high value for OL2 safety fact.. Therefore overload reserves are
available for a short period.
Permanently the current in the whole frequency range is also limited to de29 in-
verter maximum current * is21 OL2 safety fact.
The permissible total current is limited in mode 2 only if the OL2 counter exceeds a
certain value.
Figure 9: Characteristic of the current limit in relation to the time
Characteristic of the current limit in relation to the time when operating at the cur-
rent limit for different values of is20 OL2 prot gain. The higher the factor, the
steeper the descent of the current limit when the OL2 counter reaches the safety
factor.
0
20
40
60
80
100
120
140
160
Zeit
Stromgrenze (Faktor = 25)
Stromgrenze (Faktor = 100)
OL2 Counter bei Betrieb an der Stromgrenze
I OL2
SafetyFact (is21) * I OL2
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