Lenze 8400 BaseLine C - Manual (Page 104)

5 Motor control (MCTRL)
5.8 Monitoring
104
Lenze · 8400 BaseLine C · Reference manual · DMS 1.6 EN · 01/2014 · TD05
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5.8.2 Motor load monitoring (I2xt)
The Inverter Drives 8400 are provided with a simple, sensorless, thermal I 2 xt motor monitoring of
self-ventilated standard motors which is based on a mathematical model.
• In C066 displays the calculated motor load in [%]..
• If the motor load reaches the switch-off threshold set in C120 :
• The error response set in C606 will be carried out (Lenze setting: "Warning").
• The " OC6: I2xt motor overload " error message will be entered into the logbook.
• A setting of C606 = "0: No Reaction" deactivates the monitoring.
Adjustment of the motor utilisation meter
The motor utilisation meter for indicating the motor load in
C066 begins to count when the appa-
rent motor current ( C054 ) is greater than the set overload threshold ( C120 ).
The overload threshold ( C120 ) is to be set as follows:
• If you reduce C120 starting from the calculated value, the motor utilisation meter will already
be counted up before the rated overload threshold is reached.
• If you reduce C120 starting from the calculated value, the motor utilisation meter will already
be counted up before the rated overload threshold is reached.

Stop!
The I 2 xt motor monitoring does not present full motor protection! As the motor utilisa-
tion calculated in the thermal motor model is lost after mains switching, for instance the
following operating states cannot be measured correctly:
• Restarting (after mains switching) of a motor that is already very hot.
• Change of the cooling conditions (e.g. cooling air flow interrupted or too warm).
A full motor protection requires additional measures as e.g. the evaluation of tempera-
ture sensors that are located directly in the winding or the use of thermal contacts.

Note!
From version 03.04.00 , the thermal motor load displayed in C066 can be pre-initialised
when the device is connected to the mains, optionally using a fixed value or the value
used last at the time when the device was switched off. The desired initialisation is se-
lected in C122 . In the Lenze setting of C122 , the behaviour remains unchanged (no initi-
alisation).
I
r
: Rated motor current (see nameplate of motor)
I
N
: Rated controller current at a switching frequency of f = 8 kHz
C00120
I
r
I
N
----- 100% ⋅ =