Lenze 8400 BaseLine C - Motor Load Monitoring (I2 Xt)

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%⋅=