8400 StateLine C | Reference manual
Motor control (MCTRL)
Monitoring
234
L
Firmware
≤
11.00 - DMS 8.0 EN - 10/2011
5.12.2
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.
C00066
displays the calculated motor load in [%].
If the calculated motor load reaches the motor load setting (
C00120
):
– The error response set in
C00606
will be carried out (Lenze setting: "Warning").
– The "
OC6: I2xt motor overload
" error message will be entered into the logbook.
– The
bMctrlI2xtOverload
status output of the
LS_DeviceMonitor
system block will be
set to TRUE.
A setting of
C00606
= "0: No Reaction" deactivates the monitoring.
Adjustment of the motor utilisation meter
The motor utilisation meter for indicating the motor load in
C00066
begins to count when
the apparent motor current (
C00054
) is greater than the motor overload setting (
C00120
).
C00120
is to be set as follows:
If you reduce
C00120
starting from the calculated value, the motor utilisation meter
will already be counted up before the rated overload threshold is reached.
If you increase
C00120
starting from the calculated value, the motor utilisation meter
will not be counted up until the rated overload threshold is reached.
Stop!
The I
2
xt motor monitoring does not present full motor protection! As the motor
utilisation 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
temperature sensors that are located directly in the winding or the use of
thermal contacts.
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%
⋅
=
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