7.4 Motor data and characteristic curves
BU 0750 GB Technical design subject to change 87
Setting value / Description / Notes
The motor cosine fundamentally affects vectorial current control.
Measurement of the stator resistance and hence vectorial current control are essentially depend-
ent on the way the motor is connected.
Stator resistance of the motor resistance of a phase winding in the three-phase motor!
Has a direct effect on current control by the inverter. If the value is too high, overcurrent may re-
sult; if it is too low, the motor torque will be insufficient.
This parameter may be set to "zero" for measurement. Pressing the ENTER key initiates the au-
tomatic measurement between two motor phases. In the FI, the resistance on the line is meas-
ured on the basis of the delta or star circuit (P207) and the value saved.
Note: To ensure optimal working of vectorial current control, automatic measurement of the
stator resistance by the FI should be preferred.
The FI will calculate this value automatically from the motor data whenever a different setting is
made in parameter P206 >cos < and parameter P203 >Nominal current<.
Note: Users wishing to enter the no-load current on their own, should set it last of all motor
data. Otherwise the program would overwrite this value with the calculated one.
The static boost has an influence on the current producing the magnetic field. This current is
equivalent to the no-load current of the respective motor and hence is independent of the load.
The no-load current is calculated from the motor data. The 100% default setting of the static boost
is sufficient for the majority of applications
As the dynamic boost affects the torque-generating current, it is a quantity which will have to be
varied according to the load. As with the static boost, the 100% default setting will be adequate for
standard applications.
Setting too high a value may lead to inverter overcurrent, because the output voltage will be
raised too much when a load is applied. With values less than 100% the torque may turn out to be
inadequate.
Slip compensation is a feature which ensures that the speed of a three-phase asynchronous mo-
tor is maintained at a fairly constant level by raising the output frequency with increasing loads.
The 100% setting provided in the factory is an optimal one if the motors used are three-phase
asynchronous types and the data are correctly set.
If several motors (with different loads or outputs) are connected to and controlled by a
single frequency inverter, we recommend to set the slip compensation P212 = 0% to ex-
clude any adverse effect on their operation. A 0% setting should be used for synchro-
nous motors as well where no slipping occurs at all due to the way they work.
With this parameter the dynamic response of the vectorial current control (ISD control) mode of
the FI can be varied. High setting values will make the controller fast, low settings will make it
slow.
As the percentage of the ISD control gain can be optimally adjusted to the process controlled, in-
stability of operation – and other undesirable effects – are effectively prevented.
These settings depend on the motor option selected in parameter P200 .
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