KEB COMBIVERT F5-A, Applications Manual, Page: 242 / 552

Page 7.8 - 4 COMBIVERT F5-A, -E, -H © KEB, 2012-10
Torque display and -limiting
The controller is adapted by parameters dS.08 „KP Umax“, dS.09 „KI Umax“, dS.10 „Umax modulation limit“.
dS.08 has only a minor effect and can remain on value 0.
dS.09 determines the dynamics of the controller. If this parameter is adjusted too small, the drive can arrive vol-
tage limitation. If the parameter is adjusted too high, the drive starts to vibrate. If the modulation factor becomes
much noisier due to an increase of dS.09, it indicates that the controller setting is too high.
A temporary reaching of the voltage limitation is normally not a problem.
The modulation factor to be controlled is determined with parameter dS.10 . The closer this is to 100%, the
better the inverter voltage is utilised, but also the lower are the control reserves useable for the dynamic.
The default value of 97% is usually a good agreement.
For the asynchronous machine, the voltage limitation occurs by flux reduction.
The motor flow can be reduced by the controller to ¼ of the value which is required according to the magneti
-
sation characteristic.
For the synchronous machine, the voltage limitation is done by setting a negative magnetising current. The
maximum value of this current is determined with parameter dS.13 „magn. current limit“. (see chapter 7.8.3
physical torque limits of the synchronous motor about the influence and adjustment of dS.
13).
7.8.2 Physical torque limits ASM
7.8.2.1 Torque limits in base speed range
The rated torque (calculated from rated power and rated speed) of the motor is displayed in parameter dr.14.
The maximum torque (limited by the maximum current of the inverter) is displayed in dr.15.
At activated hardware current limit (uF.15 = 1 or 2) the maximum current is equal to the hardware current level
(In.18) less safety reserve of 5% of the inverter rated current.
At deactivated hardware current lim. (uF.15 = 0) the maximum current is equal to the overcurrent error limit less
safety reserve of 10%.
Additionally the motor current can be limited by software with parameter dr.37 „max. current“ (see chapter
7.10.2). This limitation also affects the maximum torque but is not displayed in dr.15.
Also the active current is limited by torque limitation in the base speed range. But nevertheless the current limit
of the inverter can be exceeded by the additional magnetizing current. Therefore, also the software current limit
should be activated.
7.8.2.2 Torque limits in base speed range
When the motor overloads, i.e., when a torque upwards of its torque limit is demanded from it, the maximum
voltage controller reduces the flux too much and thereby also reduces the maximum achievable torque.
Therefore the maximum permissible torque must be reduced in the field weakening range.
The torque limiting characteristic is defined with parameters dr.
15...dr.18.