KEB COMBIVERT F5-A, Applications Manual, Page: 246 / 552

Page 7.8 - 8 COMBIVERT F5-A, -E, -H © KEB, 2012-10
Torque display and -limiting
A typical value for dS.13 is the
motor rated current. In the field weakening range, the current needed to set a
defined torque increases.
Picture 7.8.3.2.1b Limit current in the field weakening range
Drehzahl [U/m
Motorstrom [A]
Momentengrenzkennlinie
Beginn des
"Feldschwächbereiches"
Attention:
To assure that the speed controller can control the drive, an active current must always be available that should
not fall below 0.5 x dS.13.
Pay attention to appropriate adjustment of the torque limit and the maximum current!
7.8.3.2.2 Definition of the limiting characteristic
Starting at a certain speed, the drive cannot provide the same torque in field weakening operation that it provi
-
des in the base speed range.
If the drive is to accelerate at a constant torque limit (e.g., double the rated torque), the motor is (despite field
weakening) physically unable to provide this torque.
The set torque can not be adjusted anymore and the drive ´hangs´ in the voltage limit (modulation factor ru.42
= 100%).Therefore, a limiting characteristic that mirrors the physical limits of the drive must be given. This limit
is depending on dS.13 „magnetization current limit“.
If no limiting characteristic is given, the user must insure that the motor is not asked to deliver an inadmissibly
high torque by choosing suitable acceleration /deceleration ramps and by appropriate selection of the load.
Parameters dr.33 and dr.39...47 serve for setting the limiting charcteristic.
Attention:
Value 0 should not be used for the torque values of the limiting characteristic. Also, the torque at the highest
speed (i.e., the last point on the characteristic) should minimally be set to the following value:
Magnetizing current limit (dS.13)
—————————————————
DSM rated current (dr.32)
M
min
= 0.37 x x DSM rated torque (dr.27)