Lenze DDS Function library 9300 Servo - Manual (Page 23)

Function block library Lenze9300Servo.lib
Special functions
2.1.2 Supply−failure control (L_MFAIL)
2−13
L
Lenze9300Servo.lib EN 1.1
Fine setting of the supply−failure control
For the fine setting, you will have to repeat the following points several times.
1. Obtain a very low final speed without the controller reaching the undervoltage threshold LU:
– Increase the proportional gain nVp .
– Reduce the integral−action time nTn .
2. Avoid activation of the brake unit or the overvoltage threshold:
– Increase the integral−action time nTn until the characteristic in Abb. 2−11 is almost reached.
– If necessary, also reduce the setpoint of the DC−bus voltage at nDCSet_a (in the example
C0472/19 ( FCODE_nC472_19_a )).
3. An increase of the run−down/deceleration time or reduction of the brake torque (see
Abb. 2−12) is only possible with restrictions:
– Increasing the acceleration time nTi reduces the initial brake torque and simultaneously
increases the deceleration time.
– Increasing the intergral−action time nTn reduces the initial brake torque and simultaneously
increases the deceleration time. If the integral−action times are too long, the controller
reaches the LU threshold before zero speed is reached. The drive is thus no longer under
control.
4. Re−establish any signal connections which may be required to the outputs of the drive
controller (terminals X6).
Note!
Use C0003 to save all settings im a parameter set, if they are to be retained on power−off.
t
U G
t 1 t 2
t
n
0
0
L _ C M P _ b O u t _ b
n D c S e t _ a
t 3
Q
T
S
R
Abb. 2−12 Schematic representation with different brake torques
 Switch−off threshold OU
‚ Switch−on threshold for brake unit
ƒ Threshold
„ Threshold LU
n Speed of the drive
t = t1 Supply−failure
t = t2 Zero speed with higher brake torque (short adjustment time)
t = t3 Drive reaches the LU switch−off threshold with lower brake torque (high adjustment time),
without reaching zero speed
t > t3 Drive is no longer under control (is braked by friction)