Field Current Controller; Field Reversal - ABB DCS 500B Description

Functional Software description
Field Current Con-
troller

Field Reversal

3 -phase
supply
54
The current controller of the field excitation unit is located inside the
field excitation unit. Some parameters are accessible via serial
communication if the current controller needs manual tuning. The
current controller is a PI-type controller that has parameters for P-
gain and I-time constant.
P-gain parameters:
F1 KP (1308)
F2 KP (1505)
Scaling: input
P
output 4095
I-time constant parameters:
F1 KI (1309) Scale: 1 = 10 ms
F2 KI (1506) Scale: 1 = 10 ms
The maximum output voltage of the PI-controller can be limited by
means of two parameters. When the bridge is fully open the output
voltage is 0.9 * VAC. This equals the limit value 4095. The limitation
is linear so 2048 = 0.5 * 0.9 * VAC.
F1 U LIM N (1311)
F1 U LIM P (1312)
F2 U LIM N (1508)
F2 U LIM P (1509)
Field reversal is needed when the drive has only one armature
bridge (two-quadrant). This gives the possibility to change the speed
direction and also to regenerate the energy back to the network. The
sign of the torque reference in armature control defines the direction
of the field.
Normal running as motor
I d
I exc.
F1
+
-
F2
Figure 41 Field reversal braking principle
4095
1
negative limit
positive limit
negative limit
positive limit
Field Reversal Braking
n
+
T
M
EMF
-
DCS 500 Software Description
I d
n
F1
- T -
G
I exc. EMF
+
F2
+