Optimization Of Closed-Loop Field-Current Control - Siemens SINAMICS DCM Operating Instructions Manual

8.8.2

Optimization of closed-loop field-current control

Determining the field circuit resistance (2 options)
1.
2.
Overall optimization of closed-loop field-current control
 Checking the precontrol characteristic
SINAMICS DCM DC Converter
Operating Instructions, 1.2012, C98130-A7066-A1-05-7619
- Change controller parameters Kp (p50155) and Tn (p50156) until the step
response provides a satisfactory result.
- In order to eliminate the influence of non-linearity of the armature circuit
inductance and gating unit, the armature current controller adaptation can be
activated (see function chart 6855).
Roughly estimate the field circuit resistance from the rated motor data
p50112 = rated excitation voltage/rated excitation current of motor
Determine the field-circuit resistance by comparing the field current setpoint and actual
value
- p50112=0: Results in a 180° field precontrol output and, therefore, actual field
current value of 0
- p50082=3: So that the field remains permanently switched on, even when the line
contactor drops out
- p50254=0 and p50264=0: Only field precontrol active; field-current controller
disabled
- Set p50102 to rated excitation current.
- Increase p50112 until the actual field current (r50035 converted to amperes using
r50073[1]) equals the required setpoint (p50102).
- Set p50082 back to the system's operating value.
Procedure
- Set the function generator to a triangular waveform (0 % to 100 %), period =
10000 ms
- Supply point: p50611[0] (see function diagram 6905)
- Set p50082 = 3 (field continuously on)
- Record the signals r52271 (output, precontrol) and r52260 (output, field current
controller)
- The parameters of the precontrol (Rf [p50112], Lf [p50116] and λf [p51597]) have
been correctly set if the output of the field controller has the lowest possible value
(e.g. less than 5 %) over the complete setpoint range.
Commissioning
8.8 Manual optimization
281