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

8.9.2

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
• Checking the step response
SINAMICS DCM Control Module
Operating Instructions, 12/2018, A5E34888669A
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, field current
actual value = 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.
Procedure
- Set the function generator to a squarewave, with
Step height = e.g. 5%
Offset = various values, e.g. 80%
Period = 1000 ms
Pulse width = 500 ms
- Supply point: p50611[0] (see function diagram 6905)
- Set p50082 = 3 (field continuously on)
- Record signals r52268 (If-set) and r52265 (If-act)
- Change controller parameters Kp (p50255) and Tn (p50256) until the step re-
sponse provides a satisfactory result.
- The field current controller adaptation can be activated (see function chart 6908) to
eliminate the influence of non-linearity of the field inductance and gating unit.
Commissioning
8.9 Manual optimization
313