Siemens SINAMICS DCM Manual page 321

Commissioning
8.8 Manual optimization
8.8.2 Optimization of closed-loop field-current control
Determining the field circuit resistance (2 options)
1. Roughly estimate the field circuit resistance from the rated motor data
p50112 = rated excitation voltage/rated excitation current of motor
2. Determine the field-circuit resistance by comparing the field current setpoint and actual
value
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Overall optimization of closed-loop field-current control
• Checking the precontrol characteristic
Procedure
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• Checking the step response
Procedure
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p50112=0: Results in a 180° field precontrol output and, therefore, actual field cur-
rent 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 disa-
bled
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.
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.
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)
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SINAMICS DCM DC Converter
Operating Instructions, 02.2015, A5E34763375/RS-AA/001