Commissioning
8.9 Manual optimization
SINAMICS DCM DC Converter
Operating Instructions, 12/2018, A5E34763375A
345
Calculate the armature circuit resistance p50110 from the armature current and
armature voltage
Gradually increase the main setpoint (shown at r52011) until the actual armature
current value (r50019 as a % of the unit
's rated armature current) reaches approx-
imately 70% of the motor's rated armature current.
Calculate the armature circuit resistance:
Ra[Ω] = r50038 / (r50019 × p50100) = armature voltage [V] / armature current [A]
Calculate the armature circuit inductance p50111 from the armature current at the
transition point from discontinuous to continuous current
Make an oscilloscope trace of the armature current.
Starting from 0, gradually increase the main setpoint (shown at r52011) until the
armature current reaches the transition point from discontinuous to continuous
current.
Calculate the armature circuit inductance using the following formula:
La[mH]
= 0.4 × r50015 / (r50019 × p50100)
= armature voltage [V] / armature current at the transition point from discontinuous
to continuous current [A]
Overall optimization of the armature circuit
• Checking the precontrol characteristic
Set the function generator to a triangular waveform (0% to 100%), period =
10000 ms
Supply point: p50601[4] (see function diagram 6855)
Set p50082 = 0 (field off)
p50153 = 3 (influence of EMF disabled)
Record signals r52121 (output, precontrol) and r52110 (output, armature current
controller)
The parameters of the precontrol (Ra [p50110], La [p50111] and λa [p51591]) are
correctly set if the armature current
controller output has the lowest possible value
(e.g. less than 5%) over the complete setpoint range.
• Checking the step response
Set the function generator to a squarewave, with
S
tep height = e.g. 5%
ffset = various values, e.g. 80%
eriod = 1000 ms
Supply point: p50601[4] (see function diagram 6855)
Set p50082 = 0 (field off)
Record signals r52118 (Ia-set) and r52117 (Ia-act)
Change controller parameters Kp (p50155) and Tn (p50156) until the step re-
sponse 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 ad
aptation can be activated (see
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