Closed-loop thyristor current control
System- and communication configuring D7-SYS - SIMADYN D 5-63
Edition 06.2002
5.4 Special features/issues
5.4.1 Operation from 60 [Hz] line supplies
Several parameters must be re-determined for operation on line supplies
with a frequency of 60 [Hz].
The equivalent sampling time should be specified in the "HW Config"
software according to the following equation.
.
1
Nopulsef
timesamplingEquivalent
∗
=
This data is required to convert the time-dependent quantities in interrupt
task I1 (3.3[ms] at 50 [Hz], 2.7 [ms] at 60[Hz]).
The gating unit uses input PA6.FNT as reference value for the automatic
frequency adaptation. A value of 60 should be entered at the input for a
60 [Hz] line supply.
5.4.2 Operation with unstable line supplies
The normal public utility is generally stable regarding frequency and
voltage, even under load conditions.
However, this stability can be restricted when operating the drive
converter from line supplies with a lower fault rating, especially on local
networks (island networks).
In order to be able to operate the gating unit on unstable line supplies or
with “polluted” synchronizing voltages, several functions are available in
the software at FB PA6 for the line supply monitoring and at FB EMF.
Generally, with unstable line supplies a low-frequency oscillation is super-
imposed on the line frequency. This can cause the gating unit to oscillate
and, under extreme situations, can also result in the closed-loop thyristor
current control being switched-out with "pulse position error".
Furthermore, the synchronizing voltage can have sporadic phase steps,
especially when large loads are either powered-up or powered-down on
the factory network. Using special software processing, these effects can
either be reduced or even completely eliminated
Various methods can be selected at PA6.NCM for handling the line
supply.
PA6.NCM = 0: There is no line supply handling. The zero crossovers of
the synchronizing voltage, sensed using the hardware circuit, are used,
without any software correction to determine of the firing pulses. This
setting should only be used for "clean" synchronizing voltages.
PA6.NCM = 1: As for NCM = 4 (for reasons of compatibility)
Calculation rule
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