Chapter 4
- Planning
4 - 2
DCS 500 12-Pulse Planning and Start-Up
Planning hints
Transformer
When selecting and dimensioning the mains transformer, care must
be taken to ensure that overvoltages are kept away from the power
converters’ power sections when the transformer is connected to
the mains supply. This means the transformer should have an
earthed shielding winding between the primary and secondary
windings.
This is very useful for suppressing capacitive cross-talk at switching
operations on the primary side. In addition, the shielding winding
also suppresses conducted interference (EMC) to the mains. An-
other method of avoiding overvoltages is to switch on the compo-
nents in stages: first connect the transformer to the mains, and only
then connect the power converter to the transformer. Another op-
tion is to provide the secondary sides with an RC element.
The actual design choice will depend on the electrical conditions in-
volved, like line voltage, power converter input voltage, power con-
verter rated voltage, and frequency.
Power converters The power converters are selected only from the normal product
range (standard types) against voltage and current criteria (motor
voltage; motor current x 0.5).
Interphase
reactor
The 12-pulse interphase reactor limits the cross current between
the two power sections of the 6-pulse power converters, making
possible a current flow duration of 60 degrees per valve. The inter-
phase reactor can be dimensioned by the vendor.
Field supply
For the field supply, all field supply units from the DCS 500/DCV
700 series can be used.
