Prerequisites For The Device - Siemens SINAMICS DCM Compact User Manual

4.2.2

Prerequisites for the device

Transformer
12-pulse operation is achieved in the network by an additional winding system, electrically
swiveled by 30°, belonging to the supplying transformer. Here at least one of the two
converters (master or slave) of the 12-pulse system must be supplied via a galvanically
isolated voltage (isolating transformer) (see Figure 4-5 Converter transformer dimensioning
at higher voltage level (Page 33) and Figure 4-6 Converter transformer dimensioning at low
voltage (Page 34)).
Note
Both converters must be supplied with a clockwise rotation field.
In addition, it is important to ensure that the three-phase current system on the slave device
lags behind that of the master device by 30°. This phase allocation may need to be checked
by taking a measurement.
Converter equipment
SINAMICS DCM software version V1.2 or higher.
All SINAMICS DCMs must have the same software version.
Symmetry resistor
With a 12-pulse series connection, symmetry resistors must be connected in parallel to the
individual converters connected in series, through which at least one current in the amount of
the maximum thyristor reverse current flows. This ensures that, in the range of the small
armature current or when armature current = 0, the total armature voltage is distributed
symmetrically to both individual devices.
As a result of the activation of the thyristors with long pulses, an increased reverse current
may flow. The symmetry resistors must be dimensioned so that at maximum armature
voltage, a cross-current of at least 100 mA flows. With the parallel connection of a device,
the cross-current at maximum voltage should be at least 200 mA and for two devices at least
300 mA.
Overvoltage protection
Converter equipment which is connected to the network via a separate converter transformer
must be protected against overvoltages that can occur as a result of line-side switching
operations by means of overvoltage protection.
If the converter input is protected by means of open contact gaps during primary-side
transformer switching operations, no protective circuit is required at the converter input.
12-pulse applications
Compact User Manual, 09/2015, A5E34871844H
12-pulse series connection
4.2 Configuration
31