sent to the thyristor electronics via fiber-optic cables. This initiates firing readiness in the
thyristor electronics and activates a monitoring and interlocking logic circuit. The thyristor
electronics then determine the operating status of the thyristor and relays it to the Power Stack
Adapter via the checkback fiber-optic cable. The control commands and checkback signals
correlate with each other. Any disruption to this relationship, for example an open circuit in an
FO conductor or a failed thyristor, is relayed to the open-loop/closed-loop control system as an
error message.
3.3.2.5
Current transformer
Current transformers are used to measure current. The analog output signals from the current
transformer are post-processed by the AVT combination module and sent via the fiber-optic
cable to the power stack adapter. The primary circuit is separate from the secondary circuit.
3.3.2.6
Surge arresters
Overvoltages can occur when inductive loads are switched, for example, in the case of
transformer disconnections at no load. These overvoltages can pose a danger to the converter.
For indoor systems, surge arresters without spark gap are connected in a star configuration
between the phases to limit the overvoltages.
3.3.2.7
Overview of the additional components
Table 3-1
Additional components for completion of the power module
Order number
Description
Quantity installed in the converter (not included in the scope of
delivery)
3EK7060
6 kV surge arrester, 10 kA
18
A5E00715597
Current transformer 3 kA; 0.1 A / 5 A
18
322776
Varistor for the transformer
36
A5E02425179
UM measurement
3
A5E00230662
AVT combination module
6SL3995-6LX00-0AA0
18
Set of installation materials
1
3.3.3
Principle of operation
The maximum frequency (which is determined by the operating principle of the direct converter)
is approx. 40 % – 44 % of the line frequency. Thus with 4-pole motors on a 50 Hz supply, the
maximum achievable rotational speed is approx. 660 rpm. If the machines are operated over
a wide constant power range, the rated speed is normally significantly lower than this. The high-
quality speed control range extends right down to zero speed.
Description
3.3 Power unit
SINAMICS SL150 6SL38655UM427AA02
Operating Instructions Rev.201910281507 EXAMPLE
29
