Line Reactors (Line Commutating Reactors) - Siemens SINAMICS G130 Engineering Manual

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Line reactors (line commutating reactors)

Converters with 6-pulse or 12-pulse rectifier circuits (G130, G150, S120 Basic Line Modules and S120 Smart Line
Modules) always require line reactors if
•
they are connected to a supply system with high short-circuit power, i.e. with low impedance,
•
more than one converter is connected to the same point of common coupling (PCC),
•
converters are equipped with line filters for RFI suppression,
•
G130/G150 units are equipped with Line Harmonics Filters for reducing harmonic effects on the supply,
•
converters are operating in parallel as to increase the output power (G150 parallel converters and
converters with a parallel connection of S120 Basic Line Modules or S120 Smart Line Modules).
For the converters G130 and G150 as well as for S120 Basic Line Modules line reactors with a relative short-circuit
voltage of u = 2 % are available. The S120 Smart Line Modules require line reactors with a relative short-circuit
K
voltage of u = 4 %.
K
Supply systems with high short-circuit power
The line reactor smoothes the current drawn by the converter and thus reduces harmonic components in the line
current. The use of a line reactor in conjunction with the SINAMICS devices described in this engineering manual can
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reduce the 5 harmonic by approximately 5 to 10 %, and the 7
higher harmonic numbers are not significantly affected by a line reactor. As a result of the reduced harmonic currents
the thermal loading on the power components in the rectifier and the DC link capacitors is reduced. The harmonic
effects on the supply are also reduced, i.e. both, the harmonic currents and harmonic voltages in the line supply are
attenuated.
Typical line current of a 6-pulse rectifier circuit without and with use of a line reactor
The installation of line reactors can be dispensed with only if the line inductance is sufficiencly high resp. the relative
short-circuit power RSC at the point of common coupling PCC is sufficiently low. The relevant applicable values are
unit-specific and therefore given in the chapters on specific unit types. A definition and explanation of the term
"relative short-circuit power" can be found in the section "Supply systems and supply system types".
More than one converter connected to the same point of common coupling
Line reactors must always be provided if more than one converter is connected to the same point of common
coupling. In this instance, the reactors perform two functions, i.e. they smooth the line current and decouple the
rectifiers at the line side. This decoupling is an essential prerequisite for correct operation of the rectifier circuit,
particularly in the case of SINAMICS G130 and G150. For this reason, each converter must be provided with its own
line reactor, i.e. it is not permissible for a single line reactor to be shared among converters.
Converters with line filters or Line Harmonics Filters LHF
A line reactor must also be installed for any converter that is to be equipped with a line filter for RFI suppression or
with a Line Harmonics Filter LHF for reducing harmonic effects on the supply. This is because filters of this type
cannot be 100% effective without a line reactor.
Fundamental Principles and System Description
Engineering Information
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by approximately 2 to 4 %. The harmonics with
SINAMICS Engineering Manual - May 2008
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