SINAMICS S120 Cabinet Modules
Engineering Information
SINAMICS Engineering Manual – November 2015
Ó Siemens AG
442/528
In order to determine the required DC busbar cross-sections, the potential DC link currents in normal operation must
be calculated as a function of the output of the individual Motor Modules and other general operating conditions
(simultaneity factors, overload factors, motor / generator operation). For optimum cost-effectiveness, different
combinations of DC busbar sizes can be selected. When selecting busbars, it is important to take into account that
the DC busbar systems of adjacent Cabinet Modules must be of compatible mechanical design (see table below and
options selection matrix of the S120 Cabinet Modules in Catalog D 21.3).
Option
Order code
DC busbar
Rated current I
DC
[A]
Number
of parallel
bars
Bar
Dimensions
[ mm ]
Compatible with
option order code
Permissible
Peak short-circuit current
[ kA ]
M80 1170 1 60 x 10 M83 90
M81 1500 1 80 x 10 M84 and M86 85
M82 1840 1 100 x 10 M85 and M87 80
M83 2150 2 60 x 10 M80 180
M84 2730 2 80 x 10 M81 and M86 170
M85 3320 2 100 x 10 M82 and M87 160
M86 3720 3 80 x 10 M81 and M84 255
M87 4480 3 100 x 10 M82 and M85 240
DC busbar options
If liquid-cooled Infeeds (Basic Line Connection Modules or Active Line Connection Modules) are to be operated in a
parallel connection, option M88 is required for each Infeed (DC busbar system for liquid-cooled, line-side Cabinet
Modules). This option is needed in order to establish a continuous DC busbar through the parallel-connected Infeeds
because the standard Basic Line Connection Modules and Active Line Connection Modules are not equipped with
DC busbars in the Line Connection Module.
In applications such as a gearing test stand, for example, one Motor Module might supply an asynchronous motor
that simulates a combustion engine, while other Motor Modules are supplying asynchronous motors that simulate the
load. While the asynchronous motor simulating the combustion engine operates as a motor, the two load-simulating
motors are feeding all their energy back into the DC link. As regards the total energy balance, this means that only a
small proportion of energy is drawn from the line supply (power losses of the complete drive train plus energy
required for acceleration). In this application, energy is primarily exchanged between the Motor Modules via the DC
busbar. As regards the DC busbar design, this generally means that the busbar between the Line Module / Infeed
and the first Motor Module can have a smaller cross-section than the busbars between the Motor Modules when the
modules are arranged in a line with the Infeed at the beginning of the line.
The modules must be arranged according to the relevant load conditions and simultaneity factors so that the DC
busbars can be dimensioned as efficiently as possible.
After the DC busbars have been selected, it must be verified that all parts of the DC busbar system have sufficient
short-circuit strength. The permissible peak short-circuit currents are specified in the table above. The peak short-
circuit currents of the connected Line Modules and Motor Modules are specified in the tables in section "Short-circuit
currents on the DC busbar" in chapter "Fundamental Principles and System Description".
The DC busbars between the Cabinet Modules are interconnected by means of special busbar links. These are part
of the busbar system and are attached to the right-hand face of the bar for a module / transport unit when it is
shipped. When the Cabinet Modules have been lined up, the links can be unfastened, taken into the adjacent cabinet
and fastened tight again.
If option Y11 is selected for Cabinet Modules, i.e. if they are ordered as factory-assembled transport units, a uniform
cross-section of the DC busbar must be selected for each transport unit, as a continuous copper bar is installed
within each transport unit in this case.
7.3.2.3 Required cable cross-sections for line and motor connections
Generally speaking, unshielded cables can be used to make the line connection. 3-wire or 4-wire three-phase cables
should be used wherever possible. By contrast, it is always advisable to use shielded cables and, in the case of
drives in the higher output power range, symmetrical 3-wire, three-phase cables, between the converter and motor
and to connect several cables of this type in parallel where necessary. There are basically two reasons for this
recommendation:
o This is the only method of achieving the high IP55 degree of protection at the motor terminal box, since
the cables enter the terminal box via screwed glands and the number of glands is limited by the geometry
of the box. Single cables are therefore less suitable.
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