Assembly - Siemens S7-300 Installation Manual

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Please note the following points if you wish to arrange your modules on multiple
racks:
• The interface module always uses slot 3 (slot 1: power supply; slot 2: CPU,
slot 3: interface module)
• It is always on the left before the first signal module.
• No more than 8 modules (SM, FM, CP) are permitted per rack.
• The number of modules (SM, FM, CP) is limited by the permitted current
consumption on the S7-300 backplane bus. The total current consumption may
not exceed 1.2 A per row (if 312 IFM CPU is used: 0.8 A).
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Information about the power consumption of individual modules is provided in the
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Special shielding and grounding measures are not required if you interconnect the
central units and expansion modules using suitable interface modules (Send IM
and Receive IM).
However, you must ensure the following:
• all racks are interconnected with low impedance,
• the racks of a grounded assembly are grounded in a star pattern,
• the contact springs on the racks are clean and not bent, thus ensuring that
interference currents can be dissipated.
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S7-300 Automation System, Hardware and Installation: CPU 312IFM - 318-2 DP
A5E00203919-01