Electrical Assembly, Protective Measures And Grounding; Grounding Concept And Overall Structure; Table 4-6 Cabinet Selection - Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual

Result
The figure below shows the resultant ambient temperatures, based on an accumulated
power loss of 650 W:
Table 4-6
Cabinet design
Closed with natural convection and forced convection (trend
3)
Open with through-ventilation (trend 2)
Closed with heat exchanger (trend 1)
Cabinet types suitable for horizontal installation of the S7-300:
• open, with closed ventilation
• closed, with heat exchanger
4.9

Electrical assembly, protective measures and grounding

4.9.1

Grounding concept and overall structure

This section contains information about the overall configuration of an S7-300 connected to a
grounded TN-S network:
• Circuit-breaking devices, short-circuit and overload protection to VDE 0100 and VDE
• Load power supplies and load circuits
• Grounding concept
Definition: Grounded mains
In a grounded mains network, the neutral conductor is always bonded to ground. A short-
circuit to ground of a live conductor, or of a grounded part of the system, trips the protective
devices.
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
Cabinet selection
0113
Note
An S7-300 can be used in many different ways, so we can only describe the basic rules
for the electrical installation in this document. Those basic rules are a must in order to
achieve a fully functional S7-300 system.
4.9 Electrical assembly, protective measures and grounding
Maximum permitted ambient
temperature
Operation not possible
approx. 38 °C
approx. 45 °C
Configuring
4-15