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Ethernet Networks (PROFINET, EtherCAT, Ethernet/IP, etc.) Installation Instructions


Introduction

A clear trend in the industry is to increasingly use Ethernet as the network to interconnect PLCs, remote I/O, drives, inverters, cameras and other types of devices. For a quick trial on your desk, connecting these devices with a cheap Ethernet patch cable is not a problem. However, for use in a real industrial environment, there are guidelines for the type of cable to be used, and for proper installation.
 

Cable to be used.

The designations Cat.5(e) and Cat.6 only indicate the maximum signal frequency that can be transmitted by the cable. Cat.5 and up all have enough bandwidth for industrial 100 Mbps communication. But for industrial applications, the quality of shielding is important, as we deal with electrically 'dirty' environments. To indicate the type of shielding, abbreviations are used. The new abbreviations below are according to ISO/IEC11801


 

Types of ethernet cable
Old Name New name Cable screening Pair shielding
UTP U/UTP none none
STP U/FTP none foil
FTP F/UTP foil none
S-STP S/FTP braiding foil
S-FTP SF/UTP foil, braiding none

 

 

 

 The green types with both braided shield plus foil are recommended for industrial use.
 

In the new codes, the code before the slash designates the shielding for the cable itself, while the code after the slash determines the shielding for the individual pairs:

  • TP = twisted pair
  • U = unshielded
  • F = foil shielding
  • S = braided shielding

Note that within these types, some cheaper cable on the market may have poor braid coverage (<40%), while a proper industrial cable should have coverage >80%.
 

Patch cable and Installation cable.

We distinguish two types of cable:

  • Patch cables come completely assembled, with non-removable connectors. These are used within cabinets, to link devices over short distances. The more flexible the cables are, the looser the fit of the cores within the lining. This gives them poor electrical characteristics, and therefore they are unsuitable for longer distances. Note that 'office' patch cables often have no foil or shielding, which makes them unsuitable for industrial applications.
  • Installation cable is bought 'off-the-reel' without connectors, and is used for fixed installation between cabinets. Due to a better filling of the cable, the cores are kept in place much better, and therefore the electrical characteristics are more consistent. The best quality installation cable has solid core wires which have more stable characteristics than stranded wires.  However, solid cores make the cable more rigid. If the cable is placed in a cable duct this is not such a problem. The maximum length for solid core installation cable is 90m, for stranded installation cable it is 75m.

While installing any Ethernet cable, it is important not to exceed the minimum bending radius of the cable, often specified as 5 (single bend) to 10 (multiple bends) times the diameter of the cable. Sharper bends will affect the transmission characteristics.

It is not recommended to make connections of more than 10m, e.g. between devices in different cabinets, by patch cable. Instead, the preferred method is to use installation cable (solid or stranded) for the fixed part of the connection through cable ducts.

Terminate the fixed cable in the cabinet with RJ45 sockets on both ends. From there, use patch cables (< 5m) to the first Ethernet device. (alternatively, terminate the installation cable with an industrial RJ45 plug going into the first device)

An Ethernet connection between two devices in different cabinets should consist of the following parts and be limited to the following lengths.

Patch cable (<5m)                  Socket                   Installation cable                Socket               Patch cable (<5m)
                                                              (<90m solid, <75 m stranded)



The DIN-rail sockets pictured above (by Weidmüller) have a clever trick; with a slider you can select if the cable shield should connect to ground via the DIN rail or not.
This can help you to solve or avoid ground-loop problems, by (dis)connecting the ground in various places.
 

 

 

In most industrial applications the familiar 8-core cable is used, but PROFINET recommends to use industrial 4-core 'quad' Ethernet cable, which has larger wire cores than standard 8-core Ethernet cable.

The cores are much thicker (22AWG or 0.33 mm2) than standard Ethernet cable. This makes the makes the PROFINET cable mechanically more stable but also improves electrical properties of longer cables.

This PROFINET cable, because of the thicker cores, needs specific Ethernet connectors and sockets designed for 22 AWG wire.

Weidmüller has a rugged connector suitable for standard cable as well as PROFINET quad cable (IE-PS-RJ45-FH-BK). 

For field assembly, no other tools than a cable stripper and small wire cutters are needed.

 



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Created 2012-02-17
Modified 2012-07-26
Views 13964

 

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