Pepperl+Fuchs Blog

Protect your Industrial Cables and Cable Connectors!

Posted by Tim Cicerchi on Tue, Apr 15, 2014

Pepperl+Fuchs' standard 22 AWG cordsets are rated for 4 A. But most main enclosures have a power supply that is much larger than the rating of individual industrial cables and devices.
Protect your industrial cables!
So, what if there's a situation where an output overloads, pulling 10 A or 20 A through a 4 A rated cable? The wires will start to heat up, the voltage will drop, and the cable connectors may get damaged. The worst case scenario could be a fire.

To protect the end devices, fuses or breakers are used to open the circuit in the event of cable or device failure. To do it right, you really have to fuse every sensor or fuse groups of sensors so the current limit to the cables is below the 4 A limit.

Overload or short-circuit protection must also be considered with industrial bus systems. AS-Interface is an industrial bus that provides power and communication to modules on the network. This network is designed to be completely field mountable so the use of fuses or breakers for every bus drop may not be convenient. If a power supply that is rated 4 A or less is used to power the entire bus, then no problems exist. The drop cables can’t be overloaded because the power supply can’t provide that much current.

Alternatively, what if you use an 8 A AS-Interface power supply and a 12 A auxiliary power supply? We have an auxiliary power cable with larger 13 AWG conductors that are rated for 12 A. It is possible for the drop cables off the AS-Interface trunk to be overloaded. What to do? You can’t put fuses in all the drop lines; there's nowhere to put them. And the fuse itself may interfere with AS-Interface communication. You could just mount everything to the trunk line so no drop cables are used at all, but that isn’t convenient or practical.

A simple solution comes with our series of PTC-protected drop connectors.
The idea is to limit the current that is delivered to the drop in order to protect the cable. With these cable connectors, the current is limited to 1.6 A, which is far below the 4 A cable limit. Once the short is removed or the end device is repaired, the drop cable will function normally and your network will come back up and run. LED indication on these protective devices will tell you where the short is so the problem can be easily resolved.

These drops are IP69K, washdown rated for use in the harshest conditions, and feature a 1 m pigtail with a straight M12 connector. They are available in an AS-Interface version and an AS-Interface/auxiliary version. Depending on quantity, we can provide additional versions with different connector styles and drop cable lengths.

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Topics: Cables/ Cordsets, AS-Interface

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