As the Industrial Internet of Things (IIoT) continues to gain mindshare and acceptance, the roles of the cables, connectors and wires that move the data become more important. Our panel of experts addresses what you need to keep in mind when deciding wire size, including the effects of temperature and power.
Wire size can be dictated by ampacity, but is often prescribed by the end user. Since today's PLCs need only a few mA to change an input state, does it still make sense to use 14 AWG signal wire, or are there other options? How do temperature and power requirements affect this decision?
The energy dissipated in the wire will cause a temperature rise, but the heat will also be given to the environment. The type of insulation determines the amount of thermal isolation. It also determines the maximum temperature allowable. Variables such as cable length, whether or not the cable is shielded, where and how the cable is routed, what other types of devices are nearby, ambient temperature and price need to be considered in choosing the right gauge and cable jacket for the application.
Resistance increases with temperature and exhibits the possibility of limiting small control currents. In addition, if the run is extremely long, the impedance will increase, potentially causing EMI-induced faults. The same happens when signal wires are run next to high-voltage ac conductors.
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Mike Bacidore is the editor in chief for Control Design magazine. He is an award-winning columnist, earning a Gold Regional Award and a Silver National Award from the American Society of Business Publication Editors. Email him at [email protected].
About the Author
Mike Bacidore
Editor in Chief
Mike Bacidore is chief editor of Control Design and has been an integral part of the Endeavor Business Media editorial team since 2007. Previously, he was editorial director at Hughes Communications and a portfolio manager of the human resources and labor law areas at Wolters Kluwer. Bacidore holds a BA from the University of Illinois and an MBA from Lake Forest Graduate School of Management. He is an award-winning columnist, earning multiple regional and national awards from the American Society of Business Publication Editors. He may be reached at [email protected]

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