Hybrid cables: Power and control

These new hybrid cables offer an innovative approach to the interconnection of automation equipment by providing a neat, space-saving installation that is both faster and easier than using individual cables for each function as well as ensuring additional flexibility for future reconfiguration and expansion projects.  

What is a hybrid cable?

A hybrid cable comprises a power cable as well as at least one other key automation application within a single cable cross-section. For example, the cable could comprise a power cable and one or more of the following applications: signal, bus, sensor, control and POF (plastic optical fibres) cables.

The traditional approach to the installation of automation equipment, such as servo motors or robots, is to use individual cables for each power, data and signal transmission connection between the control cabinet and the unit. This approach can be time-consuming and when there is a need to add additional units further cabling is necessary, additional plugs and sockets may also need to be mounted on the cabinet.

The use of BUS-cables has reduced this cable work by offering easy connection of each active component. Now, hybrid cables are taking the BUS-cable concept to the next level. Replacing a typical ‘star’ configuration, in which each automation unit is clustered around the control cabinet, with a de-centralized ‘loop’ or ‘daisy-chain’ configuration that connects the units to each other creates a simple system which is less time consuming in installation. It is also easy to expand as the new unit is simply plugged into one of the existing units.

Due to the wide variety of potential applications, hybrid cables are not available off the-shelf and a bespoke solution is usually required for each installation. However, every cable will comprise the following basic elements: one screened element for data transmission; at least two power conductors and one protective conductor; one to two signalling elements.

The whole cable needs shielding for protection against EMC (electromagnetic compatibility) and a TPU (thermoplastic polyurethane) sheath is recommended to ensure resistance against the various potentially damaging liquids and substances found in automation applications.

A key consideration in the development of hybrid cables is ensuring that they can handle the heat generated by the current flowing in the power element. At Nexans, for example, we have developed and tested hybrid cables capable of carrying 20A with an overall cross-section of 12mm2 .

Connectors

Choice of connector is crucial to the success of any hybrid cable installation. As part of our total systems approach, Nexans has partnered with Intercontec to develop a new generation of versatile hybrid connectors. 

Testing 

Hybrid cables form part of Nexans’ well-established Motionline brand of cable solutions developed to deliver high-performance and reliability in a variety of control chain, bus, sensor and robotic automation applications. In common with all Motionline cables, the hybrids have been subjected to rigorous testing at the Nexans MAC (Motion Application Centre) in Nuremberg. This facility enables cables to be exposed to dynamic operating loads that simulate realistic, in-service, conditions, thus ensuring that they offer the combination of bending, tension and torsional strength and vibration resistance required for their intended application. It provides proof that an automation cable will perform throughout its expected lifecycle as described in the relevant standard.

Nexans has been testing automation cables for 20+ years. The MAC was established some six years ago and is the subject of ongoing investment to reflect the changing needs of the automation industry, resulting in a current roster of 12 different machines designed to test cables to their limits. The facility enables both the electrical and data performance of the automation cables to be monitored under dynamic loading conditions. In addition to mechanical tests, environmental chambers allow the cables to be subjected to varying environmental conditions.