Enclosures, Cabling & Connectors


Ensuring the safety and integrity of cables

October 2016 Enclosures, Cabling & Connectors

Correct shielding of cables is imperative on the factory floor where electromagnetic interference (EMI) is prevalent and has the potential to interfere with signals.

According to Doug Gunnewegh of Helukabel, this is why data and signal cables are usually comprised of insulated conductors wrapped in a conductive layer. Shielding reduces electrical noise and reduces its impact on signals, and lowers electromagnetic radiation.

“Shielding not only protects cables, but it can also protect machinery and people as well,” explains Gunnewegh. “Helukabel’s Topflex EMV-UV-2YSLC11Y-J uses a double shield for electromagnetic compatible (EMC) purposes. The conductors are first wrapped using a special aluminium foil and then a tinned copper braid is applied before the cable is enclosed in its polyurethane (PUR) jacket. Our power cables are also constructed to be EMC compatible and minimise noise generation which affects many other systems like radio and data communication.”

Varying requirements

Communication cables also need to be shielded to prevent the effects on the data transmitted from EMI. To prevent cross talk and coupling, communication cables are also paired and individually shielded. In some applications, such as those needing servo cables, double or even triple shielding is required: around individual conductors, around twisted pairs, and around the entire cable.

Some applications do not require shielded cables. For example, if a cable will be used in a cabinet or otherwise away from other sources of noise, it does not need to be shielded, as it will be protected from noise and EMI already. Cable shielding uses either a braided, spiral design or metal-coated Mylar or foil shield. The shielding wraps around each conductor to mitigate noise by 85% to 100%, depending on the configuration. The maximum shielding a braided shield can have is 90%. Spiral shields can offer 98%, while metal-coated Mylar can deflect 100% of EMI.

Using a thin layer of Mylar or aluminium foil eliminates the gaps you may encounter with braided designs. The foil is attached to a polyester backing to provide 100% coverage. However, because it is thin, it can make applying connectors a challenge. Foil shielding can also be damaged in high-flex applications, so spiral or braided designs work best there.

Noisy environments

Braided shielding is made of a mesh of bare or tinned copper wires woven together. It is easy to terminate when crimping or soldering a connector. Because of the braiding, small gaps of coverage do occur, thus resulting in the 90% shield rating. If the cable is not moving or flexing, this coverage should be sufficient. However, the braided design does add cost and weight to the final design.

If an environment is extremely noisy, a cable may use multiple layers of shielding with both the braided and foil designs. Sometimes pairs of wires are shielded individually in addition to the entire cable being shielded. This is done to prevent crosstalk between pairs.

Besides the braid covering, the maximum admissible diameter of the single strand of braid and the angle of twist to the axial axis of the conductor are also determined in the manufacturing. The thinner the single strand and the smaller the angle of twist, the more flexible is the cable. However, the diameter of the single wire is restricted due to the mechanical requirements.

Complex construction

“A cable shield consists of a respective number of strands, depending on the braiding machine (16 24, 32). The total number of strands equals the number of strands in a braiding element times the number of elements. The strand diameter, the angle of twist and the folding number also determine the density of a shield. The single strands are combined to make larger strands. The larger strands are then unwound from the coils and are mounted on special braiding machines for stranding construction around the conductors.

As noted above, certain designs accommodate crimping or soldering of connectors easier than others. However, it is important to note that the connector must offer similar ratings to the cable for effective shielding. Finally, it is important the cable be grounded at one end to eliminate the potential for noise loops.

For more information contact Helukabel, +27 (0)11 462 8752, sales@helukabel.co.za, www.helukabel.co.za



Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

Monitoring for control cabinets
September 2020, Turck Banner , Enclosures, Cabling & Connectors
The IM18-CCM is particularly suitable for OEMs wishing to provide basic condition monitoring values in their IT system. It detects critical states of the control cabinet directly in the field.

Read more...
Automated marking of terminal strips
August 2020, Phoenix Contact , Enclosures, Cabling & Connectors
The Mark Master terminal strip marking system from the Phoenix Contact ClipX product range uses patented high-speed technology for the fast and efficient processing of marking tasks. In control cabinet ...

Read more...
Rittal’s range of compact and small enclosures
August 2020 , Enclosures, Cabling & Connectors
After more than 50 years and 35 million enclosures sold, Rittal has introduced its small and compact enclosures in the form of the AX and KX series. According to managing director of Rittal South Africa, ...

Read more...
New range of compact enclosures
April 2020, Rittal , Enclosures, Cabling & Connectors
After more than 50 years and 35 million enclosures sold, Rittal has introduced its small and compact enclosures in the form of the AX and KX series respectively. According to managing director of Rittal ...

Read more...
SMC offers services as well as components
April 2020, SMC Corporation South Africa , Enclosures, Cabling & Connectors
Besides being a leading supplier of industrial automation components, SMC South Africa also offers value-added services. One of these is in-house control panel design and construction. This takes a labour ...

Read more...
Enclosures with modular design
April 2020, Vepac Electronics , Enclosures, Cabling & Connectors
CamdenBoss CNMB DIN rail enclosures, feature a modular design. Terminal guards and top covers can be snap-fitted for a quick and simple assembly. PCBs can be placed into the DIN rail enclosure in five ...

Read more...
Self-venting compressed air safety couplers
April 2020, Parker Hannifin - Sales Company South Africa , Enclosures, Cabling & Connectors
Motion control technologies specialist, Parker Hannifin, has introduced a new series of safety couplings for compressed air systems. The new KP series is an ergonomic push-button, self-venting coupler ...

Read more...
Pick-to-light solutions kit
April 2020, Turck Banner , Enclosures, Cabling & Connectors
The Pick-to-Light Solutions kit is an integrated solution that consists of an enclosure, an DXM controller, a HMI, plus direct connections for PTL110 devices and power. The integrated device and power ...

Read more...
What’s the difference between round and flat cables?
Technews Industry Guide: Maintenance, Reliability & Asset Optimisation 2020, Helukabel , Enclosures, Cabling & Connectors
Understanding how to make reliable connections to an application starts with proper cable selection.

Read more...
Connectors for automotive applications
April 2020, RS Components SA , Enclosures, Cabling & Connectors
RS Components has launched the A Series of high-specification automotive connectors from Amphenol, one of the world’s leading makers of interconnection devices suitable for a huge diversity of markets ...

Read more...