Anatomy of an Electric Industrial Cable: From Jacket to Core

Without sturdy cabling, even the most heavy-duty, industrial-grade equipment can go quiet.

While not the sexiest part of a design, electrical cables and wires are amazing little workers. The anatomy of a cable is also impressive to peek at – and a great study for engineers on optimizing product performance.

Each component has an important duty, and your choice of cable will impact performance and handling requirements. Because the options are so vast for each component of a cable, you’ll benefit from an overview of each:

(We won’t discuss fiber-optic cables much today because they use specialized materials.)

5-Part Anatomy of a Cable

An industrial electric cable consists of multiple wires encased in a single covering.

You can break that definition down further to identify five parts of a cable:

• Conductors
• Insulation 
• Shielding & armor
• Jacketing
• Connectors
  
  

Conductors 

A cable’s conductor is the core that transports electrical current in one or more directions of flow. In other words, it’s that shiny, bare wire. 

Cable conductor size is one major element of a cable’s design. U.S. and international standards like IEC 60228 specify sizes for cross-sections (0.5 mm² to 2,500 mm²) for conductors in a range of electrical cable types. Requirements for numbers and resistance values of wires are also part of IEC’s standard.

Conductor material is lean on options because the ability to pass on electrical current is critical to functionality. 

• Copper – versatile and highly conductive
• Aluminum – lightweight and affordable, but less conductive
• Steel – poor conductivity, useful for grounding, excellent mechanical strength

Copper conductors can be either solid or stranded, with the latter providing more durability and flexibility. Stranded copper cables in automated assembly plants can withstand millions of flex cycles before failing. In industrial settings, copper is the clear-cut best conductor for cables.

Another reason copper tops the list is that it’s compatible with a variety of plating options. The cable manufacturer can coat the surface of each wire strand to add solderability, corrosion resistance, and electrical properties at high frequencies. 

For copper conductors, three common coatings are:

• Tin – cheap, easy to find
• Silver & nickel – durable in extreme temperatures
• Lead (largely phased out due to health hazards)
  
  

Insulation

A cable's insulation has a huge impact on service life and effectiveness.

Cable insulation separates each conductor inside, both electrically and physically. It’s a nonconductive middleman, keeping the peace by preventing damage from:

• Current leakage into nearby wires & cables
• Moisture
• Heat

The insulation determines many of the electrical properties of a cable. For example, its thickness determines voltage rating. Insulation that can work at higher operating temperatures can carry more current without failing. 

Electrical cable insulation materials are aplenty. Many, but not all, are either thermoset (rubber) or thermoplastic.

Shielding & Armoring

Much like connectors, electrical metal cable protection comes in both mechanical and electrical forms.

Cable shielding is a material that’s electrically conductive and surrounds a wire or cable. It contains electrical energy so the cable’s signal doesn’t radiate and interfere with nearby cables and circuitry. Likewise, it protects the cable’s own signal from disruption by outside interference.

Popular types of electrical cable shields include:

• Foil – 100% coverage, low cost, thin and lightweight, easy to terminate, can be color coded, effective at high frequencies 
• Braid – 40-98% coverage, stronger than foil, better against low-frequency interference, good flex life
• Spiral – Up to 97% coverage, superior flexibility, great for coil cords

Cable armoring protects the mechanical side of the operation. It’s able to withstand crushing and impact forces through use of strong metals. For example, popular cable manufacturer Belden offers these armor types:

*MC Rating = “metal clad,” referring to metallic sheathing in accordance with UL 1569 cable standards 

**MC-HL Rating = metal-clad cable for hazardous locations, in accordance with UL 2225 cable and fitting standards

Jacketing

An industrial cable’s jacket does pretty much what you’d guess based on the name. This cable component is an outer covering that goes around a group of conductors or other core components. 

Like your warmest winter coat, a cable jacket’s job is to protect. The jacket is the first line of defense against fire, the rigors of installation, and other hazards. Also like your winter coat (hopefully), cable jacketing improves aesthetics.

Most electrical cable jacketing is thermoplastic, as this material group can repeatedly become soft and formable when hot.

Many of the materials best practices from insulation apply to jacketing as well. Here are a few extra application-specific notes:

• PVC – Flame-resistant; must be combined with other ingredients so it’s not too rigid and prone to failure at processing temperatures
  
  
• Polyethylene – Good for wet locations and direct burial; not flexible at low temps; available in many density options
  
  
• Chlorinated polyethylene – Tough; chemical-resistant; flame-retardant; doesn’t outgas byproducts that can damage switches
  
  
• Thermoplastic elastomer & rubber – Great flexibility in temperatures down to -60 °C; highly resistant to solvents and water; low corrosive outgassing, acid, & alkali resistance
  
  
• Polyurethane – 2x strength and 3x abrasion resistance of PVC; temp rating of -20 °C to 90 °C
  
  
• Thermosets (SBR, CSPE, CPE) – Non-plastic and can’t be reshaped with heat; useful in harsh environments like utility, power, mining, and hard service cords
  
  

Connectors

An electric cable acts as transportation for power or signal between parts of an assembly. Think of cables and wires as roads, and cable connectors as bridges and intersections.

Connections can be both mechanical and electrical:

• Connectors – Electrical entry device with a plastic or ceramic outside and copper alloy terminal pins
• Cord grips – Mechanical entry device made of steel, brass, or aluminum

On the electric side, types of cable connectors include: 

• Twisted-pair – insulation displacement and connecting to patch panels, wall-plates, and punch-down blocks
• Coaxial – prevent interference in cables that carry high frequency, multi-megahertz signals
• Fiber-optic – align fibers so light can pass, allowing for quicker connection/disconnection than splicing

Cord grips (also called cable connectors, fittings, strain reliefs, or glands) provide protection and termination in instrumentation, automation, and communications settings. Applications prone to moisture contact or pressure use cord grips with synthetic rubber or other elastomer seals. Certain types of fittings also prevent flammable gas from entering equipment enclosures.

Beyond the Anatomy of a Cable: Best Practices for Use

Hopefully you now have an appreciation for the importance of industrial cables and wiring to an electrical device’s success. They’re not exciting on the surface (unless wearing an extra-snazzy jacket), but it’s critical you buy the right cables for your specs and requirements.

The lists above couldn’t possibly fit every nuance of cable design. A custom cable manufacturer or distributor can help you match your unique needs to a material and style.

For more tips on the design and sourcing of cable, check out our resource center: