Flat vs. Round Cables

Flat vs. Round Cables

If your industry requires dependable electrical power in demanding environments, you likely know the importance of choosing reliable cable protection.

However, the choice of flat or round cables is also critical. Flat and round cables have significant design differences that make them advantageous in different applications. Knowing how to choose the right cable is essential for maximizing durability and longevity or ensuring the flexibility and space savings you need.

Round Cable Design

Round cables have conductors arrayed in a circular formation. These conductors are covered with insulation and packed with material that gives the cable a rounded, cylindrical shape.

Round cables can contain individual conductors or twisted pairs of conductors. Either way, the elements have a cabled design, which means the conductors form a helix around the cable’s axis at a particular pitch angle. Pitch angles vary — larger angles provide greater flexibility.

Round cables also usually contain layers that provide various types of protection:

  • Fillers: Fillers are materials that affect the shape of the cable, giving it a smooth, rounded appearance.
  • Shielding: Shielding bulwarks the cable’s relatively thin insulation and prevents the emission of — and interference by — electromagnetic radiation (EMI).
  • Jacketing: Jacketing is the outer sheath that holds the cable together and protects it from environmental hazards like water, oil, gas and flame.

In theory, round cables have a design that maximizes space. A round cable has a smaller cross-section than a flat cable with the same number of connectors. Though flat cables’ flexibility allows them to fill space as they twist and bend, round cables can take up less space per the number of connectors they provide. In practice, however, the extra fillers and shielding round cables contain often negate this advantage.

Flat Cable Design

Flat Cable Design

As their name suggests, flat cables have a flatter design than round cables. Their conductors are individually encapsulated, carefully arrayed in a straight line at precise intervals and surrounded by insulation.

Unlike round cables, flat cables do not usually have layers of fillers and shielding. Placing a shield on a flat cable is relatively difficult because the shield will not hold a flat shape — it tends to become round. Consequently, providing electromagnetic interference (EMI) protection through standard shielding presents a challenge.

Because flat cables do not generally contain fillers or other materials, they are relatively compact for the number of connectors they have. They bend and stack easily for this reason.

However, flat cables’ design can be incompatible with some machine or panel openings that will not accommodate their thin, elongated shape. Companies interested in using flat cables should check to ensure compatibility before proceeding.

What’s the Difference Between Flat and Round Cables?

Round cables are standard in many industrial applications. However, flat cables are also highly desirable in use cases where their flexibility and other strengths are significant advantages.

Let’s explore the differences between flat and round cables in a few different areas.

1. Quality

Both round and flat cables provide excellent quality for use in the proper applications. However, round cables tend to have a slight edge in quality overall. Their superior built-in protections make them highly durable and long-lasting, especially in harsh industrial environments.

2. Reliability

Round cables tend to be more reliable in terms of their ability to stand up to mechanical stresses. The main mechanical stresses cables must handle are torsion, rolling flex, tic-toc and S-bend. Round cables can easily withstand these stresses because of their ability to bend along multiple axes. Flat cables offer superior resistance only in rolling flex, which involves bending only along one linear axis.

However, flat cables can be more reliable in terms of their organized, dependable wiring. Flat cables tend to have simpler construction than round cables, so they are generally free from wiring errors that could cause malfunctions.

3. Performance

Both round and flat cables provide excellent performance in the right environments. In general, however, round cables offer superior electrical performance and stronger physical performance in heavy-duty applications. They are more durable, with more protection against the elements, mechanical stressors and EMI emissions.

Flat cables are also somewhat limited in their electrical characteristics because of their connector type, as they are generally designed for mass termination in a connector. The connectors for flat cables typically have insulation displacement contacts that line up for flat cable termination. The contacts simultaneously go through the insulation to meet all the conductors in the cable.

A precise alignment for the connector and conductors is critical. Specific centerline spacings are necessary, and manufacturers must control this parameter tightly, often at the cost of the cable’s electrical characteristics.

4. Skewing

Skewing occurs when electrical signals flow at different speeds through a pair of wires. Flat cables generally minimize skewing more effectively than round cables.

In flat cables, because of the high precision and balance involved in their manufacture, the conductors are certain to have the same physical and electric length, along with a continuous dielectric. These factors tend to reduce the time delays between the signals in different conductors.

5. Current Carrying Capacity

In terms of current carrying capacity, flat cables offer a superior option because of their higher surface-area-to-volume ratio. This characteristic enables them to dissipate heat more readily, providing greater thermal efficiency. Consequently, they can handle higher temperature rise and current levels per conductor cross-section.

6. Cost

Flat cables are relatively easy and cost-effective to make, mainly because they allow for mass termination, with all wires coming together in a line in a connector. This design reduces labor requirements and helps minimize costs.

Round cables, on the other hand, are more labor-intensive to make and generally more expensive.

7. Versatility

Flat cables are more flexible than their round counterparts, and this characteristic can make them highly versatile. Their flexibility enables them to adapt well to various shapes, sizes and configurations. Their ability to bend and twist easily without breaking makes them ideal for a vast range of applications.

However, round cables are more versatile in the sense that they can bend in many different directions. A flat cable wire bends easily in only two directions, while a round cable, though it is less flexible, can bend along any axis. This characteristic makes round cables highly desirable for applications that require extensive bending and twisting in long cable runs, especially raceways or conduits.

8. Space Efficiency

In terms of space efficiency, flat cables offer a clear advantage. Because they are flat, they can pack more tightly together than round cables can. Because they bend and flex well too, they maximize available space. Where round cables might leave large air gaps around them because of their minimal flexing capabilities, flat cables can bend and fold to minimize gaps and compress into a small area.

9. Weight

Flat cables are lighter than round cables because of their minimalist design. The extra shielding and fillers in round cables tend to give them extra heft.

Companies looking to minimize weight — especially for robotics, medical devices or consumer applications where convenience is a priority – may want to consider flat cables as a quality option.

10. Maintenance

In general, round cables are easier to maintain than flat cables, primarily because flat cables require much more precision in their construction. Flat cables require precise weighing and balancing to ensure the uniformity of their movements, for instance.

Replacing components on a round cable is typically easier than on a flat cable. Unlike round cables, flat cables also require special tools for the process of encapsulating their components into a single cable strand. For these reasons, maintenance on flat cables can be highly time-consuming and lead to excessive downtime for the machinery involved.

How Do Environmental Factors Affect Flat and Round Cables?

Effective cable design is what prevents cables from failing when exposed to various environmental factors. For instance, a cable designed for sturdiness will stand up well against harsh abrasion or weathering. Below are a few common environmental factors and how they affect flat and round cables:

  • Animals: Rodents often chew on cables to sharpen their teeth, create pathways or collect nesting materials. Round cables can sometimes be advantageous against rodents because their larger size offers less purchase for small jaws. However, both flat and round cables may need extra protection like rodent-resistant braided sleeving to withstand this predation.
  • Plants: As plants grow, they sometimes abrade electrical cabling. Their tough roots, in particular, may damage the cables they come into contact with. Round and flat cables may need extra protection to prevent abrasion and cracking.
  • Direct sunlight: Over time, direct sunlight harms cables by degrading the plastic polymers in their outer sheaths. UV-resistant casing can help extend cables’ life spans. For protection against intense sunlight damage, as well as damage from other light and heat sources, consider high-temperature or heat-resistant braided cable sleeving for both flat and round cables.
  • Water: Water can damage electric cables by seeping into small cracks in the plastic, corroding or mildewing them, and then corroding or shorting out the wires inside, potentially causing fires or posing electric shock hazards. Plastic or metal liquid-tight conduits are often excellent options for protecting round and flat cables from water damage.
  • Chemicals: Chemicals weaken round and flat cables by eating through the outer sheath and damaging the wiring. Chemical damage is particularly common in oil refining, pharmaceuticals manufacturing and similar industries. Specially designed chemical-resistant protectors such as our ROHRflex conduits are often necessary for these applications.
  • Voltage: Voltage damage sometimes occurs if a power surge sends more current through a flat or round cable than it can handle. This damage can cause fires and other hazards. External damage to the cable can also lower its breakdown voltage, or the level of voltage it can handle before the insulation becomes conductive. Protective conduits and sleeves help minimize that damage to reduce the risk of voltage issues.
  • Radiation: Round cables are generally the superior choice for protection against radiation. The shielding in most round cables offers an effective buffer against EMI. Radiation-resistant coverings like certain braided cable sleeves are also excellent for providing extra protection for both types of cables.
  • Abrasion: Abrasion poses a challenge for round and flat cables if their cable jackets are too thin. In that case, the cable jackets quickly wear down and break open. However, abrasion resistance is generally superior on round cables because their jacket materials tend to be more durable — polyvinyl chloride (PVC) or polytetrafluoroethylene (PTFE), for instance. Many flat cables use soft materials like silicone that stand up poorly to abrasion.

Best Applications for Flat vs. Round Cables

Let’s take a closer look at the applications flat and round cables are best suited for.

Best Applications for Flat vs. Round Cables

Best Applications for Round Cables

In general, round cables are highly suitable for applications that involve more environmental stressors and call for higher levels of protection:

  1. Rail transportation: Round cables are ideal for rail transportation because of the tremendous physical demands of a railroad environment. Long-term exposure to harsh weather and the stress of constant motion often requires rugged round cables.
  2. Material handling: Material handling also involves an intense physical environment of heavy loads and vibrations. Round cables have the durability to withstand these stressors.
  3. Nuclear power: In nuclear power plants, round cables are essential because they stand up well to constant heat and radiation exposures. When coupled with the proper protection, they offer the necessary dependability and resilience for a long service life.
  4. Waste processing: Waste processing operations often use round cables because they are durable enough to withstand a wet environment with heavy-duty moving parts when paired with the right protection.

Best Applications for Flat Cables

Best Applications for Flat Cables

In general, flat cables are highly suitable for applications that require flexibility or have tighter space requirements. Because they are flat and thin, they bend more easily and can conform to tight angles or cramped spaces without breaking. Here are a few of the applications in which their use is common:

  1. Telecommunications: Telecommunications applications involve complex, tightly packed arrays of wires. Flat cables are ideal for navigating cramped areas and preserving space.
  2. Medical displays: Medical displays need to be relatively small and lightweight so they are convenient to use. Flexible flat cables can easily conform to the available space.
  3. Robotics: Robotics applications typically involve a highly complex design in a highly compact area. As our technology becomes smaller and lighter every day, having the right cables for a tiny space is essential.
  4. Overhead cranes: Some overhead crane companies choose flat festoon cables over round cables because of space limitations and the necessity of continual flexing. They provide power and control signals while standing up to the moderate rigors of the environment.

Contact AerosUSA for Dependable Cable Protection

Contact AerosUSA for Dependable Cable Protection

Whether you use flat or round cables, you need reliable ways to keep them safe from physical and environmental stressors. We offer numerous forms of trusted cable protection, including braids and sleeves, plastic conduitsmetal conduitsROHRflex conduits, and special protective conduits tailored to various industries and protection needs. Our fast quote responses, quick product turnaround and high-quality customer service also make us ideal long-term partners for your business.

Contact us to learn more about how our products help you protect your flat and round cables.

Reviewed for accuracy by: George Sims.
George Sims is an engineering and service-oriented leader in Cable Protection and Cable Management Products. Focus is on 100% commitment to customer satisfaction. AerosUSA is a small, agile, independent company whose focus is on our customers.