Importance of Knowing the Recommended Minimum Bend Radius for Cable
Posted on 9/28/20 3:23 PM
Cable is made up of specialized material and components that are vital parts of making a world-class power cord or cord set. If one of the cable components is damaged, it can directly affect the product. Making sure you know the recommended minimum bend radius for cable is critical to the performance and longevity of your product and its ultimate success.
Definition and Prevention
What is the recommended minimum bend radius for cable?—how far can it bend without causing damage? The National Electrical Code Handbook (NEC) and HD 516 lists minimum bend radius requirements.
Calculating how far a cable can bend without causing damage depends on the jacket material and the wires and insulators inside—and the diameter of the cable. The outer diameter of the cable times the cable multiplier equals the minimum bend radius. Cable multipliers vary according to the type of cable and per industry standards.
“It depends on the size of cable and the material,” Dan Ford said, Technical Support Specialist at Interpower. “Some types of cable bend easier than others with their jacket materials offering varying degrees of flexibility. Fillers or shielding inside the cable will decrease its ability to bend.” Ford added that finer strands of wire allow for more flexibility than larger strands.
If cable is allowed to exceed the minimum bend radius repeatedly, problems that can result over time include cracked insulation, broken conductors, and/or tears in the jacket or conductor wires. For example, if the jacket material is a harder material, it may not survive an “8” radius, but possibly a “12.” The harder the material, the more prone it is to damage due to less flexibility.
“It is important to avoid unnecessarily damaging the cable which can shorten its life, potentially leading to shock or fire,” Ford said. “The end use of the cable plays a big role in what the actual bend radius will be—how it will be used? For example, if the cord is plugged into the wall and then jerked on from the side to get it out, that will violate the bend radius. If the cord is twisted a lot, that also will affect it.”
Ford compared the bend radius of a cable to that of a garden hose that is bent to the point where it kinks and blocks the flow of water. In the same way a cable can be bent to where it can no longer transmit the flow of power.
“Bend radius failures usually happen over time and eventually the cable will no longer transmit power,” he said. “However, instant failure can occur if the wire in the cable is broken by jerking on the cord, especially at sharp angles.”
Determining Minimum Bend Radius
Cable manufacturers will typically issue recommendations for minimum bend radius that are rather conservative to cover a wide range of end user applications, due to the fact that the end application whose stress factors are not known. Therefore, if a manufacturer wants to use a cable at a smaller bend radius recommendation, it is advised they seek guidance from the manufacturer of the cable.
Indicators of Bend Radius Failures
- Discoloration of the cable
- Wrinkling, pinching, or kinking of the cable
- Stress tears on the cable jacket
- Increased resistance of the cable with the meter (a high resistance rating can indicate damage).
The important factor to remember is that the purpose of minimum bend radius is to protect the cable so that it does not become damaged. For questions, please contact Customer Service at Interpower.
For more information on specifications regarding cable offered by Interpower, see the Cable product line. Most cable part numbers found on the Interpower website include the minimum bend radius in the specifications