Cable Bend Radius

The manufacturers of cables publish the minimum bending radii of their cables. Cables bent to smaller radii will either kink, break or survive intact with varying degrees of irreversible change, depending on the method of construction. The manufacturer publishes these data as an indemnity on the product and as a guide to good practice. Calculation is rarely necessary.

When I was in the school, we learned this radius can bee around 5 times the cable diameter for light cables but more for heavy cables. The best way is to look at the data sheets. For optical cables it must bee much more.

Anders

There is a way to calculate it: look to the insulation stress and thickness reduction that will occur when you bend the cable. It must stay within the limits for that polymer and the applicable voltage.

As mentioned in other answers: just look it up for the cable that you plan to use. The bend are usually small and temperature depending.

Please note that bending radius of cables depend on their diameters / type. Canadian Electrical Code / Section 12 (Wiring methods) identifies all requirements.

Veysel

Per the NEC 300.34 Conductor Bending Radius

The conductor shall not be bent to a radius less than 8 times the overall diameter for nonshielded conductors or 12 times the overall diameter for shielded or lead-covered conductors during or after installation. For multiconductor or multiplexed single conductor cables having individually shieleded conductors, the minimum bending radius is 12 times the diameter of the individually shielded conductors or 7 times the over diameter, whichever is greater.

Hi,

all recommendations read before are concerning cables with fixed positions. If they are moved (like, p.example, in an elevator or another machine), or when you have a vibrating system, you need highly flexible cables which have the advantage of smaller bending radius but higher prices.
regards uwe

Your question obviously relates to MINIMUM bending radius only. This figure strongly depends on the cable construction i.e, Is this a solid conductor or stranded cable, is this a single wire or multi-conductor cable, type of insulation, operating temperature, environmental considerations, electrical stress grading etc. The NEC given figures allows for very large margins and in most cases it can be bent to smaller radii. As indicated before, your only exact information will be given by the cable manufacturer, and these instructions must be followed. You shouldn't intent to calculate it yourself, and if no manufacturer or other information is available, follow your national electrical codes.

Hope it helps.

Wangito.

the common rule is min-radius=8X(cable diameter), this value is a proven value for data and power cables,

jbenary@teldor.com

Last recommendation:

Listen to the last reply of guest, jbenbary, he knows. They are experienced cable manufacturers, and know what they are talking about. The 8X rule of thumb, applies in 95% of cases.

Wangito.

you don't calculate it - you ask the manufacturer - he knows what happens when the radius is too tight - i.e. with shielded motor cable the outside radius opens the braid too much - on the inside the wire can get too tightly bent - result is heat which burns the insulation - - speaking of insulation - this also affects the bend radius - i.e high temps are stiffer - willnot bend small radiuss - lower temps are softer and easier to lay down in cable trays - -

also, note if cable is intended to always be moving? or stationary - different ratings

you may also want to check standards - UL, NEC, EN, IEC, etc