RKL4521 by Bosch Rexroth Indramat

The RKL4521 is a flexible motor power cable manufactured by Bosch Rexroth Indramat in the RKL Motor Power Cables series. It is intended for servo axes, frequency inverters, and other drive systems where simultaneous delivery of power and low-level signals is required during continuous machine motion. The cable has an overall diameter of 14.8 mm and encloses four 2.5 mm² power conductors plus four 0.75 mm² control cores, allowing brake release or temperature sensors to share the same routed bundle. By combining these functions in one jacket, the cable reduces routing complexity in automated equipment such as gantries, pick-and-place heads, and transfer lines.

The mechanical life of the cable is rated at 5,000,000 bending cycles, so it tolerates frequent travel in drag chains before conductor fatigue becomes critical. In moving applications, the minimum dynamic bend radius is 7.5 × D, so moving loops should stay above 111 mm to prevent jacket kinking; a tighter 5 × D limit applies when the cable is fixed. Each power core is sized at 2.5 mm² to carry continuous motor phase current, while feedback or brake circuits use individual conductors of 0.75 mm². A braided and foil combination provides a Total Shield around all elements, limiting electromagnetic emission and helping protect encoder feedback signals from inverter switching noise.

The outer sheath is molded from PUR, a material that resists oils, abrasion, and weld slag and is colored Orange (RAL 2003) for easy identification in the cabinet. The compound is also halogen-free and silicone-free, reducing corrosive gas release during a fire and preventing surface contamination in paint lines. Hydrolysis resistance keeps the insulation stable in humid environments, and the conductors remain operational up to 80 °C.