Determining the cross-sectional area of ​​an electrical cable is fundamentally based on its ability to dissipate the heat generated by the Joule effect (I2R) without exceeding the maximum operating temperature of its insulation. In continuous operation (100% of the time under maximum load), the sizing is conservative, as it assumes the worst thermal scenario in equilibrium.

However, in numerous industrial applications with moving cables—such as in overhead cranes, lifting equipment, and automation systems—operation is inherently intermittent or cyclical. In these scenarios, the cable is subjected to periods of load alternating with periods of rest (no load or reduced load). This thermal dynamic allows for a careful reassessment of ampacity, opening the possibility of technical and economic optimization of the project.

Duty Cycle Analysis

The central concept for this analysis is the Load Factor (LF), or Duty CycleIt quantifies the relationship between the time the cable is actually conducting current and the total duration of the operating cycle.

In this case, the Load Factor is 40%. During the 15 minutes of inactivity, the cable actively dissipates accumulated heat, preventing it from reaching the maximum temperature it would reach during continuous operation.

Application of Correction Factors and Engineering Implications

With the Load Factor properly calculated, it is possible to apply correction factors — such as those specified in our technical tables — to the nominal ampacity of the cable (that defined for continuous operation). This allows the current carrying capacity to be increased for that specific duty cycle.

The direct result is the possibility of specifying a cable with a smaller cross section for the same load current, without compromising the safety or lifespan of the component.

Advantages of Intermittent Regime Analysis:

1. Cost Optimization: Reducing the cable gauge implies lower acquisition costs, not only due to the conductor material, but also due to the reduced weight and volume.
2. Weight Reduction and Reduced Mechanical Effort: In mobile applications, lighter and thinner cables reduce mechanical stress on cable carriers, reels, and the equipment itself.
3. Flexibility and Radius of Curvature: Smaller diameter cables generally offer greater flexibility and allow for smaller bending radii, a critical advantage in dynamic and compact systems.

Innovcable's application engineering team is at your disposal to assist in a detailed analysis of your equipment's duty cycle, ensuring a specification that combines maximum efficiency, safety, and economic viability, avoiding unnecessary oversizing and delivering the smartest solution for your operation.