Cable basics: Understanding Dynamic Load-Bearing Capacity

Choosing the best cable for an industrial application is one of the most critical design decisions of any complex automated system. That said, cable selection is often an afterthought and not given the
cable.
time or respect it deserves. As the lifeblood of the system, cables and wires are vital to transmitting power and sending control signals and data across wide expanses in a timely and reliable manner. Here we take a look at some of the most important factors to consider when specifying industrial

Wires and cables intended for use within cable tracks are subject to enormous loads. Especially in highly dynamic applications, several factors should be considered when choosing the right cable—durability, reduced weight, a small minimum bending radius and the ability to fit within tight spaces.
Many of today’s automated production environments must meet rigorous productivity benchmarks, often requiring components to handle speeds of 5 m/s and acceleration of 50 m/s2, along very lengthy paths. To meet these demands, every component in the system must be optimized to work together,
including the cable, wiring, cable tracks and carriers.

Knowing the specific application and industrial setting in which the cable track will be used will help determine the characteristics required in its interior parts—the cables and wires. A good place to start is understanding the physical forces acting on the system. Regarding mechanics, the following loads
must be considered:

PUSH AND PULL LOADS. These forces act in the longitudinal direction of the wire.

• Static—Vertical forces such as gravity act on stationary cables (ex. fountain submersible pumps).
• Dynamic—Horizontal forces from acceleration/ deceleration act on the wires within the cable track.
• Static and dynamic—Cables moving vertically in cable tracks are subjected to both gravity and acceleration/ deceleration, for example in an elevator.

BENDING LOADS. Three distinct bending methods include the following.


• Simple flexing (tick/tock)—Flexing at a single, defined break point.
• Continuous flexing—Flexing that occurs along the entire cable length.
• Guided flexing—Continuous flexing using a guiding component. (ex. pulleys)


Cables used in tracks are exposed to bending along their entire length and are therefore subjected to continuous flexing. When specifying components for this type of use, it is important to choose cable specifically designed to handle these forces. For example, ÖLFLEX® FD and ÖLFLEX® CHAIN power and control cables from Lapp are carefully engineered for this purpose.

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Basic Mechanical Terms used in Drives Applications

Basic Mechanical Terms used in Drives Applications

Terms below are the basic mechanical terms associated with the mechanics of DC drive operation. Many of these terms are familiar to us in some other context.

1. Force
2. Net Force
3. Torque
4. Speed
5. Linear Speed
6. Angular (rotational) Speed
7. Acceleration
8. Law of Inertia
9. Friction
10. Work
11. Power
12. Horsepower

 

Force

In simple terms, a force is a push or a pull. Force may be caused by electromagnetism, gravity, or a combination of physical means. The English unit of measurement for force is pounds (lb).

 

Net Force

Net force is the vector sum of all forces that act on an object, including friction and gravity. When forces are applied in the same direction they are added. For example, if two 10 lb forces were applied in the same direction the net force would be 20 lb.


If 10 lb of force were applied in one direction and 5 lb of force applied in the opposite direction, the net force would be 5 lb and the object would move in the direction of the greater force.



If 10 lb of force were applied equally in both directions, the net force would be zero and the object would not move.

 

Torque

Torque is a twisting or turning force that tends to cause an object to rotate. A force applied to the end of a lever, for example, causes a turning effect or torque at the pivot point.
Torque (tau) is the product of force and radius (lever distance).
Torque (tau) = Force x Radius
In the English system torque is measured in pound-feet (lb-ft) or pound-inches (lb-in). If 10 lbs of force were applied to a lever 1 foot long, for example, there would be 10 lb-ft of torque.



An increase in force or radius would result in a corresponding increase in torque. Increasing the radius to 2 feet, for example, results in 20 lb-ft of torque.




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