Nowadays, automation and various types of electrical devices are used very often, for example, in production plants. For the proper and effective operation of such devices, it is necessary to use high-quality electrical cables and appropriate harnesses. The right choice guarantees the durable and long-lasting operation of the systems, thanks to that the risk of failure or damage of the machines can be minimized. As a result, the production of wiring harnesses is an essential part of any industry.
Correct selection of the electric harness
Regardless of the type of machine we use, in order for it to function properly, its automation systems require a power supply and two-way data transmission. Due to the fact that there are many different types of advanced devices on the market today, there are no universal or adaptable wiring harnesses. Thus, when choosing a harness, one can check the general standards for crimping parameters and the continuity of electrical connections.
Based on the general information about the machine, components and various solutions are properly selected so that the device can work in an optimal way and fulfill its functions in the best possible manner.
The main factors worth paying attention to in order to properly select electrical harnesses for industrial machines are:
- machine working environment temperature,
- ambient humidity,
- various types of mechanical stress,
- influence of chemical factors (including oil) and radiation,
- harness flammability,
- electromagnetic interference.
When selecting wiring in automation systems, one of the first aspects that should be taken into account is the conditions in which the device will be used and to what additional factors it will be exposed to (e.g. whether the electric harness will withstand many repetitive movements of the machine).
High temperature and electric harnesses
When the electrical harness is exposed to high temperature, it is necessary to use cables and connectors with increased thermal resistance or even special covers for the entire bundle. Incorrectly selected cables with insufficient thermal resistance parameters may result in a decrease in insulation resistance and, as a result, a breakdown, which implies malfunction of the device. This situation may also impose a hazard for people in the vicinity of the harness and in direct contact with it.
Humidity and parameters of materials used in a harness
When designing a cable harness exposed to increased humidity of the working environment, not only its tightness should be taken into account, but also the type of materials used for its production. For example, if copper or copper alloy components are used that will come into direct contact with air, accelerated oxidation will occur at increased humidity. As you might know, oxides most often do not conduct electricity, so eventually the element becomes a break in the circuit, which results in the fact that the device with such a harness simply stops working.
Mechanical properties of the harness
When selecting the appropriate wiring harness, it is also worth paying attention to the tensile strength of the harness. Achieving a sufficiently high force, at which the terminal or connector breaks, allows for obtaining the appropriate mechanical resistance according to the class of the harness.
A high level of the breaking force is influenced by a number of factors. The most important ones include:
- proper selection of the cable and the terminal,
- proper crimping of the terminal on the cable,
- application and correct assembly of strain reliefs or other stress-transmitting elements on the housing of the device or connector
The flexibility of the cable is also an important aspect. Additionally, properly selected cable and its preparation with the use of appropriate strain reliefs allowing the transfer of stress to the connector housing allow for a long and failure-free use of the harness.
How do chemicals and radiation affect the harness?
The key to selecting and designing a harness is to take into account the chemical factors and radiation to which the harness will be exposed during operation. Chemical factors and the influence of radiation (especially ionizing and UV) can lead to accelerated aging processes of the harness insulation.
Harness flammability – is it essential?
In most of the currently designed installations, the key is to use non-flammable cables, or more precisely – with reduced flammability. On the one hand, such cables extend the working time of critical infrastructure elements, often allowing people to safely leave the building during a fire, but also while burning, they do not emit toxic fumes that can be fatal to humans and are harmful to the environment.
EMC (electromagnetic compatibility) – electromagnetic compatibility of a harness
Any device through which an electric current flows produces electromagnetic waves that propagate around it. Such waves can affect other devices and people. Hence, standardization that defines permissible emission limits is common for all countries across the globe. Cable harnesses, due to their distributed architecture, are unfortunately very exposed to the absorption of radiation from the environment – they act like an antenna. They are also a source of radiation. Therefore, it is common to use harnesses that are shielded, i.e. contain elements that block the propagation of electromagnetic waves, increasing user safety and reliability of devices.