Wire selection is a key part of the electrical component design as it affects the safety, functionality, ease of use and maintainability of the component. As there are thousands of types of wire and cable, choosing the right wire or cords can be complex and daunting.
To clarify, I define 'wire' as a single, flexible electrical conductor surrounded by an insulating layer. Typically, the conductor material is copper; however, it may vary from application to application. Having said that, before you start designing anything, you need to fully understand how the electrical component will be used. What is its job and what type of environment will it work in?
Once you have determined its end use, you can begin to answer the following five questions that will help you choose the best wire for your application
There are two parts to the wire size question: thickness (gauge) and length. To determine what size wire you need, consider the wire's carrying capacity and the amount of current (measured in amperes or amps) you need to conduct. Wire gauge is directly related to how much amperage you need to pass.
The distance you need the wire to travel will also affect the gauge of wire you need. Because there is no perfect conductor, the longer the wire, the more voltage will be lost through resistance/heat. You can offset the voltage drop by increasing the gauge of the wire, thus increasing the current capacity. This allows you to pump more amps to ensure the right amount of power is received, even if you lose a little in the process.
Different types of wire offer different levels of wire flexibility.
Solid core wire - almost no flexibility in lower gauge wires; becomes more flexible at higher gauges
Coarse stranded wire - moderately flexible; it will retain the shape you give it
Fine stranded wire - highly flexible; won't hold its shape
The environment in which the component operates will determine the type of insulation you need for your wire.
Voltage - the higher the voltage level, the thicker the insulation needed to reduce the risk of electric shock
Environmental factors - exposure to sunlight and UV rays, extreme temperatures, and the presence of chemicals or oils can affect performance
Regulatory considerations - UL, SA, SAE, CE, etc.
Abrasion resistance - higher vibration environments require thicker insulation
Coatings - some coatings can be more easily printed on wires or pushed/pulled through conduit
Using different colored wires in your electrical assembly can help you, the end user and anyone who may need to service the assembly in the future to understand the purpose of each wire. Many companies use standardized wire colors to indicate hot, ground and neutral wires; some even color code the different circuits in an electrical assembly.
Although copper is the most conductive metal, it can be heavy and expensive. Therefore, for high-voltage, long-distance electrical applications, aluminum wire can be used. It is an acceptable conductor and usually requires a thicker gauge, but it is lighter and cheaper than copper wire. For example, aluminum wire is used for power cables instead of copper.
Each industry has different specifications for the wire it uses, so all the different types of wire available are needed. However, each of these industries usually sticks to a small number of wire types that meet their requirements, which can help to simplify the wire selection process.
For example, the automotive industry mainly uses GXL wire, which is well suited to the working environment (temperature, wear and tear, oil, etc.) usually found inside a vehicle. On the other hand, MTW (machine tool wire) is often used in electrical control cabinets because it has a higher voltage rating and the insulation is suitable for the working environment.
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