When planning a cabling project, one of the first questions to ask is whether the need is for a DC cable, or whether the application calls for AC power, which might mean the use of a different type of cable. In his post we’ll talk about the two types of currents (SC and DC), and we’ll also explore the differences between an AC and DC power cable.
Whether it’s a 600v DC cable that you are looking for, or a 12V AC power cord that you need for an electronic device – the question many non-engineers ask is: What type of wire do I need? Well, most technical-minded individuals would frown at the question, because of the nuances associated with it. You see, when it comes to electrical applications, there is a great difference between “cables” and “wires”. And therefore, it is essential to ensure you are using the appropriate “wiring” for a project.
People tend to use these two terms interchangeably, however, there is a difference between the two. Not to get too technical, but wires are single conductors of electricity, while cables contain multiple conductors. Wires may be bare, or may be encased in sheaths. On the other hand, whether they are AC or DC cables, they typically contain several wires, either exposed or shielded, which are then encased in an outer sheath to form the cable.
So, now that we have the basics in place, let’s talk cables. Specially, we’ll address the question about the differences between the types of electrical current (power) and two common types of cables – AC and DC.
Current Makes a Difference
There are two basic types of currents, alternating current (AC), popularized by Nikola Tesla, and direct current, much favored by inventor Thomas Edison. When selecting a cable for a specific electrical application, engineers typically also consider the type of current that the cable must support. The characteristics of the current intended to flow through those cables impacts the choice of an AC or DC cable for the project.
With AC current, as supply flows through the cables, the current’s polarity (negative versus positive) changes, alternating as it flows in one direction, and then changing as it flows the other direction. DC current, however, does not change polarity. It flows in one direction only, and passes evenly through the cable with no alternating characteristics. These differences in the current entail different choices of cables too.
For instance, AC power is comparatively easier to step down, and therefore is used for cabling applications such as the wiring of mains power generation. In addition to residential applications, AC power is mostly used in industrial machines, such as packaging machines and other intelligent equipment manufacturing.On the other hand, solar panel applications (PV cells) typically use DC cables. Current from a solar panel can’t directly be used by, for example, your Tv or laptop computer. Such DC power usually requires a converter, to “transform” and use it in alternating current cables.
So, can you use DC cables instead of its AC counterpart? Well, the answer is: It depends. The two main differences to consider, when deciding on the substitution, are Voltage and Current. The thickness and type of insulation determines the maximum voltage allowed for the application. On the other hand, the amount of current that the cable will carry will determine the thickness and type of material that the cable is made from. By way of example, it is ill-advised to substitute a cable built for a 5V, 1A DC application for an application designed to power an 220v, 5A AC device. The result? Due to excessively high current, it is likely to cause the cable to melt. This may also be a fire hazard.
So, the general principle of any such substitution of AC for DC cable is that that it’s ok to do when using the substituted cable at a lower voltage than rated. However, for cables of smaller diameters, there’s no significant difference between Direct Current and low-frequency Alternating Current. In such cases, any substitution should have minimal impact on the application.If the ratings are the same, or closely similar, then substituting an AC cable with a DC one might not matter. Bottom line: Depending on the application and the environment, you might be able to use DC power cables instead of AC. However, doing so might draw more current which leads to higher losses.
Pricing often determines what type of cable you choose for your project. You may decide that using a 6MM DC cable might make better sense because of the price advantage it offers over other choices available to you. Alternately, the application might call for a 12V DC cable, but might require use of a 12C AC adaptor or transformer to implement your project design. Each of those decisions will have a pricing and cost impact on the overall project’s budget.
Depending on what your application is, cabling costs can account for a significant amount of the overall projects’ budget. It is therefore essential that, before you plan and design a cabling project, you must analyze the pricing of these two cables, and decide whether a DC power cable makes more sense, or whether you should stick with alternating power.
The pricing of a DC cable might initially look more expensive than its AC counterpart. However, depending on other aspects of the project, including the application, the installation approach and the volume of cabling involved, AC cable price might work out to be more expensive than their DC options. That’s because, although the cost of converters (used to convert DC to AC) might be higher than the transformers used in AC application, other costs might make DC the better choice.
DC power uses two poles – negative and positive, and therefore the construction of these cables (DC) is less complex. This makes the manufacturing process comparatively simple, which lessens the cost of the finished product. Unlike DC, an AC cable has 3-phase, four or five-wire systems. This makes it more costly to insulate during the manufacturing process. A DC cable price is sometimes three times less expensive than its SC counterpart.