A power cord consists of cable with a country-specific plug (molded or hand-wired) on one end and exposed conductor wires, terminated conductors, or blunt/flush cut conductors on the other end. A power cord is used to connect the equipment directly to the power mains.
A power supply cord is an essential element of all cord connected electrical equipment; it supplies the connection between the equipment and the electrical mains. The power cord can be hard wired to the equipment or it can be detachable. The hard wired (non-detachable) power cord consists of a plug, the cordage, and a strain relief device to secure the cord to the equipment enclosure. The detachable power cord, also known as a power cord set, consists of a plug, cordage and a connector or receptacle. Though seemingly a simple component, when it comes to regulatory approvals, it can become an exceedingly complicated component.
This article shall cover some of the aspects of power cords intended for use in information technology equipment (ITE) and consumer products applications. Other types of power cords, such as those for outdoor use or for hazardous locations, are a topic for another article.
Power supply cords typically have two or three wires. These wires are “line,” “neutral” and “ground.” The International Electrotechnical Commission’s standard IEC 60446 uses the following color codes:
In North America, the line wire is black in color, while it is either brown or grey in the rest of the world;
In North America, the neutral wire is white, while it is blue elsewhere; and
In North America, the ground wire is typically green, while it is green with yellow stripes in the rest of the world.
It is crucial to ensure that the electrical rating of the UK power cord supplied with the product is higher than that of the product being powered. Most product standards require the plug to be rated at least 125 percent of the rated current of the equipment. An under-rated power cord can result in the power cord overheating, and possibly causing an electrical fire. Power cords designed for use with ITE equipment in North America are rated as 125Vac/10A, but other higher ratings are also available.
Non-Detachable Power Cords
The non-detachable power cord is hard wired to the equipment enclosure, and is generally not meant to be removed from the equipment enclosure. The power cord consists of a plug, the cordage and a strain relief connector to secure the cord to the device.
A common means of attaching the stripped end of a non-detachable power cord (see Figure 1) is a lug/ring terminal. One end of the terminal consists of a metallic ring or “loop” that slips over and is attached to a power terminal post or screw. The other end of the lug/ring terminal is generally crimped onto the stripped power cord wire. One lug-ring terminal is attached to one power cord wire. It is important to remember that, when using this form of terminal, the crimp tool must be approved for the terminal for which it is being used. It is good engineering practice to double crimp the lug/ring terminals.
Manufacturers of large equipment that use non-detachable power cords will occasionally ship their power supply cords disassembled from the equipment. This is because the power supply cords are typically very large and very long, and the cords may be damaged during shipping. In such instances, U.S. nationally recognized testing laboratories (NRTLs) do allow for this, provided certain conditions are met. These conditions include:
