Power Supply Cord
Power supply cords are detachable means of supplying electricity from a main power source to electrical equipment or appliances. Most power supply cords are AC power supply cords, meaning they conduct electricity in the form of an alternating current. Power supply cords consists of a flexible cord with electrical at each end, one male and one female. The connecting cord itself is a cable assembly comprised of a conducting medium, typically copper, surrounded by cord covers of insulating material and an outer polymer or rubber jacket which protects the wire. Power supply cords, which are permanently affixed to electrical equipment, and power supply cables are utilized anywhere that electrical equipment and appliances are in use, including industrial, office, commercial and domestic settings. Power supply cords are used in such applications as electrical power tools, lighting, sound equipment, shop equipment and many personal uses. Industries that benefit from power supply cords include retail, residential, industrial, commercial, electronics, food processing and telecommunications.
Power supply cables manufacturers follow various specifications, including voltage rating, current rating, length and maximum cable temperature, as well as the type of molded plug and female connector. The female connector attaches to the appliance or electrical equipment. The male plug connects the electrical receptacle, electrical outlet or power supply. The two most commonly used North American "NEMA" power supply cord plug types are Type A, which have two conducting blades or prongs, and Type B, which have an additional third grounding rod. Both plug types are configured with a molded plastic body called a "jack" which holds the two blades apart, while the cord connects to the blades within the plug body. Electric cord application determines which jack material is ideal; jacks may be thermoformed from PVC, rubber, polychloroprene (neoprene) and textile construction. Inserting the blades into an electrical outlet, or receptacle, energizes the blades. Electricity then flows through the blades, the blade-cord connection and the power supply cord, providing electricity to the equipment. In addition, the size of the cord wire is determined by the amount of voltage that will be required to flow through the cord. Cord wire sizes and voltage capacities are is given a designation in accordance with the American Wire Gauge (AWG) standards for wire sizes.
The National Electrical Manufacturers Association (NEMA) sets the standards power supply cord companies follow for both male electric plugs and female electric plugs. An electric plug is polarized when the physical characteristics of the blades allow the plug to be connected to the electrical outlet in only one way. Non-polarized plugs do not restrict the way the electrical plug is connected to the electrical outlet. Three-prong electrical plugs are inherently polarized, while two-prong electrical plugs do not have a grounding pin but may be polarized if one blade is larger than the other. In addition, the power supply cable may also include non-insulated conductors that can be used for polarization. Polarization and grounding is especially important for certain higher voltage appliances and electrical equipment that could have a higher risk of electric shock when they become live. Polarization of an electric plug ensures that the equipment is connected to the neutral, or grounded, side of the circuit. Sensitive electrical equipment and products should only be used with polarized or grounding type power supply cords.