View A Video on Power Cords - A Quick Introduction
Also referred to as
electric cords, power cords can be used to transfer direct electrical current (DC) or alternating electrical current (AC). Most cords are
AC power cords that conduct energy in which the direction of current flow is periodically reversed. The
power supply cord, or
cable assembly, is comprised of a wire composed of highly conductive material such as copper, surrounded by an insulative material and then sealed in a protective outer jacket, with a
plug cover to ensure safety around the electrical outlet. In North America,
NEMA power cords (National Electrical Manufacturers Association) are the standard for electrical plugs, cord voltage capabilities and receptacle configuration.
International power cords and
plug adapters are used in conjunction with electrical appliances in countries different from those in which they were designed to operate.
Cord sets are used in any application which requires the existence of electrical energy to operate, such as office space, industrial operations, medical machinery, commercial appliances etc. For specialty equipment such as construction machinery, sound and lighting equipment, emergency medical defibrillators and electrical power tools, used in locations without a convenient power source,
extension cords are used to carry the electrical current up to hundreds of feet away from an outlet.
When determining the appropriate power cord type to be used for different applications, there are many factors to be considered such as equipment location, duration of use, strain of the operation etc. Power cord manufacturers adhere to standard regulations for voltage ratings, current, wire diameter and length, jacket material, maximum cable temperature, as well as the type of molded plug and female receptacle to be used. The capability of a cord to successfully handle the required flow of electrical energy will depend on these factors, and the quality of electricity transmitted will be affected accordingly. Cord wire sizes and voltage capacities are designated according to the American Wire Gauge (AWG) standards. The appropriate wire size is therefore determined by the amount of voltage required to flow through the cord. Wire shape can be either flat or round according to whichever is more appropriate for the application. Jacket material is another consideration and may be determined by the intended use and location of the power cord. For example, if the cord is purposed for rugged, outdoor usage, a jacket material will be waterproof and more durable than a cord intended only for use indoors, for instance with a laptop computer. Another consideration for jackets is the possible existence of electromagnetic interference and whether or not the wires in a power cord require further protection, such as those used with medical equipment.
One end of the power cord holds an electrical plug known as male, which connects to the main power supply through an electrical outlet. The two most commonly used plugs in North America are: Type A plugs and Type B plugs. Type A plugs have two conducting prongs, and Type B plugs have a third prong which, in addition to supplying electrical current flow, connects the power cord to a grounding rod. The prongs on the electrical plug fit into the corresponding holes in the wall socket, or electrical receptacle, thus providing a connection to allow the flow of electrical energy from the power source, through the extension cord and to the appliance. The optimum flow of energy through the power cord depends on a tight fit between the socket and the plug. Electricity flows through the connection and the conducting material in the power cord to the electrical equipment.
The National Electrical Manufacturers Association (NEMA) is responsible for setting the stringent standards used in North America for electrical supply components, and this ensures a high quality of electrical supply is maintained. Other countries have their own voltage systems and electrical component layouts, and so those respective countries determine the standards and controls implemented in their power cords. Manufacturing standards such as those enforced by NEMA help to maintain consistency in power cord production, and decrease the chance of malfunctions due to quality standards. As with any component used in the transferring of electrical power, there are important safety precautions to be undertaken in the use of power cords. Personal injury, death and/or extensive property damage can occur as the result of deterioration, malfunction or misuse of electrical equipment, and it is important for there to be measures in place to reduce these risks. Polarization, or grounding, is an important aspect of electrical plugs and appliances, especially for higher voltage appliances or for electrical equipment that has a higher risk of causing electric shock when live. Sensitive electrical equipment and products should only be used with polarized or grounded cord sets. Other safety precautions for electrical supply components include plug covers, waterproof protective materials, fuses and circuit breakers.
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Power Cord Types
- conduct alternating current from
one point to another. AC power cords consist of a conducting medium,
typically copper, surrounded by insulation and a jacket.
- are used for computers and related electronic
equipment.
- consist of several wires or cables collected into
a single unit with connectors on at least one end.
- are protective covers that guard loose cords and wires from hazardous situations.
- are power cords with a male electrical plug at one end and a female plug at the other.
- are conductive cables used to transfer AC power from a plug to an electrical device.
- Electrical plugs male electrical connectors with metal-blade contact prongs that connect
electrically with holes in the matching female electrical receptacle.
- are commonly known as outlets or sockets.
- are marked with necessary information pertaining
to their use, size and wattage rating. Extension cords are available
in
many lengths and are marked with a size, or gauge, which is based on
the American Wire Gauge (AWG) system.
- are
specially designed for rough, heavy-usage environments in industrial
or commercial applications. The head is constructed with
large flats having deeply contoured ridges that afford a non-slip grip,
and a heavy molded strain relief shroud protects the cord/plug union.
- are designed to meet the critical needs of medical
equipment applications. Heavy-duty solid brass blades and pins are
soldered or
welded to the conductors for added durability.
- International power cords are detachable means of supplying electricity from a foreign power
source to native electrical equipment or appliances that would
otherwise have been incompatible.
- NEMA power cords re the standard for North American electrical plugs, cord voltage capacities and electrical receptacles' configuration
- have
one blade that is wider than the other, which helps reduce the potential
for shock. Three-prong plugs are automatically
polarized, since they can be inserted only one way.
- are
flexible lengths of cord that have an attachment plug molded to their
ends and are used to transmit electrical energy
from the main supply to an electrical device. A power supply cord,
which could also have terminations or a molded strain relief on the
opposite end of the plug, is permanently installed in the device being
powered, as opposed to a cord set, which is detachable.
- Plug adapters are electrical devices that allow for sockets to connect to plugs that are otherwise incompatible to each other.
- Plug covers provide protection against hazards such as electrical shock that result from uncovered electrical outlets.
- allow users to plug in electrical equipment
close to walls without bending or damaging power cords and are available
in both a two-conductor (polarized or non-polarized) or three-conductor
configuration. The three-conductor plug could have the grounding
pin in the top or bottom location.
- have two vertical blades and a grounding
pin. They are polarized by default, since they can be plugged in
just one way.
- consist of two vertical
blades, one if which is neutral and the other is referred to as hot.
Two-conductor plugs,
which
have no grounding pin, are polarized or non-polarized.
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Power Cord Terms
- The ability of a
power cable
or material to resist surface wear.
- A current flow whose direction changes
in regular cycles.
- The North American standardized wire
and cable-sizing system for identifying wire diameter of copper conductors.
The higher the gauge number, the smaller the cable.
- Also known as "current carrying capacity," it
is the capability of handling electric current, as expressed in amperes.
- The time it takes for an arc to create a conductive
path in a material.
- Expressed in
decibels (db) per unit length, it is the loss of power in an electrical
system.
- A protective layer covering any part of a conductor or cable,
as well as its insulation or jacket.
- A covering of one or more wires made from fibrous or metallic
filaments that are interwoven in cylindrical form.
- The amount of voltage at which the insulation
between two conductors or a conductor and ground deteriorates.
- The twisting of wires together within the same
frequency, in order to achieve a specific gauge.
- Irreversible damage of the insulation due to the mechanical
force of pressure.
- A term describing the capability of any material
to carry an electrical charge, typically expressed in terms of the percentage
of conductivity of copper, which has 100% conductivity.
- Any material in which electrons can freely move from
atom to atom (i.e. electrical current flow). Conductors, which are usually
metal, could be a wire that is solid or a stranded multi-wire cable.
- A tube or trough through which wires and cables are run.
- A test used to determine if an electrical current
will flow continuously throughout the length of a wire or cable.
- A small insulated flexible cable made to withstand mechanical
abuse.
- An insulating material used in a cable to shield one
conductor from another.
- Electric
current that flows in one direction only.
- The complete path of an electrical current.
An electrical circuit is considered to be an open circuit when the continuity
is broken and a closed circuit when continuity is maintained.
- An international plug used by many European countries.
Europlug is the common name for the CEE 7/16 2.5 amp, Class II plug.
- A unit of electrical capacity.
- Resistance to the crystallization of metal,
eventually leading to the breakage of conductors and wires due to flexing.
- A flanged nylon housing that permits mounting
in a panel on the front of the equipment for an electrical inlet or outlet,
which is held in place by screws and bolts.
- The number of times an alternating current repeats
its cycle in one second, measured in Hertz (Hz). The standard international
frequency is 50Hz, while the standard North American frequency is 60Hz.
- An indication of the physical size of a wire or the wire
diameter specifications. The number of the gauge is in an inverse relationship
to the size of the wire (i.e. the larger the wire, the smaller the gauge
number).
- A complete circuit accomplished through a conductive connection
between an electrical circuit and the earth or another large conducting
body.
- A test applied to a cable to determine whether any damage
has occurred during shipment.
- Generally considered to be any operating voltage
over 600 volts.
- Formerly "IEC 320," it is the International
Electrotechnical Commission standard that applies to a series of connectors,
plugs, outlets and inlets designed for use on electrical or electronic
equipment, including such portable equipment as computers, printers and
medical equipment.
- A conductor of electricity covered by a non-conducting
material.
- Any material having high resistance to the flow of
electric current that protects the inner conductors of an electrical
cord.
- Material, usually extruded plastic or elastomer, that
covers wire and cable, providing protection and additional insulation.
- A cord that ends with a plug at one end and is utilized
for connecting equipment to a power outlet.
- The dissipation of energy without accomplishing useful work.
- A connector molded on one or both ends of a cable
or cord.
- A cord or cable complex containing more than one
conductor.
- A compilation of wiring practices
and requirements from the National Fire Protection Association (NFPA).
- Also called "polychloroprene," it is a synthetic
rubber that has good resistance to chemical, oil and flame.
- An abrasion resistant thermoplastic with effective chemical
resistance that is utilized for cable and wire jacketings, wiring devices,
connectors and plugs.
- A unit of measurement referring to electrical resistance.
- A female connection that supplies access to electricity
from a source of power.
- A receptacle, connector or plug that has round
pins or sleeve-type contacts.
- Also called an "attachment plug," it is the
cable mount portion of an electrical connection or male contact device
that has pins or blades protruding from the face.
- Often referred to as a jacket, it is the material that
is applied to the outermost part of a wire or cable. Sheaths are typically
made of extruded plastic or elastomer.
- In cables, a metallic layer that prevents electrostatic
or electromagnetic interference between wires and external fields when
placed around a conductor or group of conductors.
- An information conveying current, including digital, analog,
audio and video information.
- An electrical circuit that has a neutral, a line
and a ground.
- A device that establishes an electrical connection with
plugs through tension connections. Sockets could be metal contacts that
are either bent to receive the blade or pin or spring-loaded.
- Also called a "transient," it is the temporary
and relatively large increase in the voltage in an electric circuit or
cable.
- An electrical circuit that holds three lines and
a ground or three lines, a neutral and a ground. The three lines are
1201/4 out of phase with each other.
- The maximum voltage that can be continuously applied
to a wire in conformance to standards or specifications.
- Formerly designated as "FR-1," it is a rating
established by UL for wire and cables that pass a specifically designed
vertical flame test for flammability.
- Any cord that is designated
by Underwriters Laboratories, Inc. (UL) for outdoor use.
- A unit of measurement that refers to electric power.
- Any standard system of numerical designations for
wire sizes (e.g. the AWG).
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