AC Power Cord

Chapter 1: What is the principle behind AC power cords?

This chapter will cover the basics of AC power cords, including their construction and how they function.

What is an AC Power Cord?

An AC power cord is a detachable component that supplies alternating current (AC) from a mains power source to electrical appliances or equipment. Used across various industries including retail, commercial, industrial, electronics, entertainment, and residential sectors, AC power cords serve numerous applications such as lighting, power tools, household appliances, shop equipment, musical instruments, and other personal uses.

Construction of an AC Power Cord

AC power cords carry alternating current (AC), where electrons periodically reverse direction. This flow of electrons transfers energy from a power source to electrical equipment through the cord. The cord consists of conducting wires, typically made of copper, which are encased in insulation and covered by an outer jacket made of rubber or polymer. The specific construction of the cord varies depending on its intended application.

The construction and materials of AC power cords are primarily determined by three main factors:

• Operating voltage determines the thickness of insulation.
• Current-carrying capacity determines the cross-sectional area of the conductor.
• Environmental conditions like mechanical impact, water, chemical, and temperature or sunlight exposure determine the composition and form of the outer cable jacket.

Conductor: Copper Wire

Copper is an electrical conductor in various types of electrical wiring. Copper wire is utilized to generate power, transmit power, power distribution, electronic circuitry, telecommunications, and numerous kinds of electrical devices. Copper and its alloys are also used to produce electrical contacts. Electrical wiring in construction is the most vital market for the copper wire industry. Approximately half of all mined copper is utilized to produce cable conductors and electrical wire.

Two or more copper wires in a cord are often braided, twisted, or bonded together into a single assembly. Stranding these wires enhances the flexibility of the electrical cord.

Copper wiring in cords may be left bare or plated with a thin layer of tin to reduce oxidation. In some cases, silver or gold plating is used to further extend the wire's lifespan and facilitate soldering. Coaxial cables and twisted pairs are designed to minimize electromagnetic interference, prevent signal radiation, and ensure specific transmission characteristics. Shielded cables are covered with a wire mesh or foil to provide additional protection.

Electrical Conductivity

Electrical conductivity measures how effectively a material allows electric charge to flow. This property is crucial in electrical wiring systems. Copper, known for its exceptional conductivity, has a resistivity of 16.78 nΩm at 20 degrees Celsius. Copper's high conductivity is explained by solid-state metal theory: in a copper atom, the conduction band, or the outermost 4s energy level, is only partially filled, allowing numerous electrons to facilitate electric current. When an electric field is applied to a copper wire, electron movement increases towards the positive end, generating an electric current.

Electrons in a conductor encounter resistance due to collisions with impurities, lattice ions, vacancies, and imperfections. The average distance between these collisions is known as the "mean free path," which is inversely proportional to the metal's resistivity. Copper, with its high conductivity, is the standard for comparison with other conducting materials. Electrolytic-tough pitch (ETP) copper, which contains a minimal amount of oxygen, is commonly used in electrical applications due to its excellent conductivity.

While many metals have lower density than copper, they require larger cross-sectional areas to conduct the same amount of charge. For example, aluminum, which has 0.6 times the conductivity of copper, needs a cross-sectional area 0.56 times larger than copper to carry the same current. This can be a drawback in applications where space is limited.

Silver surpasses copper in electrical conductivity, being 1.06 times more conductive on the International Annealed Copper Standard (IACS) scale. Silver's electrical resistivity is 15.9 nΩm at 20 degrees Celsius.

Tensile Strength

Tensile strength measures the maximum force required to pull a material, such as a structural beam, rope, or wire, to the point of breaking. It represents the highest tensile stress that the material can withstand before failure.

The high tensile strength of copper makes it resistant to necking, stretching, breaking, and creep, which helps prevent service interruptions and failures. However, copper is heavier than aluminum for conductors with the same current-carrying capacity. This increased weight can offset its high tensile strength advantage.

Ductility of Copper

Ductility refers to a material's ability to deform under tensile stress, often demonstrated by its capability to be drawn into a wire. This property is crucial in metalworking because materials that break or crack under stress cannot be effectively rolled, hammered, or drawn. Copper exhibits high ductility, surpassing most other metal conductors except silver and gold. Its exceptional ductility allows copper to be drawn into very fine wires with precise tolerances.

Ease of Installation

The hardness, flexibility, and strength of copper make it straightforward to work with. Copper wire can be installed easily without requiring special tools, pigtails, washers, or joint compounds. Its flexibility simplifies joining, while its hardness ensures that connections remain secure. Copper can be twisted or bent without breaking and can be terminated and stripped during installation with minimal risk of damage. Furthermore, it can be terminated without the need for specialized fittings or lugs. These qualities combined make copper an ideal material for manufacturing power cables.

Conductor: Aluminum Wire

Aluminum wire is a kind of electrical wire for residential houses or construction that utilizes aluminum electrical conductors. Aluminum offers a better weight to conductivity ratio than copper. Therefore it is also used for power grid wiring, including power distribution lines, and overhead transmission lines. It has weight and cost benefits over copper wires.

Aluminum is a good electrical and thermal conductor, with approximately 60% of the conductivity of copper for both electrical and thermal applications, while having only about 30% of copper's density. Due to its high electrical conductivity, aluminum is significantly affected by AC magnetic fields through eddy current induction.

However, aluminum has certain properties that make it less desirable as an electrical conductor compared to copper. These properties can lead to potential fire hazards due to loose connections. The key issues are outlined below:

Electrical Resistance

Aluminum has higher electrical resistance compared to copper, which means that for the same current load, aluminum wires need to be thicker than copper wires to achieve the same performance.

Aluminum Ductility

Aluminum is less ductile than copper and tends to break and fatigue more easily when bent or subjected to stress. This fatigue can cause internal breakdown of the wire, increasing resistance and leading to heat build-up.

Galvanic Corrosion

When exposed to moisture, aluminum can experience galvanic corrosion if it comes into contact with certain dissimilar metals.

Oxidation of Aluminum

Exposure to oxygen causes aluminum to oxidize more readily than copper. The resulting aluminum oxide is less conductive than oxidized copper, which can degrade connections over time and pose fire hazards.

Aluminum Malleability

Aluminum's malleability and softness make it prone to compression and deformation. If an aluminum wire is overtightened, it can deform and cause loose connections, increasing resistance and potential hazards.

Thermal Contraction and Expansion

Aluminum undergoes more significant thermal expansion and contraction than copper. Over time, this can lead to degradation of connections between the wire and devices.

Excessive Vibration

Aluminum is more susceptible to vibration caused by electrical current compared to copper. Over time, this increased vibration can lead to loose connections.

Wire Insulation

Insulation is a non-conductive material used in cord construction to prevent current leakage and protect the conductor from environmental threats like heat and moisture. Effective insulation is crucial for maintaining the wire’s integrity and ensuring long-term performance.

There are many different types of wiring and cord insulation materials available, each suited to specific applications. The three primary insulating materials are rubber, plastic, and fluoropolymer. Wire insulation refers to the material used to cover an individual conductor, while cord insulation pertains to the insulation of a cable comprising multiple conductors or wires. Cord insulation can refer to either the type of insulation covering each individual wire within the cord or the overall insulation of the cord itself. The choice of insulation type and level depends on the intended application of the cord.

Plastic Insulation

Plastic insulation can include various types such as:

Polyvinyl Chloride (PVC)

PVC is quite cheap and easy to implement cable and wire insulation materials with the ability to be utilized in various applications. PVC insulation material ranges in temperatures from -55° Celsius to 05° Celsius and is flame resistant, abrasion, and moisture. It can also withstand exposure to ozone, gasoline, acids, and solvents.

PVC is often used as insulation for food-related and medical applications due to its odorless, nontoxic, and tasteless properties. It is suitable for both thin-wall and heavy-duty applications. However, PVC is not ideal for situations requiring extended flexibility and low-temperature performance. Its flexibility is subpar in retractile cord applications. Additionally, PVC exhibits capacitance loss and high attenuation, which means it can lead to energy loss in electrical systems.

Semi-Rigid PVC (SR-PVC)

Semi-Rigid PVC is primarily used as primary insulation and is highly resistant to abrasion. It is also resistant to acids, heat, water, and alkalis, and is flame-retardant.

Plenum Polyvinyl Chloride (Plenum PVC)

Plenum PVC is designed for use in plenum spaces, which are areas above ceilings or below floors used for air circulation. Unlike standard PVC, plenum PVC meets stricter fire safety standards required for such spaces.

Polyethylene (PE) Insulation

Polyethylene is commonly used in low-capacitance and coaxial cables due to its favorable electrical properties. It is cost-effective and can be foamed to achieve a low dielectric constant of 1.50, making it ideal for high-speed transmission applications.

PE can also be cross-linked to enhance resistance to cut-through, cracking, solvents, and soldering. It functions well in temperatures ranging from -65°C to +80°C. PE is hard, stiff, and inflexible, and it is flammable. Flame retardants can be added, but this may increase power loss due to a higher dielectric constant.

Polypropylene Insulation (PP)

Polypropylene insulation, similar to PE, offers a wider temperature range of -30°C to +105°C. It is commonly used for thin-walled primary insulation and can be foamed to improve its electrical performance.

Polyurethane (PUR) Material

Polyurethane is valued for its exceptional durability, flexibility, and resistance to low temperatures. It also provides excellent chemical, abrasion, and water resistance. PUR is suitable for retractable cord applications and is often used in military applications requiring resistance to salt spray and low temperatures.

However, PUR is flammable, and while it can be treated to be flame-retardant, this may compromise its surface finish and strength. Its primary drawback is its poor electrical properties, making it more suitable for jackets than for insulation.

Chlorinated Polyethylene (CPE)

Chlorinated Polyethylene is highly resistant to oil, heat, and weather conditions. It is a more affordable and eco-friendly alternative to CSPE. CPE’s reliable fire resistance makes it a good substitute for PVC insulation and is commonly used in control and power cords, as well as in industrial applications.

Nylon Insulation

Nylon is preferred over softer insulation materials for its toughness. It offers strong resistance to chemicals, cut-through, and abrasion, especially in thin-walled applications. It is also highly flexible. A downside is that nylon absorbs moisture, which can degrade some of its electrical properties.

Rubber Insulation

Rubber insulation comes in various types, including:

Thermoplastic Rubber (TPR)

TPR is a replacement for traditional thermoset rubber. It offers better colorability, a broader temperature range, and faster processing speeds. TPR provides excellent resistance to weather, aging, and heat without the need for curing. While it lacks resistance to cut-through, it is suitable for applications where its other properties are beneficial.

Neoprene (Polychloroprene)

A synthetic thermoset type of rubber, neoprene should be vulcanized to achieve its desired properties. It shows excellent cut-through, oil, abrasion, and solvent resistance. Neoprene is also popular for its extended life service, extensive range of temperature, and usability. It is outstandingly retardant to flame and self-extinguishes. Neoprene is particularly best for portable cord sets and is mostly utilized in military products.

Silicone Insulation

Silicone is highly flame-retardant and heat-resistant, capable of withstanding temperatures up to 180°C. It offers average resistance to abrasion while being exceptionally flexible. Its benefits include strong bonding properties and a long shelf life, making it valuable for a wide range of electrical applications.

Ethylene Propylene Rubber (EPR)

EPR is favored for its outstanding thermal and electrical properties, allowing for a smaller cross-sectional size while carrying the same load as other cords. It is commonly used in high-voltage applications. EPR is resistant to oxidation, heat, weathering, water, alcohol, acids, and alkalis.

This rubber’s flexibility makes it ideal for temporary applications and installations in mining. EPR can operate within temperatures ranging from -50°C to 160°C. However, it is less tear-resistant compared to other insulation materials and is relatively soft, which may require careful handling during installation to prevent damage.

Rubber Insulation

Rubber insulation typically refers to both SBR compounds and natural rubber, available in various formulations for diverse applications. These formulations vary in temperature range and key properties. While this insulation type generally has low ozone and oil resistance, it offers good electrical properties, flexibility at low temperatures, and resistance to alcohol, water, and abrasion.

Fluoropolymer Insulation

Fluoropolymer insulation can include:

PFA Insulation

PFA insulation offers temperature ratings from -65°C to 250°C, depending on the cord construction. It has a low dissipation factor, which makes it an electrically efficient option. PFA lacks thermoset properties, limiting its use to specific applications. It is also a costly insulating material.

Polytetrafluoroethylene (PTFE) Insulator

PTFE is a thermoplastic insulator with a temperature range from -73°C to +204°C. It is highly flexible and resistant to oil, water, heat, and chemicals. However, its mechanical properties are generally lower compared to other fluoropolymer rubbers.

Thermoplastic Elastomers (TPE)

Thermoplastic elastomers combine polymers, typically rubber and plastic, to merge the benefits of both materials into a single insulating solution. TPE can be extruded, molded, and recycled like plastic while retaining the elasticity and flexibility of rubber.

TPE is commonly used in applications where conventional elastomers do not meet the required physical properties. It is widely used in household appliances and automotive applications. However, TPE has drawbacks including poor heat and chemical resistance, higher cost compared to other insulation types, and lower thermal stability.

Jacket Material

• (PVC) Polyvinyl chloride is a material that is thermoplastic best for indoor use.
• Rubber has exceptional mechanical hardness and is utilized to provide power to motors, appliances, and electric tools. Polychloroprene rubber has higher thermal stability when compared to plain rubber jackets.
• Textile jackets have exceptional durability.

End Type for Power Cords

• NEMA stands for National Electrical Manufacturers Association. NEMA standardizes connectors. The various kinds of NEMA connectors have different voltages, pin arrangements, phases, amperages, and grounding choices.
• Hard wired cords ends have hard wires that are either fitted or stripped with terminal connectors.
• Local agencies standardize International connectors. Other standards, like EN 60320 and CE 7, refer to all European power connectors.

How an AC Power Cord Functions

AC power cords transmit alternating current from an AC power source, such as a wall socket, to an electrical device or appliance. They provide a low-resistance pathway for the alternating current to flow. The live wire carries 230V/120V AC from the power source to the appliance, with the current alternating periodically at 50 times per second. The neutral wire returns the current to the power source, specifically to a busbar or ground connected to the distribution box. This setup ensures a complete current flow through the electrical system, allowing for effective utilization of electricity. The earth wire safeguards users from electric shocks by providing a path for any fault current to flow to the ground. It also triggers the fuse or circuit breaker to disconnect the current in the event of a fault.

Considerations for Choosing AC Power Cords

When selecting AC power cords, consider the following factors:

Rated Current

The current rating of a cord indicates the maximum amount of current it can carry without overheating or sustaining damage. This rating depends on various factors, including the cord's insulation, the frequency of the current, its electrical resistance, and the ambient temperature.

Rated Voltage

Rated voltage is a crucial specification when choosing an AC power cord. It influences other design aspects of the cord, such as the thickness and type of insulation used. High-voltage cords typically feature thick thermoplastic insulations, which have largely replaced the older paper and oil-based insulations.

Chapter 2: What are the different types of AC power cords?

AC power cords are distinguished by their connectors, also known as couplers. These connectors facilitate the link between electronic devices or appliances and available power outlets. In addition to connectors, plugs are also used. There are various types of connectors and plugs, with the most common ones discussed below.

C13/C14 AC Power Cord

The International Electrotechnical Commission (IEC) established the IEC 320 C13/C14 connector standard. The "320" refers to the specification that outlines power connectors. While "60320" is the official designation of the standard, it is commonly shortened to "320" in everyday use.

The C13 line socket is widely used in the AV and PC industries. The C14 plug serves as the male connector for the C13 female socket and is typically mounted on a recessed chassis or panel, such as those found on power transformers or PC power supplies.

C5 "Mickey Mouse" AC Power Cord

A polarized power connector is commonly used on notebook computer AC power cords. The C5 connector features three circular prongs arranged in a triangular pattern, which has led to the informal nickname "Mickey Mouse ears connector" due to its resemblance to the Disney cartoon character's silhouette. This type of power cord is typically used with laptop power supplies.

C7 AC Power Cord

The C7 power connector is a 2-pronged, non-polarized plug commonly used in AC power cords for various electronic devices, including radios and power transformers. It features two round pins placed side-by-side and is typically employed to power low-voltage equipment such as portable laptop power supplies, CD players, and audio or video equipment.

C7 Polarized AC Power Cord

The C7 connector also has a polarized version, characterized by a square-shaped overmold that ensures the prongs are oriented correctly on one side of the connector. This design ensures that the neutral terminal of a device is consistently connected to the neutral wire of the AC power supply.

C15/C16 AC Power Cord

The C15/C16 connectors are designed for use in environments where equipment temperatures can be high. For example, they are commonly used in data centers where devices are positioned closely together in confined spaces. These connectors feature keys that prevent mismatching the inlet and connector, ensuring correct "cold" and "hot" configurations. The shape of the C15/C16 is similar to the C13/C14 connectors, except for a notch at the bottom.

The C15/C16 connector has a higher temperature rating compared to the C13/C14 connector. There is also a variant, the C15A/C16A, designed for even higher temperature applications. This version features a rectangular ridge at the upper end of the molding. These AC power cords are commonly used in industrial settings.

C19/C20 AC Power Cord

The terminals of the C15/C16 connector are horizontally oriented. The connector molding is rectangular with rounded edges. This connector is used in power cords for high-power electrical devices and power supplies where C13/C14 connectors are insufficient, such as in servers or professional IT equipment. It has a maximum amperage rating of 15A and can be used in Class I equipment.

C13/Type G AC Power Cord

The Type G plug features a built-in fuse, typically rated at 13A. Its primary purpose is to protect the flexible power cord connecting the appliance to the plug, thereby also safeguarding the appliance from overload. A Type G socket can also accommodate a Type C plug.

This practice is unsafe and not recommended. The primary standard for Type G plugs and sockets is BS 1363. Additional standards based on BS 1363 follow the same specifications for these plugs and sockets.

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Chapter 3: AWhat are the applications and benefits of an AC power cord?

This chapter will explore the applications and advantages of AC power cords.

Applications of AC Power Cords

AC power cords are used in a variety of applications, including:

Building Applications

• Church equipment
• Public outdoor lighting
• Libraries
• Public service buildings
• Data centers
• Airports
• Home appliances

Industrial Applications

• Refineries and oil platforms
• Chemical facilities
• Heat treatment of materials
• Pharmaceutical plants
• Foundries
• Nuclear power stations

Benefits of AC Power Cords

• AC power cords offer a means of connecting AC equipment to the main supply.
• Energy losses in AC power cords are lower when compared to other types of cables,
• When specifications like the range for input voltage change, the response of changing AC power cords is possible.
• Simple to substitute in the event that the power supply fails.
• By utilizing the power supply, the number of components used for the appliances can be reduced along with the cost.
• AC power cords are flexible and may fit in any place when installed.
• They offer a safer means of handling AC current because of their excellent insulation.
• Low internal resistance in the cable because of the quality of alternating current.

Drawbacks of AC Power Cords

• AC power cords generate magnetic fields when current flows and this may interfere with appliances and communications systems.
• Poor conductors in power cables result in heat accumulation burning the insulations.
• Cable sheath degrades overtime.
• AC power cords degrade when subjected to higher currents.

AC Power Cord Standards and Specifications

When dealing with materials that transfer electrical current, it's crucial to observe safety considerations. Polarization and grounding are especially important for higher-voltage electrical equipment and appliances, which may pose a greater risk of electric shock. Polarizing an electric plug ensures that the appliance is properly connected to the ground or neutral side of the circuit, reducing the risk of electric shock for users. Sensitive electrical products and equipment should always be used with properly grounded or polarized AC power cords.

AC Power Cord Maintenance

AC power cords require minimal maintenance since they are passive devices with no moving parts. However, several practices can help extend their lifespan. Ensure that the power cord is used within the manufacturer's specified amperage to prevent overheating. In environments with numerous power cords, such as server rooms, they should be organized and tied to avoid entanglement. It's also important to use AC power cords in dry areas to prevent moisture from entering the connectors. Regular dusting of the power cords helps keep them clean and in good condition.

Conclusion

An AC power cord is a removable means of offering alternating current of electric energy from a mains power supply to an electrical appliance or equipment. Serving industries like retail, commercial, industrial, electronics, entertainment, and residential, AC power cords are utilized for applications such as lighting, electrical power tools, household appliances, shop equipment, musical instruments, and many personal uses. They offer a low resistance path for alternating current to flow through. Live wire carries the 230V/120V AC from the power supply to the appliance. The current alternates periodically at 50 times per second. The cord is a cable made of a conducting wire, generally copper, covered by cord covers, insulation, and an outer rubber or polymer jacket which protects the wire. AC power cords are differentiated by their connectors or more formally known as couplers. AC power connectors enable the connection between electronic devices and appliances to available power outlets. Besides connectors, plugs are also used. The choice of an AC power cord is determined by rated current and voltage.

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