Power plugs are male connectors that are used to distribute power to electrical devices. They connect to electrical receptacles, wall outlets, or sockets and draw current from these female connectors. The male features (blades/pins) are generally brass and plated with tin or nickel. These materials interface mechanically and electrically to the mains. The plugs have a live contact, a neutral contact, and often a ground contact.

Power plugs provide either alternating current (AC) or direct current (DC). As electrical connectors, both AC power plugs and DC power plugs are equipped with metal blades or pins that mate with slots or holes. Grounded plugs provide protection from electrical shock. Polarized plugs can be inserted in only one way so that the live and neutral poles of the plug can connect only to the live and neutral conductors of the receptacle.

Types of Power Plugs

There are many different types of power plugs. The chart below gives a comparison of the many different types of power plugs.

 Chart and Note Credit: Wikipedia. Image Credit: US Department of Commerce

Power plugs that do not bear lettered designations include the NEMA 14-30 and NEMA 14-50 plugs that are used in North America with ovens and dryers. IEC 60906-1 is a proposed common standard for power plugs.

Specifications

Power plugs bear lettered designations and carry specifications such as:

• Input and output voltage (V)
• Amps (A)
• Poles control one path of the circuit. A pole is an outlet terminal for a switching device, a combination of mating contacts, or both.
• Wires transfer the power between devices. In general, a single phase volt system will have two wires if only the lower voltage is available. One wire is for the phase and the other is neutral. If higher and lower voltages are available, the power plug will have three wires; Two phase wires and the neutral.
• Color is important to consider for the aesthetics of the home or commercial space. Color may also be important to serve as a warning of high voltage or dangerous lines.

Blade and Pin Type

The blade or pin fits into the female end of the power plug.

Straight- Straight blades are non-locking plugs. They are inserted at a right angle to the plane of the matching device face.	Image Credit: Grainger
Locking- Locking blades lock into their matching connectors. The locking occurs when the plug or receptacle is rotated wither clockwise or counter clockwise.	Image Credit: Automationdirect
Pin and Sleeve- Pin and Sleeve plugs have round pin contacts. The mating plugs are inserted at a right angle to the plane of the receptacle face.	Image Credit: LappUSA

Grounding

Grounding is the term used to describe a safe path for electricity to move from a defective outlet, fixture, appliance or tool back into the earth, which is a very good electrical conductor. There are different grounding options available based on the needs of the system. These include:

• Non-grounding plugs do not have a ground option.
• Standard grounding devices have a standard embedded ground terminal.
• Isolated grounding devices use a ground path that is isolated from the facility's grounding systems. This increases the resistance of sensitive electronics to surges. They also provide a clear grounding path to the service panel and help reduce electromagnetic noise that can interfere with equipment operation. 
• Self-grounding plugs establish a connection to en existing grounding path such as a metal wiring device or metal conduit, gas or water pipe, or ducting or structural steel. 
• Ground fault circuit interrupter (GFCI) plugs include a built-in circuit that detects leakage current to ground on the load side of the device. When leakage current is detected, GFCI interrupts power and prevents hazardous ground fault conditions. National Electric Code NFPA-70 requires GFCI use in many indoor and outdoor locations.

Features

Power plugs have several features available that may be beneficial for user application.

Corrosion resistant- Corrosion resistant devices are made of special materials and/or plated metal parts that are designed to withstand corrosive environments. Corrosion resistant devices must pass the ASTM B117-13 five-hundred hours Salt Spray (Fog) Test with no visible corrosion.

Dust proof- Devices are designed so that dust will not interfere with their operation. The IP suitability rating describes the degree of protection that a device offers against the ingress of foreign objects (e.g., IP 20).

Power light- Devices include a power light to indicate if they are live. The receptacle may also be illuminated to make connection easier in dim or dark work spaces.

Tamper resistant- Devices are constructed so that access to their energized contacts is limited. Tamper resistant receptacles are required by the National Electric Code NFPA-70 in specific pediatric care areas in health care facilities.

Watertight- Devices are constructed so that water cannot enter under specified test conditions. The IP Suitability Rating designates the degree of protection a device offers against the ingress of moisture and water (e.g., IP-55, IP-44). Some devices may also be approved for moisture resistant, and under water applications.

Quick connect / disconnect- Connectors incorporate a quick-connect mating geometry, typically by twisting and seating for positive contact. They can be disconnected quickly and then easily connected to another machine or device.

Integral features are built into the design of the power plug.

Fuse protection- Devices include integral fuse protection against mild to moderate spikes or peaks in electrical supply. The fuse will blow before connector is damaged.

Integral surge protection- Devices include integral surge protection against mild to moderate spikes or peaks in electrical supply.

Integral circuit breaker- Devices include an integrated circuit breaker that will "trip", severing the connection to the electrical supply, in the event of an excessive power transfer.

Integral switch- Devices are equipped with an integral switch. Toggling the switch to the "off" position stops the electrical power transfer through the connector.

Integrated filter- Devices provide protection against unwanted signals or magnetics and may provide signal conditioning or isolation. Typically, filters are designed to reduce electromagnetic interference (EMI) and radio frequency (RFI).

Applications

Specialized power plugs are used for specific types of instruments, equipment, machinery, and computers. Some electrical connectors are designed for use in hazardous environments or marine environments. Power plugs are used in almost every industry including residential, commercial, industrial, and medical facilities.

Standards

These power connectors are designed to meet requirements from several organizations including,

• National Electrical Manufacturers Association (NEMA) - NEMA sets standards for electrical cabling and connectors.
• The International Electrotechnical Commission (IEC) - IEC is a worldwide body responsible for developing consensus global standards in the electrotechnical field.
• Consortium for Energy Efficiency (CEE) - CEE is a European organization for electrical standards.
• Japanese Industrial Standards (JIS) - JIS is a Japanese organization for electrical standards.

There are many organizations across the world that determine and maintain electrical standards to ensure safe and efficient use of power plugs. Engineering360 allows users to search by country to ensure they select a power plug that can be safely incorporated into their system.

Resources

Power Connector Tutorial

Electrical Current Worldwide

Image credit:

Interpower