NEMA聯結器

NEMA非鎖扣聯結器都使用各種扁平和摺疊形狀的接片（接地聯結器上使用的圓形引腳除外）。 透過拉回插頭體，可以將插頭與插座分離。 這些聯結器的插槽與接片設計使不同型號的聯結器不會意外地互通。

NEMA壁式插座可以安裝在任何方向上。 NEMA、美國國家電氣法規和加拿大電氣法規都沒有規定首選方向，但國家電氣承包商協會的國家電氣安裝標準（NECA 130-2010）都規定接地的首選位置位於上方。 當插座的接地刀片在底部時，中性線在左上角，火線在右上角。 以下所有描述都假設了這種方向（即120V插座版本的順時針順序為接地、中性線、火線；插頭則按逆時針順序）。

扭鎖聯結器由Harvey Hubbell III於1938年首次發明，「Twist-Lock」仍然是Hubbell Incorporated的註冊商標，儘管該術語通常用於指任何公司製造的NEMA鎖定聯結器。 鎖定聯結器使用彎曲的接片。 一旦推入插座，插頭就會旋轉，其旋轉的接片就會鎖入插座。 要拔出插頭，就需要反向旋轉後拔出。 扭鎖連接器在工業和醫用環境中提供了更可靠的連線，因為振動或撞擊可能會斷開非扭鎖聯結器。

扭鎖聯結器有各種標準化配置，除了名稱包括「鎖定（ Locking） 」的「L」外，這些型號也遵循與直插型號相同的命名方案。 扭鎖聯結器的設計使電壓、電流不同的型號不會意外地互通。其存在許多型號，而下面只列出了少數型號。 其他型別包括用於船舶的聯結器、用於飛機的400Hz電路和直流應用。

然而，扭鎖聯結器的一個明顯缺點就是，如果電纜被不小心拉得太用力，插頭不會從插座上掉出來，而是電導體可能會從插頭中暴露出來，如果電路正在運作，這就會造成危險的短路或觸電危險。不過 在大多數情況下，這可以透過品質優秀的連結器來避免。

注意！以下內容來自英語維基百科，未經翻譯，請在翻譯完全後刪除本內容！

A North American NEMA-5 receptacle halfway through a corrective re-installation. The fluorescent green spacers, which firmly attach the receptacle to the metallic sub-structure, are made necessary by using 5⁄8 in (16 mm) sheetrock instead of 1⁄2 in (13 mm), or by slightly-misplaced device box housings.

Over time, electrical codes in the US and Canada began to require additional safety features in the basic NEMA 5-15R and 5-20R configurations to address specific electric shock hazard concerns. The safety features listed below are not mutually exclusive; for example, tamper-resistant GFCI receptacles are available.

Ground fault circuit interrupter (GFCI) receptacles

Tamper-resistant GFCI duplex receptacle type 5-20RA, which can take 5-15 and 5-20 grounded plugs and 1-15 ungrounded plugs

These versions of the 5-15R or 5-20R receptacle are residual-current devices, and have "Test" and "Reset" buttons (and sometimes an indicator light which may be normally on or normally off per the vendor's design). In the US and Canada, GFCI protection is required for receptacles in many potentially wet locations, including outside outlets, bathrooms, and some places in kitchens, basements, and crawl spaces. This is an expedient way to provide that protection at the receptacle itself.

These safety devices work by comparing the currents flowing in the live and neutral conductors, and disconnect the circuit if their difference exceeds 4 to 6 milliamperes. Installing a single receptacle is often cheaper or more convenient than providing this GFCI protection at the circuit breaker. In addition, a tripped GFCI receptacle may be more easily noticed and reset, as compared to a tripped GFCI located in a remote circuit breaker panel far from the point of usage.

Like most current interrupting devices, a GFCI receptacle can optionally be wired to feed additional "downstream" outlets; correctly installing one GFCI receptacle in a circuit can protect all the plugs, lights, switches, and wiring which receive power from it. This allows for cost-effective retrofits on older installations where branch circuits were often daisy-chained between wet and dry locations. A GFCI receptacle may be installed indoors where it is sheltered from dampness and corrosion, while still protecting an outdoors receptacle wired downstream.

GFCIs are also recommended for power tool outlets and any locations where children might insert conductive objects into the receptacles, although this safety measure does not substitute for additional requirements for tamper-resistant receptacles.

Tamper-resistant receptacles

Starting with the 2008 National Electrical Code and the 2009 Canadian Electrical Code, listed tamper-resistant receptacles that address electric shock hazards to children must now be installed in almost all areas of new or renovated dwellings. According to statistics cited by the NFPA, the code change adds only $40 to the cost of building an average, 75-receptacle home in the US.[citation needed]

This safety measure reduces shock hazards to a child that attempts to insert a single conductive object into the receptacle. Inserting a normal, two-blade electrical plug applies simultaneous pressure on both sides of the receptacle to open an internal, spring-loaded shutter, but a foreign object fails to do so and therefore cannot make contact with the live electrical contacts. However, the device can still be defeated by inserting two objects simultaneously. Despite its weaknesses, the tamper-resistant receptacle is superior to protective plastic outlet caps which must be individually installed on each receptacle (and are a choking hazard when removed), and to sliding covers that children easily learn to defeat.

AFCI receptacles

The National Electrical Code has been updated for 2014 to address the use of Outlet Branch Circuit (OBC) Arc Fault Circuit Interrupter (AFCI) receptacles as an alternative to traditional circuit breakers when used for modifications, extensions, replacement receptacles, or in new construction. AFCI receptacles reduce the dangers associated with potentially-hazardous arcing conditions (parallel arcs and series arcs), by interrupting power to arcing devices (e.g. a damaged appliance cord) that might otherwise not draw enough current to trip the primary circuit protection device.

AFCI protection is mandated by the 2014 Code in residential family rooms, dining rooms, living rooms, kitchens, parlors, libraries, dens, bedrooms, laundry rooms, sunrooms, recreation rooms, closets, hallways or similar rooms.[citation needed] It is also required in dormitory units. AFCI receptacles look similar to GFCI receptacles in that they have a "Test" and "Reset" button on the face of the device for localized testing. This saves a homeowner a trip to the breaker panel, should the device trip. Unlike AFCI breakers, AFCI receptacles can be used on any wiring system, regardless of the panel.[citation needed] When installed as the first receptacle on a branch circuit, AFCI receptacles can provide series arc protection for the entire branch circuit. They also provide parallel arc protection for the branch circuit downstream of the AFCI receptacle.

Surge protective receptacles

See also: Surge protector

Surge protective devices are designed to reduce the random energy surges of voltage transients and electrical noise on the power supply line, which can damage sensitive electronics such as TVs, computers, and smart appliances. They are available for 120 V, 15/20 A applications, in different form factors such as surge protective receptacles in single, duplex, four-in-one, and six receptacle configurations, as well as surge-protective power strips. These devices provide point-of-use protection and are the last line of defense in a whole-house surge protection network.

Weather-resistant receptacles

Weather-resistant (WR) receptacles are made with ultraviolet-resistant insulating materials having excellent cold-temperature impact resistance to withstand longterm exposure to weathering and abuse. Metallic components are required to be resistant to corrosion. Mandated by the 2008 National Electrical Code in outdoor damp or wet locations, WR receptacles are required in patio, deck, and pool areas.[citation needed] They are available in a variety of variations, including GFCI and tamper-resistant.

For added protection, WR receptacles should be shielded by "Extra-Duty While In-Use" or "Weather-Resistant" covers.[citation needed] These covers are ruggedly constructed to keep out moisture (either dripping or condensing), dust, debris, and insects, while providing easy access to receptacles to allow their use with power tools, trimmers, sprinkler systems, and pumps.

Leak-current detection and interruption (LCDI) cordsets

Damaged power cords of portable air conditioners have caused many electrical fires, and about 350 deaths per year.[citation needed] To combat this, the 2017 NEC requires each portable air conditioner sold in the United States to have either a leakage current detector interrupter (LCDI) or a ground-fault circuit interrupter (GFCI) protective device built into its power cord. The device can be integral with the power plug, or a separate module within 12 inches of the plug. The protection device is equipped with "Test" and "Reset" buttons on the housing. An LCDI cord has a fine wire mesh around the conductors, and circuitry to detect current leaking from the conductors to the mesh, which would happen if the cord were damaged or frayed. The plugs are normal NEMA 5-15, 5-20, 6-15, 6-20, or 6-30 plugs, depending on the air conditioner design, and are typically molded-on designs.

Color code

The color of a device neither identifies its voltage class nor power system. Because the colors are not specified by NEMA standards, the purpose of color-coding a receptacle may be set by the building owner, who may select brown, ivory, white, almond, grey, or black receptacles in the 5-15 configuration to blend with the decor of a room.

However, although colors are not standardized by NEMA, some industries utilize colors for certain applications, following de facto standards:

• A receptacle with a green dot is a so-called "hospital grade" device; The primary reason to use a hospital-grade receptacle at a patient bed location is to ensure that a receptacle with a greater contact tension is provided to minimize possibilities that an attachment plug supplying medical or life support equipment may be disconnected because the attachment plug slipped out of the receptacle. Also such devices are tested to survive harder use while limiting electrical leakage, compared to wiring devices intended for residential or commercial purposes.
• Per UL Standard ANSI/UL 498, a receptacle (any color) with an orange triangle, is an isolated ground (IG) device, where the grounding pin of the receptacle is connected to ground independently of the frame of the receptacle and wiring outlet box. This is also a requirement of the National Electrical Code (NFPA 70), Article 406. While neither UL nor the CSA require the face of the receptacle to be a specific color, most IG receptacles are orange.
• A blue receptacle may indicate built-in surge suppressors.
• A red receptacle may indicate a special-service outlet such as one connected to an emergency standby power source. The Canadian Electrical Code requires that "essential" receptacles in hospitals, connected to emergency power systems, must be red.
• At least one manufacturer makes a yellow receptacle, which identifies it as corrosion-resistant.

Break-away tabs

Most duplex receptacles have metal tabs connecting the top and bottom receptacles. These tabs can be broken off to allow the top and bottom receptacles to be wired onto separate circuits. This may allow for one switched receptacle for a lamp, or for two separate supply circuits when heavy loads are anticipated. Two branch circuits may optionally share a common neutral wire terminating on duplex receptacles, a condition sometimes referred to as "split-wiring", "split-receptacle", or "half-split".

Related standards

The dimensions and configurations for NEMA connectors are given in ANSI/NEMA standard WD-6. Underwriters Laboratories maintains UL Standard 498, which specifies construction performance (e.g. durability, electrical safety, and fire-resistance) for NEMA connectors. These additional requirements allow connectors to be manufactured to be compliant with the National Electrical Code. The Defense Logistics Agency and General Services Administration maintain Federal Specification W-C-596 and its associated specification sheets. This specification references WD-6 and UL 498, and provides additional durability and electrical safety performance criteria for connectors intended for military use.