NEMA connector: Difference between revisions

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== Precedents ==
{{Main|History of AC power plugs and sockets}}
In the early days of electrification, residential use was almost exclusively for illumination, with rooms normally having just a single electrical outlet spot in the center. Along with his lightbulb, [[Thomas Edison]] developed the [[Edison screw]] in the early 1880s, for which he received a patent inpatented 1881.<ref name="USP0251554_1881">{{US patent|0251554}} (applied 1881, awarded 1881) Two examples of screw system appear, including the kerosene-can lid, but their overall formations are incompatible with today's Edison sockets. No explicit claims for the screw system. Beware patents.google.com's preview mode lacks several pages, must download full PDF.</ref> The Edison screw was very successful, and quickly became the first ''de facto'' standard for electric connection.<ref>{{Cite journal |last=Schroeder |first=Fred E. H. |date=1986-01-01 |title=More "Small Things Forgotten": Domestic Electrical Plugs and Receptacles, 1881-1931 |journal=Technology and Culture |volume=27 |issue=3 |pages=525–543 |doi=10.2307/3105384 |jstor=3105384|s2cid=112928824 }}</ref> In the early 1900s, table and floor lamps became more popular, and sockets were mounted on walls for secondary connections. One big disadvantage of screw connectors was that the cord inevitably got twisted after being connected to the receptacle.
 
=== Harvey Hubbell's inventions ===
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==== Other American manufacturers ====
It is worth noting that in addition to Hubbell's system, circulated a large variety of different plugs and receptacles, some of them compatible with Hubbell's, some not. In 1919, Hubbell unsuccessfully tried to prevent other manufacturers from making receptacles and plugs to the dimensions used by Hubbell. The report of the court proceedings<ref name="HH-v-GEC">[Harvey Hubbell Inc. V. General Electric Co. et.al. (262 Fed.Rep. 155) District Court of the United States, Southern District of New York, October 20, 1919. Reported in "The Trade Mark Reporter" Vol 10, 1920, Pages 164 - 175164–175. The court observed that Hubbell's plugs were readily distinguishable from those of other makes by the provision of "nicks" in the pins of Hubbell's plug pins, designed to provide retention when mated with Hubbell's receptacles, so there was no confusion as to their origin. The report of the trial is available from Google Books here: https://books.google.co.uk/books?id=XOgsAAAAYAAJ&printsec=frontcover&dq=the+trademark+reporter+volume+10&hl=en&sa=X&ved=0ahUKEwjHgZr29YvXAhUCSRoKHWQaDOAQ6AEIJjAA#v=onepage&q&f=false</ref> includes a comprehensive review of the development of the art in the US prior to 1919, based on evidence presented to the Court. Separable plugs had been available for more than a decade prior to Hubbell's 1904 design.
 
=== NEMA ===
In 1926, the [[National Electrical Manufacturers Association]] (NEMA) was founded by the merger of the Electric Power Club and the Associated Manufacturers of Electrical Supplies<ref>{{Cite web |date=2020-03-06 |title=History |url=https://www.nema.org/about/history |access-date=2022-09-30 |website=NEMA |language=en}}</ref> and represented manufacturing companies of the electrical segment in a national level. NEMA provided a forum between companies for reaching standardization, but it was not until the 1940s that NEMA started to publish standards on receptacles and plugs, much later than UK,<ref>{{Cite web |title=Museum of Plugs and Sockets: history of British plugs and sockets |url=https://www.plugsocketmuseum.nl/British-plugSocket_history.html |access-date=2022-09-30 |website=www.plugsocketmuseum.nl}}</ref> France and Germany.<ref>{{Cite web |title=Museum of Plugs and Sockets: DIN VDE 9400 - 94039400–9403 |url=https://www.plugsocketmuseum.nl/ContEUR_VDE9400.html |access-date=2022-09-30 |website=www.plugsocketmuseum.nl}}</ref> Since NEMA was a forum between manufacturers and not an governmental body, any decision had to be thoroughly discussed and agreed upon by its members, which substantially slowed the standardization process.
 
==Nomenclature==
[[File:NEMA simplified pins.svg|thumb|350px|alt="Row and column table of NEMA receptacles."|NEMA receptacles, with their common US uses listed (in purple text)]]
NEMA connectors are named following an alphanumeric code consisting of: <blockquote>(prefix "L" (lockingfor typeslocking), numerals, a hyphen, numerals, (suffix "R" orfor receptacle, "P" for "receptacle"plug).</blockquote>There orare two basic classifications of NEMA connectors: straight-blade and locking. The metal conductive blades are often informally called ''prongs'' (as in ''3-prong "plug"''). Numbers prefixed by 'L' are curved-blade, twist-locking connectors. Twist-locking types are used for heavy industrial and commercial equipment, where increased protection against accidental disconnection is required.
 
The numerals preceding the hyphen encode the number of poles (current-carrying terminals) and wires connected to it, the voltage, and single- or [[three-phase]] power. {{citation needed|date=August 2024}} A connector with ground terminal is described as havinghas more wires than poles, e.g.: two-pole, three-wire; or four-pole, five-wire; etc. A non-groundinggrounded device may be two-pole, two-wire; three-pole, three-wire; etc. {{citation needed|date=August 2024}}
There are two basic classifications of NEMA connectors: straight-blade and locking. The metal conductive blades are often informally called "prongs" (as in "3-prong plug"). Numbers prefixed by 'L' are curved-blade, twist-locking connectors. Twist-locking types are used for heavy industrial and commercial equipment, where increased protection against accidental disconnection is required.
 
The numerals following the hyphen is the current rating of the device in amperes. This number is followed by the letter 'R' to indicate a receptacle (socket) or 'P' to indicate a plug (prongs).
The numerals preceding the hyphen encode the number of poles (current-carrying terminals) and wires connected to it, the voltage, and single- or [[three-phase]] power. {{citation needed|date=August 2024}} A connector with ground terminal is described as having more wires than poles, e.g. two-pole, three-wire; or four-pole, five-wire; etc. A non-grounding device may be two-pole, two-wire; three-pole, three-wire; etc. {{citation needed|date=August 2024}}
 
The numerals following the hyphen is the current rating of the device in amperes. This number is followed by the letter 'R' to indicate a receptacle or 'P' to indicate a plug.
 
As an example, the 5-15R is the common 125&nbsp;V two-pole, three-wire receptacle rated for 15&nbsp;A. The L5-15R, while sharing the same electrical rating, is a locking design that is not physically compatible with the straight-blade 5-15 design. The 5-30R has the same two-pole, three-wire configuration and 125&nbsp;V rating, but is rated for 30&nbsp;A.
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Other types of NEMA connectors that do not follow this nomenclature include: the ML series (so-called "Midget Locking" connectors named for their diminutive size), TT (for connecting [[travel trailers]] and other [[recreational vehicles]] to external power sources), SS series ("ship-to-shore" connectors for connecting boats to [[shore power]]) and the FSL series (used in military and aircraft applications).
 
The small hole near the end of the power (non-ground) blades of some NEMA plugs is used for convenience in manufacturing; if present, it must be of specified diameter and position.<ref name=WD6>{{Cite book|url=https://archive.org/details/NEMA-WD-6-2016/page/n24/mode/1up|access-date=2021-08-15|title=ANSI/NEMA WD 6-2016: Wiring Devices - {{dash}}Dimensional Specifications|publisher=National Electrical Manufacturer's Association|year=2016|pages=17}}</ref> Small specialized [[padlock]]s are available to fit these holes, allowing "[[Lockout-tagout|lockout]]" of hazardous equipment, by physically preventing insertion of locked plugs into a power receptacle. Since at least 1949, numerous receptacle devices have also been invented to use these holes to hold the prongs inside the receptacle slots, using a corresponding latch or locking mechanism. <ref> [https://patents.google.com/patent/US2664734 e.g., US Patent 2,664,734, H.McEneaney, issued January 5, 1954] </ref>
 
The blades of a NEMA connector are identified within the dimensional standard as follows: 'G' identifies the grounding conductor, 'W' identifies the (grounded) neutral conductor, and 'X', 'Y', and 'Z' are the "hot" line conductors. Single-phase connectors have only a single terminal identified as 'X' or two terminals, 'X' and 'Y'. Three-phase connectors will use 'X', 'Y' and 'Z'.<ref name="WD6"/>
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Criticism has been aimed{{By whom|date=October 2021}} at the design leaving a gap with exposed prongs. This safety flaw has been exploited by a January 2020 [[Internet phenomenon]] known as the ''[[Outlet challenge]]'', where conductive materials, usually coins or paper clips were dropped into the gap, causing [[electric spark]]s, which once led to a building [[Emergency evacuation|evacuation]] in [[Westford Academy]].<ref>{{cite web |last1=Lee |first1=Bruce Y. |title=What Is The 'Outlet Challenge'? How It Can Electrocute Or Burn You |url=https://www.forbes.com/sites/brucelee/2020/02/23/what-is-the-outlet-challenge-how-it-can-electrocute-or-burn-you/ |website=Forbes |language=en |date=2020-02-23}}</ref><ref>{{cite web |title=Dangerous TikTok Challenge Sparks Warning From Firefighters |url=https://www.nbcboston.com/news/local/fire-officials-warn-parents-about-outlet-challenge/2065446/ |website=NBC Boston |date=2020-01-21}}</ref><ref>{{cite news |title=Authorities warn about dangerous TikTok 'outlet' challenge |url=https://abcnews.go.com/US/authorities-warn-dangerous-tiktok-outlet-challenge/story?id=68531391 |access-date=5 November 2020 |work=ABC News |date=2020-01-25 |language=en}}</ref>
{{anchor|Receptacle chart}}<!-- Shorter, more convenient, anchor -->
{{anchor|Receptacle and plug chart (nonnon–twist-twist lock)}}<!--Note: Pages like "NEMA 5-15P" redirect to this anchor.-->
{| class="wikitable" style="text-align: center;"
|+NEMA Receptacle chart (non-twist lock)<ref name=WD6/>
Line 80 ⟶ 78:
!125 V
!1
|[[File:NEMA_1-15R.svg|frameless|60x60px|class=skin-invert]]<br>1-15R
|[[File:NEMA_1-15P.svg|frameless|60x60px|class=skin-invert]]<br>1-15P
|''5-20R''
|[[File:NEMA_1-20P.svg|frameless|60x60px|class=skin-invert]]<br>1-20P
|''5-30R''
|[[File:NEMA_1-30P.svg|frameless|60x60px|class=skin-invert]]<br>1-30P
| colspan="2" | -
| colspan="2" | -
Line 94 ⟶ 92:
!2
|''6-15R''
|[[File:NEMA_2-15P.svg|frameless|60x60px|class=skin-invert]]<br>2-15P
|[[File:NEMA_2-20R.svg|frameless|60x60px|class=skin-invert]]<br>2-20R
|[[File:NEMA_2-20P.svg|frameless|60x60px|class=skin-invert]]<br>2-20P
|[[File:NEMA_2-30R.svg|frameless|60x60px|class=skin-invert]]<br>2-30R
|[[File:NEMA_2-30P.svg|frameless|60x60px|class=skin-invert]]<br>2-30P
| colspan="2" | -
| colspan="2" | -
Line 118 ⟶ 116:
!125 V
!5
|[[File:NEMA_5-15R.svg|frameless|60x60px|class=skin-invert]]<br>5-15R
|[[File:NEMA_5-15P.svg|frameless|60x60px|class=skin-invert]]<br>5-15P
|[[File:NEMA_5-20R.svg|frameless|60x60px|class=skin-invert]]<br>5-20R
|[[File:NEMA_5-20P.svg|frameless|60x60px|class=skin-invert]]<br>5-20P
|[[File:NEMA_5-30R.svg|frameless|60x60px|class=skin-invert]]<br>5-30R
|[[File:NEMA_5-30P.svg|frameless|60x60px|class=skin-invert]]<br>5-30P
|[[File:NEMA_5-50R.svg|frameless|60x60px|class=skin-invert]]<br>5-50R
|[[File:NEMA_5-50P.svg|frameless|60x60px|class=skin-invert]]<br>5-50P
| colspan="2" | -
| colspan="2" | -
Line 132 ⟶ 130:
!250 V
!6
|[[File:NEMA_6-15R.svg|frameless|60x60px|class=skin-invert]]<br>6-15R
|[[File:NEMA_6-15P.svg|frameless|60x60px|class=skin-invert]]<br>6-15P
|[[File:NEMA_6-20R.svg|frameless|60x60px|class=skin-invert]]<br>6-20R
|[[File:NEMA_6-20P.svg|frameless|60x60px|class=skin-invert]]<br>6-20P
|[[File:NEMA_6-30R.svg|frameless|60x60px|class=skin-invert]]<br>6-30R
|[[File:NEMA_6-30P.svg|frameless|60x60px|class=skin-invert]]<br>6-30P
|[[File:NEMA_6-50R.svg|frameless|60x60px|class=skin-invert]]<br>6-50R
|[[File:NEMA_6-50P.svg|frameless|60x60px|class=skin-invert]]<br>6-50P
| colspan="2" | -
| colspan="2" | -
Line 146 ⟶ 144:
!277 V
!7
|[[File:NEMA_7-15R.svg|frameless|60x60px|class=skin-invert]]<br>7-15R
|[[File:NEMA_7-15P.svg|frameless|60x60px|class=skin-invert]]<br>7-15P
|[[File:NEMA_7-20R.svg|frameless|60x60px|class=skin-invert]]<br>7-20R
|[[File:NEMA_7-20P.svg|frameless|60x60px|class=skin-invert]]<br>7-20P
|[[File:NEMA_7-30R.svg|frameless|60x60px|class=skin-invert]]<br>7-30R
|[[File:NEMA_7-30P.svg|frameless|60x60px|class=skin-invert]]<br>7-30P
|[[File:NEMA_7-50R.svg|frameless|60x60px|class=skin-invert]]<br>7-50R
|[[File:NEMA_7-50P.svg|frameless|60x60px|class=skin-invert]]<br>7-50P
| colspan="2" | -
| colspan="2" | -
Line 173 ⟶ 171:
!10
| colspan="2" | -
|[[File:NEMA_10-20R.svg|frameless|60x60px|class=skin-invert]]<br>10-20R
|[[File:NEMA_10-20P.svg|frameless|60x60px|class=skin-invert]]<br>10-20P
|[[File:NEMA_10-30R.svg|frameless|60x60px|class=skin-invert]]<br>10-30R
|[[File:NEMA_10-30P.svg|frameless|60x60px|class=skin-invert]]<br>10-30P
|[[File:NEMA_10-50R.svg|frameless|60x60px|class=skin-invert]]<br>10-50R
|[[File:NEMA_10-50P.svg|frameless|60x60px|class=skin-invert]]<br>10-50P
| colspan="2" | -
| colspan="2" | -
Line 186 ⟶ 184:
250 V
!11
|[[File:NEMA_11-15R.svg|frameless|60x60px|class=skin-invert]]<br>11-15R
|[[File:NEMA_11-15P.svg|frameless|60x60px|class=skin-invert]]<br>11-15P
|[[File:NEMA_11-20R.svg|frameless|60x60px|class=skin-invert]]<br>11-20R
|[[File:NEMA_11-20P.svg|frameless|60x60px|class=skin-invert]]<br>11-20P
|[[File:NEMA_11-30R.svg|frameless|60x60px|class=skin-invert]]<br>11-30R
|[[File:NEMA_11-30P.svg|frameless|60x60px|class=skin-invert]]<br>11-30P
|[[File:NEMA_11-50R.svg|frameless|60x60px|class=skin-invert]]<br>11-50R
|[[File:NEMA_11-50P.svg|frameless|60x60px|class=skin-invert]]<br>11-50P
| colspan="2" | -
| colspan="2" | -
Line 212 ⟶ 210:
!125/ 250 V
!14
|[[File:NEMA_14-15R.svg|frameless|60x60px|class=skin-invert]]<br>14-15R
|[[File:NEMA_14-15P.svg|frameless|60x60px|class=skin-invert]]<br>14-15P
|[[File:NEMA_14-20R.svg|frameless|60x60px|class=skin-invert]]<br>14-20R
|[[File:NEMA_14-20P.svg|frameless|60x60px|class=skin-invert]]<br>14-20P
|[[File:NEMA_14-30R.svg|frameless|60x60px|class=skin-invert]]<br>14-30R
|[[File:NEMA_14-30P.svg|frameless|60x60px|class=skin-invert]]<br>14-30P
|[[File:NEMA_14-50R.svg|frameless|60x60px|class=skin-invert]]<br>14-50R
|[[File:NEMA_14-50P.svg|frameless|60x60px|class=skin-invert]]<br>14-50P
|[[File:NEMA_14-60R.svg|frameless|60x60px|class=skin-invert]]<br>14-60R
|[[File:NEMA_14-60P.svg|frameless|60x60px|class=skin-invert]]<br>14-60P
| colspan="2" | -
| colspan="2" | -
Line 228 ⟶ 226:
250 V
!15
|[[File:NEMA_15-15R.svg|frameless|60x60px|class=skin-invert]]<br>15-15R
|[[File:NEMA_15-15P.svg|frameless|60x60px|class=skin-invert]]<br>15-15P
|[[File:NEMA_15-20R.svg|frameless|60x60px|class=skin-invert]]<br>15-20R
|[[File:NEMA_15-20P.svg|frameless|60x60px|class=skin-invert]]<br>15-20P
|[[File:NEMA_15-30R.svg|frameless|60x60px|class=skin-invert]]<br>15-30R
|[[File:NEMA_15-30P.svg|frameless|60x60px|class=skin-invert]]<br>15-30P
|[[File:NEMA_15-50R.svg|frameless|60x60px|class=skin-invert]]<br>15-50R
|[[File:NEMA_15-50P.svg|frameless|60x60px|class=skin-invert]]<br>15-50P
|[[File:NEMA_15-60R.svg|frameless|60x60px|class=skin-invert]]<br>15-60R
|[[File:NEMA_15-60P.svg|frameless|60x60px|class=skin-invert]]<br>15-60P
| colspan="2" | -
| colspan="2" | -
Line 244 ⟶ 242:
120/ 208 V
!18
|[[File:NEMA_18-15R.svg|frameless|60x60px|class=skin-invert]]<br>18-15R
|[[File:NEMA_18-15P.svg|frameless|60x60px|class=skin-invert]]<br>18-15P
|[[File:NEMA_18-20R.svg|frameless|60x60px|class=skin-invert]]<br>18-20R
|[[File:NEMA_18-20P.svg|frameless|60x60px|class=skin-invert]]<br>18-20P
|[[File:NEMA_18-30R.svg|frameless|60x60px|class=skin-invert]]<br>18-30R
|[[File:NEMA_18-30P.svg|frameless|60x60px|class=skin-invert]]<br>18-30P
|[[File:NEMA_18-50R.svg|frameless|60x60px|class=skin-invert]]<br>18-50R
|[[File:NEMA_18-50P.svg|frameless|60x60px|class=skin-invert]]<br>18-50P
|[[File:NEMA_18-60R.svg|frameless|60x60px|class=skin-invert]]<br>18-60R
|[[File:NEMA_18-60P.svg|frameless|60x60px|class=skin-invert]]<br>18-60P
| colspan="2" | -
| colspan="2" | -
Line 277 ⟶ 275:
! no !! yes !! no !! yes !! no !! yes !! no !! yes
|-
| hot–neutral
| hot-neutral
| 120&nbsp;V || [[#NEMA_1|1]]; [[#ML|ML1]] || [[#NEMA_5|5]]; [[#NEMA_TT-30|TT]];
[[#SS|SS1]]; [[#ML|ML2]]
Line 284 ⟶ 282:
| 240&nbsp;V || - || 25
|-
| hot–hot
| hot-hot
| 240&nbsp;V (split-phase)<br />208&nbsp;V (wye) || [[#NEMA_2|2]] || [[#NEMA_6|6]]
| 480&nbsp;V || - || [[#NEMA_8|8]]
Line 290 ⟶ 288:
| 415&nbsp;V || - || -
|-
| hot–hot–neutral
| hot-hot-neutral
| 120/240&nbsp;V (split-
phase)<br />120/208&nbsp;V (wye)
Line 301 ⟶ 299:
| 240/415&nbsp;V || - || -
|-
| hot–hot–hot
| hot-hot-hot
| 240&nbsp;V (delta)<br />208&nbsp;V (wye) || [[#NEMA_11|11]] || [[#NEMA_15|15]]
| 480&nbsp;V || [[#NEMA_12|12]] || [[#NEMA_16|16]]
Line 307 ⟶ 305:
| 415&nbsp;V || - || -
|-
| hot–hot–hot–neutral
| hot-hot-hot-neutral
| 120/208&nbsp;V || [[#NEMA_18|18]] || [[#NEMA_21|21]]
| 277/480&nbsp;V || [[#NEMA_19|19]] || [[#NEMA_22|22]]
Line 374 ⟶ 372:
In [[stage lighting]] for film and theater, this connector is sometimes informally known as ''PBG'' (''Parallel Blade with Ground''), ''U-ground'', ''Edison'' or ''Hubbell'', the name of a common manufacturer.<ref>Drew Campbell ''Technical Film and Tv for Nontechnical People'', Skyhorse Publishing Inc., 2002 {{ISBN|1581159986}} Chapter 9</ref> (The name "Hubbell" can be confusing as several different connectors share this name depending on the company, industry, and use.) In the motion picture and TV production industries, an extension cord that uses this type of connector (usually with 12 AWG or 10 AWG wire)<ref name="tftv">{{cite book|last=Campbell|first=Drew|title=Technical Film and TV for Nontechnical People|publisher=Allworth|year=2002|page=133|isbn=1-58115-229-9|url=https://books.google.com/books?id=CARrSo742ycC|access-date=2010-02-16}}</ref> is called a "stinger".{{citation needed|date=November 2013}} Generally, [[lighting technician]]s use these extension cords to deliver power to lights rated at 2,000&nbsp;watts or less.<ref name="slth">{{cite book|last=Box|first=Harry C.|title=Set Lighting Technician's Handbook: Film Lighting Equipment, Practice, and Electrical Distribution|publisher=Focal|year=2003|edition=3rd|page=20|isbn=0-240-80495-3|url=https://books.google.com/books?id=EfUlyxSlBYMC|access-date=2010-02-16}}</ref>
 
Internationally, the NEMA 5-15P plug and NEMA 5-15R receptacle are the basis for the [[International Electrotechnical Commission]]'s IEC 60906-2 standard ''IEC system of plugs and sockets-outlets for household and similar purposes - {{dash}}Part 2: Plugs and socket-outlets 15 A 125 V a.c. and 20 A 125 V a.c.''<ref>{{cite web|url=https://webstore.iec.ch/publication/3883|title=IEC 60906-2:2011 IEC Webstore|website=webstore.iec.ch|access-date=2016-04-13}}</ref>
 
===NEMA 6===
Line 419 ⟶ 417:
All NEMA 14 devices offer two hots, a neutral, and a ground, allowing for both 120 and 240&nbsp;V when supplied by [[Split-phase electric power|split-phase power]], or 120 and 208&nbsp;V if the supply is [[three-phase electric power|three-phase]]. The 14-30 has a rating of 30&nbsp;A, and an L-shaped neutral blade. The 14-50 has a rating of 50&nbsp;A, and a straight neutral blade sized so that it does not mate with 14-30 connectors.
 
NEMA 14-50 devices are frequently found in [[RV park]]s, since they are used for "[[Shorepower|shore power]]" connections of larger [[recreational vehicle]]s. Also, it was formerly common to connect [[mobile home]]s to utility power via a 14-50 device. Newer applications include electric vehicle charging.<ref>{{cite web |title=TeslaMotors.com: Go Electric - {{dash}}Ready, Set, Charge |url=http://www.teslamotors.com/goelectric#charging |publisher=Tesla Motors, Inc. |access-date=7 June 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130620090910/http://www.teslamotors.com/goelectric#charging |archive-date=20 June 2013 }}</ref> The 6-50 is a smaller size receptacle lacking a neutral fourth prong, exclusively providing 240 V, also used for electric vehicle [[charging station]] purposes.<ref name=":0">{{Cite web |date=June 24, 2021 |title=Home EV charging: How to know which plug type is right for you |url=https://www.enelxway.com/us/en/resources/blog/home-ev-charging-how-to-know-which-plug-type-is-right-for-you}}</ref>
 
{{gallery|width=150 |height=150|align=center