Schuko
SchuKo is an acronym for Schu TZ Ko ntakt and refers to a system of connectors ( CEE 7/4 ) and outlets (CEE 7/3), which in Europe is very common. International, this system is also available as plug-type F known and some are compatible with the " French " system called plug-type E . The term is protected and administered by the SCHUKO trademark association.
history
In 1925 Albert Büttner , founder of Bayerische Elektro Zubehör GmbH (today ABL Sursum Bayerische Elektro Zubehör GmbH and Co. KG) developed the SCHUKO plug; for this he was granted patent DE 489003 in 1930 for a plug with earthing device. Büttner's patent DE 370538 is often cited as a reference to Schuko, but it actually refers to a method of holding all parts of the plug or socket together with a single screw; here there is no mention of the earth connection.
The patent, which then showed the Schuko plug-in system in the form it has been using until today, was registered by Siemens-Schuckertwerke AG on December 24, 1929 in Germany. Siemens chief engineer Wilhelm Klement was named as the inventor (DRP 567906, registered on December 24, 1929; issued on January 12, 1932).
construction
The Schuko plug has two round contact pins with a diameter of 4.8 mm, a length of 19 mm and an axis spacing of 19 mm for the outer conductor and neutral conductor . A third pole , the protective contact , is intended to divert fault currents that can occur, for example, in the event of a short to body as soon as the electrical circuit is closed by the other two poles. Therefore, the connection with the protective contact must be made first, i.e. it must be leading . With the Schuko plug, this is guaranteed by the contact surfaces on the plug side and the associated contact springs on the socket.
The base level of the cover is surrounded by an approximately 19 mm high collar for contact protection. This means that the contact pins can only be touched from the side as long as they do not yet touch the contact sockets.
Connector
The Schuko plug is a plug-in device that can be plugged in and disconnected as intended under electrical voltage or load. A prerequisite for such a plug device is the leading contact of the protective conductor, which is fulfilled with a Schuko plug. The opposite is a plug connection that must never be connected and disconnected under load and sometimes not even under electrical voltage.
connection
A three-core cable is used for the connection: an outer and a neutral conductor plus the earthed protective conductor . Since the German Schuko connection is not reverse polarity protected, it does not matter with CEE 7/4 how the outer conductor and neutral conductor are connected.
Electrically conductive housing materials must be connected to the protective conductor. If the device has protective insulation , a Euro plug and a contour plug (CEE 7/17) with a two-core cable can also be used. If such devices are nevertheless provided with a grounding line, this only needs to be connected to the Schuko plug and short cut on the device side.
Voltage and current
When using the Schuko plug system , it is assumed that a voltage of 207 V to 253 V ( nominal voltage : 230 V, tolerance ± 10%) at 50 Hz (tolerance ± 2.5 Hz) is available. Standard design earthed sockets may be fused with a maximum of 16 amps.
For high continuous currents (also up to a maximum of 16 A), the blue connectors according to IEC 60309 , commonly known as "camping or caravan connectors", are better suited because their contacts are larger and a higher contact pressure is possible. These connectors are also suitable for outdoor use.
Due to the more than double the nominal voltage compared to the 110 V US blade connector system ( connector type A or B ), the Schuko system can - for physical reasons - transmit more than twice the power with the same wire cross-sections and nominal currents.
compatibility
The "French" 2P + T system (plug type E) is mechanically incompatible with the Schuko system despite its electrical compatibility, as the earth contact springs of the sockets obstruct the French plugs and the French earthing pin obstruct the Schuko plug. That is why the more general system CEE 7/7 was developed. It is a type of connector that mechanically combines both protection systems. They have springs for the French earthing spigot and contact surfaces for the earth contact springs of the Schuko system.
There is also the Gost-7396 system, a Schuko variant, which is characterized by a smaller diameter of the current-carrying pins and is used in some Eastern European countries and parts of Russia.
The CEE 7/7 system has a CEE 7/17 variant without protective contacts, the so-called contour plug. The plug has the same footprint, but is not as deep and has suitable cutouts for both protective contact systems. This plug is often used in devices with protective insulation, such as vacuum cleaners or hair dryers, whose power consumption is higher than 2.5 A and is therefore no longer permitted in the area of application of the euro plug. Due to the approval for higher currents, the pins of the contour plug are conductive over their full length, the cover with the cut-outs for the grounding contacts is for finger safety.
The Euro plug according to CEE 7/16 is a minimalist, schuko-compatible plug variant without protective contact. With him, the power contacts are still at the same distance, but thinner. Due to the thinner contacts, this plug also fits into Italian or Spanish sockets. Due to the flat design and the omitted protective contacts, this connector also fits in Switzerland ( SEV 1011 ) and Denmark ( connector type K ). It is used for double-insulated devices, but because of the thinner contacts, it is not approved for powerful devices (maximum 2.5 A). The fact that the plastic pins cover the conductors and only have a short metallic cover at the front makes the Euro plug in the large round opening of a Schuko socket safe to touch; The fact that the pins do not run parallel, but rather slightly conically to each other and are anchored somewhat elastically, makes them more secure in contact.
safety
Protection against accidental contact is provided by the collar of the socket, which surrounds the entire plug base area, and the contact that only takes place when the plug is half inserted. Since this protective collar is not available on Euro plugs, these only have 9 mm long conductive contact pins, the top 10 mm are insulated. The insertion of round plugs, which were previously used for devices of protection class 0 (ungrounded, no protective insulation according to protection class II), into earthed sockets is prevented by the protective collar. Conversely, non-earthed sockets should also be able to accept Schuko plugs, but then there is not always contact protection, since such sockets often only have a small or no protective collar. In this case, there is also no grounding, so that protection against electric shock is only provided by the insulating properties of the surrounding area.
Due to the dimensions of the plug-in system, a single-pole insertion of the plug into a protective contact socket or coupling is impossible. This is not always the case for unearthed sockets or couplings.
Due to the leading protective contact, the conductive housing parts of devices of protection class I are earthed before the contact pins reach the live sockets. The protective measures against indirect contact are effective immediately.
Reverse polarity protection
The Schuko system is not reverse polarity protected . The outer conductor can be exchanged with the neutral conductor by turning the plug by 180 °.
When the Schuko system was introduced after the First World War, the polarity of the two current-carrying conductors did not play a role in terms of safety: At that time it was still common to work with a triangular voltage of 220 V ( three-phase current 3 × 127 V). With this connection technology, both current-carrying conductors had the same voltage with respect to earth, and it was therefore not necessary to differentiate between the two conductors.
In today's common TN systems with a star voltage of initially 220, today 230 V (triangular voltage initially 380, today 400 V), on the other hand, the full voltage to earth is applied to one conductor, the outer conductor. The other conductor, the neutral conductor, is earthed via the equipotential bonding rail of the building installation. However, because it carries the current, it has a higher voltage than the protective conductor (voltage drop on the conductor).
All newer connector standards, such as the British system introduced in 1947 (connector type G) or the IEC-60906-1 system proposed in 1986 as a uniform solution worldwide , are designed to be protected against polarity reversal. Compared to the Schuko system, such modern systems have the advantage that even a single-pole device switch always switches off the external conductor carrying voltage to earth. For example, it is then ensured that the voltage is always applied to the foot contact of an incandescent lamp and not to the thread that is easier to touch and that no contact of the socket is live when switched off. With the Schuko system, this depends on the direction in which the plug is inserted into the socket. There are no regulations stating which side of a Schuko socket the outer conductor should be connected to. However, it is advisable to keep this consistent within a system. If the outer conductor is connected on the left with horizontally arranged poles, then compatibility with the French system is at least established in what is certainly the most common type of use (angle plug with cable pointing downwards).
Increased contact protection
The sockets are generally not separately secured against the insertion of objects. In Germany, however, such security is mandatory in kindergartens. This topic is often dealt with under the headings " child safety devices for sockets" or "socket outlet safety devices". The aim is to prevent electrical accidents .
There are sockets with integrated "increased contact protection". Today's models usually remain closed when only one of the two openings is pressed. Only when a plug exerts even pressure contact on both openings does the closure spring back and release the openings.
Covers are available for retrofitting and must be removed before using the socket. This can be done with a special key or by inserting the contacts of the plug.
In contrast, so-called “child protection plates” remain in the socket. The openings of the socket are released when the plug is pressed into the recesses of the plate and rotated at the same time. These inserts allow the contact pins to penetrate less deeply, which means that under certain circumstances no secure contact is made. In the worst case, this can lead to the plug-in system heating up if the load is greater. According to the Austrian regulations for electrical engineering ÖVE-IG 31c / 1988, the dimensions of the plug-in devices may not be changed by subsequently attached devices, which is why a ban on placing them on the market was pronounced for these uses. Even according to the VDE regulations, the dimensions may not be changed.
Compared to other systems
In comparison with the even older American system and systems without protective contacts, the Schuko system was considered one of the safest plug-in systems many decades after its introduction, which is characterized by:
- Finger safety (no contacts - apart from the protective contacts - can be reached with the fingers)
- Leading protective contact
- secure mechanical hold
- good mechanical strength
- strong current-carrying contacts (up to 16 A)
In the meantime, however, the advantages of the Schuko system can no longer be compared with those of modern concepts. The main problems are:
- Lack of reverse polarity protection, which is desirable in modern TN networks,
- low protection against moisture and contact with foreign bodies (e.g. children playing with knitting needles - colloquially called child protection). Child safety locks (increased protection against accidental contact according to VDE0620) are already integrated by well-known socket manufacturers and can be converted to protection class IP44 with accessories .
- Much larger connector dimensions than would be necessary today thanks to modern plastic injection molding technology for good mechanical strength and
- mechanically susceptible protective contacts that are easy to bend or contaminate with paint when painted.
For these reasons, the Schuko system was rejected as a European or worldwide standard and instead the IEC-60906-1 system was proposed in 1986 as a modern successor; practical initiatives to introduce it have fallen asleep in Europe since the mid-1990s.
distribution
The more general system CEE 7/7 is one of the most common plug-in systems in the world - at least in terms of the number of plugs and sockets.
The following countries, among others, use the CEE 7/4 Schuko system as their primary system:
- Afghanistan
- Algeria
- Andorra
- Bosnia Herzegovina
- Belarus
- Bulgaria
- Germany
- Estonia
- Finland
- Greece
- Indonesia
- Iran
- Iceland
- Italy / San Marino / Vatican State (standard: CEI 23-50 P 30, S 30, S 31, together with CEI 23-50 L-type plugs)
- Korea (standard: KSC 8305)
- Croatia
- Latvia
- Lithuania
- Luxembourg
- North Macedonia
- Montenegro
- Republic of Moldova
- Netherlands
- Norway
- Austria
- Portugal
- Romania
- Russia
- Sweden
- Serbia
- Slovenia
- Spain
- South Korea
- Syria (there is no official standard, often used)
- Turkey (there is no official standard, often used)
- Ukraine
- Hungary
These countries, among others, use the "French" system, which is compatible with CEE 7/7:
- Belgium
- France and part of the former colonies
- Morocco
- Monaco
- Poland
- Slovakia
- Czech Republic
- Tunisia
These European countries have their own mechanically and partially electrically incompatible systems:
- Denmark : plug type K
- Great Britain , Ireland , Malta and Cyprus : plug type G
- Italy : Plug type L , but with newer sockets possible as a combination of type L and Schuko
- Switzerland , Liechtenstein : SEV 1011 (the installation of Schuko sockets is not permitted there)
Testing, approval, certification
In the respective countries that use the Schuko or CEE 7/7 plug, there are government organizations and associations that carry out the testing, approval and certification of these plugs and systems. These facilities generally take on the certification of electrical devices and installation material and thus guarantee a constant level of safety. In Europe this is done by the following companies:
| country | organization |
|---|---|
| Austria | ÖVE |
| Switzerland | Electrosuisse |
| Germany | VDE |
| Finland | FIMKO |
| Netherlands | KEMA |
| Russia | GOST-R |
| Belgium | CEBEC |
| Norway | NEMKO |
| Denmark | DEMKO |
| France | LCIE |
| Italy | IMQ |
| Sweden | SEMKO |
Since certification is voluntary and expensive, many manufacturers do without certification in all countries. Thanks to European liberalization, however, non-certified devices can now also be used. The certifications are largely equivalent to each other. The end user can therefore care less about the imprint as long as at least one is attached to it.
particularities
Colours
In some safety-critical areas such as hospitals, Schuko sockets in different colors are used. The color coding is not standardized. The following colors are often chosen:
| colour | labeling | designation | meaning |
|---|---|---|---|
| (neutral) | normal socket, connected directly to the local supply network | ||
| red | it | IT network | IT network with overvoltage protection, separate distributions. Some of these connections are protected by galvanic isolation from the mains using isolating transformers. In addition, the connections can be bridged with the help of a UPS in the event of a brief failure for a few seconds. |
| orange | ZSV | Central security supply | Network with uninterruptible supply using a battery-backed network. For the further supply of critical infrastructure such as operating theater lighting, ventilators, heart-lung machines and patient monitoring in intensive care. |
| green | SV | Security supply | As with the ZSV, the safety supply can be battery-backed. However, this can usually only bridge the time until the supply from an emergency power system is available. |
| (unspecific) | filtered, but not fail-safe network; Here there is a clean current pattern and therefore no non-linear consumers should be connected there | ||
| (unspecific) | X-ray, CTG, ... | specially marked sockets for med. Device; X-ray, CTG, etc., which are secured with an AC / DC sensitive residual current circuit breaker . This also detects creeping direct currents against earth. |
In some workshops, red Schuko sockets indicate galvanic separation from the rest of the power supply, for example via an isolating transformer ( IT system ). Green can also mean that the corresponding sockets are not disconnected from the mains by emergency stop switches in the room .
Bayonet lock
In organizations such as the fire department or the relief organization specific come bayonet couplings with sealing rubber used, which meet the requirements of protection meet IP67 (temporary immersion). Correctly locked connections can be used safely in the rain, in areas that are affected by extinguishing water, or in flooded basement rooms. There are also splash-proof Schuko connectors .
Norms
The plug form Schuko is described in the standards:
- DIN 49440/441
- IEC / TR 60083: Plugs and socket-outlets for domestic and similar general use standardized in member countries of IEC . International Electrotechnical Commission , May 2004. This 359-page report describes all national standards for power plugs and sockets for domestic use worldwide. It replaces CEE publication 7, which summarized this information in 1963 only for European systems.
- CEE 7/4 (without receptor for plug type E , French system)
- CEE 7/7 (with receptor for plug type E, French system)
brand
The word SCHUKO is a registered trademark for the goods "electrical installation device, especially plugs and sockets". This brand is owned by the SCHUKO trademark association .
See also
- power strip
- Device plug
- Connection technology (electrical engineering)
- CEE three-phase connector , CEE power distribution
- Country overview connector types, line voltages and frequencies
- Perilex
- Terko
Web links
Individual evidence
- ↑ Patent No. 489 003. (PDF) German Patent and Trademark Office, accessed on February 18, 2015 .
- ↑ Patent No. 370538. worldwide.espacenet.com, accessed on February 18, 2015 (original document: DE370538 © - 1923-03-03).
- ↑ Reiner Hahn: The origin of Schuko. Museum of Plugs and Sockets, accessed March 6, 2016 .
- ↑ Practice electrical engineering . 13th edition. Europa-Lehrmittel , Haan-Gruiten 2015, ISBN 978-3-8085-3266-9 , p. 209 .
- ↑ The Schuko plug and its special features. In: elektrofachkraft.de. Retrieved March 6, 2016 .
- ^ Federal Association of Accident Insurance Funds (Ed.): Guidelines for Kindergartens - Construction and Equipment (PDF; 90 kB) , October 1992 edition, March 2001 version, point 5.1.
- ↑ a b c Dr. Franz Gubitz: Child safety devices on sockets. Bavarian State Office for Health and Food Safety, October 12, 2016, accessed on October 22, 2018 .
- ↑ Socket protection , Kinderprodukte.de
- ↑ Child protection plate - for sticking in safety sockets (PDF; 139 kB). Information sheet of the City of Vienna, Municipal Department 36, 03/2005
- ^ Frieder Fischer: Child safety devices in sockets. In: i-Punkt edition 02/2008. Unfallkasse Sachsen, 2008, accessed on October 22, 2018 .
- ↑ Can I retrofit an increased protection against accidental contact with a SCHUKO socket outlet? Gira , accessed on October 22, 2018 .
- ↑ Personal experience, welt-steckdosen.de
- ↑ SCHUKO trademark association e. V.