Referring a really famous brand during socket and plug industry. That is Schuko brand. The term Schuko basically refers to AC power and socket systems. We can simply call it a security contact. We're just going to talk about Shuke here. If we look back at the history of the shuko plug, we will know that this plug was first designed in Germany shortly after World War II. Then it went back to the 1926 patent (de370538) granted by Albert B ü ttner, a Bavarian electrical equipment manufacturer.
About Schuko company and Schuko plug and socket
Schuko originated in Germany. It is believed to date back to 1925 and was made by Albert Bü ttner, a Bavarian manufacturer of electrical accessories. Büttner company, Bayerische Elektrozubehör AG, patent DE 489 003 in 1930, Stecker MIT erdungseinrichtung (plug with grounding device). Büttner’s patent de370538 is often cited as Schuko, but in practice it refers to a method of holding all parts of a plug or socket together with a screw, which also provides clamping for the wire; there is no mention of a ground connection in de370538. At that time, Germany used a 220 volt central tap, which supplied 127 volts from the current pin to the ground, which meant that both sides of the appliance and the bipolar switch needed to be fused. Today, more than 40 countries (including most countries on the European continent) use the original Schuko plug.
"Schuko" is a registered trademark referring to AC power plug and socket system, which are defined as "CEE 7 / 3" (socket) and "CEE 7 / 4" (plug). The Schuko plug has two 4.8 mm diameter round pins (19 mm long, 19 mm center to center) for line and neutral contacts, and two flat contact areas at the top and bottom of the plug for protective grounding (grounding). The socket outlet (commonly incorrectly referred to as CEE 7 / 4) has a predominantly circular notch, 17.5 mm deep, two symmetrical round holes, and two grounding clamps on both sides of the socket to ensure that it is always grounded before live pin contact is made. Schuko plugs and sockets are symmetrical AC connectors. They can be paired in two ways, so the line can be connected to any pin of the electrical plug. As with most types of European outlets, Schuko outlets can accept euro-plugs. Schuko plugs and socket are considered to be a very safe design when using Schuko sockets, but they can also work with other sockets to give an unsafe result.
About Socket from Schuko
When inserted into the socket, the Schuko plug covers the socket cavity, and a protective grounding connection is established through the grounding clamp before the line and the neutral pin establish contact, thus preventing the user from contacting the connected pin. A pair of non-conductive guide notches on the left and right provide additional stability, enabling large and heavy plugs (such as built-in transformers or timers) to be used safely.
Schuko socket can accept two pin ungrounded euro-plug (CEE 7 / 16) and CEE 7 / 17. Less secure is that the Schuko plug can be inserted into a number of two pin ungrounded CEE 7 / 1 sockets, or into sockets with different forms of grounded connections (e.g., some variants of Danish sockets). Many of these sockets also lack the cavities needed to prevent the user from touching the pins when inserting the plug. CEE / 7, if it is a CEE / 7 type, including a CEE 7 ground plug. Therefore, it can realize grounding connection with cee7 / 3 (Schuko) and cee7 / 5 sockets. In Italy, Chile, Peru and Uruguay, the hybrid version of the Schuko socket (known as the P30) is seen to have an extra hole that will take a smaller variant of the Italian cei23-50 plug. There are also hybrid Schuko plug and socket (called P40), which have three extra holes and a wider cavity, and will also accept a larger Italian plug variant. The Schuko socket is not polarized and cannot distinguish two live contacts (about 230V between line and ground and 0V for neutral wire) unless the voltage to ground is measured before use. The IEC 60906-1 standard aims to solve some polarization related problems and replace Schuko, but the only country adopting the standard is South Africa.
Technical information about Schuko plug:
The Schuko plug consists of two round pins 4.8 mm in diameter (19 mm in length and 19 mm in center) for line and neutral contacts, while the two flat contact areas at the top and bottom of the plug are used for protective grounding (grounding). The other part, the socket, which is usually wrong, has a main circular groove, 17.5 mm deep, consisting of two symmetrical circular holes and two grounding clamps on the side of the socket to ensure that it is always grounded before making live pin contact.
Schuko plugs and sockets are basically symmetrical AC connectors. They can be coupled in two ways, so the wire can be connected to any pin of the application plug. There are various types of shuck plugs, which are classified by ground clip, not by ground pin. The standard, usually designated as “Schuko”, is accepted by a large number of Central European countries, because these Schuko plugs are generally considered to be very safe when used with Schuko sockets, but when coupled with other types of Schuko sockets, they will produce unsafe results.
Types of plug and socket from Schuko
There are usually three types of shuck plugs, and the first one involving shuck sockets, which are safety coupled. It is described as follows:
First of all, we have a (Schuko) type socket with two openings (live and neutral; non polarized) and two grounding clamps. All types of sockets are fixed to ensure that the connection between fingers / hands and pins is not possible even if the plug is not fully inserted into the socket.
The second is the (Schuko) plug, with a working current of 16a and a voltage of 250V. Its live and neutral pin diameters are 4.8mm. The green arrow indicates the guide rail.
The third type is female Schuko plug working between 10-16a and 250V. The change of rated current shows that these plugs can be used in both domestic 10A circuit and 16A circuit.
The last one is a plug with an additional opening to connect to the ground pin of the French socket (green arrow). So, that's why this plug can be plugged into both the schuko and French outlets.
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