The composition of grounding devices in addition to the main structural units includes additional elements that perform auxiliary functions. These include the ground terminal, through which it is convenient to connect and commute copper conductors. For this purpose, special clamping parts are provided in its design, ensuring the reliability of the clamp formed.
Design and purpose
The simplest examples of terminals for grounding buses consist of the following parts:
- two movable pressure plates;
- fastening their axis;
- spring element.
The industry has launched the production of easy-to-use and convenient grounding terminals from the KZ line, mounted with one click. Another type of contact connectors resembles a clamp of reduced size.
The main purpose of all types and types of terminals is the use in working circuits as devices providing reliable contact with grounding copper conductors. By means of these products it is possible to ground not only workers, but also protective tires.
Variety of products
In grounding devices use the following types of terminals, differing in their design:
- clamping connectors;
- threaded terminals;
- magnetic products;
- special terminals.
According to the method of application, they distinguish between the disposable ground terminal block and the “instrument” one.
Specialists call the clamping terminals fang, in a simple way - a "dog" or "crocodile". This is because they have two parts that look like jaws. The movable components are connected by a spring, as in a regular clothespin. In the domestic market, these products are represented by a line under the common name "KZ", which includes the model KZ-20, for example.
Popular clamps such as KS-124 or TWT-LSA-CRML belong to this class of clamps.
Threaded connectors are a compact clamp designed for crimping conductors and tightened securely by means of a threaded nut. A typical representative of these products is the Russian terminal UN 42-171 and 300A (USA). They are not very convenient in operation, since it takes more time to mount on the grounding rail. On the other hand, these terminals provide a more reliable connection with good surface contact.
Magnetic products are mainly used in hard-to-reach places or with large sizes of a grounded structure. They are preferred in cases where it is not possible to use other types of terminals.
These samples allow you to connect the grounding conductor to the following structural elements:
- typical DIN rail;
- metal pipes with thick walls;
- wire mesh.
You can recognize Russian magnetic type products by the abbreviation MKZ.
Disposable terminals are used in low-current and signal electrical circuits mounted in PCs, sound equipment and cable systems. They got their name due to the fact that they are removed together with a piece of wire, therefore they are unsuitable for further use. To samples of this type include products of the German company "ADC Krone".
Special terminals are in demand if it is necessary to connect grounding conductors to elements of electrical structures. Their typical representatives are products used when grounding trays for laying electrical cables. They are made on the basis of the grid, which allows to increase the removal of thermal energy from cable lines.
The trays should be grounded not only to prevent destruction of the insulating layer, but also to level and drop the induced potential. To do this, special fasteners with conductors fixed in them are arranged on their walls. The instrument terminals can be recognized by their characteristic designation “C” (their import name is “banana”). They are available in the form of a connecting bus mounted to ground electrical panels and metal frames.
Technical specifications
The main technical indicators of grounding terminals include:
- the maximum current that they can withstand without deteriorating the quality of the contact;
- opening angle of moving parts for canine and threaded specimens;
- dimensions and weight.
The main characteristic of the products is the maximum transmitted current, which is usually indicated on the case in the form of several digits. To get the exact value, the marking number must be multiplied by 10.
It is more convenient to consider the technical parameters on the example of terminal blocks of the KZ-300 Crass brand. They are characterized by increased resistance to current discharges of high power and have a convenient opening angle for operation. For another model (KZ-50, for example), a current indicator of 500 Amps is characteristic.
Choosing the right sample
The main criteria considered when choosing clamping terminals include:
- The elasticity of the springs, providing reliable fastening. A loose clamp will not support the weight of the cable being fixed.
- Sufficient opening angle, allowing you to mount them on large structural elements.
- The material the terminal is made of. Preference is usually given to copper.
There are often inexpensive terminal products on sale, the working parts of which are made of metal with the thinnest layer of copper coating, which is more like a fake. The problem point of any such products is their strong heating during the flow of electric current. Moreover, in appearance, it is almost impossible to distinguish them from real, purely copper terminals.
To identify fakes, experts advise using a magnet that does not respond to copper materials.
If a fake steel terminal is nevertheless acquired by mistake, it is not difficult to make a completely copper product on its basis. You need to find a copper or brass blank and use the purchased terminal to make a new high-quality thing yourself using a stencil. When choosing dog-type terminals, attention is drawn to the position of the copper or copper-coated strip.
If during operation it will come into contact with the elements of metal structures - you will have to refuse the product. The presence of such a contact will lead to overheating of the terminal spring material, which in exceptional cases can cause severe burns to the operator (in the absence of heat dissipation). In addition, products made of material deformed from overheating are no longer suitable for use. To avoid unpleasant consequences, experts advise you to choose a clamp brand with a convenient arrangement of a strip that does not contact with metal parts of structures.
Before buying the necessary fasteners, you will first need to familiarize yourself with the existing varieties of terminals available on the domestic market. For products of the required class, the following properties are characteristic:
- use of high quality materials;
- elastic spring;
- large opening angle.
The purchase of a low-grade product can lead to its breakdown and turn into an unjustified expenditure of time and money. This will cause a delay in the welding or similar process and does not exclude the possibility of equipment breakdown.
Any quality product is accompanied by a certificate that is presented to the buyer at his first request.
