In addition to the main structural units, the grounding devices include additional elements that perform auxiliary functions. These include the grounding terminal, through which it is convenient to connect and switch copper conductors. For this purpose, special clamping parts are provided in its design, ensuring the reliability of the formed clamp.
Design and purpose
The simplest examples of terminals for grounding bars consist of the following parts:
- two movable pressure plates;
- the axis that holds them together;
- spring element.
The industry has established the production of easy-to-use and convenient grounding clamps from the line of short circuit, mounted with one click. Another type of contact connectors resembles a reduced-size clamp.
The main purpose of all types and types of terminals is to be used in working circuits as devices that ensure reliable contact with grounding copper conductors. By means of these products, not only the working, but also the protective busbars can be grounded.
Varieties of products
In grounding devices, the following types of terminals are used, which differ in their design:
- clamp connectors;
- threaded terminals;
- magnetic products;
- special terminals.
According to the method of application, a disposable grounding terminal block is distinguished and "instrumental".
Experts call the clamping clamps canine, in a simple way - "dog" or "crocodile". This is because they have two parts that look like jaws. The movable components are connected by a spring, just like in a regular clothespin. On the domestic market, these products are represented by a line under the general name "KZ", which includes the KZ-20 model, for example.
The same class of clamps includes such popular types of terminals as KS-124 or TWT-LSA-CRML.
Threaded connectors are a compact wire clamp designed for crimping conductors and securely tightened by means of a wing nut. A typical representative of these products is the Russian terminal UN 42-171 and 300A (USA). They are not very easy to use because they take longer to mount on the earthing 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 dimensions of the earthed structure. They are preferred in cases where it is impossible to use other types of terminals.
These samples allow you to connect the grounding conductor to the following structural elements:
- typical DIN rail;
- thick-walled metal pipes;
- 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 along with a piece of wire, therefore they are unsuitable for further use. The samples of this type include the products of the German company "ADC Krone".
Special terminals are in demand when it is necessary to connect grounding conductors to elements of electrical structures. Typical examples are products used in the grounding of electrical cable trays.They are made on the basis of a mesh, which makes it possible to increase the removal of heat energy from cable lines.
Trays should be grounded not only to prevent destruction of the insulating layer, but also to equalize and release the induced potential. To do this, special fasteners with conductors fixed in them are equipped on their walls. Instrument terminals can be identified by their characteristic "C" designation (their import name is "banana"). They are produced in the form of a connecting bus, mounted for the purpose of grounding electrical panels and metal frames.
Technical specifications
The main technical indicators of grounding terminals include:
- the maximum current that they can withstand without degrading the quality of the contact;
- opening angle of moving parts for canine and threaded specimens;
- dimensions and weight.
The main characteristic of products is the maximum permeable current, which is usually indicated on the case in the form of several numbers. To obtain an exact value, the marking number must be multiplied by 10.
It is more convenient to consider the technical parameters using the example of terminal blocks of the KZ-300 "Krass" brand. They are distinguished by increased resistance to high-power current discharges and have a convenient opening angle for work. For another model (KZ-50, for example), a current indicator of 500 Amperes is characteristic.
Selecting the desired sample
The main criteria to be considered when choosing clamping terminals are:
- The elasticity of the springs, ensuring a secure fit. A weak clamp will not support the weight of the cable to be clamped.
- Sufficient opening angle, allowing them to be attached to large structural elements.
- The material from which the terminal is made. Copper is usually preferred.
Inexpensive terminal products are often on sale, the working parts of which are made of metal with the thinnest layer of copper plating, which looks more like a fake. The problematic place of any such products is their strong heating when an electric current flows. Moreover, in appearance, it is almost impossible to distinguish them from real, pure copper terminals.
To identify fakes, experts advise using a magnet that does not react to copper materials.
If a fake steel terminal is nevertheless acquired by mistake, it is not difficult to make an all-copper product based on it. You need to find a blank of copper or brass and, using the purchased terminal, make a new high-quality thing with your own hands using a stencil. When choosing pawl type terminals, be sure to pay attention to the position of the copper or copper-plated strip.
If during operation it comes into contact with the elements of metal structures, the product will have to be abandoned. The presence of such a contact will lead to overheating of the material of the terminal spring, 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 location of the strip that is not in contact with the metal parts of the structures.
Before buying the necessary fastener, you first need to familiarize yourself with the existing varieties of terminals on the domestic market. Products of the required class are characterized by the following properties:
- 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 waste 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, which is presented to the buyer at his first request.
