When installing power distribution circuits and complex electronic devices, it is impossible to do without special connecting devices. The electric shoe is one of the structural elements widely used in the arrangement of wiring connections. This product is available in a variety of designs, each of which will need to be familiar with in more detail.
The principle of operation of electrical pads and their types
The basis of the operation of electrical connecting blocks is the principle of creating a reliable contact, obtained by means of clamping mechanisms of various types. When arranging it, two switched conductors are inserted into the contact holes on both sides, and then clamped into them.
The possibility of arranging contact without direct contact makes it possible to use these products for connecting electric buses made of dissimilar metals.
The wide selection of contact connectors offered by the domestic market is explained by the variety of their designs, which differ in the following features:
- the material from which the body is made;
- the method used to create a reliable contact;
- the location of the terminal mounts.
Body material
Pads for wires differ in the material used for their manufacture. Available in ceramic or plastic. In the second case, polypropylene, polyamide, ebonite and carbolite are used as the body material. Ceramics are mainly used in high-temperature modes of operation of switched circuits and equipment (in electric heaters, for example).
Plastic polypropylene is suitable for situations where it is necessary to withstand loads associated with increased deformations. A typical example of its application is the connection of connecting circuits to lighting equipment. Carbolite and hard rubber products are vibration-resistant, and polyvinyl chloride is traditionally used for the arrangement of low-current connections.
Conductor attachment method
In accordance with the method of fastening the conductors and the mechanism for their fixing, the following types of terminal blocks are distinguished:
- barrier or building connectors (most often called screw connectors);
- clamping type clamps, including a self-clamping version;
- linear type blocks, consisting of several terminals located in one row;
- knife terminal blocks.
Connecting blocks for electrical wiring with screws ensure high-quality contact when currents flow in the load circuits not exceeding the calculated values. With their help, during the installation of the electrical network, the sockets are connected, and also the conductors are connected during their laying in niches or cable channels. The reliability of the contact formed in this case is ensured by special screw clamps. This type of connector is not recommended for use with aluminum wires.
Clamping (or self-clamping) clamps are equipped with elastic spring terminals. To fix the wiring, it is enough to strip its end, and then push it inside the block until it stops. To remove the inserted core, simply pull the lever on the terminal to the side.In more advanced models, an automatic clamping function is provided. The body of such clamps is made on the basis of polymers, and they use two brass plates as contacts.
Such pads are convenient to use as an adapter element in small junction boxes, where it is sometimes very difficult to establish a reliable connection. To complete the connection, the conductor is simply inserted into the terminal until it stops, where it is independently fixed with a spring clip. Knife connectors are traditionally used in the arrangement of grounding and grounding. If there is insulation on the wires to be connected, it is not necessary to specially strip it, since it is automatically cleaned off during compression.
Contact arrangement
According to the location of the connecting contacts, the known switch blocks are divided into linear (in the form of a series of terminals) and through. The former are designed to connect the same type of conductors (ground buses, for example), combined on one completely metal ruler. Pass-through products are in demand when organizing a linear connection of wires and, if necessary, splicing veins from dissimilar metals (copper and aluminum, for example).
In another type of such connectors, the terminals are separated by dielectric plastic partitions. If necessary, the required number of contacts is cut from such a workpiece with a knife.
Another type of clamps, called barrier clamps, looks similar to feed-through terminal blocks, but the partition wall is more solid. The dielectric fence protrudes far beyond the contact plane, reliably protecting it from contact with metal objects (a screwdriver, for example).
Requirements for pads
Any type of connector usually meets the following requirements:
- the material is resistant to high temperatures, preventing direct combustion;
- with strong heating, deformation of the case is excluded, the protective shell is made only of non-combustible materials;
- the conductors to be mounted are fixed in the terminals very reliably and inserted into them without much effort;
- the contact plates are arranged in such a way as to prevent corrosion when using dissimilar conductors.
In addition, the technical specifications separately indicate that the terminal strip must be marked with the diameter of the cores and the value of the permissible voltage. According to their moisture-proof characteristics, they must correspond to the conditions in which they are supposed to be used.
Terminal strip selection rules
Many users often encounter difficulties when choosing connectors for connecting wiring. Before buying switching products, you first need to carefully examine the wire with which you have to work, and first of all, decide on its cross section.
Further, it is recommended to pay attention to the following points:
- the quality of the housing material, which guarantees reliable insulation of the terminal;
- steel is preferred when evaluating screw terminals and connector brackets;
- the terminals are selected as compact as possible to accommodate confined spaces.
Another requirement for connectors is ease of installation and subsequent maintenance.
It is desirable that the surface allows for additional marking. The interior of individual samples is filled with a special rubber-based gel, which prevents oxidation of the contacts and increases their reliability.
Installation features
Joining wires and cables by means of terminal blocks does not require special skill and special skills from the performer.To carry out such an operation, you will need the electrical distribution block itself and two connected ends of the conductors. To form a reliable contact, it is necessary to select it correctly according to the size of the socket, which is optimal for the cross-section of the bare conductors. After that, the ends of the wires are inserted into it, which are then fixed with screws. But even earlier, insulation is removed from them at a distance of about 5-7 mm.
Multi-section pads are usually cut into the desired number of segments. When working with soft aluminum conductors (when it is impossible to do without them), tighten them with screws with extreme caution, excluding the possibility of punching and breaking the metal.
Positive and negative sides
The terminal block for electrical wiring has gained wide popularity in electrical engineering due to the following advantages:
- Ease of combining two or more conductors made of dissimilar metals with different conductor cross-sections. No special tool required.
- The ability to save the state of the wires in a form convenient for re-installation.
- The safety of the resulting joint due to the high quality of the housing insulating material.
- Reliability of the formed contacts.
- Resistance of the terminals to mechanical and temperature influences, as well as to dangerous stretching and vibration.
- Small dimensions of the products, allowing them to be freely placed in the junction box and the switch body.
A significant drawback of these devices is the relatively high price (10-12 rubles per piece). With significant volumes of electrical installation operations, this indicator can be sensitive to the budget.
Over time, the cost of connectors will decrease markedly. This is explained by the rapid development of modern technologies and competition in the market for relevant materials. All this makes users even more attracted to easy-to-use and reliable terminal products.
