When organizing the electrical connection of cable products, as well as when assembling an electrical cabinet, it is impossible to imagine a high-quality and assembled circuit without terminals. In this case, the terminal connection performs several functions at once:
- organizing a large number of wires, as well as dividing them into groups inside the cabinet;
- reliable isolation between connected nodes;
- wire markings to simplify operation and repair.
Types of possible connections and terminals
However, what kind of screw terminals to choose or self-clamping that appeared not so long ago?
According to PUE p2.1.21 it is possible to connect the conductors of the wires by welding, soldering, as well as screw and bolt connections, so that twisting this procedure is prohibited, although, it should be noted, many electricians still use it, thereby violating regulations. Welding and soldering without special equipment and without the presence of voltage to power the soldering iron is also very problematic in many cases. Thus, terminal blocks are one of the universal and quick elements for making a reliable electrical connection of two or more wires.
They are available in two types:
- screwwhere the core is attached to the jumper inside the terminal by pressing it with a screw with a special plate or just a washer;
- self-clamping, which, due to the spring mechanism, clamp the current-carrying core, forming an electrical contact.
Self-clamping terminal blocks, contrary to the opinion of unpretentiousness and an increase in the speed of installation work, are more capricious in terms of wire quality, its cutting, cross-section compliance, compliance and quality protection. A significant disadvantage of such products is also the non-reversibility of the process, if heating begins to occur inside the self-clamping terminal structure.
And in power circuits with an operating current of more than 5 Amperes, the self-clamping mechanism does not justify expectations, since it begins to warm up due to the deterioration of the contact.
Advantages of screw terminals
The terminal, which is equipped with a screw mechanism, serves for compact connection and connection of phase, neutral and protective (earth) conductors of different cross-sections and materials. It is installed mainly on a DIN rail and often comes with a marker for applying a number or a terminal designation.
They are used both for high-quality connections in power circuits according to GOST 18311-80and for connecting control circuits of control and lighting equipment. In this case, the contact screw terminals must meet the requirements GOST 25034, which is supported in almost all types of terminal blocks, both currently produced and previously.
The advantages of screw clamping in terminals are obvious:
- reliability and durability of the connection, as well as the presence of high-quality electrical contact with low transfer resistance;
- use in power circuits with voltages up to 1000 volts;
- the ability to connect not only conductors with different cross-sections of conductors, but also trouble-free connection of copper and aluminum conductors;
- due to the non-combustible material of the body, such a connection is fireproof;
- the ability to create a non-disposable connection, if necessary, you can always unscrew the screw, clean the contact, or even replace the conductor;
- the compactness of the connection allows for easy access and visual inspection when installing clamping terminal blocks inside electrical cabinets;
- ease of maintenance and installation, without the use of additional equipment and experience in working with this type of electrical products.
Thus, if you choose between a self-clamping terminal block and a screw, rotary electricians prefer more reliable, dismountable, serviceable during operation connection made on the basis of a screw clamp.