Conventional designation in electrical circuits. Conditional graphic and letter designations

If you are engaged in electrical work, then you need to know the symbols in the electrical diagrams. The ability to read electrical circuits is an important quality of builders, fitters of instrumentation and instrumentation, circuit designers. And if you do not have special training, you will not be able to understand all the intricacies immediately. But we must remember that the symbols on the schemes that are developed for Russian consumers differ from the generally accepted standards abroad - in Europe, the United States, and Japan.

History of designations in diagrams

Even in the Soviet years, when electrical engineering developed rapidly, there was a need for the classification of devices and their designation. It was then that the Unified System of Design Documentation (ESKD) and state standards (GOST) appeared. Everything was standardized so that any engineer could read the symbols on the drawings of his colleagues.

But in order to make out all the subtleties, you need to listen to a lot of lectures and learn a lot of special literature. GOST is a huge document, and it is almost impossible to fully understand all graphic designations and their standard sizes, notes. Therefore it is necessary to have always at hand a small "cheat sheet" that will help you to orient yourself in all the variety of electrical components.

Electrical wiring in the drawings

Electrical wiring is a generalized concept, it implies conductors with very low resistance. With their help, the voltage is transferred from the source of electricity to consumers. This is a general concept, since there are many types of wiring.

People who do not understand the wiring diagrams and electrical wiring may decide that the conductor is an insulated cable that is connected to switches and sockets. But in fact, there are many types of conductors, and on schemes they are designated differently.

Conductors in diagrams

Even the copper tracks on the PCBs are a conductor, you can even say that this is an electrical wiring option. Indicated on electrical circuits in the form of a straight connecting line, passing from one element to another. In the same way, the electric wires of the high-voltage line, laid in the fields between the posts, are also indicated in the diagram. And in the apartments, the connecting wires between the lamps, switches and sockets are also denoted by straight connecting lines.

But it is possible to divide into three subgroups the designation of conductive elements:

1. Wires.
2. Cables.
3. Electrical connections.

The wiring plan is an incorrect definition, since wiring refers to both wiring and cables. But if you significantly expand the list of elements, as it is necessary in the detailed scheme, it turns out that it is necessary to include more transformers, circuit breakers, residual current devices, grounding, insulators.

Sockets on the circuits

Sockets are plug-in connections intended for non-rigid connection (there is a possibility to manually break the connection) of electrical circuits. The symbols in the drawings are strictly regulated by GOST. With its help, rules are established for the designation of apparatuses and lighting devices and various other electric consumers on the drawings. Sockets plug type can be divided into three categories:

1. Designed for outdoor installation.
2. Designed for concealed installation.
3. A unit that includes a socket and a switch.

These three categories can be further divided into several subgroups, depending on the connection options and the presence of protection:

1. Single-pole sockets.
2. Two-pole.
3. Bipolar and protective contact.
4. Three-pole.
5. Three-pole and protective contact.

This is enough, there are no special features for the outlets, there are many options for execution. All devices have a degree of protection, the choice should be made on the basis of what conditions to use: humidity level, temperature, the presence of mechanical influences.

Switches on wiring diagrams

Switches are devices by means of which an electric circuit is broken. This can be done automatically or manually. The conditional graphic designation by GOST is regulated, as well as at sockets. The designation depends on the conditions under which the element operates, what its design is, and the degree of protection. There are several types of switch constructions:

1. Single-pole (including double and built-in).
2. Two-pole.
3. Three-pole.

On the diagrams, the parameters of the disconnect device must be specified. And the graphic designation shows which type is used: a simple switch, a button with and without fixing, an acoustic device (responsive to cotton) or an optical device. If there is a condition that the lighting is turned on at nightfall and turned off in the morning, you can use an optical sensor and a small control circuit.

Fuses (fuse links)

There are many types of protection devices - fuses (disposable and self-healing), circuit breakers, RCDs. Many types of design, applications, different speed of operation, reliability, use under certain conditions characterizes these devices. The conventional designation of the fuse is a rectangle, parallel to the long side, the conductor passes through the center. This is the simplest and cheapest element, able to protect the electrical circuit from short circuit. It should be noted that such components are rarely used in electric principal schemes. Conventional symbols of another type can be found - these are self-healing fuses, which, after opening the circuit, come to the initial state.

The wide name of the fuses is a fuse-link. It is used in many devices, in distribution electrical panels. In single-use traffic jams, you can meet them. But there are also devices used in high-voltage switchboards. They are structurally made of metal tips and the main ceramic part. Inside is a section of the conductor (its cross-section is selected depending on which maximum current must pass through the circuit). The ceramic body is filled with sand to exclude the possibility of ignition.

Automatic switches

Conditional designations of devices of this type depend on the design, the degree of protection. The reusable device can be used as a simple switch. In fact, it performs the functions of a fuse-link, but it is possible to translate into the original state - close the circuit. The structure consists of the following elements:

1. Plastic housing.
2. Lever to turn on and off.
3. Bimetallic plate - when heated, it deforms.
4. Contact group - it is included in the electrical circuit.
5. Arc interrupter - allows you to get rid of the formation of sparks and arcs during disconnection.

These are the elements that make up any circuit breaker. But we need to remember that after the trigger, it can not return immediately to its original position, it should take time for the bimetallic plate to cool. The service life of automatic machines is measured in the number of operations and fluctuates in the range of 30000-60000.

Earthing in circuits

Grounding is the connection of the current conductors of the electric machine or the device to the ground. In this case, both the ground and part of the circuit of the device has a negative potential. Due to grounding in case of breakdown of the case there will be no destruction of the device or electric shock, the whole charge will go to the ground. Earthing is the following types of GOST:

1. The general concept of grounding.
2. Clean ground (noiseless).
3. Protective grounding type.
4. Connection to the body (body) of the device.

Depending on what kind of grounding is used in the circuit, the symbol will be different. An important role in the drawing up of diagrams is played by the drawing of the element, it depends both on a particular section of the circuit and on the type of device.

If it is a question of the automobile technics there will be "mass" - the general conductor connected to a body. In the case of wiring at home - driven into the ground conductors, connected to sockets. In logic, you can not confuse "digital" grounding and the usual - these are different things and they work in different ways.

Electric motors

On electric equipment schemes for cars, workshops, devices, electric motors are often found. And in industry more than 95% of all used motors are asynchronous with a squirrel-cage rotor. They are designated as a circle, to which three wires (phases) are suitable. Such electric machines are used together with magnetic starters and buttons ("Start", "Stop", "Reverse" if necessary).

DC motors are used in automotive engineering, control systems. They have two windings - working and exciting. Instead of the latter, permanent magnets are used on some types of motors. With the help of excitation winding, a magnetic field is created. It pushes the rotor of the engine, which has a counter-directed field - it is created by a winding.

Wire color coding

In the case of single-phase supply, the conductor with phase is black, gray, purple, pink, red, orange, turquoise, white. Most often you can find brown. This marking is generally accepted and is used in the design of schemes, installation. The zero conductor is marked with:

1. Blue color - zero work (N).
2. Yellow with green stripe - grounding wire, protection (PE).
3. Yellow with green and blue marks on the edges - protective and zero conductors are combined.

It should be noted that blue marks should be applied during installation. The symbol in the electrical diagrams must also have a reference to the presence of labels. The conductor must be indicated by the PEN index.

For functional purposes, all the conductors are divided as follows:

1. Wires of black color - for switching power circuits.
2. Wires of red color - for connections of control elements, measurement, signaling.
3. Conductors of blue color - control, measurement and signaling when working with direct current.
4. Blue marking is performed by zero working conductors.
5. Yellow and green are the wires for grounding and protection.

Alphanumeric symbols on diagrams

The clamps have the symbol in the following diagrams:

• U, V, W - wiring phases;
• N is the neutral conductor;
• E - grounding;
• PE - the wire of the protective circuit;
• TE - conductor for noiseless connection;
• MM - conductor connected to the body (mass);
• SS is an equipotential conductor.

Marking on the wiring diagrams:

• L - the letter designation (general) of any phase;
• L1, L2, L3 - 1st, 2nd and 3rd phases respectively;
• N is the neutral wire.

In DC circuits:

• L + and L- - positive and negative poles;
• M is the average conductor.

These are the notations most often used in diagrams and drawings. They can be found in the descriptions of simple devices. If you need to read the diagram of a complex device, you will need a lot of knowledge. After all, there are active elements, passive devices, logic devices, semiconductor components, and many others. And each has its own designation on the diagrams.

Winding elements

There are many devices that convert electric current. These are inductors, transformers, chokes. The conventional designation of the transformer on the circuits is two coils (represented in the form of three semicircles) and a core (in the form of a straight line usually). A straight line designates a core of transformer steel. But there may be transformer designs that do not have a core, in this case there is nothing in the circuit between the coils. Such a symbol for elements can also be found in radio receiver circuits, for example.

In recent years, the technology has increasingly used transformer steel for the manufacture of transformers. It is very heavy, it is difficult to dial plates in the core, there is a buzz when blotting. The use of ferromagnetic cores is much more effective. They are whole, have the same permeability in all areas. But they have one minus - the complexity of repair, as dismantling and assembling is problematic. The conventional designation of a transformer with such a core practically does not differ from that in which steel is used.

Conclusion

This is not all the symbols of the electrical circuits, the size of the components is also regulated by GOST. Even simple arrows, connection points have requirements, their drawing is strictly according to the rules. It is necessary to pay attention to one feature - the differences in the schemes made by domestic standards and imported. Crossing of conductors on foreign circuits is denoted by a semicircle. And still there is such concept, as the sketch is an image of something without observance of requirements of GOST to elements. Separate requirements are made to the very sketch. Such images can be performed to visualize the future design, wiring. Subsequently, a drawing is drawn up on it, where even the symbols of conditional cables and connections meet the standards.