From the foreword to the book Practical methods for reading electrical wiring diagrams

Work in electrical installations for memory, without circuits, it is impossible: it is dangerous. A scheme must be able to read, ie, to obtain from them the information necessary to perform a certain work. If the circuit is read incorrectly, it entails wrong actions. Installers, for example, attach (disconnect) is not (or not there), which follows. The drivers and repairmen, instead of fixing (repairing) some chains, can spoil the other, serviceable. Operationalists make mistakes in switching, can not understand the causes of the malfunction, and so on.

So, the electrical diagrams should be clear to everyone who has to work on them: electricians and commissioners, repairmen and maintenance workers. Therefore, the schemes are carried out in standard symbols (and the state standards of the USSR have the force of law) and apply them according to a certain system established by standards. It is therefore natural to begin the book with an explanation of the basic concepts: what is a schema, what kinds and types of schemes there are, for which each of them serves, and also consider: the system for constructing the notation, the notation itself and the rules for their application. The first chapters of the book are devoted to these questions.

Drawing up schemes is complicated and responsible. It requires:

A) the implementation of the instructions of regulatory documents - the Electrical Installation Rules (PUE), which establish what should be done; Building regulations and rules (GNiP), determining how to perform work; Safety Rules (PTB), etc., as well as guidance materials, for example, on the calculation of short-circuit currents, the choice of equipment, etc.;

B) compliance with the requirements of manufacturers of electrical products for use, installation and operation;

C) taking into account the climatic conditions, the category of accommodation and the degree of protection of electrical equipment. This information is needed by readers, since one of the tasks of reading diagrams is precisely to reveal deviations from norms and rules. Another category of issues dealt with in the book is the effect on heating and cooling electrical products, the environment, vibrations and other factors that determine the reliability and durability of electrical installations. The ability to correctly assess whether the circuit takes into account the actual conditions of operation, this is also a problem that must be solved when reading the schemes. And, finally, the third category of issues is the means by which the necessary results can be obtained. For example, the use of resistors, capacitors, contacts, semiconductor devices, motors, light sources, etc. This also includes the features of power supplies, the properties of the types of connections, etc. Assessing whether these tools and properties are correctly used is an important task of reading circuits.

The methods of reading and analyzing schematic diagrams are considered and explained, and such techniques as are available to readers with general education in the volume of a secondary school. In a separate chapter, typical regular components of electrical installations of wide application are described: power supply, protection, measurement, control of electric motors and lighting electrical installations, signaling devices, monitoring of technological parameters (temperature, level, etc.). Descriptions of these nodes are needed, since any electrical installation is a combination of several typical nodes. Therefore, the ability to select the necessary node from the schemes and evaluate it is one of the ways of reading circuits.

Particular attention is paid to identifying and eliminating the causes of false chains, as well as agreeing on the timing characteristics of cooperating devices and devices in general. And, finally, in Appendix 1, we talked about how, guided by the schematic diagram, you can check the installation and fix the problem. Appendix 2 contains brief information about the algebra of logic, the properties of the binary number system, and some other questions, the consideration of which is not included in the book's task. However, this information is useful for readers as an introduction to reading books, especially devoted to issues of current importance.

The reader's attention is drawn to the following.

1. The book contains exercises with control questions for self-examination. Readers are advised to first perform the exercise independently, and then, turning to the answers, check yourself.

2. Symbols of conditional graphic in the second and third chapters are given, as a rule, not in the form of tables (as done in the standards), but in many cases directly in the schemes, ie, just as they are used in practice. However, these are training schemes. On the training scheme for comparison, various forms of notation are used; In the practical scheme, one form most appropriate to the design of the scheme is usually used. On the training schemes (each of which is devoted to the explanation of a certain group of notation), some elements of the devices are not shown, so as not to distract attention from the topic under consideration.

3. Special radio engineering designations and designations, used mainly in communication technology, complex automation and computer technology, are not considered in the book.

4. About the schemes of connections, connections, and also the designations of electrical equipment and postings on the plans, only the most general information is given. The fact is that according to the correctly drawn up conceptual diagram, it is quite easy to execute the working documentation (although this is a very laborious work). In addition, working documentation is carried out on departmental regulatory documents, and they are different in different organizations.