Each electrical circuit consists of many elements, which, in turn, also include various parts in their design. The most striking example is household appliances. Even an ordinary iron consists of a heating element, a temperature regulator, a control light, a fuse, a wire and a plug. Other electrical appliances have an even more complex design, supplemented by various relays, circuit breakers, electric motors, transformers and many other details. An electrical connection is created between them, ensuring the full interaction of all elements and the fulfillment by each device of its intended purpose.
In this regard, the question very often arises of how to learn to read electrical circuits, where all components are displayed in the form of conventional graphic symbols. This problem is of great importance for those who regularly encounter electrical installations. Proper reading of the diagrams makes it possible to understand how the elements interact with each other and how all work processes proceed.
Types of electrical circuits
In order to correctly use electrical circuits, you need to familiarize yourself with the basic concepts and definitions that affect this area in advance.
Any diagram is made in the form of a graphic image or drawing, which, together with the equipment, displays all the connecting links of the electrical circuit. There are various types of electrical circuits that differ in their intended purpose. Their list includes primary and secondary circuits, signaling, protection, control systems and others. In addition, there are and are widely used fundamental and, full-line and deployed. Each of them has its own specific features.
Primary circuits include circuits through which the main technological voltages are supplied directly from sources to consumers or receivers of electricity. Primary circuits generate, convert, transmit and distribute electrical energy. They consist of a main circuit and circuits that provide their own needs. Main circuit circuits generate, convert and distribute the main flow of electricity. Auxiliary circuits ensure the operation of the main electrical equipment. Through them, the voltage is supplied to the electric motors of the installations, to the lighting system and to other areas.
Secondary are those circuits in which the applied voltage does not exceed 1 kilowatt. They provide the functions of automation, control, protection, dispatching service. Through the secondary circuits, control, measurement and metering of electricity is carried out. Knowing these properties will help you learn how to read electrical circuits.
Full line circuits are used in three-phase circuits. They display the electrical equipment connected to all three phases. Single-line diagrams show equipment located on only one middle phase. This difference must be indicated on the diagram.
Schematic diagrams do not indicate secondary elements that do not perform primary functions. Due to this, the image becomes simpler, allowing a better understanding of the principle of operation of all equipment. Wiring diagrams, on the contrary, are carried out in more detail, since they are used for the practical installation of all elements of the electrical network. These include single-line diagrams displayed directly on the building plan of the facility, as well as cable route diagrams along with transformer substations and distribution points plotted on a simplified master plan.
In the process of installation and commissioning, detailed schemes with secondary circuits became widespread. They are allocated additional functional subgroups of circuits associated with turning on and off, individual protection of a section, and others.
Designations in electrical diagrams
In every electrical circuit there are devices, elements and parts that together form a path for electric current. They are distinguished by the presence of electromagnetic processes associated with electromotive force, current and voltage, and described in physical laws.
In electrical circuits, all components can be divided into several groups:
- The first group includes devices that generate electricity or power sources.
- The second group of elements converts electricity into other forms of energy. They perform the function of receivers or consumers.
- The components of the third group provide the transfer of electricity from one element to another, that is, from a power source to electrical receivers. This also includes transformers, stabilizers and other devices that provide the necessary quality and voltage level.
Each device, element or part corresponds to a symbol used in graphic representations of electrical circuits, called electrical circuits. In addition to the main symbols, they display power lines connecting all these elements. Sections of the circuit along which the same currents flow are called branches. The places of their connections are nodes, indicated on electrical diagrams in the form of dots. There are closed paths for the movement of current, covering several branches at once and called circuits of electrical circuits. The simplest electrical circuit diagram is single-circuit, and complex circuits consist of several circuits.
Most circuits consist of various electrical devices that differ in different modes of operation, depending on the value of current and voltage. In idle mode, there is no current in the circuit at all. Sometimes such situations arise when connections are broken. In the nominal mode, all elements operate with the current, voltage and power that are indicated in the device passport.
All components and symbols of the elements of the electrical circuit are displayed graphically. The figures show that each element or device has its own symbol. For example, electrical machines may be depicted in a simplified or expanded manner. Depending on this, conditional graphic schemes are also built. Single-line and multi-line images are used to show winding leads. The number of lines depends on the number of leads, which will be different for different types of machines. In some cases, for the convenience of reading the diagrams, mixed images can be used, when the stator winding is shown in expanded form, and the rotor winding is shown in simplified form. Others are done in the same way.
They are also carried out in a simplified and expanded, single-line and multi-line methods. This determines the way the devices themselves are displayed, their outputs, winding connections and other constituent elements. For example, in current transformers, a thick line marked with dots is used to depict the primary winding. For the secondary winding, a circle can be used with a simplified method or two semicircles with an expanded image method.
Graphic images of other elements:
- Contacts. They are used in switching devices and contact connections, mainly in switches, contactors and relays. They are divided into closing, opening and switching, each of which has its own graphic pattern. If necessary, the image of contacts in a mirror-inverted form is allowed. The base of the moving part is marked with a special unshaded dot.
- . They can be single pole or multi pole. The base of the moving contact is marked with a dot. For circuit breakers, the type of release is indicated in the image. Switches differ in the type of action, they can be push-button or track, with break and make contacts.
- Fuses, resistors, capacitors. Each of them corresponds to certain icons. Fuses are depicted as a rectangle with taps. For fixed resistors, the icon can be with or without taps. The moving contact of a variable resistor is indicated by an arrow. Capacitor drawings show fixed and variable capacitance. There are separate images for polar and non-polar electrolytic capacitors.
- Semiconductor devices. The simplest of these are diodes with a p-n junction and one-sided conduction. Therefore, they are depicted as a triangle and an electrical connection line crossing it. The triangle is the anode and the dash is the cathode. For other types of semiconductors, there are their own designations defined by the standard. The knowledge of these graphic drawings greatly facilitates the reading of electrical circuits for dummies.
- Sources of light. Available on almost all electrical circuits. Depending on the purpose, they are displayed as lighting and signaling lamps with the help of the corresponding icons. When displaying signal lamps, it is possible to shade a certain sector corresponding to low power and low luminous flux. In alarm systems, along with light bulbs, acoustic devices are used - electric sirens, electric bells, electric horns and other similar devices.
How to read electrical diagrams correctly
The circuit diagram is a graphic representation of all elements, parts and components between which an electronic connection is made using current-carrying conductors. It is the basis for the development of any electronic devices and electrical circuits. Therefore, every novice electrician must first master the ability to read a variety of circuit diagrams.
It is the correct reading of electrical circuits for beginners that allows you to understand well how to connect all the parts in order to get the expected end result. That is, the device or circuit must fully perform its assigned functions. For the correct reading of the circuit diagram, it is necessary, first of all, to familiarize yourself with the symbols of all its components. Each detail is marked with its own conventional graphic designation - UGO. Typically, such conventional signs display the general design, characteristics and purpose of a particular element. The most striking examples are capacitors, resistors, speakers and other simple parts.
It is much more difficult to work with components represented by transistors, triacs, microcircuits, etc. The complex design of such elements also implies a more complex display of them on electrical circuits.
For example, each bipolar transistor has at least three terminals - base, collector and emitter. Therefore, their conventional representation requires special graphic symbols. This helps to distinguish between parts with individual basic properties and characteristics. Each symbol carries certain encrypted information. For example, bipolar transistors can have a completely different structure - p-p-p or p-p-p, so the images on the diagrams will also be noticeably different. It is recommended that before reading the circuit diagrams, carefully read all the elements.
Conditional images are very often supplemented with clarifying information. On closer examination, you can see Latin alphabetic characters next to each icon. Thus, this or that detail is indicated. This is important to know, especially when we are just learning to read electrical circuits. There are also numbers next to the letters. They indicate the corresponding numbering or technical characteristics of the elements.
Ministry of Education and Science of the Russian Federation Federal Agency for Education State Educational Institution of Higher Professional Education "SAINT PETERSBURG STATE UNIVERSITY OF INFORMATION TECHNOLOGIES OF MECHANICS AND OPTICS" FACULTY OF SECONDARY PROFESSIONAL EDUCATION
electrical diagramsexecution rules
Saint Petersburg
Introduction
Within the framework of the discipline "Computer modeling" it is necessary to develop a set of circuits of a previously created computing device. Schemes must be drawn up in accordance with the rules of GOST.
The implementation of the scheme in accordance with GOST implies:
Use of a stamp in accordance with GOST 2.104;
The use of graphic symbols in accordance with GOST 2.721 and GOST 2.743;
Location of UGO and image of electrical interconnection lines according to GOST 2.702;
Arrangement of conditional alphanumeric designations in accordance with GOSTs 2.702 and 2.710;
Compliance of the scheme with its type and type according to GOST 2.701;
GOST 2.702 "Rules for the implementation of electrical circuits" is subject to consideration, since the device is electronic.
The standard in question applies to all electrical circuits and establishes the rules for their implementation.
GOST 2.702 is one of the components of a unified system of design documentation (ESKD), a set of GOSTs that establish interrelated rules, requirements and norms for the development and execution of design documentation.
Terms and Definitions
Relationship line: A line segment that indicates that there is a connection between the functional parts of the product.
Element designation(positional designation): A mandatory designation assigned to each part of an object and containing information about the type of part of the object, its number and, if necessary, an indication of the function of this part in the object.
Device: A collection of elements representing a single structure.
Functional group: A set of elements that perform a specific function in a product and are not combined into a single design.
Functional chain: A set of elements, functional groups and devices with interconnection lines that form a channel or path for a specific purpose.
Functional part: Element, device, functional group.
Circuit element: A component of a circuit that performs a specific function in a product and cannot be divided into parts that have an independent purpose and their own symbols.
Electric scheme: A document containing in the form of symbols the component parts of the product, acting with the help of electric current, and their relationship.
Types of circuits and their code
All types and types of circuits established by GOST have their own designation in the code in accordance with GOST 2.701, which is formed from a letter denoting the type and a number denoting the type of circuit.
Only the “Electrical” view is subject to consideration, therefore, in the coding of the scheme, they will have the letter “E”.
Electrical circuits, depending on the main purpose, are divided into the following types:
Structural - diagrams designed to depict all the main functional parts of the product in the form of UGO and the main relationships between them.
An example of an electrical structural diagram is shown in Figure 1. The diagram contains the functional parts of the product (keyboard encoders for entering hexadecimal and decimal numbers, a node that cancels the input result when two keys are pressed simultaneously) in the form of UGO and interconnection lines indicating the direction of the process, in this case, the data is sent to the keyboard encoders, from them they go to the blocking unit, from which they exit for further transformations.
Picture 1.
Functional - diagrams designed to explain the processes occurring in individual functional circuits of the product or in the product as a whole. The diagram shows the functional parts of the product involved in the process illustrated by the diagram, and the relationship between these parts.
An example of a functional electrical circuit is shown in Figure 2. The difference between a functional circuit and a structural one is that on a functional electrical circuit, processes that require explanation unfold to functional parts (elements, devices, functional groups).
In this case, it is required to explain how the data enters the hexadecimal keyboard encoder and the double-click blocking node. To do this, the line included in the encoder and the blocking node were deployed.
Figure 2.
Schematic - diagrams designed to depict all electrical elements and devices necessary for the implementation and control of established electrical processes in the product, all electrical relationships between them, as well as electrical elements that end the input and output circuits.
An example of an electrical circuit diagram is shown in Figure 3. A circuit diagram, unlike a functional or structural one, is not intended to depict ongoing processes, but is used to depict all components of the device.
This diagram shows all the logical elements involved in the process of converting a positional code into binary and generating a signal indicating the correctness of the input (only one click is allowed), and the lines of electrical interconnection between them.
Figure 3
Connections - diagrams designed to depict all devices and elements that make up the product, their input and output elements, as well as connections between these devices and elements.
An example of an electrical connection diagram is shown in Figure 4. In contrast to the circuit diagram, which depicts all the functional parts of the product and the connections between them, the connection diagram depicts all the devices included in the product without expanding them to functional parts, but expands all input and output elements and depicts the connections between them.
This example shows how the components (keyboard encoders, arithmetic unit and output device) are interconnected in a product (computing device).
Figure 4
Connections - diagrams designed to depict the product, its input and output elements, and the ends of wires and external cables connected to them.
An example of an electrical connection diagram is shown in Figure 5. The connection diagram differs from the connection diagram in that it does not depict the connection of the devices included in the product, but the input and output elements of the product intended for connection to external devices that are not included in the product.
Figure 5
General - diagrams designed to depict all devices and elements included in the complex, as well as wires, bundles and cables connecting these devices and elements.
An example of an electrical connection diagram is shown in Figure 6.
Figure 6
Locations - diagrams designed to depict the components of the product, and if necessary, the connection between them - the structure, room or area on which these components will be placed.
An example of an electrical connection diagram is shown in Figure 7. In this example, the diagram shows the components of the cooling system (radiators and the unit attached to the processor) and the system unit case to which they are attached.
Figure 7 
Structural, functional and schematic diagrams are subject to consideration within the framework of this course, since they are basic and mandatory, other types of diagrams will be passed and performed at the request of the student.
The specification for instruments and automation equipment is carried out in the form presented in Table. 3. This form can only be recommended for educational work.
In the right column "Position number" indicate the position of instruments and automation equipment according to the automation scheme. In the column "Name and brief characteristic" the name of the device, its technical characteristics and features are indicated. For example, a sensor for measuring hydrostatic pressure (level). In the column "Type of device" the brand of the device is indicated, for example, Metran-150-L. In the "Note" column, if necessary, indicate "Supplied as a kit", "Development by a special design bureau" or "Development of IGHTU" and so on.
Rice. 14. Detailed scheme of heat exchanger automation
Instruments and automation equipment specified in the specification should be grouped according to parameters or functional characteristics.
Table 3
Specification for instruments and automation equipment
Description of the automation scheme
The description of the automation scheme implies explanations in a concise form, which tasks for the automation of a given technological object were set and how they were solved. A detailed description of how the signal passes from the measuring point through the functional blocks to the place of application of the control action (regulating element) needs to be done only for those circuits that are:
- the most responsible
- complex, the work of which requires explanation.
3.2. Schematic diagrams
Schematic diagrams are compiled on the basis of automation schemes, based on the specified algorithms for the functioning of individual control, signaling, automatic control units and general technical requirements for an automated object.
The development of circuit diagrams always contains certain elements of creativity and requires the skillful use of electrical circuits and typical functional units, their optimal layout into a single system, taking into account the satisfaction of the requirements for circuits, as well as the possible simplification and minimization of circuits. The scheme should provide high reliability, simplicity and economy, clarity of actions in emergency conditions, convenience of operational work, operation, and clarity of design.
This circuit must provide power supply to all electrical receivers (PLC-software-logic controllers, PCs, sensors, converters, secondary devices, control devices, etc.)
According to the PUE (ed. 7 of 07/08/2002), the reliability of the power supply of receivers is divided into three categories. Electrical receivers first category- electrical receivers, the power supply of which may lead to a danger to human life, material damage, disruption of a complex technological process, defective products, disruption of the functioning of especially important elements of public utilities. Electrical receivers second category- electrical receivers, the interruption in the power supply of which leads to a massive undersupply of products, equipment downtime. Third category- all other electrical receivers that do not fall under the definitions of the first and second categories. Power receivers of the first and second categories must have two independent sources of power supply with automatic reserve input (ATS) in case of failure of the first source. ATS should lead to uninterrupted power supply to the circuit. For objects assigned to the third category, it is enough to have one input. If there are consumers of different categories at the facility, then the power supply scheme for the highest category should be used for power supply. We can recommend the use of the following AVR modifications: UAVR-SCHAP12, UAVR-SCHAP23, UAVR-Y8301, UAVR-Y8302, SUE3000, ASCO300, ASCO7000.
Depending on the voltage of the power receivers, single-phase or three-phase power supply circuits are used. If there are no electrical receivers in the designed object that require a voltage of 380V, the power supply circuit is built single-phase. To power devices with a DC voltage of 24V or 36V, special power supplies are used, or step-down transformers with rectifiers after them.
Graphic design of circuit diagrams
Graphic designations of circuit elements are established by the group of standards "Conditional graphic designations in diagrams": GOST 2.721-74 (general use designations) and a number of other GOSTs. The general rules for the implementation of schemes are determined by the standards: GOST 2.701-84 “Schemes. Types and types. General requirements for implementation”; GOST 2.702-75 "Rules for the implementation of electrical circuits"; GOST 2.708-81 "Rules for the implementation of electrical circuits of digital computer technology."
In cases where there is a need to use any graphic images that are not provided for by the standards, it is allowed to use non-standardized graphic symbols, while providing the necessary explanations in the diagram. Conditional graphic symbols of elements, the dimensions of which are not established in the standards, are depicted on the diagrams in the sizes in which they are made in the relevant standards for graphic symbols.
It is allowed to reduce all values proportionally, however, the gap between two adjacent lines of the symbolic graphic designation must be at least 1 mm. The size of conventional graphic symbols can also be increased if, for example, it is necessary to enter explanatory signs into them.
Circuit designation
The designation of circuit sections serves to identify them and may also reflect their functional purpose in the electrical circuit. Requirements for the designation of circuits of circuit diagrams are defined by GOST 2.709-72. According to this standard, all sections of electrical circuits, separated by contacts of devices, relay windings, devices, machines, resistors and other elements, must have a different designation. Sections of circuits passing through detachable, collapsible or non-separable contact connections must have the same designation.
To designate sections of circuits of electrical circuits, Arabic numerals and capital letters of the Latin alphabet are used. The numbers and letters included in the designation should be done in the same font size.
Reading circuit diagrams and especially the operation of electrical installations are greatly simplified if, when developing a circuit, circuits are designated according to a functional feature, depending on their purpose. So, for example, it may be recommended to use a group of numbers 1-399 for control, regulation and measurement circuits, for signaling circuits 400-799, for power circuits 800-999. Instead of groups of numbers, the functional affiliation of the circuits of the circuit diagram can also be expressed in conditionally accepted letters.
Common AC power circuits are marked with phase letters (eg A800, B801, etc.). The neutral wire is marked with the addition of the letter N.
DC power circuits are designated: odd numbers - sections of circuits of positive polarity, even - sections of circuits of negative polarity.
The sequence of designations should be from the input of the power source to the consumer, and branching sections are designated from top to bottom in the direction from left to right.
On fig. 15 shows an example of a circuit diagram of a distribution network. The circuit is made using AVR - A1, to power sensors with a unified current output signal, a power supply is used to convert the mains voltage 220V into a stabilized voltage 24V - A2. We can recommend the use of the following modifications of power supplies: Metran-602, Metran-604, Metran-608, Metran-602-Ex, BP KARAT-22, BP-96. Automatic circuit breakers - QF, for example VA-47-29, are used to protect electrical consumers. The scheme is supplemented by a list of elements of the distribution network circuit diagram, which provides for the reference designation, name, brief description and number of power supplies for sensors with a unified output signal, power supplies for the controller, automatic switches, etc. (Table 4).
Table 4
List of elements of the electrical circuit diagram of the distribution network
Lesson 3
ELECTRICAL PRINCIPAL DIAGRAM OF RADIO ENGINEERING AND ELECTRICAL
PRODUCTS
Guidelines
The process of developing electrical equipment is conditionally divided into several stages: technical proposal, draft design, technical design, working design documentation. At almost every design stage, it becomes necessary to graphically depict the structure of a device or system, showing only its constituent parts and the relationships between them. The actual geometric shape and dimensions of the elements, as well as their actual location in the structure in this case, are not essential for the developer.
ESKD standards provide for a graphic design document called "Scheme" and developed rules for its design. According to GOST 2.102-68, a scheme is defined as a design document, on which the component parts of the product and the links between them are shown in the form of conditional graphic images or symbols. The circuit thus developed becomes the directive for product design, manufacture and control.
In operation, according to the schemes, they study the principle of operation of the product and the processes occurring in it. Therefore, the significance of the conventions and rules for the graphic design of diagrams should be considered as an integral part of the general training of a specialist in the field of engineering graphics.
Of all the types of circuits in the design of electrical equipment, electrical circuits of various types are most widely used, first of all, electrical circuit diagrams, the basic rules for the execution of drawings of which are set out in these guidelines.
Goal of the work- to familiarize students with the rules for graphic design of the design document "Electrical Schematic Diagram".
The main tasks of the work:
1. To acquaint the student with the types of electrical circuits (GOST 2.-2011).
2. To acquaint the student with the basic rules for the implementation of electrical circuit diagrams (GOST 2.701-2008).
3. To acquaint the student with the ESKD section “Conditional graphic symbols in diagrams” (GOST 2.721-74, etc.)
The student must:
1. Run a circuit with the least number of kinks and intersections of electrical communication lines.
2. Draw the electrical elements shown conditionally.
3. Designate the circuit, circuit elements, input and output circuits.
4. Designate identical elements connected in series or in parallel.
5. Complete the list of elements.
The work must be done on A3 drawing paper. It is allowed to use stencils "Elements of electrical circuits". The basis for the performance of the work is the theoretical knowledge obtained in the study of engineering graphics; elementary concepts from the field of electrical engineering obtained in a secondary school; skills in using reference literature; graphic skills acquired while studying engineering graphics.
2. GENERAL INFORMATION ABOUT SCHEMES
Terms, definitions. The schemes are based on the principle of dividing the product and its scheme into structural units, between which a one-to-one correspondence is established, which is achieved by using adequate conventional graphic symbols or images and indicating the characteristics of the functional parts of the product and processes on the diagram.
According to GOST 2.701-2008, structural units of a product can be:
Circuit element - a component of the circuit that performs a specific function in the product and cannot be divided into parts that have an independent purpose (resistor, transformer, pump, distributor, coupling, etc.);
Device - a set of elements representing a single structure (block, board, cabinet, mechanism, dividing panel, etc.), which may not have a specific functional purpose;
Functional group - a set of elements that perform a specific function in the product and are not combined into one design;
functional part - element, device, functional group;
functional circuit - a line, channel, path for a specific purpose (audio channel, video channel, microwave path, etc.);
Installation - the code name of the facility of power facilities for which the scheme is issued, for example, main circuits;
Relationship line - a line segment indicating the presence of a connection between the functional sections of products.
Each functional part of the product is characterized by:
Name indicating its specific function in the product and the nature of the processes occurring in it;
Parameters of implemented physical processes.
Elements and devices, in addition, characterize the type and technical data that determine their specific design (shape, dimensions, methods of attachment and connection, etc.) and operational (permissible currents, voltages, pressure, etc.) properties.
Types and types of schemes. In accordance with GOST 2.701-84, all schemes, depending on the types of elements and connections that make up the product, are divided into types presented in Table. 1. Depending on the main purpose, the schemes are divided into types, presented in Table. 2.
Structural diagrams are developed when designing products (installations) that precede the development of other types of diagrams, and they are used for general familiarization with the product (installation).
Functional diagrams are used to change the principles of operation of products (installations), as well as during their adjustment, control and repair.
Schematic diagrams are used to study the principles of operation of products (installations), as well as during their adjustment, control and repair. They serve as the basis for the development of other design documents, such as wiring diagrams (installation) and drawings.
Connection diagrams (installation) are used in the development of other design documents, primarily drawings that determine the laying and methods of fastening wires, bundles, cables or pipelines in a product (installation), as well as for making connections and when monitoring, operating and repairing products (installations).
Connection diagrams are used in the development of other design documents, as well as for connecting products and during their operation.
General schemes serve to familiarize with the complexes, as well as during their control and operation. A general scheme for an assembly unit can be developed if necessary.
Layout schemes are used in the development of other design documents, as well as in the operation and repair of products (installations).
Designation of schemes. Each scheme is assigned a cipher consisting of a letter, which determines the type of scheme, and a number, which indicates the type of scheme. For example, an electrical circuit diagram is designated EZ, a hydraulic circuit diagram - GZ, an electrical connection diagram - E4, etc.
Some general requirements for the implementation of schemes. A set (nomenclature) of diagrams for a product (installation) should be minimal, but contain information in an amount sufficient for the design, manufacture, operation and repair of the product (installation).
The formats of the sheets of schemes are selected in accordance with the requirements established by GOST 2.301-68 and GOST 2.004-79; with basic formats being preferred. The selected format should provide a compact implementation of the scheme, without violating its visibility and ease of use.
The schemes are drawn without observing the scale, the actual spatial arrangement of the components of the products (installation) is not taken into account or is taken into account approximately.
Graphic designations of elements (devices, functional groups) and communication lines connecting them are placed on the diagram in such a way as to provide the best idea of the structure of the product and the interaction of its components.
The distance (clearance) between two adjacent lines of the graphic designation must be at least 1.0 mm. The distance between adjacent parallel communication lines must be at least 3.0 mm. The distance between individual graphic symbols must be at least 2.0 mm.
When executing schemes, as a rule, the conventional graphic symbols established by the ESKD standards, as well as the symbols built on their basis, are used. If necessary, non-standard conventional graphic symbols are used.
Conditional graphic symbols of elements are depicted in the sizes established in the standards of conventional graphic symbols.
If necessary, all sizes of graphic symbols can be proportionally changed.
Graphic designations on the diagrams are made with lines of the same thickness as the communication line.
Symbols of elements on the diagram in the position in which they are given in the relevant standards, or rotated by an angle multiple of 90o, if there are no special instructions in the relevant standards. Conventional graphic designations are allowed - rotate by an angle multiple of 45 °, or depict them as mirrored. In the latter case, the meaning or readability of the designation should not be violated.
Symbols containing numeric or alphanumeric symbols may be rotated counterclockwise only at an angle of 90o or 45°.
Communication lines are made with a thickness of 0.2 to 1.0 mm, depending on the formats of the circuit and the size of the graphic symbols. The recommended line thickness is from 0.3 to 0.4 mm.
Communication lines should consist of horizontal and vertical segments and have the least number of angles and mutual intersections. In some cases, it is allowed to use inclined segments of communication lines, the length of which should be limited if possible.
The list of elements is placed on the first sheet of the diagram or performed as a separate document. It is allowed to place various textual information on the diagrams (technical data of elements and devices, diagrams, tables, necessary technical instructions, etc.). Such information may be located:
Next to the graphic symbols;
Inside graphic symbols;
Above the lines of communication;
In the break of communication lines;
Near the ends of communication lines;
On the free field of the diagram (if possible, above the main inscription).
RULES FOR THE PERFORMANCE OF ELECTRIC PRINCIPAL DIAGRAM
General information. Schematic diagram – a design document that shows in the form of conditional graphic images or symbols all the electrical elements or devices necessary for the implementation and control of the specified electrical processes in the product, all electrical connections between them, as well as electrical elements (sockets, clamps, etc.), which end the input and output circuits.
Conditional graphic images of some electrical and radio elements are given in the appendix.
The circuit diagram reflects the complete composition of the parts of the product and all the connections between them, so it gives a detailed idea of the principle of operation of the product. The circuit diagram is the most important among all types of circuits.
Being the result of the theoretical and research development of the product, it serves as a task for its design, and is also used in the manufacture of the product, its adjustment, control and repair.
Implementation of the concept. When performing electrical circuit diagrams, one should, first of all, be guided by the general requirements for the implementation of circuits, some of which are outlined above. Here are additional rules and guidelines for making electrical circuit diagrams.
Schematic diagrams are performed for products that are in the off position. In technically justified cases, it is allowed to depict individual elements of the circuit in the selected working position with an indication of the mode for which these elements are depicted on the field of the circuit.
Elements and devices are depicted on the diagrams in a combined or spaced way.
With the combined method, the components of elements or devices are depicted in the diagram in close proximity to each other. On fig. 1 shows in a combined way an electrical element "relay", including a coil and contacts.
Rice. 1. Combined way of depicting an electrical element.
With the spaced method, the components of the elements and devices are depicted on the diagram in different places in such a way that the individual circuits of the product are depicted most clearly (Fig. 2).
Rice. 2. Exploded way of depicting electrical elements
It is allowed to depict all and individual elements or devices in a spaced way.
Positional designations of elements. Each element or device included in the product and shown in the diagram must have a reference designation in accordance with the requirements of GOST 2.710-81. Positional designations for elements (devices) should be assigned within the product (installation).
Positional designation of an element (device) consists of one or two letters assigned to a group of elements (devices) of the product, and a serial number assigned to each element (device) within the group, for example C1, C2, etc.; KM1, KM2, etc., starting from one.
The letter codes of the elements are established by GOST 2.710-81. Codes for some elements are given in Appendix A.
The serial numbers of the elements are assigned in accordance with the sequence of their location on the diagram from top to bottom in the direction from left to right (Fig. 3). If the product has only one element with this code, then its serial number is not included in the reference designation of this element.
In the case when the product contains only one type of element belonging to a certain group, only the first (mandatory) letter of the code assigned to this group of elements is used to designate it.
Positional designations are put down on the diagram next to the conditional graphic designations of elements (devices) on the right side or above them.
Rice. 3. Fragment of an electrical circuit diagram
It is impossible to separate the positional designation from the conditional graphic designation of the element by relationship lines.
Characteristics of circuit elements. In some cases (for example, in circuit diagrams for a semiconductor integrated circuit), the values \u200b\u200bof resistors and capacitors are indicated near the conditional graphic and reference symbols. In this case, it is allowed to use a simplified method for designating units of measurements (Fig. 4):
for resistors
from 0 to 999 Ohm - without indicating units of measurement (3.6; 10; 180, etc.);
from 1 ∙ 10 3 to 999 ∙ 10 3 Ohm in kiloohms with the designation of the unit of measurement by a lowercase letter k (12k; 180k, etc.)
from 1 ∙ 10 6 to 999 ∙ 10 6 0m in megaohms with the designation of the unit of measurement with a capital letter M (2.7M; 100M, etc.);
over 1 ∙ 10 9 ohms - in gigaohms with the designation of the unit of measurement with a capital letter G (1G; 2.7G, etc.);
for capacitors
from 0 to 9999 ∙ 10 -12 F - in picofarads without indicating units of measurement;
from 1 ∙ 10 -8 to 9999 ∙ 10 -6 F - in microfarads without indicating units of measurement. In this case, the capacity is written either as a decimal fraction (0.05; 0.15; 0.5, etc.), or as an integer with zero separated by a comma (1.0; 10.0; 500.0, etc.).
Rice. 4. A simplified way to designate units of measurement near conventional graphic symbols
An important parameter of the resistor is the rated power dissipation, i.e. power that is dissipated by a resistor for a long time without harm to its performance. The rated power dissipation is indicated on the diagrams by conventional signs inside the resistor symbol. For example, a power of 62 mW is indicated by three slashes; 0.125 W - two; 0.25 W - one; 0.5 W - a line parallel to the large sides of the rectangle; and powers of 1, 2.5 W and more - with the corresponding Roman numerals (Fig. 5)
Rice. 5. Symbol for power dissipation of resistors
For electrolytic and oxide-semiconductor capacitors, in addition to the nominal capacitance value, the allowable voltage in volts is also indicated (Fig. 3). The voltage value is put down after the capacitance value through the “×” sign (multiplication) indicating the unit of measurement, for example 10.0x6V - a capacitor with a capacity of 10 microfarads with a permissible voltage of 6 volts.
Complete data about the elements is given in the list of elements, the connection of which with the scheme is provided using the reference designations of the elements.
Table of input (output) data. The characteristics of the input and output circuits of the product (frequency, voltage, current strength, etc.) are recommended to be written in tables placed instead of conventional graphic symbols for input and output elements - connectors, boards, etc. On fig. 6 (a) shows the dimensions of the table of input (output) data and an example of filling. In the column "Kont" the numbers of the contacts of the connector are indicated, in the column "Chain" the characteristics of the electrical circuits of the products are recorded. For the convenience of depicting the diagram, the table can be made mirror-rotated, as shown in Fig. 6(b).
Each table is assigned a position designation of the element, instead of the conventional graphic designation of which it is placed.
Above the table, it is allowed to indicate the conditional graphic designation of the contact - a socket or a pin.
Conventions and simplification of the implementation of schemes. If the product has several identical (by name, type and rating) elements connected in parallel, it is recommended that instead of depicting all elements of a parallel connection (Fig. 7, a) depict only one branch, indicating
the number of branches using the designation of a branch (Fig. 7, b, c). Near the graphic designations of the elements depicted conditionally in one branch, their reference designations are put down, while all the elements included in this parallel connection must be taken into account.
If the product has three or more identical (by name, type and denomination) elements connected in series, it is recommended to depict only the first and last elements instead of depicting all the elements connected in series (Fig. 8, a), showing the electrical connections between them with dashed lines. When assigning designations to elements, elements that are not shown in the diagram should be taken into account.
Rice. 6. Table of input (output) data: a - an example of filling in the table;
b - version of the mirrored table
Rice. 7. Image of several identical elements connected in parallel:
a) valid; b) conditional; c) symbol dimensions
Above the dashed line, the total number of identical elements is indicated. For example, five identical resistors connected in series will appear as shown in Fig. 8, b.
List of elements. All information about the elements that make up the product and shown in the diagram is recorded in the list of elements, which is placed on the first sheet of the diagram or is performed as an independent document.
Rice. 8. Image of several identical elements connected
sequentially: a - real, b - conditional
The continuation of the list of elements is placed to the left of the main inscription, repeating the head of the table.
When issuing a list of elements in the form of an independent document, its cipher must consist of the letter P (list) and the cipher of the scheme for which the list is issued. For example, the code for the list of elements for an electrical circuit diagram would be PES. The list of elements in this case is performed on A4 format with the main inscription in accordance with GOST 2.104-68 (form 2 and 2a).
Rice. 9. The form of the table of the list of elements
The columns of the list indicate the following data:
in the column "Pos. designation” – positional designation of an element, device or designation of a functional group;
in the column "Name" - the name of the element (device) in accordance with the document on the basis of which this element (device) is used, and the designation of this document (main design document, state standard, technical specifications), for example, resistor MLT-0.5-300 kOhm ± 5% GOST 7113-76;
in the column "Note" - technical data not contained in its name (if necessary).
The list of elements is filled from top to bottom in groups in alphabetical order of letter designations. If positional designations made up of letters of the Latin and Russian alphabets are used on the diagram, then elements with positional designations made up of letters of the Latin alphabet and then from the Russian alphabet are first written to the list.
Within each group having the same reference designations, the elements are arranged in ascending order of serial numbers.
Elements of the same type, having the same electrical parameters, are recorded in the list in one line if they have consecutive serial numbers. If there are two such elements, then in the column “Pos. designation" record positional designations of these elements. If there are more than two such elements, then only positional designations with the smallest and
the largest serial numbers, separating them with ellipsis, for example P 1, P 2; C1...C5. In the column "Col." indicate the total number of elements.
If the group includes several elements with the same name, then it is not written on each line, but is taken out as a heading. The title is written in the column "Name" and underlined. Between the heading and the beginning of the enumeration, one free line is left, between groups of elements - one or two lines (Fig. 10).
Rice. 10. An example of designing a group of elements in the list of elements
The designation of the document can be added to the title if all the enumerated elements are applied on its basis (Fig. 11). An example of filling in the list of elements is shown in fig. 12.
Rice. 11. An example of designing the header of a group of elements
Rice. 12. Fragment of the list of elements
4. INSTRUCTIONS FOR THE PERFORMANCE OF GRAPHIC WORK
Exercise. As a task, the student receives an electrical circuit diagram of the product, which correctly reflects the components of the product, the electrical processes occurring in it, but requires registration in accordance with GOST ESKD.
Drawing a diagram according to the proposed task is recommended to be performed in the following sequence:
1. Sheet layout. Draw a frame on the A3 format of drawing paper, located horizontally, allocate space for the main inscription and the list of elements.
On the remaining format field, arrange the scheme so that the distances from its borders to the format frame are the same. Conditional graphic images of elements should be evenly distributed within the scheme.
2. Draw a diagram with the least number of kinks and intersections of electrical communication lines.
3. Draw identical elements connected in series or in parallel.
4. Assign alphanumeric designations to the elements.
5. Run a table of input and output circuits.
6. Run a table of the list of elements.
7. Fill in the main inscription.
8. Submit a diagram made in thin lines to the teacher for verification. With the correct implementation of the scheme, the teacher gives permission for the design of the scheme, puts his signature in the column "Checked."
9. Design of the scheme. Correct errors and circle the diagram. After that, submit the diagram to the teacher for final verification.
Task options in Appendix A
