Connection diagrams for ME with several network interfaces. Device and design, technical characteristics, maintenance. Symbols in electrical diagrams

Content:

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 a regular iron consists of a heating element, temperature regulator, pilot light, fuse, wire and plug. Other electrical appliances have an even more complex design, complemented by various relays, circuit breakers, electric motors, transformers and many other parts. An electrical connection is created between them, ensuring full interaction of all elements and each device fulfilling its purpose.

In this regard, the question very often arises of how to learn to read electrical diagrams, where all components are displayed in the form of conventional graphic symbols. This problem is of great importance for those who regularly deal with electrical installations. Correct reading of 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 in advance with the basic concepts and definitions affecting this area.

Any diagram is made in the form of a graphic image or drawing, on which, together with the equipment, all the connecting links of the electrical circuit are displayed. Exist different kinds electrical circuits that differ in their intended purpose. Their list includes primary and secondary circuits, alarm systems, protection, control and others. In addition, there are and are widely used principled and fully linear and expanded. Each of them has its own specific features.

Primary circuits include circuits through which the main process 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. The main circuit circuits generate, convert and distribute the main flow of electricity. Self-service circuits ensure the operation of essential electrical equipment. Through them, voltage is supplied to the electric motors of the installations, to the lighting system and to other areas.

Secondary circuits are considered to be those in which the applied voltage does not exceed 1 kilowatt. They provide automation, control, protection, and dispatch functions. Through secondary circuits, control, measurement and metering of electricity are carried out. Knowing these properties will help you learn to read electrical circuits.

Full-linear circuits are used in three-phase circuits. They display 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 minor elements that do not perform primary functions. Due to this, the image becomes simpler, allowing you to better understand the principle of operation of all equipment. Installation diagrams, on the contrary, are carried out in more detail, since they are used for the practical installation of all elements electrical network. These include single-line diagrams displayed directly on the construction plan of the facility, as well as diagrams of cable routes along with transformer substations and distribution points plotted on a simplified general plan.

During the installation and commissioning process, extensive circuits with secondary circuits have become widespread. They highlight additional functional subgroups of circuits related to switching on and off, individual protection of any section, and others.

Symbols in electrical diagrams

Every electrical circuit contains devices, elements, and parts that together form a path for electrical 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:

1. The first group includes devices that generate electricity or power sources.
2. The second group of elements converts electricity into other types of energy. They perform the function of receivers or consumers.
3. The components of the third group ensure the transfer of electricity from one element to another, that is, from the power source to electrical receivers. This also includes transformers, stabilizers and other devices that provide the required quality and voltage level.

Each device, element or part corresponds to a symbol used in graphic images electrical circuits, called electrical circuits. In addition to the main symbols, they display the power lines connecting all these elements. The 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 current paths that cover several branches at once and are called electrical circuit circuits. The most simple circuit the electrical circuit is single-circuit, and complex chains consist of several circuits.

Most circuits consist of various electrical devices that differ in different operating modes, 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 nominal mode, all elements operate with the current, voltage and power specified 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 diagrams. Single-line and multi-line images are used to show winding terminals. The number of lines depends on the number of pins, which will be different for various types cars In some cases, for ease of reading diagrams, mixed images can be used, when the stator winding is shown in expanded form, and the rotor winding is shown in a simplified form. Others are performed in the same way.

They are also carried out in simplified and expanded, single-line and multi-line methods. The way of displaying the devices themselves, their terminals, winding connections and other components depends on this. For example, in current transformers, a thick line, highlighted with dots, is used to depict the primary winding. For the secondary winding, a circle can be used in the simplified method or two semicircles in the expanded image method.

Graphic representations of other elements:

• Contacts. They are used in switching devices and contact connections, mainly in switches, contactors and relays. They are divided into closing, breaking and switching, each of which has its own graphic design. If necessary, it is allowed to depict the contacts in a mirror-inverted form. 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. U circuit breakers The image indicates the type of release. Switches differ in the type of action; they can be push-button or track, with normally open and closed contacts.
• Fuses, resistors, capacitors. Each of them corresponds to certain icons. Fuses are depicted as a rectangle with taps. For permanent resistors, the icon may have taps or no taps. Movable contact variable resistor indicated by an arrow. The pictures of capacitors show constant and variable capacitance. There are separate images for polar and non-polar electrolytic capacitors.
• Semiconductor devices. The simplest of them are pn junction diodes with one-way conduction. Therefore, they are depicted in the form of 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. Knowing these graphical drawings makes reading electrical circuits for dummies much easier.
• Sources of light. Available on almost all electrical circuits. Depending on their purpose, they are displayed as lighting and warning lamps with corresponding icons. When depicting 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 schematic diagram is graphic image all elements, parts and components between which an electronic connection is made using live 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 diagrams for beginners that allows you to understand well how to connect all the parts to get the expected end result. That is, the device or circuit must fully perform its intended functions. For correct reading schematic diagram It is necessary, first of all, to familiarize yourself with the symbols of all its components. Each part is marked with its own graphic designation - UGO. Typically, such symbols reflect the general design, characteristic features 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 distinguish between parts with individual basic properties and characteristics. Each symbol carries certain encrypted information. For example, bipolar transistors may have completely different structures - p-p-p or p-p-p, so the images on the circuits will also be noticeably different. It is recommended that you carefully read all the elements before reading the electrical circuit diagrams.

Conditional images are often supplemented with clarifying information. Upon closer examination, you can see Latin alphabetic symbols next to each icon. This way, this or that detail is designated. This is important to know, especially when we are just learning to read electrical diagrams. Near letter designations There are also numbers. They indicate the corresponding numbering or specifications elements.

1.2 Basic ME connection diagrams

When connected corporate network to global networks it is necessary to limit access to the protected network from global network and from the protected network to the global network, as well as to ensure protection of the connected network from remote unauthorized access from the global network. At the same time, the organization is interested in hiding information about the structure of its network and its components from users of the global network. Working with remote users requires establishing strict access restrictions information resources protected network.

There is often a need to have several segments within a corporate network with different levels of security:

· freely accessible segments (for example, a WWW advertising server);

· segment with limited access(for example, for access by employees of an organization from remote sites);

· closed segments (for example, the financial local subnet of an organization).

To connect the ME, various schemes can be used, which depend on the operating conditions of the protected network, as well as the number of network interfaces and other characteristics used by the ME. The following schemes are widely used:

· network protection using a shielding router;
unified defense local network;

· unified local network protection;

· with protected closed and unprotected open subnets;

· with separate protection of closed and open subnets.

Let's take a closer look at a scheme with protected closed and unprotected open subnets. If the local network contains public open servers, then it is advisable to place them as an open subnet to the ME (Figure 1).

This method has high security for the closed part of the local network, but provides reduced security for open servers located before the firewall.

Some MEs allow you to host these servers on your own. However, this solution is not the best from the point of view of the security of the ME itself and the computer boot. It is advisable to use the ME connection scheme with a protected closed subnet and an unprotected open subnet only if there are low security requirements for the open subnet.

If increased requirements are placed on the security of open servers, then it is necessary to use a scheme with separate protection of closed and open subnets.

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1. Dual Homed

In this connection option, the firewall physically and logically separates the two networks, making a decision about the possibility of establishing a connection between them.

1.1. Demilitarized Zone (DMZ)

In some cases, the firewall allows the use of multiple network adapters with different security policies set. For this purpose, DMZ is used.

As a rule, the DMZ hosts services that must be available to both external network clients and clients of the protected network. Since access to DMZ services must be carried out from an open network, the DMZ defines less stringent requirements for network security, but sufficient to organize protection against threats. If the network uses groups of users with a clear distinction between available services or different levels of confidentiality of the processed information, then the firewall can control network flows not only to external networks, but also between internal network segments. The allocation of DMZ, as well as support for multiple network interfaces, allows for centralized management of the protection of network resources with various adopted security policies.

Example: Let there be a corporate web server that publishes company data on the corporate network. This data is retrieved by the web server from the internal database server. Access to the database server is allowed only on the internal network. To ensure the operation of the interface of the web database management system, it is necessary to allow access from the web server to the database server. Then, when gaining access to web servers, we can easily access the database server.

Dedicating a web server to the DMZ not only solves the problem of protection against external threats, but also minimizes the possibility of penetration into the local network.

1.2. Allowing routing between network interfaces

In most cases, routing is allowed between network interfaces at the operating system, with dynamic and static filtering mechanisms driven by traffic. During the loading/rebooting process of the operating system, there is a short moment in time during which network stack with the loaded routing service enabled, but the firewall with its filtering rules has not yet loaded.

When the firewall uses only application brokers, there is no need to route packets. In this case, application brokers establish mediation between the client and the server without routing support from the OS. In this case, routing between network interfaces can be prohibited.

1.4. Firewall on local computer network

A firewall can be used to segment a local computer network in order to increase its level information security and protection of individual network segments. Segmentation in the local network is used then:

When there are functional groups in the local network that process information with different levels of access,

When it is necessary to provide controlled access to application and service services,

When it is necessary to control the exchange of information flows between different functional groups.

2. Screening screen

Unlike a multi-interface firewall that separates two or more networks, a bastion host firewall is connected only to the internal network and has one network interface. In this design, a lot of attention is paid to setting up the routing tables so that all incoming traffic is sent to the firewall interface, and on the internal network the gateway is set to the firewall's IP address.

1. Shielding subnet

The shield subnet configuration adds an additional layer of security to the shield configuration by introducing a network segment to improve the isolation of the shield network.

ME technologies

1. Network address translation (NAT).

When using NAT, the firewall acts as an intermediary between two IP nodes, organizing 2 data transmission channels. In this case, a firewall using NAT interacts with an external IP node on behalf of the internal one, but using its own IP address.

Types of IP addressing of local networks:

1. 10.0.0.0 – 10.255.255.255
2. 172.16.0.0 – 172.31.255.255
3. 192.168.0.0 – 192.168.255.255

NAT provides simple and reliable protection by establishing so-called “unidirectional routing”, when network packets are transmitted through the firewall only from the internal network. Network address translation is carried out in three modes:

Dynamic

Static

Combined.

There is also a distinction between source address translation and destination address translation. NAT is used in the following cases:

1. Security policy requires hiding the internal address space of the network

2. Changing host addresses on the network is impossible

3. You need to connect a network with a large number of hosts, but with a limited number of static IP addresses

Dynamic broadcast

In dynamic mode, called port translation, the firewall has one external address. All calls to the public network by the internal network client are made using this address. When a client contacts, the firewall allocates a unique transport protocol port for the external IP address. Number of ports: 65000

Example: The local network uses a non-routable network with an address space of 10.0.0.0. The local network client wants to establish a connection to the web server 207.46.130.149.

The OS generates regular IP packets and sends them to the network. When packets pass through the firewall, the latter changes the source address to the address of the external interface, and the source transport port to the first free one from the pool of unused ports and recalculates checksum. For a web server, the client is a host with an IP address of 200.0.0.1, that is, the ME. The server responds to the client in the usual way.

Dynamic broadcast with dynamic selection of IP addresses

In dynamic mode with dynamic sampling, external IP addresses are allocated dynamically from a pool of external addresses. As with dynamic translation, a transport port is used for each connection. The difference is that when the entire port pool is exhausted, the next external IP address is allocated.

Static address translation

With static translation, the external interface of the ME is assigned as many registered IP addresses as there are hosts on the internal network.

Example:

1. The client of the public network segment accesses the web server at 200.0.0.21. 2. The firewall finds the corresponding rule in its routing table and replaces the destination address with 10.0.0.21.

3. The server returns a response packet with the source address 10.0.0.21.

4. When leaving the local network, the ME replaces its address with 200.0.0.21.

Static broadcast with dynamic selection of IP addresses

This type broadcast does not use transport ports, and each client is dynamically assigned an IP address from a pool of external addresses.

Windshield wiper, device

The car can be equipped with SL-191A or SL-191B windshield wipers, which have different fastenings of the blade arms. In SL-191A they are fastened with a spring plate, and in SL-191B - with a nut. The SL-191A windshield wipers use an ME-241 electric motor, and the SL-191B uses an ME241 or ME-241A motor. In 1970-1972 SL-191 windshield wipers were also used. They had an ME-241A electric motor and fastening of the brush arms using a spring plate.

On BA3-2103 cars, SL-193 windshield wipers are used. They differ from the windshield wipers of the VAZ-2101 car in their installation dimensions, blade arms and the blades themselves, which have less aerodynamic resistance. In addition, the SL-193 windshield wiper is slightly different in the configuration of the glass area being cleaned. These windshield wipers are equipped with ME-241 electric motors.

In the windshield wiper switching circuit on the BA3-2103 car, a switch was added in the washer pump windshield(see Fig. 336, b).

The windshield wiper consists of an electric motor, a lever mechanism, brushes with levers and is installed under the hood in the air intake box (Fig. 331). The force of pressing the brushes against the glass is 400-500 gf, and the frequency of swinging the brush arms is in the range of 50-70 double strokes per minute. The axes of the brush levers rotate in metal-ceramic bushings impregnated with oil and do not require lubrication during operation.

Electric motor ME-241

(Fig. 332) - direct current with excitation from permanent magnets. A worm gearbox is combined into one unit with an electric motor.

Rice. 330. Electrical diagram of the RS528 switching relay sound signals by car BA3-2103

Rice. 331. General view of the windshield wiper electric motor installed on a vehicle: .1 - electric motor; 2 - gearbox cover; 3 - plug block

Rice. 333. Electric motor ME-241A: 1 - cover; 2 - panel; 3 - switch pusher; 4 - switch contact disk; 5 - cam; 6 - gear wheel; 7 - gear housing; 8 - axis; 9 - crank; 10 - armature shaft; 11 - thrust bearing; 12 - body; 13 - stator winding; 14 - stator pole; 15 - anchor; 16 - brush holder; 11 - felt ring; 18 - bushing; 19 - thrust washer; 20 - tightening screw

The electric motor has a stamped steel housing 16, inside of which two permanent magnets 11 are secured with spring holders, forming a stator together with the housing. In the grooves of the armature core, made of steel plates, a wave winding is laid, the leads of the sections of which are soldered to the copper plates of the collector.

The armature shaft 12 rotates in two metal-ceramic bushings 15. Felt rings 13 impregnated with oil are placed around the bushings. Therefore, during operation, the armature shaft bearings do not require lubrication. The axial force acting on the armature shaft from the worm gear is perceived by the textolite washer 14, against which the rear end of the shaft rests. The front end of the shaft is pressed by a thrust bearing 6 with a spring.

The electric motor housing is closed with a cover 4, which is also the gearbox housing. A plastic brush holder 9 with two graphite brushes is riveted to the inside of the cover, and in the gearbox housing there is a plastic worm gear 3 with a cam 8. The gear is pressed onto the axle 5. The other end of the axle has a conical knurled surface onto which the crank is put on and secured with a nut. The axis rotates in a metal-ceramic bushing pressed into the cover.

Steel and textolite washers are installed between the gear and the crankcase. On the outside, the axle is sealed with a rubber ring, then a textolite washer and a steel elastic wavy washer are located. Then the water deflector ring and snap ring are installed. The gear ratio is 51:1.

Rice. 334. Electrical diagram of the ME-241A electric motor: 1 - armature; 2 - shunt coil of the stator winding; 3 - brake coil of the stator winding; 4 - serial stator winding coil; 5 - electric motor switch Wire color designation: G - blue; GB - blue with white stripes; GC - blue with black stripes; 3 - green; K - red

The gear housing is closed with a plastic panel 2 and a cover 1. The panel contains contact posts to which wires are soldered and a spring plate 7 is attached with switch contacts that stop the electric motor when the brushes are in the lower position. The contacts of the spring plate are pressed against the lower post (in the figure) connected to the power source. When the gear cam lobe is against the plate, it forces it away from the lower post and presses it against the upper post connected to ground.

The ME-241A electric motor (Fig. 333) has electromagnetic mixed excitation.

The housing 12 of the electric motor is made of steel pipe. Inside it, two steel poles 14 with stator winding coils 13 are secured with screws. One (serial) coil 4 (Fig. 334) is connected in series with the armature winding, and the other (shunt) 2 is connected in parallel to it. In addition, there is another coil - brake 3, placed together with the serial coil on the same pole. It turns on only when the electric motor is turned off, creates a magnetic flux directed towards the flow of the serial coil and, thus, ensures a quick stop of the armature.

The armature grooves are spiral, and the collector is located on the side of the back cover. The axial movement of the shaft 10 (see Fig. 333) of the armature is eliminated using a nylon thrust bearing 11 with a spring. The gearbox worm is double-threaded and the gear ratio is 34:1.

The crank 9 is riveted to the gear axis 8, and the torque from the gear to the axis is transmitted through a stamped steel cam 5.

One steel washer is installed between the gear and the gearbox housing, and one textolite, two steel and a corrugated steel washer are placed between the housing and the crank.

The electric motor switch consists of a pusher 3 with a contact disk 4 and two contacts riveted to panel 2. The contact disk is pressed against the contacts by a spring and closes them. When cam 5 presses on the pusher, the contact disk moves away and opens the contacts.

The windshield wiper relay (Fig. 335) is used to obtain intermittent operation of the windshield wiper. It is installed under the instrument panel on the left side.

The relay has an elastic plastic casing and a getinax base, to which a core 3 with a winding and an electromagnet yoke 4 is riveted. A plastic support with two pairs of fixed contacts is attached to the yoke on one side by a screw, and on the other side armature 2 swings on the yoke. The current-carrying plate of the armature closes the upper or lower pair of contacts. The spring pulls the armature away from the core, and therefore the upper pair of contacts is normally closed, and the lower one is normally open.

Rice. 335. Electrical diagram of the RS514 relay. Wire color designation: G - blue; GB - blue with white stripes; F - yellow; K - red

A breaker 1 is also attached to the base, having a bimetallic plate with a winding of nichrome wire. A resistor 5 is installed under the base, designed to reduce sparking between the contacts of the breaker.