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An electronic circuit controls the operation of the device. Designation of radioelements on diagrams. Electronic key management schemes

Computer structure Answer the test questions: 1) Electronic circuit, work manager external device called: a) Adapter (controller) b) Driver c) Bus d) Hard drive 2) CD designed for multiple write new information is called: a) CD-ROM b) CD-RW c) DVD-ROM d) CD-R 3) System unit includes: a) motherboard, power supply, controllers, communications and communications b) modulator-demodulator, disk drives, controllers, communications and communications c) power supply, modulator-demodulator, disk drives, communications and communications d) motherboard, power supply , memory, controllers 4) The microprocessor is designed to: a) control the operation of the computer and process data b) input and output information c) process text data 5) Clock frequency microprocessor is measured in: a) gigahertz b) gigabits c) symbol table codes d) megabytes 6) Read-only memory is intended for: a) long-term storage of information b) storage of immutable information c) short-term storage of information at the current time 7) Random access memory is intended for : a) long-term storage of information b) storage of immutable information c) short-term storage of information at the current time 8) External memory designed for: a) long-term storage of information b) storage of immutable information c) short-term storage of information at the current moment in time 9) A set of metal or ceramic disks (pack of disks) coated with a magnetic layer. a) Hard drive b) DVD-ROM c) Floppy disks d) Magnetic tapes 10) What type of memory is characterized by the following method of reading information: Protrusions reflect the light of a laser beam and are perceived as one (1), depressions absorb the beam and are perceived as zero (0 ). a) Operational b) Flash c) Optical d) Hard drive 11) Burning devices powerful laser microscopic depressions on the surface of the disk. a) DVD-ROM b) Monitor c) Video card d) Scanner 12) K internal memory include: a) Hard drive, optical discs and flash memory b) Operational and permanent c) Operational, permanent and HDD d) RAM, hard drive and flash memory 13) A type of memory that is distinguished by high performance and limited capacity. a) Internal b) Floppy disk c) External d) Optical 14) The microprocessor is an extremely large integrated circuit(VLSI). The word "ultra-large" refers to: a) the size of the integrated circuit b) the number of components contained in it electronic components c) to ultra-fast operating speed 15) What standard set of devices can be connected to a computer using a sound card? a) display, headphones, printer b) scanner, sound speakers, headphones c) microphone, headphones, speakers d) headphones, speakers, keyboard Answer additional questions: 1. Explain why a computer needs two types of memory: internal and external. 2. What types of optical disks do you know? 3. Which types of memory are built-in and which are removable? 4. Determine the characteristics of your home computer.

Hello, friends! Today we will look at one of the stages of designing electrical devices - drawing up electrical diagrams. However, we will consider them very superficially, since much of what is necessary for design is still unknown to us, and minimal knowledge is already necessary. However, this basic knowledge will help us in the future when reading and drawing electrical diagrams. The topic is quite boring, but rules are rules and must be followed. So…

What is an electrical circuit? What are they? Why are they needed? How to compose them and how to read them? Let's start with what kind of schemes exist in general. In order to unify the preparation of technical documentation (and diagrams are nothing more than part of this documentation) in our country, the State Standard (GOST) was introduced by Decree of the USSR State Committee for Standards dated August 29, 1984 No. 3038 one system design documentation. Scheme. Types and types. General requirements for implementation", otherwise known as GOST 2.701-84, to which any diagrams, manually or automatically, of products from all industries, as well as electrical circuits energy structures (power plants, electrical equipment of industrial enterprises, etc.). This document defines the following types schemes:

  • electrical;
  • hydraulic;
  • pneumatic;
  • gas (except pneumatic);
  • kinematic;
  • vacuum;
  • optical;
  • energy;
  • divisions;
  • combined.

We will be primarily interested in the very first point - electrical diagrams that are drawn up for electrical devices. However, GOST also defines several types of circuits depending on the main purpose:

  • structural;
  • functional;
  • fundamental (complete);
  • connections (installation);
  • connections;
  • are common;
  • location;
  • united.

Today we will look at electrical circuit diagrams and the basic rules for their compilation. It makes sense to consider the remaining types of circuits after the electrical components have been studied, and the training approaches the stage of designing complex devices and systems, then other types of circuits will make sense. What is an electrical circuit diagram and why is it needed? According to GOST 2.701-84, a schematic diagram is a diagram that defines the complete composition of elements and connections between them and, as a rule, gives a detailed idea of ​​the operating principles of the product (installation). Such circuits, for example, were supplied in the documentation for old Soviet televisions. These were huge sheets of paper in A2 or even A1 format, on which absolutely all the components of the TV were indicated. The presence of such a scheme greatly facilitated the repair process. Now such circuits are practically not supplied with electronic devices, because the seller hopes that it will be easier for the user to throw away the device than to repair it. What a marketing ploy! But this is a topic for another conversation. So, a schematic diagram of the device is necessary, firstly, in order to have an idea of ​​what elements are included in the device, secondly, how these elements are connected to each other and, thirdly, what characteristics these elements have. Also, according to GOST 2.701-84, the circuit diagram should provide an understanding of the principles of operation of the device. Here is an example of such a scheme:

Figure 7.1 – An amplification stage based on a bipolar transistor, connected according to a common emitter circuit, with thermal stabilization of the operating point. Electrical circuit diagram

However, we are faced with a small problem: we actually don’t know any electronic elements... What, for example, are the rectangles or parallel lines drawn in Figure 7.1? What do the inscriptions C2, R4, +Epit mean? We will begin our examination of electronic components through the lesson and gradually learn the main characteristics of each of them. And we will definitely study the principle of operation of this device with such a terrible name according to its circuit diagram. Now we will study the basic rules for drawing electrical circuit diagrams. In general, there are a lot of rules, but they are mainly aimed at increasing the clarity and understandability of the diagram, so they will be remembered over time. We will get to know them as needed, so as not to immediately fill our heads with unnecessary things until necessary information. Let's start with the fact that each electrical component on the electrical diagram is indicated by the corresponding conventional graphic symbol (UGO). We will consider the UGO of the elements in parallel with the elements themselves, or you can immediately look at them in GOST 2.721 - 2.768.

Rule 1. Serial numbers for elements (devices) should be assigned, starting with one, within a group of elements (devices) that are assigned the same letter position designation in the diagram, for example, R1, R2, R3, etc., C1, C2, C3, etc. .d. Skipping one or more serial numbers on the diagram is not allowed.

Rule 2. Serial numbers must be assigned in accordance with the sequence of arrangement of elements or devices on the diagram from top to bottom in the direction from left to right. If necessary, it is possible to change the sequence of assigning serial numbers depending on the placement of elements in the product, the direction of signal flow or the functional sequence of the process.

Rule 3. Positional designations are placed on the diagram next to the symbolic graphic designations of elements and (or) devices with right side or above them. In addition, the intersection of the position designation with communication lines, UGO element or any other inscriptions and lines is not allowed.

Figure 7.2 – To rule 3

Rule 4. Communication lines should consist of horizontal and vertical segments and have the least number of kinks and mutual intersections. In some cases, it is allowed to use inclined sections of communication lines, the length of which should be limited as much as possible. Intersection of communication lines that cannot be avoided is performed at an angle of 90°.

Rule 5. The thickness of the communication lines depends on the circuit format and dimensions graphic symbols and is selected from the range 0.2 – 1.0mm. The recommended thickness of communication lines is 0.3 – 0.4mm. Within the diagram, all communication lines must be depicted with the same thickness. It is allowed to use several (no more than three) communication lines of different thicknesses to identify functional groups within the product.

Rule 6. Symbolic graphic symbols of elements are shown on the diagram in the position in which they are given in the relevant standards, or rotated by an angle multiple of 90°, if there are no special instructions in the relevant standards. It is allowed to rotate conventional graphic symbols by an angle that is a multiple of 45°, or depict them as mirror images.

Rule 7. When indicating the nominal values ​​of elements (resistors, capacitors) near the symbolic graphic symbols, it is allowed to use a simplified method of designating units of measurement:

Figure 7.3 – To rule 7

Rule 8. The distance between the communication lines, between the communication line and the UGO element, as well as the edge of the sheet must be at least 5 mm.

To begin with, these eight rules are enough to learn how to correctly draw simple electrical circuit diagrams. In we looked at power sources for electrical circuits, in particular, “dry” cells and batteries, and in Lesson 6 we looked at an incandescent lamp as a consumer of electrical energy. Let's, based on the rules described above, try to create a simple circuit diagram consisting of three elements: a source ( accumulator battery), receiver (incandescent lamp) and switch. But first, let’s give the UGO of these elements:

Now let’s connect these elements in series, assembling an electrical circuit:

Figure 7.4 – First circuit diagram

Contact SA1 is called a normally open contact because in its initial position it is open and no current flows through it. When SA1 is closed (for example, this could be the switch we all use to turn on the lights at home), the HL1 lamp will light up, powered by the energy of the GB1 battery, and it will burn until the SA1 key opens or the battery power runs out.
This diagram absolutely accurately and clearly shows the sequence of connecting elements and the type of these elements, which eliminates errors when assembling the device in practice.
That's probably all for today, another terribly boring lesson is over. See you soon!

In this article we will look at the designation of radio elements on diagrams.

Where to start reading diagrams?

In order to learn how to read circuits, first of all, we must study what a particular radio element looks like in a circuit. In principle, there is nothing complicated about this. The whole point is that if the Russian alphabet has 33 letters, then in order to learn the symbols of radio elements, you will have to try hard.

Until now, the whole world cannot agree on how to designate this or that radio element or device. Therefore, keep this in mind when you collect bourgeois schemes. In our article we will consider our Russian GOST version of the designation of radioelements

Studying a simple circuit

Okay, let's get to the point. Let's look at a simple electrical circuit of a power supply, which used to appear in any Soviet paper publication:

If this is not the first day you have held a soldering iron in your hands, then everything will immediately become clear to you at first glance. But among my readers there are also those who encounter such drawings for the first time. Therefore, this article is mainly for them.

Well, let's analyze it.

Basically, all diagrams are read from left to right, just like you read a book. All sorts of different scheme can be represented as a separate block to which we apply something and from which we remove something. Here we have a circuit of a power supply to which we supply 220 Volts from the outlet of your house, and a constant voltage comes out of our unit. That is, you must understand what is the main function of your circuit?. You can read this in the description for it.

How are radioelements connected in a circuit?

So, it seems that we have decided on the task of this scheme. Straight lines are wires or printed conductors through which electric current will flow. Their task is to connect radioelements.


The point where three or more conductors connect is called knot. We can say that this is where the wiring is soldered:


If you look closely at the diagram, you can see the intersection of two conductors


Such intersection will often appear in diagrams. Remember once and for all: at this point the wires are not connected and they must be isolated from each other. In modern circuits, you can most often see this option, which already visually shows that there is no connection between them:

Here, it is as if one wire goes around the other from above, and they do not contact each other in any way.

If there was a connection between them, then we would see this picture:

Letter designation of radioelements in the circuit

Let's look at our diagram again.

As you can see, the diagram consists of some strange icons. Let's look at one of them. Let this be the R2 icon.


So, let's first deal with the inscriptions. R means . Since we have him not the only one in the scheme, the developer of this scheme gave him the serial number “2”. There are as many as 7 of them in the diagram. Radio elements are generally numbered from left to right and top to bottom. A rectangle with a line inside already clearly shows that this is a constant resistor with a dissipation power of 0.25 Watt. It also says 10K next to it, which means its denomination is 10 Kilohms. Well, something like this...

How are the remaining radioelements designated?

Single-letter and multi-letter codes are used to designate radioelements. Single letter codes are group, to which this or that element belongs. Here are the main ones groups of radioelements:

A - This various devices(eg amplifiers)

IN – converters of non-electrical quantities into electrical ones and vice versa. This may include various microphones, piezoelectric elements, speakers, etc. Generators and power supplies here do not apply.

WITH – capacitors

D – integrated circuits and various modules

E – miscellaneous elements that do not fall into any group

F – arresters, fuses, protective devices

H – indicating and signaling devices, for example, sound and light indicating devices

K – relays and starters

L – inductors and chokes

M – engines

R – instruments and measuring equipment

Q – switches and disconnectors in power circuits. That is, in circuits where high voltage and high current “walk”

R – resistors

S – switching devices in control, signaling and measurement circuits

T – transformers and autotransformers

U – converters of electrical quantities into electrical ones, communication devices

V – semiconductor devices

W – microwave lines and elements, antennas

X – contact connections

Y – mechanical devices with electromagnetic drive

Z – terminal devices, filters, limiters

To clarify an element after a single letter code goes the second letter, which already means element type. Below are the main types of elements along with the letter group:

BD – ionizing radiation detector

BE – selsyn receiver

B.L. – photocell

BQ – piezoelectric element

BR – speed sensor

B.S. – pickup

B.V. - speed sensor

B.A. – loudspeaker

BB – magnetostrictive element

B.K. – thermal sensor

B.M. – microphone

B.P. - pressure meter

B.C. – selsyn sensor

D.A. – integrated analog circuit

DD – integrated digital circuit, logical element

D.S. – information storage device

D.T. – delay device

EL - lighting lamp

E.K. - a heating element

F.A. – instantaneous current protection element

FP – inertial current protection element

F.U. - fuse

F.V. – voltage protection element

G.B. - battery

HG – symbol indicator

H.L. – light signaling device

H.A. – sound alarm device

KV – voltage relay

K.A. – current relay

KK – electrothermal relay

K.M. - magnetic switch

KT – time relay

PC – pulse counter

PF – frequency meter

P.I. – active energy meter

PR – ohmmeter

PS – recording device

PV – voltmeter

PW – wattmeter

PA – ammeter

PK – reactive energy meter

P.T. - watch

QF

QS – disconnector

RK – thermistor

R.P. – potentiometer

R.S. – measuring shunt

RU – varistor

S.A. – switch or switch

S.B. – push-button switch

SF - Automatic switch

S.K. – temperature-triggered switches

SL – switches activated by level

SP – pressure switches

S.Q. – switches activated by position

S.R. – switches activated by rotation speed

TV – voltage transformer

T.A. - current transformer

UB – modulator

UI – discriminator

UR – demodulator

UZ – frequency converter, inverter, frequency generator, rectifier

VD – diode, zener diode

VL – electrovacuum device

VS – thyristor

VT –

W.A. – antenna

W.T. – phase shifter

W.U. – attenuator

XA – current collector, sliding contact

XP – pin

XS - nest

XT – collapsible connection

XW – high frequency connector

YA – electromagnet

YB – brake with electromagnetic drive

YC – clutch with electromagnetic drive

YH – electromagnetic plate

ZQ – quartz filter

Graphic designation of radioelements in the circuit

I will try to give the most common designations of elements used in the diagrams:

Resistors and their types


A) general designation

b) dissipation power 0.125 W

V) dissipation power 0.25 W

G) dissipation power 0.5 W

d) dissipation power 1 W

e) dissipation power 2 W

and) dissipation power 5 W

h) dissipation power 10 W

And) dissipation power 50 W

Variable resistors


Thermistors


Strain gauges


Varistors

Shunt

Capacitors

a) general designation of a capacitor

b) varicond

V) polar capacitor

G) trimmer capacitor

d) variable capacitor

Acoustics

a) headphone

b) loudspeaker (speaker)

V) general designation of a microphone

G) electret microphone

Diodes

A) diode bridge

b) general designation of a diode

V) zener diode

G) double-sided zener diode

d) bidirectional diode

e) Schottky diode

and) tunnel diode

h) reversed diode

And) varicap

To) Light-emitting diode

l) photodiode

m) emitting diode in the optocoupler

n) radiation receiving diode in the optocoupler

Electrical quantity meters

A) ammeter

b) voltmeter

V) voltammeter

G) ohmmeter

d) frequency meter

e) wattmeter

and) faradometer

h) oscilloscope

Inductors


A) coreless inductor

b) inductor with core

V) tuning inductor

Transformers

A) general designation of a transformer

b) transformer with winding output

V) current transformer

G) transformer with two secondary windings (maybe more)

d) three-phase transformer

Switching devices


A) closing

b) opening

V) opening with return (button)

G) closing with return (button)

d) switching

e) reed switch

Electromagnetic relay with different groups of contacts


Circuit breakers


A) general designation

b) the side that remains energized when the fuse blows is highlighted

V) inertial

G) fast acting

d) thermal coil

e) switch-disconnector with fuse

Thyristors


Bipolar transistor


Unijunction transistor


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 an ordinary iron consists of heating element, temperature controller, 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. Chains for own needs ensure the operation of basic 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. 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 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 installation and commissioning wide use received detailed circuits with secondary circuits. They highlight additional functional subgroups of circuits related to switching on and off, individual protection of any section, and others.

Symbols in electrical diagrams

Each electrical circuit contains 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:

  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 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 An electrical circuit is single-circuit, while complex circuits 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 are also constructed. 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 secondary winding a circle can be used with a simplified method or two semicircles with an 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. 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 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

A schematic diagram is a graphical representation of all the 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 thoroughly understand how to connect all the parts to get the expected end result. That is, the device or circuit must fully perform its intended functions. To correctly read the circuit 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.

Conventional 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. There are also numbers next to the letter designations. They indicate the corresponding numbering or specifications elements.

All electrical circuit diagrams of machines, installations and machines contain a certain set of standard blocks and assemblies that are combined with each other in a certain way. In relay contactor circuits, the main elements of motor control are electromagnetic starters and relays.

Most often used as a drive in machines and installations. These engines are easy to design, maintain and repair. They satisfy most requirements for the electric drive of machine tools. The main disadvantages of asynchronous motors with a squirrel-cage rotor are large starting currents (5-7 times more than the rated current) and the impossibility simple methods smoothly change the rotation speed of the engines.

With the advent and active implementation of such motors in electrical installation circuits, such motors began to actively displace other types of motors (asynchronous wound-rotor motors and motors direct current) from electric drives, where it was necessary to limit starting currents and smoothly regulate the rotation speed during operation.

One of the advantages of using squirrel-cage induction motors is the ease of their connection to the network. It is enough to apply three-phase voltage to the motor stator and the engine starts immediately. In the very simple version To switch on, you can use a three-phase switch or a batch switch. But these devices, despite their simplicity and reliability, are manual control devices.

In the diagrams of machine tools and installations, the operation of one or another engine in an automatic cycle must often be provided, the sequence of switching on several engines, automatic change in the direction of rotation of the engine rotor (reverse), etc. must be ensured.

It is impossible to provide all these functions with manual control devices, although in a number of old metal-cutting machines the same reverse and switching of the number of pairs of poles to change the speed of rotation of the motor rotor is very often performed using packet switches. Switches and package switches in circuits are often used as input devices that supply voltage to the machine circuit. Still, motor control operations are performed.

Switching on the engine via an electromagnetic starter provides, in addition to all the convenience of control, zero protection. What this is will be described below.

Three electrical circuits are most often used in machines, installations and machines:

    control circuit for a non-reversible motor using one electromagnetic starter and two “start” and “stop” buttons,

    control circuit for a reversible motor using two starters (or one reversing starter) and three buttons.

    control circuit for a reversible motor using two starters (or one reversing starter) and three buttons, two of which use paired contacts.

Let's look at the operating principle of all these schemes.

The diagram is shown in the figure.


When you press SB2 “Start”, the starter coil is supplied with a voltage of 220 V, because it turns out to be connected between phase C and zero (N). The moving part of the starter is attracted to the stationary part, thereby closing its contacts. The starter's power contacts supply voltage to the engine, and the locking contact closes parallel to the "Start" button. Thanks to this, when the button is released, the starter coil does not lose power, because In this case, the current flows through the blocking contact.

If the blocking contact were not connected in parallel with the button (for some reason it was missing), then when the “Start” button is released, the coil loses power and the power contacts of the starter open in the motor circuit, after which it turns off. This mode of operation is called “jog”. It is used in some installations, for example in crane-beam schemes.

Stopping a running engine after starting in a circuit with a blocking contact is performed using the SB1 “Stop” button. In this case, the button creates a break in the circuit, the magnetic starter loses power and, with its power contacts, disconnects the engine from the supply network.

If the voltage disappears for any reason, the magnetic starter is also turned off, because this is equivalent to pressing the "Stop" button and creating an open circuit. The engine stops and restarting it in the presence of voltage is possible only by pressing the SB2 “Start” button. Thus, the magnetic starter provides the so-called. "zero protection". If it were absent from the circuit and the engine was controlled by a switch or batch switch, then when the voltage returned, the engine would start automatically, which poses a serious danger to operating personnel. See more details here -.

An animation of the processes occurring in the circuit is shown below.


The scheme works similarly to the previous one. Changing the direction of rotation (reverse) the motor rotor changes when the phase order on its stator changes. When the KM1 starter is turned on, phases A, B, C arrive to the motor, and when the KM2 starter is turned on, the phase order changes to C, B, A.

The diagram is shown in Fig. 2.



The engine is turned on for rotation in one direction using the SB2 button and the KM1 electromagnetic starter. If it is necessary to change the direction of rotation, you must press the SB1 “Stop” button, the engine will stop and then, when you press the SB 3 button, the engine begins to rotate in the other direction. In this scheme, to change the direction of rotation of the rotor, an intermediate press on the “Stop” button is necessary.

In addition, the circuit requires the use of normally closed (NC) contacts in the circuits of each starter to provide protection against simultaneous pressing of two “Start” buttons SB2 - SB 3, which will lead to short circuit in the motor power supply circuits. Additional contacts in the starter circuits prevent the starters from turning on at the same time, because When you press both “Start” buttons, any of the starters will turn on a second earlier and open its contact in the circuit of the other starter.

The need to create such a blocking requires the use of starters with a large number of contacts or starters with contact attachments, which increases the cost and complexity of the electrical circuit.

An animation of the processes occurring in a circuit with two starters is shown below.


3. Scheme for controlling a reversible motor using two magnetic starters and three buttons (two of which have mechanically coupled contacts)

The diagram is shown in the figure.


The difference between this circuit and the previous one is that in the circuit of each starter, in addition to the common SB1 “Stop” button, 2 contacts of the SB2 and SB 3 buttons are connected, and in the KM1 circuit, the SB2 button has a normally open contact (no contact), and SB 3 has a normally open contact - closed (break) contact, in the KM3 circuit - button SB2 has a normally closed (break) contact, and SB 3 has a normally open contact. When each button is pressed, the circuit of one of the starters is closed, and the circuit of the other is simultaneously opened.

This use of buttons makes it possible to avoid the use of additional contacts to protect against the simultaneous activation of two starters (this mode is impossible with this scheme) and makes it possible to perform reverse without intermediately pressing the “Stop” button, which is very convenient. The "Stop" button is needed to completely stop the engine.

The diagrams presented in the article are simplified. They do not have protection devices (circuit breakers, thermal relays) or alarm elements. Such circuits are also often supplemented with various contacts of relays, switches, switches and sensors. It is also possible to power the coil of the electromagnetic starter with a voltage of 380 V. In this case, it is connected from any two phases, for example, from A and B. It is possible to use a step-down transformer to reduce the voltage in the control circuit. In this case, electromagnetic starters with coils for voltages of 110, 48, 36 or 24 V are used.