Switches are used to turn on the lighting, and buttons and switches are used for household electrical appliances. This electrical equipment has one thing in common: they consume little power. And also - they are not switched on remotely or by automation devices. These tasks are solved with the help of magnetic starters.

Magnetic starter circuit. Device

The starter consists of two parts located in one housing: a control solenoid and a contact system.

The control solenoid includes a coil with a magnetic circuit, which includes a movable and a fixed part, held in the open state by a spring. When voltage is applied to the coil, the moving part of the magnetic circuit is attracted to the stationary part. The moving part is mechanically connected to the contact system.

The contact system includes movable and fixed groups of contacts. When voltage is applied to the starter coil, the magnetic circuit attracts the moving contacts to the fixed ones and the power circuits are closed. When the voltage is removed from the coil, under the action of a spring, the movable part of the magnetic circuit, together with the contacts, are brought to their original position.

An additional contact group is added to the power contacts of the starter, designed for use in control circuits. Its contacts are normally open (designated by the numbers "13" and "14") or normally closed ("23" and "24").

Electrical characteristics of magnetic starters

Rated starter current- this is the current that the power contacts can withstand for a long time. For some models of obsolete starters, for different current ranges, the overall dimensions or “value” change.

Rated voltage- supply voltage, which withstands the insulation between the power contacts.

Control coil voltage- operating voltage at which the starter control coil operates. Starters are available with coils operating from a DC or AC mains.

The starter control is not necessarily powered by the voltage of the power circuits; in some cases, the control circuits are independently powered. Therefore, control coils are available for a wide range of voltages.

Starter control coil voltages
Alternating current12 36 48 110 220 380
D.C12 36 48 110 220

Reversing magnetic starter, push-button station

The most common application of starters is motor control. Initially, the name of the device is derived from the word "start". The circuits use additional contacts built into the case: to pick up the command from the "Start" button. Normally closed contacts of the "Stop" button break the power supply circuit of the coil, and the starter disappears.

Issued reversible blocks incorporating two conventional starters connected electrically and mechanically. Mechanical interlock does not allow them to turn on at the same time. Electrical connections provide two-phase reversal when operating different starters, as well as the elimination of the possibility of supplying power to both control coils at the same time.


For ease of installation, starters produce in housings together with control buttons. To connect, just connect the power cable and the outgoing cable to them.

In other cases, to control the work are used pushbutton stations, switching the control coil circuit and connected to the starter by a control cable. For conventional starters, two buttons are used, combined in one housing - "Start" and "Stop", for reversing - three: "Forward", "Back" and "Stop". Stop button for quick shutdown in the event of an accident or danger, they are mushroom-shaped.


Depending on the purpose, the starters are made with three or four poles. But there are also devices that have one or two poles.

Manufacturers complement the line of manufactured devices accessories expanding their capabilities. These include:

  • additional contact blocks that allow you to connect signal lamps to the control circuit and generate commands depending on the state of the starter for the operation of other devices;
  • time delay blocks that delay the operation or shutdown of the starter;
  • sets of accessories that turn two starters into a reversing assembly;
  • pads that allow you to connect larger cables to the starter.

To protect electric motors from overloads, together with starters, thermal relays. Manufacturers produce them for the corresponding models of devices. The thermal relay contains a contact that opens when triggered and breaks the power supply circuit of the starter coil. To re-enable the contact must be returned to its original position by pressing the button on the body. To protect against short circuits, a circuit breaker is installed in front of the starter, which is detuned from the starting currents of the electric motor.

For the needs of industrial enterprises and companies, a sufficiently large number of equipment and devices are produced to ensure uninterrupted and standards-compliant operation. One of these devices is a magnetic starter.

Special purpose

The electromagnetic starter is an electromechanical device used to distribute the supply voltage and control the operation of the connected loads, the operation of which is regulated by a low voltage circuit. The list of tasks for which a magnetic starter is needed looks like:

  • Starting an electric motor with subsequent acceleration to the rated speed;
  • Maintaining the continuous operation of the engine;
  • Stopping the supply voltage to the motor;
  • Protective disconnection of the load from the network in case of overloads or non-standard situations.

Since magnetic starters are structurally simple devices and are capable of switching quite powerful loads with huge currents, they are also used to control the operation of melting furnaces, ventilation and air conditioning units, liquid electric pumps, pneumatic blowers and other similar consumers.

Design and technical parameters

Magnetic starter device:

  • Core;
  • Electromagnet coil;
  • Anchor;
  • polymer frame;
  • Mechanical work sensors;
  • Central and additional group of contactors.

The main parameters displayed in the technical documentation:

  • The measure of the current passing through the central terminals is the magnitude of the currents at which the device is operational for a long period of time with the given parameters;
  • The maximum value of the current that the device can operate;
  • The voltage of the connected circuit is the voltage of the operated circuit, at which the insulation between the central terminals retains its technical parameters;
  • The control voltage of the coil of an electric magnet is an alternating or constant supply voltage of the electromagnet;
  • Relay and electromechanical wear resistance - the indicator is expressed in the number of cycles for closing and opening the terminals. Relay durability is determined according to the corresponding schedule displayed in the accompanying documentation for the device. By substituting the values ​​of the supply voltage and current strength of the operated network, it is possible to determine the parameter yourself;
  • Boundary number of operations per unit of time;
  • The number of additional terminals and the method of their implementation;
  • The length of time to connect and disconnect.

In addition, the electromagnetic starter can be supplemented with:

  1. Protective relay to prevent overheating and electrical overloads of the end user;
  2. Additional set of terminals;
  3. starting device for the engine;
  4. Electrical fuses.

Varieties of magnetic starters

The following types of magnetic starters stand out from the general assortment:

  1. Reversible - providing rotation of the motor rotor in the opposite direction to the initial one;
  2. Non-reversible - supporting the rotation of the motor rotor in one direction;
  3. Fencing type - designed for installation in an area with a small amount of dust;
  4. Dustproof - used for outdoor placement and can be exposed to sunlight, rain and snow;
  5. Open type - used in rooms with no dust and foreign objects.

The principle of operation of the magnetic starter

The principle of operation of the magnetic starter is as follows. When a control signal is applied to the winding of the electromagnet coil (6), it becomes magnetized and, together with the fixed Ш-shaped part of the core (7), attracts the armature (5) on the plastic traverse (4), which is smoothly closed by the contact bridges (2) of the contact plates ( 3), thanks to the contact springs (1), which, in turn, create the necessary pressing force. Additional contacts (8) can be used at the discretion of the consumer.

The group of terminals is made in the form of a three-pole electric magnet of alternating current with auxiliary contacts made of silver-containing metal, it carries out switching of the main circuits, the current amplitude of which varies from 3 Amperes to 200 Amperes. Based on the fact that the main terminals conduct the operating current of the load for a long time and produce a large number of connection and disconnection cycles, cermet is used as the material for the main contacts. To simplify the use of stationary and moving terminals, it is customary to mount them easily removable.

In connection with the use of arc-extinguishing elements in the contactors, it became possible to reduce the distance between the working terminals and, accordingly, weaken the power of the electromagnet, shrink the dimensions and weight of the electromagnetic starter as a whole. The arc extinguishing device is used to prevent the occurrence of sparking of the terminals at the moment of closing and opening the contacts. At operating currents of more than 10 A, the arc extinguishing device is implemented in the form of an arc extinguishing grate for each opening. Arc-extinguishing grates are implemented on the principle of electric arc compensation by a transverse magnetic field in chambers with longitudinal holes. The negative consequences of sparking are burning, charring, excessive heating of contacts.

To move the armature with contacts, direct-directed systems of electromagnets with П, - and Ш, - shaped type-setting magnetic cores are used. Since, when the magnetic starter is triggered, an alternating current passes through the retracting coil, which in its magnitude significantly exceeds the current of the retracted state, for such starters the manufacturer sets a limit on the number of connections and disconnections per hour.

Depending on the throughput currents of the magnetic starter, contacts of various shapes and with different contact planes are used, as shown in the picture below.

For the control circuits of the magnetic starter, point contacts (a) are used, namely:

  • Point-plane (1);
  • Point-sphere (2);
  • Sphere-plane (3);
  • Sphere-sphere (4);

For power circuits of an electromagnetic starter, longitudinal contacts (b) are used, namely:

  • Prism-plane (5);
  • Cylinder-plane (6);
  • Cylinder-cylinder (7);
  • Plane-plane (8).

An additional bridge type contactor is used for switching low current control circuits and is operated by the same pull-in coil as the main contacts. Auxiliary contacts are based on copper coated with a thin layer of silver or bimetal. Manufactured magnetic starters in their composition have from two to four additional contacts, which can also work both for closing and opening.

In the operation of asynchronous motors, an integral part is the presence of a magnetic starter, the main task of which is to protect the device from overloads. When the engine is running, there are cases of a break in one of the phases due to blown fuses or for other reasons. It is clear that such a phenomenon leads to a sharp increase in current on the stator windings, which leads to overheating and failure of the electric motor. To prevent such breakdowns, magnetic starters with thermal relays are used. The bulk of thermal relays is built on the basis of bimetallic elements. The principle of operation of a bimetallic element is incorporated in its design, the essence of which is a rigid fastening, by hot rolling or welding, of two metal plates with different expansion coefficients. Since, when such an element is heated, the metal plate on one side will expand linearly faster than the plate on the reverse side, the plate will physically bend. Accordingly, there is a conversion of thermal energy into mechanical work by disconnecting the load in case of overheating.

Note! Since the thermal process is inertial, thermal relays cannot be a means of protecting equipment from short circuit currents. Even a short time to disconnect the load during a short circuit can be enough for the load to burn out or fail.

As metals with different coefficients of linear expansion used in bimetallic elements, chromium-nickel steel and invar are used.

Types of magnetic starters

Typical magnetic starters include:

  1. The PML class is operated with electric motors up to 75 kW. The main mechanism can be supplemented with a temperature relay and surge arresters;
  2. The PMA series is used in tandem with electric asynchronous motors, the rotor of which is squirrel-cage, and has a power of up to 100 kW with an operating voltage of 380V to 660V. The mechanism is complemented by a temperature relay, voltage limiter and positron protection;
  3. The functioning of asynchronous motors with power up to 11kW, with supply voltage up to 660V, is complemented by magnetic starters of the PME series. This series is completed with AC-3, AC-4 class terminals and thermal relays;
  4. The equipment of the ships is completed with electromagnetic starters of the PMM class. For areas of activity with more stringent safety conditions, magnetic starters have been created in a waterproof or drop-proof housing;
  5. The purpose of the magnetic starter of the PM-12 group is to connect to the network, reverse and turn off asynchronous motors with a squirrel-cage rotor, with a power of up to 125 kW and with a mains supply voltage of 380V to 660V.

Understanding the device and the principle of operation of the magnetic starter, it will not be difficult to choose a specific device to perform a specific task. When operating the device, do not forget about the maintenance and regular inspection of the magnetic starter, while the device will last a long time with the specified characteristics.

Video

An electrical contactor (magnetic starter) is a switching device, in fact, a large relay. Traditionally, a contactor has been used to switch current supplying electric motors or other high power loads. Often powerful electrical contactors for electric motors and other equipment are complemented by overload protection and other criteria. For this, sensitive bimetallic relays and blocking groups are used in the design of the device.

PUBLICATION CONTENT:

Design of electrical classic contactors

Electric classic contactors - they are also magnetic starters, usually have groups of contacts - main and auxiliary.

Contact groups (most often) are in a normally open state. Only when the supply voltage is applied to the induction coil of the device, the contact groups of the device change their state.

The three upper terminals of the main group are used to connect the input three-phase alternating current, as a rule, with a voltage of at least 380 volts. This contact group is equipped with reinforced screw terminals marked "L1", "L2", "L3".


Terminal assignments: 1 - line voltage supply; 2, 11 - output under load; 3, 5 - coil power; 4, 6 - auxiliary; 7 - sensitivity; 8, 9 - manual shutdown and reset buttons; 10 - auxiliary group

The second main group of terminals, assigned to power the load (or other), is located at the bottom of the device structure and also has screw terminals marked "T1", "T2", "T3".

Each device is traditionally marked with an alphanumeric combination of symbols. The marking is located on the body of the device and carries basic information about the device. For example:

A - 26 - 30 - 10

Here, the symbol "A" denotes the series of the device. Further, the number "26" marks the rated current (26A) for the load in the form of an asynchronous electric motor.

The number "30" indicates the number of normally open and normally closed power contacts (respectively 3 and 0). The number "10" indicates the number of auxiliary "NO" and "NC" contacts (1 and 0).

Auxiliary Switching Purpose

Auxiliary contacts are often used as part of a relay logic circuit or used as part of some other part of a load control circuit. The typical switching voltage here is 220VAC.


Wiring diagram (classic): 1 - magnetic starter; 2 - current protective relay; 3 - electric motor; 4 - button "STOP"; 5 - button "START"; 6 - accident reset button

Auxiliary contact groups may have a different configuration, depending on the instrument model and manufacturer. Contacts can be either normally closed or normally open. Usually there is a combination of states.

The auxiliary interface terminal set is usually rated for a current rating substantially lower than that of the main contacts.

However, the auxiliary group mechanism operates in conjunction with the main switching mechanism of the electrical contactor.

Auxiliary terminals are usually marked with a numerical code. For example, "13" and "14", "82" and "83", etc. To some extent, the power terminals of the inductive coil of the electromagnetic system of the device also belong to the same category.

The contact terminals of the coil power supply traditionally have the marker "A1" and "A2". The control voltage of the electromagnetic mechanism is applied to these terminals, usually according to the classical scheme (see above).

Additional protection module

Often the design of the electrical contactor complements. There are designs of electrical contactors where a thermal relay is an integral part.

True, modern versions of electrical contactors provide, rather, a modular build-up.


The protective module, often used in tandem with a magnetic starter, can have a different configuration. It looks like one of the classic options for a load of relatively low power

The most common are contactor relay modules of classes 5, 10, 20, 30. Accordingly, the values: 5, 10, 20, 30 indicate the response time (5, 10, 20, 30 seconds). Class 5 is generally used on motor contactors requiring instantaneous disconnection.

Electrical Contactors for Special Purposes

Control electrical circuits at high currents (up to 5000A) it is carried out using contactors of increased power. Also, devices of special design are used to control asynchronous motors with a phase rotor.


Special execution: 1 — the top power connector; 2 - two main connectors with an arc chute; 3 - frame of the device; 4 - output under load; 5 - auxiliary terminals; 6 - frame for the periphery; 7 - coil power; 8 - electromagnet

The nominal switching power parameter for devices of this type reaches 1500 kW. The operating current can be 1520A with a supply voltage of 440 volts.

The R series electrical contactors for AC or DC control are used where:

  • distribution of electrical energy,
  • control of induction furnaces,
  • switching of alternative energy systems,

Starter (MES 441-14-38) - a combination of all switching devices required to start and stop the motor, with overload protection.


Electromagnetic starter (magnetic starter) - a starter in which the force necessary to close the main contacts is provided by an electromagnet.


Magnetic starter (MP) is the most common electrical device for starting electric motors. Its main advantages are: remote control of starts, simplicity of circuits, protection against voltage reduction and overload, acceptable weight and size parameters, which can be called external properties, since they to a certain extent affect the quality of the entire system.


The external properties of the MP are constantly being improved (for example, in Russia a MP scheme with protection against network phase failure was recently patented). Large manufacturers representing these products in Russia: OJSC Kashin Plant of Electrical Equipment, 000 Uralelectrocontactor, OJSC Novosibirsk Plant of Low-Voltage Equipment, OJSC Cheboksary Electrical Apparatus Plant (Russia), EKFelectrotechnica (Russia), Schneider Electric (France), General Electric (USA), Moeller (Germany), АВВ (Germany), Siemens (Germany), Legrand (France), ChintGroupCo (China) and others.


Magnetic starters are selected depending on the environmental conditions and the control scheme according to:


Rated voltage;


Rated current;


Heating element current thermal relay;


The tension of the retracting coil.


Ump ≥ Un set; (1.1)
Imp ≥ Inset, (1.2)


where Ump, Imp are the nominal values ​​of voltage (V) and current (A) of the magnetic starter, respectively;


Un set, In set - respectively, the nominal values ​​\u200b\u200bof the voltage (V) and current (A) of the electrical installation.


Thermal relays are checked for compliance with their rated current 1tr n, the rated current of the heating element Ine, the upper Iset max and the lower Iset min limits for setting the current setting and the set current setting Iset r to the rated motor current In motor:


Itr n ≥ Ine ≥ In dv; (1.3)
Iset max ≥ In motor ≥ Iset min; (1.4)
Iset p \u003d In motor. (1.5)


For electric motors with a low load factor and operating current Iр dv, in order to increase the reliability of protection, the ratio is used:


The rated phase current of the electric motor Iн dv or according to the symbols adopted in electrical machines - I1 nom f is determined by the formula:



where P2 nom is the rated power of the electric motor, kW;


U1l - rated linear voltage, V;


m - efficiency factor, r.u.;


cos f - power factor, p.u.


The most common and common requirement that a consumer makes when choosing an MP is the value of the switched current, and according to this parameter, the MP of the above manufacturers can be divided into several groups:


1) MP with currents (we are talking about limiting current values) up to 100 A, and this includes MP of the PML series for currents of 10-80 A, the PMU series for currents of 9-95 A;


2) MP with currents up to 400 A, whose representatives are MP of the PMA series for currents of 40-160 A, the PM12 series for currents of 10-250 A (Russia) and foreign magnetic starters ChintGroupCo of the NC1 and NC3 series for currents of 9-370 A;


3) MP with currents up to 1000 A, which is represented by Moeller MP of the DIL series for currents of 20-855 A;


4) MP with currents above 1000 A, which include MP GE Power Controls of the CL and CK series for currents of 25-1250 A and MP ChEAZ-Benedikt for currents of 10-1200 A.


Among other things, for switching currents from 100 A to 1000 A, Russian manufacturers offer contactors of the KT-6000, MK6 series and vacuum contactors of the KV1 and KT12 series for general industrial use. Table 1.1 shows the indicators of the first group of SE, as the most massive.


For the MPs shown in Figure 1.1, belonging to groups 1, 2, 3 and 4, the corresponding indicators are presented in Table 1.





Rice. 1.1.


An analysis of the characteristics (see Table 1.1) shows that all MPs have practically the same parameters (the differences are insignificant). In this case, as a rule, when choosing a MP, they are guided by two fundamental indicators: the mode of operation and the load power. However, with strict restrictions on dimensions, preference should be given to MP No. 7 and No. 5, the dimensions of which are almost one and a half times smaller than those of the others, all other things being equal.


In terms of the power consumed by the coils when turned on, MP No. 6 is the most economical, while the savings range from 13 to 30%. In terms of the total work resource, preference should be given to MPs No. 1, 2, 3, 6. In terms of estimated cost, MPs No. 1 and No. 2 are in the lead, since the cost of other MPs is significantly higher.


It should be noted that in practice, especially when using MP in automated control systems, preference is given to imported devices, because. their auxiliary contacts provide the so-called "dry contact" used in microprocessor technology devices.


In addition, the undoubted advantages of imported MPs include:


MP version with DC coils (the exception is JSC VNIIR, which supplies PM12 starters with DC coils);


Table 1.1 Specifications magnetic starters

MP nomenclature

Engine power, kW

Power consumed by the coils when turned on, VA

Power consumed by the coils when holding, VA

Mechanical durability, switching frequency per hour

Total resource, million cycles

Electrical durability, switching frequency per hour

Operation time: closing, ms

Operation time: opening, ms

Minimum incl. ability: voltage V, / current A

Dimensions, HxWxT mm

Weight, kg

A very wide range of not only standard accessories for MP (auxiliary contact blocks, thermal relays, surge arresters), but also all kinds of devices that greatly simplify the installation and maintenance of devices.


Taking into account the fact that the uninterrupted operation of an electric motor largely depends on the reliability of the MP, such an important indicator of reliability as the coefficient of technical readiness deserves special consideration. This indicator takes into account not only the failure rate, but also the time required to restore the health of the MP, characterizing the probability that the device will work at the right time and the system will perform the required tasks. For most of the MPs listed in Table 1.1, manufacturers do not specify indicators such as mean time between failures or failure rates in the product specifications. However, the accumulated statistical data of the operation of the above series of MPs make it possible to obtain the following averaged data on the availability factor: for MP Russian production No. 1, 3, 7 (Table 1.1) the readiness factor is 0.9905, for MP of Ukrainian production No. 2 - 0.9812, and for imported MP No. 4, 5, 6 - 0.9383. Thus, at objects of increased importance, where high reliability is required, it is more expedient to use MP No. 1,3,7.


Given the exceptionally wide distribution of MF, it is of great importance to reduce the power consumed by them. In an electromagnetic starter, power is consumed in an electromagnet and a thermal relay. Losses in an electromagnet are approximately 60%, in thermal relays - 40%. In order to reduce losses in the electromagnet, cold-rolled steel E-310 is used. MP of the PML and PM12 series have a switching capacity of up to 20 * 106 operations and a switching frequency of up to 1200 per hour (Table 1.1). The choice of MP is carried out according to the rated voltage of the network, the rated supply voltage of the coils and the rated switching current of the power receiver.


It is allowed to select MP according to the "starter size": 1 value - 10 A, 4.5 kW; 2nd value - 25 A, 11 kW, 3rd value - 40 A, 18 kW; 4th value - 63 A, 30 kW; 5th value - 100 A, 45 kW; 6th value - 160 A, 75 kW; 7th value - 250 A, 110 kW.


This term characterizes admissible current MP through power contacts at a voltage of 380 Volts and in the operating mode of the AC-3 starter.


MP application categories: AC-1 - MP load is active or slightly inductive; AC-3 - mode of direct start of a motor with a squirrel-cage rotor, turning off a rotating motor; AC-4 - start of an electric motor with a squirrel-cage rotor, shutdown of stationary or slowly rotating motors, countercurrent braking.


All the necessary parameters are indicated on the MP cases. This allows during installation to check the compliance of the mounted MP for a specific circuit. For imported MPs, the main parameter is not the “starter size”, but the power for which the MP is designed under various conditions. More often it turns out to be more convenient when choosing the desired MP.


The design of many MPs provides for the possibility of quick surface mounting on them: additional normally closed or normally open contacts; delay relay ON or OFF with delay time up to 160 s; thermal relays.


Electromagnetic starters of the PML series are designed for remote starting by direct connection to the network, stopping and reversing three-phase asynchronous electric motors with a squirrel-cage rotor at voltages up to 660V AC with a frequency of 50 Hz, and in the version with three-pole thermal relays of the RTL series - to protect controlled electric motors from overloads of unacceptable duration and from the currents arising from the breakage of one of the phases. MP can be equipped with surge arresters of the OPN type. With this configuration, the MP is suitable for operation in control systems using microprocessor technology when shunting the switching coil with an interference suppression device or with thyristor control. Rated AC voltage including coils: 24, 36, 40, 48, 110, 127, 220, 230, 240, 380, 400, 415, 500, 660V 50Hz and 110, 220, 380, 400, 415, 440V 60Hz. MP type PML for currents 10 ... 63 A have a linear magnetic system of the Ш-shaped type. The contact system is located in front of the magnetic one. The movable part of the electromagnet is integral with the traverse, in which movable contacts and their springs are provided. Thermal relays of the RTL series are connected directly to the starter housings.


Marking structure of MP type PML.


PML-X1 X2 X3 X4 X5 X6 X7 X8:


PML - a series of electromagnetic starters;


X1 - the value of the starter for rated current;


1 - 10 (16) A; 2- 25 A; 3 - 40 A; 4 - 63 (80) A; 5 - 125 A; 6 - 160 A; 7 - 250 A.


X2 - MP version according to its purpose and the presence of a thermal relay:


1 - non-reversible MP without thermal relay;


2 - non-reversible MP with a thermal relay;


5 - reversible MP without thermal relay with mechanical interlock for degree of protection IP00, IP20 and with electrical and mechanical interlocks for degree of protection IP40, IP54;


6 - reversible MP with a thermal relay with electrical and mechanical interlocks;


7 - MP with a star-delta circuit of protection degree IP54 (MP for a three-phase asynchronous motor, in the starting position of which the stator windings are connected by a star, and in the operating position - by a triangle).


X3 - MP version according to the degree of protection and the presence of control buttons and a signal lamp:


0 - IP00; 1 - IP54 without buttons; 2 - IP54 with "Start" and "Stop" buttons;


3 - IP54 with "Start", "Stop" buttons and signal lamp (manufactured only for voltages of 127, 220 and 380 V, 50 Hz);


4 - IP40 without buttons; 5 - IP40 with "Start" and "Stop" buttons; 6 - IP20.


X4 - number and type of auxiliary circuit contacts:


0 - 1z (for current 10 and 25 A), 1z + 1p (for current 40 and 63 A), variable



1 - 1r (for current 10 and 25 A), alternating current;


2 - 1z (for current 10, 25, 40 and 63 A), alternating current;


5 - 1z (for 10 and 25 A), direct current;


6 - 1r (for current 10 and 25 A), direct current).


X5 - seismic version MP (S);


X6 - MP version with mounting on standard rails R2-1 and



X7 - climatic version (O) and category of placement (2, 4); X8 - version for switching wear resistance (A, B, C). MP series PML (Fig. 1.2) consist of a fixed part (Fig. 1.2, pos. 2) fixed in the base, and a movable part (Fig. 1.2, pos. 3) with contacts for switching the power circuit. MP operation is controlled by an electromagnetic coil


control (Fig. 1.2, pos. 4) located on the middle rod of the fixed part of the Ш-shaped magnetic circuit.


Under the influence of the electromagnetic field of the retracting coil (Fig. 1.2, pos. 4), which occurs when current flows through it, two parts of the magnetic circuit are closed (Fig. 1.2, pos. 3, 4) with overcoming the resistance of the return spring (Fig. 1.2, pos. . 9), as well as moving contact springs. In this case, the contacts close and the device is switched.




Rice. 1.2.


1 - base made of heat-resistant plastic; 2 - fixed part of the magnetic circuit; 3 - moving part of the magnetic circuit; 4 - electromagnetic control coil; 5 - contact clamps; 6 - metal platform (for starters rated over 25 A); 7 - traverse with moving contacts; 8 - fixing screw; 9 - return spring; 10 - aluminum rings; 11 - fixed contact; 12 - clamp with a notch for fixing the conductor


On the MP, you can install a 2-pin or 4-pin prefix with a different set of break and make contacts. Contact attachments (CP) are mechanically connected to the MP from the side of the input terminals (top) and fixed above the MP traverse. The fastening method provides a rigid and reliable connection between the gearbox and the MP.


The contact attachment of the PKL series (Fig. 1.3) is designed to increase the number of auxiliary contacts in electric drive control circuits up to 440 V DC and up to 660 V AC


current with a frequency of 50 and 60 Hz. KPs are installed on the MP of the PML-1000.. PML-4000 series and on the intermediate relays of the RPL series. Structure symbol KP series PKL PKL-X1 X2 X3 X4 4 X5:


PKL - symbol of the series;


X1 - number of closing contacts (0; 1; 2; 4);


X2 - number of opening contacts (0; 1; 2; 4);


X3 - execution of the prefix according to the degree of protection;






Rice. 1.3


X4 - climatic version O, OM according to GOST 15150-69;



X5 - version for switching wear resistance in normal switching mode:


A - 3-106 cycles; B - 1.6-106 cycles.


Intermediate relays (RP) of the RPL series (Fig. 1.4) are intended for use as components in stationary installations, mainly in electric drive control circuits at voltages up to 440 V DC and up to 660 V AC with a frequency of 50 and 60 Hz. The relays are suitable for operation in control systems using microprocessor technology when the pull-in coil is shunted by an arrester arrester or with thyristor control. If necessary, one of the prefixes PKL or PVL can be installed on the RP. RP version M also allow the installation of one or two side PKB attachments. Rated contact current -16 A.


The structure of the symbol RP series RPL RPL-X1 X2 X3 X4 X5 4 X6:


RPL - symbol of the series;


X1 - relay version according to the type of control circuit current:


1 - with AC control;


X2 - number of closing contacts;


X3 - number of opening contacts;


X4 - version of the attachment according to the degree of protection:


M - execution with degree of protection IP20;


The absence of a letter means a prefix with a degree of protection IP00;




Rice. 1.4.


X5 - climatic version O, OM according to GOST 15150-69;



X6 - Execution on switching wear resistance in the mode of normal switching: A - 3⋅10 6 cycles; B - 1.6⋅10 6 cycles.


The PPL-04 memory attachment turns the RPL series RP into a two-stable one. It consists of an electromagnet and a latch that allows you to keep the relay contact system in the on position after the relay winding is de-energized. When voltage is applied to the winding of the memory attachment, the latch is released, and the RP returns to the state corresponding to the initial state of the single-stable RP.


Pneumatic time delay attachments of the PVL series (Fig. 1.5) or simply “attachment” are designed to create a time delay when the MP is turned on or off. Attachments can only be installed on the RP relay of the RPL series and on the MP of the PML-1000 ... PML-4000 series.


The prefix is ​​installed on top of the MP, sliding along the guides until it stops, while the latch of the prefix with its protrusions goes beyond the protrusions on the MP body. The mounting method provides a rigid and reliable connection between the attachment and MP.




Rice. 1.5.


Set-top boxes of the PVL series are produced: with a range of time delays from 0.1 to 15 s, from 0.1 to 30 s, from 10 to 100 s and from 10 to 180 s; with a degree of protection IP00 and IP20, in two versions in terms of wear resistance: A - 3⋅10 6 cycles; B - 1.6⋅10 6 cycles.


To increase the number of auxiliary contacts of the MP control circuit (with a prefix of the PVL series installed), a side attachment of the PKB series is used. The main characteristics of attachments of the PVL series are given in Table 1.2.


Relays of the RTL series (hereinafter referred to as the "relay") are designed to protect three-phase asynchronous motors with a squirrel-cage rotor from overload currents of unacceptable duration, including those arising from current asymmetry in the phases and from loss of one of the phases.

The relays can be attached directly to the MP of the PML series or mounted individually on a rail or screwed to a panel. Individual installation of the relay is carried out using terminal blocks of the KRL type (up to 100A). For currents up to 93 A, relays RTL-1000, 2000, 2000D are used.


The overall and mounting dimensions of the RTL-1000 and RTL-2000 relays are shown in Figure 1.6.


The structure of the symbol of the RTL series relays.


RTL-X1 XXX2 X3 X4 X5 X6 4:


RTL - letter designation of the relay series;


X1 - a figure indicating the rated current of the relay:


1 - version for currents up to 25A; 2 - version for currents up to 93A;


ХХХ2 - digits indicating the setting current range (see Table 1.3);


X3 - version of the relay with reduced overall dimensions:


D - letter indicating the version of the RTL-2000 relay for installation with magnetic starters PML-4160DM, PML-4560DM;


K - a letter indicating the version of the RTL-2000 relay for installation with PML-3000D magnetic starters;


M - letter designating the version of the relay with the degree of protection of the terminals IP20 according to GOST 14255-69;


X4 - relay reset method: 1 - manual reset; 2 - self-return;


X5 - trip class: B - trip class 10, absence of a letter - trip class 10A;


X6 - climatic version O, OM according to GOST 15150-69;



It is allowed to operate the relay when built into the MP shell or a complete device for the UHL3 version.


The main characteristics of the RTL series relays are given in Table 1.3.





Rice. 1.6. a) RTL-1000 and c) RTL-2000 - for connection to a contactor; b) RTL-1000 and d) RTL-2000 - for individual installation with terminal block type KRL-1 and 2, respectively


By analogy with the relay of the RTL series, the electrothermal relays of the RTL-M and RTL-M2 series (Fig. 1.7) are intended primarily for overload protection of asynchronous electric motors with a squirrel-cage rotor and are used in conjunction with the PML and PML-N contactors as part of the MP. The relays are manufactured in two sizes to be used with the corresponding group of contactors. The housing is made of heat-resistant molded plastic and consists of a base and a cover. The design of the relay is “bulk” and pre-prepared functional units are laid in the base during assembly: thermobimetallic plate heaters with hard leads welded to them for connection to the contactor and output terminals, a reset rail, a control mechanism with bridge contacts for “secondary” switching circuits.

Table 1.3 Technical characteristics of the RTL series relay

Starter rated current, A

Fault current regulation limits, A

Rated voltage, V

Power consumed by one pole, W

Motor power, kW at voltage, V

50Hz, 60Hz

RTL2061DM04

RTL2063DM04



Rice. 1.7.


The design of the relay includes a mechanism for accelerating operation in case of sudden overloads, which makes it possible to practically eliminate the failure of the protected electric motor in the event of a sudden jamming of the rotor or destruction of the bearings. All versions of the relay are regulated by the operating current, which makes it possible to accurately set the setting for a specific consumer (electric drive, process unit, etc.).


The RTL-M series covers the current range of 0.1-80 A and has 20 versions, somewhat simpler in design than RTL-M2, since it does not have a "Manual automatic" switch (Fig. 1.8) to return to the initial state after actuation.


 


Rice. 1.8. : a) – RTL 1001-M–RTL 2063-M; b) - RTL 1001-M2 - RTL 2065-M2


The RTL-M2 series covers the current range of 0.1-93 A and has 21 versions.


Advantages of RTL-M and RTL-M2 relays:


The relays are fixed with the help of a special protrusion and hard leads of the power connection directly to the MP;


The series are made in two sizes: size 1 fits with MP of the PML series for current up to 25 A, size 2 - for MP for current from 40-95A;


The presence of two groups of free contacts: 95-96 - for opening, 97-98 - for closing;


Two modes of resetting the relay mechanism after the thermobimetallic heaters have cooled down: manual with the "Reset" button, automatic;


The presence of an acceleration mechanism for 40% operation at high overload currents or phase imbalance with thermal compensation elements;


Possibility of sealing the relay after adjustment to the operating parameters of the protected equipment.


Thermal relays of an overload of the RTL series. Schneider Electric's Telemecanique brand is designed to protect AC circuits and electric motors from overload, phase asymmetry, delayed start-up and rotor jamming and can be installed directly under the MP of the PMU series (Fig. 1.9).





Rice. 1.9.


Relay type: RTL1U cover the current range of 0.1-25 A and has 14 versions; RTL2U cover the current range of 23-40 A and has 3 versions; RTL3U cover the current range 17-104 A and has 7 versions and RTL4U cover the current range 51-630 A and has 10 versions.


The average operating time depending on the multiplicity of the setting current for the RTL.U series relays is shown in Figure 1.10.


Advantages of RTL.U series relays:


Relays have built-in protection against phase failure or loss, rotor jamming in the form of a mechanical system of "rocker arms";


The relays have two modes: manual (relay cocking by pressing a button) and automatic (spontaneous relay cocking after the bimetallic plates have cooled down);


The relay has a "Testing" function (imitation of the operation of a thermal relay without overload);


The current settings are set by turning the dial. The disk is closed with a transparent cover, which can be sealed;


Relays RTL1U-RTL3U have movable contact leads, which makes it easy to connect them to different standard sizes of MP type PMU09-95 without the use of additional tools;


The RTL4U relay is mounted separately from the contactor. The electrical connection is made with wires.





Rice. 1.10. : 1 - symmetrical three-phase mode from a cold state; 2 - symmetrical two-phase mode from the cold state; 3 - symmetrical three-phase mode after a long current flow equal to the setting current (hot state); 4 - three phases from the hot state (maximum setting); 5 - three phases from hot state (minimum setting)


To change the settings of the RTL.U series relays, it is necessary to open the transparent cover (Fig. 1.11, pos. 1) above the setting adjustment dial. Set the setting current in amperes by rotating the disk (fig. 1.11, pos. 1).


To change the re-arming mode, you must first open the transparent cover and turn the blue "RESET" switch (Fig. 1.11, pos. 4):


Turn to the left (Fig. 1.12, a) - manual re-arming;


Turn to the right (Fig. 1.12, b) - automatic re-platoon.


The RESET switch remains in the automatic position.


re-arming until forced return to the manual re-arming position. When the cover is closed, the switch is blocked. Manual re-arming is carried out by pressing the blue "RESET" button.




Rice. 1.11.




Rice. 1.12.

The "Stop" function is activated by pressing the red "STOP" button (Fig. 1.11, pos. 5). Pressing the "STOP" button (Fig. 1.13, a):


Changes the state of a normally open (NO) contact;


Does not change the state of a normally closed (NC) contact. The STOP button can be blocked by a U-shaped bracket


(Fig. 1.13, b). Closing the lid locks the device.




Rice. 1.13.




Rice. 1.14.


The "Testing" function is activated by pressing the red "TEST" button with a screwdriver (Fig. 1.11, pos. 6). Pressing the "TEST" button (Fig. 1.14, a) simulates the operation of the relay during overload and:


Changes the position of NO and NC contacts;


Changes the position (Fig. 1.14, b) of the relay operation indicator (Fig. 1.11, pos. 7).


Thermal overload relays type LRD and LR97 of the D series of the Telemecanique brand are designed to protect AC circuits and electric motors (with a rated current of 0.1-150 A) from overload, phase asymmetry, delayed start-up and rotor jamming and can be installed directly under the LC1 type MP : LC - designation of the main module of the Tesys series contactor, 1 - non-reversing contactor.


Relay class 10A type: LRD-01-35 (No. ° according to the catalog) cover the current range 0.1-38 A and has 16 versions; LRD-3322-3365 cover the current range 17-104 A and has 8 versions; LRD-4365-4369 covers the current range 80-140 A and has 3 versions.


The mounting kit (Fig. 1.15, a, pos. 1) is designed for direct connection of the NC contact of the LRD relay (Fig. 1.15, a, pos. 2) to the LC1 MP (Fig. 1.15, a, pos. 3).


The terminal block (Fig. 1.15, b, pos. 1) is designed for mounting the LRD relay (Fig. 1.15, b, pos. 2) on a 35 mm rail or screw connection to the circuit board (Fig. 1.15, b, pos. 3) with a landing size of 110 mm. The design of the relay allows you to install a device for remote shutdown or electric return (Fig. 1.15, b, pos. 4), as well as a device for remote activation or electric return (Fig. 1.15, b, pos. 5). In addition, on the front panel of the relay, you can install a blocking (Fig. 1.15, b, pos. 6) of the "Stop" button.


With the help of flexible conductors LAD-7305 (fig. 1.15, c, pos. 1) for relay type LRD (fig. 1.15, c, pos. 2) and LA7-D305 (fig. 1.15, c, pos. 3) for relays LRD-3 (Fig. 1.15, c, pos. 4) can be carried out remote control return function.


The adapter for the door blocking mechanism (Fig. 1.15, d, pos. 1) allows remote control of the LRD type relay (Fig. 1.15, d, pos. 2) and LRD-3 (Fig. 1.15, d, pos. 3) using a handle with spring return for the "Stop" button (Fig. 1.15, d, pos. 4) and / or for the "Return" button (Fig. 1.15, d, pos. 5).




Rice. 1.15.


The average operating time depending on the multiplicity of the setting current for a three-pole thermal overload relay of the D series, type LRD, is shown in Figure 1.16.





Rice. 1.16.


1 - symmetrical load, 3 phases, from a cold state;


2 - symmetrical load, 2 phases, from a cold state;


3 - symmetrical load, 3 phases, with continuous flow of the set current (from the hot state)


The electronic overcurrent relay LR97 D (Fig. 1.17) is designed to provide the most complete protection of electric motors and complements the range of existing relays of the LRD type.


The use of these electronic relays is recommended to ensure the protection of electric motors operating in mechanisms with increased load torque, as well as devices with high inertia or with a high probability of jamming in steady state operation:


Conveyors, crushers and mixers;


Fans, pumps and compressors;


Centrifuges and dryers;


Presses, lifts, processing machines (sawing, planing, broaching, belt grinding).


An electronic relay can be used to protect motors during long starts or frequent starts.


Relay LR97 D has two protective functions with preset parameters: 0.5 s for blocked rotor of electric motors and 3 s for phase failure.


Relay LR97 D can be used to protect the mechanical part of an industrial installation. To implement this function, the minimum value on the O-TIME disk is set (Fig. 1.17, pos. 7), which provides a shutdown within 0.3 s.





Rice. 1.17. : 1 – RESET button; 2 – TEST/STOP button; 3 - readiness / operation status indicator; 4 – relay actuation indicator; 5 – current setting LOAD; 6 - setting the start time D-TIME; 7 - setting the delay O-TIME; 8 - manual / automatic installation of a repeated platoon; 9 - mode setting: 1-phase / 3-phase


The monitoring and protection functions provided by the LR97 D relay are most suitable for the following applications:


Control of the operation of electric motors with a significant starting time, with a high probability of a difficult start: electric motors with increased load torque, having significant inertia;


Monitoring the operation of electric motors in a steady state of operation, the function of detecting an increased load torque: (electric motors with a high probability of "jamming" or blocking of moving parts, electric motors with increasing torque);


Control of mechanical failures and damages;


Fast overload detection compared to thermal protection devices based on the I2t function;


Protection of electric motors for special applications: (long start; frequent starts: from 30 to 50 per hour); electric motors with a variable nature of the load when operating in a steady state, when a thermal overload relay cannot be used due to its characteristics (inertia of "thermal memory").


Relay LR97 D has two setting time ranges:


D-TIME (fig. 1.17, pos. 6): start time;


O-TIME: non-operating time (maximum allowable deviation time during steady state operation).


The D-TIME function is used only when starting the motor. At the time of starting, the overload detection function is not activated, which allows you to start the motor without tripping the protection relay, even with significant overloads. In steady state operation, when the current exceeds the set value due to overload or phase failure, the relay will operate after the time entered using the O-TIME dial has elapsed.


The red LED indicator (Fig. 1.17, pos. 3) signals the disconnection that has occurred.


To configure the relay, just follow 5 simple steps:


Set maximum values ​​on all three setting dials (LOAD, D-TIME and O-TIME);


Set the time value on the D-TIME disk corresponding to the start time of the electric motor;


When the motor enters constant load mode, set the current value by turning the LOAD dial (fig. 1.17, pos. 5) counterclockwise until the red LED starts flashing;


Slowly rotate the LOAD dial clockwise until the LED stops flashing;


Set relay threshold time using dial



For quick diagnosis of conditions, two LED indicator(green and red), showing the state of the relay and modes of operation (Table 1.4).


The electrical circuit for switching on the LR97 D relay connected to the KM1 contactor when controlling the electric motor is shown in Figure 1.18.



Rice. 1.18.

Table 1.4




Relay operation diagrams for three modes of operation of the electric motor: start, mechanical jamming of the rotor and overload are shown in Figure 1.19. At the moment of starting, the overload detection function is not active, and the starting time set on the D-TIME dial is longer than the time at which the motor starting current is greater than the setting current (Fig. 1.19). As a result, the protection relay does not work. If during the operation of the electric motor the rotor is jammed, then after a time equal to 0.5 seconds from the moment the current in the stator windings of the motor reaches a value equal to three times the set current, the relay is activated (Fig. 1.19).





Rice. 1.19. Diagram of the operation of the LR97 D relay during start-up and mechanical jamming of the rotor, short-term and long-term overload


In the event of a variable load, in which the current in the stator windings of the electric motor during its change does not exceed three times the set current, and the duration of the current change is less than the O-TIME relay non-operation time (Fig. 1.19), the relay operation mode remains unchanged (the protection does not operate ). If the time of action of the variable load is greater than or equal to the non-operation time of the O-TIME relay (Fig. 1.19), the protection relay is activated.


The relay is reset to its original state in three ways: 1 - manually, using the "Return" button (Fig. 1.17); 2 - automatic, implemented using the re-arming button (Fig. 17) after a fixed time equal to 120 s, except for


cases when the protection actuation is due to the start of the rotor (the time setting on the D-TIME disk is incorrectly selected), the rotor jammed and in case of operation due to a phase failure; 3 - electric, provided with a short-term power off for at least 0.1 s.


Relay operation diagrams for the case: phase failure at start-up, phase failure in the steady state operation of the electric motor and overload are shown in Figure 1.20. From the above diagrams it can be seen that in the event of a phase failure or its breakage, the protection relay is activated after a time equal to 3 s (preset parameter). In case of overload, the relay operation diagrams coincide with those shown for the corresponding modes in fig. 1.19.





Rice. 1.20. Diagram of the LR97 D relay operation in case of phase loss during start-up and steady operation of the electric motor, short-term and long-term overload


The relay operation diagram for the case of protecting the electric motor from mechanical overloads (shocks) from the rotor side is shown in Figure 1.21. As noted above, to implement the relay protective function against mechanical shock, it is necessary to select the setting on the O-TIME dial that corresponds to minimum value, which will ensure shutdown within 0.3 s (Fig. 1.21).





Rice. 1.21. Diagram of the LR97 D relay operation with mechanical overloads from the rotor of the electric motor


The essence of the connection scheme of any MP is to control the power supply of its coil. It is known that the operation and disconnection of the MP (retraction and return of power contacts) occurs by closing and opening the power supply circuit of the coil.


The connection diagram of a magnetic starter with a control coil for a voltage of 220 V is shown in Figure 1.22.





Rice. 1.22.


Power is supplied to the coil of the KM1 magnetic starter through the contacts of the "Start" button - SB2, "Stop" SB1 and thermal relay P connected in series in its circuit. When the "Start" button is pressed, its contacts close and power is supplied to the coil further through the closed contacts of the button "Stop". The MP core attracts the armature, closing the power moving contacts, and voltage is applied to the load.


When the “Start” button is released, the coil circuit does not break, since the KM1 block contact with closed contacts is connected in parallel with SB2 (the armature of the magnetic starter is retracted) - the phase voltage L3 will be supplied to the coil through them.


By pressing the "Stop" button, the power supply circuit of the coil is broken, the group of moving contacts returns to its original state and the load is thus de-energized. The same thing happens when the electric motor is overloaded with current, additional thermal energy is released on the heating elements of the thermal relay P, which leads to the opening contact of the thermal relay, interrupting, in this case, zero N, which feeds the KM1 coil of the magnetic starter.


The connection diagram of a magnetic starter with a 380 V coil is shown in Figure 1.23.


The differences between these two MP connection schemes are only in the supply voltage of the coil. In the first case, when connecting the MP with a coil operating voltage of 220 V, zero and phase L3 were used to power it, in the second, two supply phases L2 and L3.





Rice. 1.23.


The reverse circuit of connecting the electric motor to the supply network using the MP is shown in Figure 1.24. Connecting a three-phase electric motor in a reverse circuit is in demand in cases where, during its operation, it is necessary to quickly change the direction of rotation of the shaft. Unlike the usual connection scheme, this scheme contains two magnetic starters, two "Start" buttons and one "Stop".


The change in the direction of rotation of the motor shaft occurs due to a change in the phasing (the order of connecting the phases) in its power supply and is set by pressing the "Start1" or "Start2" button.


The power contacts of the KM1 and KM2 magnetic starters are connected in such a way that when one of them is triggered, the phase order in the power supply will differ from the phasing when the other is triggered.


The circuit works as follows: by pressing the "Start1" (SB1) button, the power supply circuit of the KM1 coil is closed, the KM1 power contacts are retracted and closed (highlighted in the diagram by a dotted line) and the power with the phase sequence L1, L2, L3 is supplied to the motor terminals. To avoid erroneous activation of the Start2 button, a normally closed auxiliary contact of the second KM2 magnetic starter is connected in series to the KM1 coil circuit.



Rice. 1.24.


The engine is stopped by pressing the "Stop" button (SB3) - its contacts "break" the supply phase of the L3 coil. An interruption in the supply of the KM1 coil leads to the return of the movable power contacts of this MP to its original position, so the electric motor is turned off.


By pressing the "Start2" (SB2) button, by analogy, the power supply circuit of the KM2 coil is closed, the KM2 power contacts are retracted and closed (highlighted in blue in the diagram) and the power is now


already with the sequence of phases L3, L2, L1, enters the motor terminals. Thus, the motor shaft will now rotate in the opposite direction.


The blocking of the magnetic starter KM1, in case of erroneous activation of the Start1 button, is also carried out here by sequentially connecting a normally closed auxiliary contact of another MP to the power circuit of the coil. In this case, a normally closed auxiliary contact KM1 is connected in series to the KM2 circuit.


The electrical circuit diagram of a non-reversible MP with a relay, with control buttons and signal lamps built into the shell, is shown in Figure 1.25.


Submission switching device from the distribution board (circuit breaker, knife switch) of the voltage to the terminals of the three-pole circuit breaker QF (the red signal lamp HL1 is lit), the circuit is being prepared for operation.





Rice. 1.25.


After the circuit breaker is turned on (the green signal lamp HL2 is on), voltage is applied to its terminals and to the main closing contacts of the KM magnetic starter. The coil of the KM magnetic starter is connected to the network through the contacts of the thermal relay and the Start (SB2) and Stop (SB1) control buttons. When the "Start" button is pressed, voltage is supplied to the coil of the KM magnetic starter through the closed contacts of the "Stop" button and the closed contacts of the KK thermal relay. The electric current passes through the KM coil, creates a magnetic field that attracts the armature to the core, and thereby closes the main and auxiliary contacts of the KM magnetic starter, shunting the closing contacts of the Start button, which can then be released. Voltage is applied to the windings of the electric motor M, and it is started, as indicated by the lamp HL3.


To turn off the motor, the "Stop" button is pressed. The coil loses power, after which the armature moves away from the core under the action of the return springs, and the contacts open.


In case of current overload of the electric motor, additional thermal energy is released on the heating elements of the KK thermal relay, which leads to the opening contact of the KK thermal relay, and the KM coil circuit opens.


The electrical circuit diagram of a reversible MP with a relay, with control buttons and signal lamps built into the shell, is shown in Figure 1.26.





Rice. 1.26. Electrical circuit diagram of a reversible MP with a relay, with control buttons and signal lamps built into the shell


When the "Forward" button (SB2) is pressed, a voltage of 380 V is supplied to the coil of the KM1 magnetic starter through the closed contacts of the "Stop" button (SB1) and the closed contacts of the KK thermal relay. The control electric current passes through the KM1 coil, creates a magnetic field that attracts the armature to the core, and thereby closes the main and auxiliary contacts of the KM1 magnetic starter, shunting the closing contacts of the "Forward" button. Voltage is applied to the windings of the electric motor M, and it is started, as indicated by the lamp HL3. To turn off the motor, the "Stop" button is pressed.


Changing the direction of rotation of the rotor of the electric motor is carried out by pressing the "Back" button SВ3). In this case, the electric control current passes through the KM2 coil, the main and auxiliary contacts of the KM2 magnetic starter are closed, shunting the closing contacts of the SB3 button. Voltage is applied to the windings of the electric motor M (the HL4 lamp is on), but the direction of rotation of the magnetic field changes (phase “A” voltage is applied to terminal “3”, and phase “C” voltage to terminal “1” of the electric motor), then there is a change in the phase sequence.


To avoid erroneous activation of the “Back” button, a normally closed auxiliary contact of the second magnetic starter KM2 is connected in series to the KM1 coil circuit.


The presence of a mechanical interlock in the design of the reversible MP prevents the occurrence of a short circuit between the phases while closing the main closing contacts of the KM1 and KM2 magnetic starters. Due to this, the appearance of voltage on the coil of the second contactor does not lead to its operation. In addition, after turning on the KM1 magnetic starter, the KM1 NC contact breaks the coil circuit of the KM2 magnetic starter, and when the SB3 button is pressed, no emergency modes. There is a similar electrical interlock in the KM1 coil circuit (NC contact KM2).


It should be noted that electrical interlocking can be performed by using break contacts of the “Forward” and “Back” buttons, which include KM1 and KM2 instead of break contacts, for example, in the absence of break contacts in the MP design. Then, when the SB2 button is pressed, the power circuit of the KM2 coil is interrupted and when the SB3 button is pressed, the KM2 coil will remain de-energized.


The high return coefficient of the electromagnets of the AC contactors makes it possible to protect against a decrease in the mains voltage (the electromagnet releases at U = (0.6-0.7) ^other). When the mains voltage is restored to the nominal value, the spontaneous switching on of the MP does not occur, because the closing auxiliary contacts KM1 and KM2 and the closing contacts of the "Forward" and "Back" buttons are open.


The circuit provides for grounding - the motor housing is connected to the neutral N. In the event of a breakdown of the insulation of the electric motor or the supply cable to the housing, a short circuit mode will occur in the circuit (a short circuit current will flow through the "phase - housing - zero" circuit), which will lead to operation electromagnetic release of the QF circuit breaker. The circuit breaker will de-energize the circuit.

The magnetic starter is most often used to control electric motors. Although it also has other areas of application: control of lighting, heating, switching of powerful loads. Their activation and deactivation can be performed both manually, using control buttons, and using automation systems. We will talk about connecting control buttons to a magnetic starter.

Starter control buttons

In general, two buttons are required: one to turn on and one to turn off. Please note that they use contacts of different purposes to control the starter. At the "Stop" button, they are normally closed, that is, if the button is not pressed, the group of contacts is closed, and opens when the button is activated. The opposite is true for the start button.

These devices can contain either only a specific element necessary for operation, or be universal, including one closed and one open contact each. In this case, you must choose the correct one.

Manufacturers usually supply their products with symbols that allow you to determine the purpose of a particular contact group. The stop button is usually painted red. The color of the launcher is traditionally black, then green is welcomed, which corresponds to the “On” or “Enable” signal. These buttons are mainly used on cabinet doors and machine control panels.

For remote control, push-button stations are used, containing two buttons in one housing. The station is connected to the installation site of the starter using a control cable. It must have at least three cores, the cross section of which may be small. The simplest working circuit of a starter with a thermal relay

Magnetic switch

Now about what you should pay attention to when considering the starter itself before connecting it. The most important thing is the voltage of the control coil, which is indicated either on it itself or nearby. If the inscription says 220 V AC (or there is an AC icon next to 220), then a phase and zero are required for the control circuit to work.

An interesting video about the operation of a magnetic starter, see below:

If it is 380 V AC (the same alternating current), then two phases will control the starter. In the process of describing the operation of the control circuit, it will be clear what is the difference.

For any other voltage values, the presence of the DC sign or the letters DC, it will not be possible to connect the product to the network. It is intended for other circuits.

We also need to use an additional starter contact, called an auxiliary contact. For most devices, it is marked with the numbers 13NO (13NO, just 13) and 14NO (14NO, 14).

The letters NO mean “normally open”, that is, it closes only on the pulled starter, which, if desired, can be checked with a multimeter. There are starters that have normally closed additional contacts, they are not suitable for the control scheme under consideration.

Power contacts are designed to connect the load they control.

At different manufacturers their labeling is different, but there is no difficulty in identifying them. So, we fix the starter to the surface or DIN-rail in the place of its permanent deployment, lay power and control cables, and start connecting.

220 V starter control circuit

One wise man said: there are 44 schemes for connecting buttons to a magnetic starter, of which 3 work, and the rest do not. But only one is correct. Let's talk about it (see the diagram below).
It is better to leave the connection of power circuits for later. This will make it easier to access the coil screws, which are always covered by the main circuit wires. To power the control circuits, we use one of the phase contacts, from which we send the conductor to one of the outputs of the Stop button.

It can be either a conductor or a cable core.

Two wires will already go from the stop button: one to the "Start" button, the second - to the contact block of the starter.

To do this, a jumper is placed between the buttons, and a cable core to the starter is added to one of them at the place of its connection. From the second output of the "Start" button, there are also two wires: one to the second output of the auxiliary contact, the second to the output "A1" of the control coil.

When connecting the buttons with a cable, the jumper is already placed on the starter, the third core is connected to it. The second output from the coil (A2) is connected to the zero terminal. In principle, there is no difference in what order to connect the outputs of the buttons and auxiliary contact. It is only desirable to connect the output "A2" of the control coil to the neutral conductor. Any electrician expects zero potential to be only there.

Now you can connect the wires or cables of the power circuit, not forgetting that next to one of them at the input there is a wire to the control circuit. And only from this side the starter is energized (traditionally - from above). Trying to connect buttons to the output of the starter will not lead to anything.

380 V starter control circuit

Everything is the same, but in order for the coil to work, the conductor from the “A2” output must be connected not to the zero bus, but to any other phase that has not been used before. The whole circuit will work from two phases.

Connecting a thermal relay to the starter circuit

The thermal relay is used for overload protection. Of course, it is still protected by an automatic switch, but its thermal element is not enough for this purpose. And it cannot be adjusted exactly to the rated current of the motor. The principle of operation of the thermal relay is the same as in the circuit breaker.

The current passes through the heating elements, if its value exceeds the specified value, the bimetallic plate is bent and switches the contacts.

This is another difference from the circuit breaker: the thermal relay itself does not turn off anything. It just gives a signal to turn off. which must be used correctly.
The power contacts of the thermal relay allow you to connect it to the starter directly, without wires. For this, each the lineup products complement each other. For example, IEK produces thermal relays for its starters, ABB - for its own. And so it is with every manufacturer. But the products of different companies do not fit with each other.

Thermal relays can also have two independent contacts: normally closed and normally open. We need a closed one - as in the case of the Stop button. Moreover, functionally it will work in the same way as this button: break the power circuit of the starter coil so that it disappears.

Now you need to embed the found contacts into the control circuit. Theoretically, this can be done almost anywhere, but traditionally it is connected after the coil.

In the case described above, this will require from the output "A2" to send the wire to the contact of the thermal relay, and from its second contact - already to where the conductor was previously connected. In the case of control from 220 V, this is a zero bus, with 380 V - a phase on the starter. The operation of the thermal relay for most models is not noticeable.

To return it to its original state, there is a small button on the instrument panel that flips when pressed. But this should not be done immediately, but let the relay cool down, otherwise the contacts will not lock. Before putting into operation after installation, it is better to press the button, eliminating the possible switching of the contact system during transportation due to shaking and vibrations.

Another interesting video about the operation of a magnetic starter:

Schema health check

In order to understand whether the circuit is assembled correctly or not, it is better not to connect the load to the starter, leaving its lower power terminals free. So you protect the switched equipment from unnecessary problems. We turn on the circuit breaker that supplies voltage to the object under test.

Needless to say, while editing is in progress, it should be disabled. And also any accessible way accidental activation by unauthorized persons is prevented. If, after applying voltage, the starter does not turn on on its own, it’s already good.

Press the "Start" button, the starter should turn on. If not, we check the closed position of the contacts of the "Stop" button and the state of the thermal relay.

When diagnosing a malfunction, a single-pole voltage indicator helps, with which you can easily check the passage of the phase through the "Stop" button to the "Start" button. If, when the Start button is released, the starter is not fixed, but disappears, the auxiliary contacts are connected incorrectly.

Check - they should be connected in parallel to this button. A correctly connected starter must be fixed in the on position by mechanical pressing on the moving part of the magnetic circuit.

Now we check the operation of the thermal relay. We turn on the starter and carefully disconnect any wiring from the relay contacts. The starter should fall off.