How to assemble a starter with a button. Magnetic starter in automation systems

Not two, but three wires are connected to the second terminal of the closed “Stop” button: two “blocking” and one supplying the “Start” button, connected in parallel to each other. With this connection scheme, the “Stop” button turns off any of the connected starters and stops the electric motor.

All installation and repair work in the wiring diagrams for connecting a magnetic starter are carried out with the voltage removed, even if the control circuit switches the neutral.

An example of using a reversing magnetic starter - connection diagram on video

Starter, star-delta circuit

I immediately refer the reader to the articles that precede this one -, and. I highly recommend reading it before further reading.

I will also say that in the language of electricians, “contactor” and “starter” are very intertwined, and in the article I will speak both ways.

I'll repeat it to refresh my memory. A magnetic starter is a device that necessarily contains a contactor (as the main switching element), and may also contain:

• automatic motor either (as a working or emergency shutdown device),
• (as an emergency shutdown device in case of overload and phase loss),
• “Start”, “Stop” buttons, various circuit mode switches,
• control circuit (may contain the same buttons, or maybe a controller),
• indication of operation and failure.

We will consider various connection diagrams for magnetic starters and their differences below.

Typical diagram for connecting a motor via a magnetic starter

This wiring diagram for a three-phase motor should be given the closest attention. It is most common in all industrial equipment produced until about the 2000s. And in new Chinese machines and other simple equipment with 2-3 engines they are still used to this day.

An electrician who does not know it is like a surgeon who cannot distinguish an artery from a vein; as a lawyer who does not know Article 1 of the Constitution of the Russian Federation; like a dancer who does not distinguish a waltz from a tectonic.

In this circuit, three phases go to the motor not through the machine, but through the starter. And the starter is turned on/off using the “ Start" And " Stop”, which can be brought to the control panel via 3 wires of any length.

An example of such a circuit is in the article about, see the last circuit in the article, KM0 starter.

5. Diagram of connecting the motor through a starter with start-stop buttons

Here, the control circuit power comes from phase L1 (wire 1 ) through a normally closed (NC) “Stop” button (wire 2 ).

Often in such schemes the starter does not turn on due to the fact that the contacts of this button “burn out”.

The diagram does not show a control circuit breaker; it is placed in series with the “Stop” button, the rating is several amperes.

If you now press the “Start” button, the power circuit of the coil of the KM electromagnetic starter will close (wire 3 ), its contacts will close, and three phases will go to the motor. But in such schemes, in addition to three “power” contacts, the starter has one more additional contact. It is called a “locking” or “self-latching contact”.

Not to be confused with blocking in reverse circuits, see below.

The “Self-Pickup” contacts are physically located on the same mount with the power contacts of the contactor, and operate simultaneously.

When the electromagnetic starter is turned on by pressing the SB1 “Start” button, the self-retaining contact also closes. And if it is closed, then even if the “Start” button is pressed, the power circuit of the starter coil will still remain closed. And the engine will continue to run until the “Stop” button is pressed.

It often happens in such schemes that the starter does not “self-retain.” It's about that fourth contact.

Connection diagram for a starter with a thermal relay

In the circuit above, I left out the thermal protection for the sake of simplicity of the circuit. In practice, they must use it (at least, it was accepted until 2000 for us and until 1990 for “them”)

6. Connection diagram of the starter with buttons and thermal relay

As soon as the motor current increases above the set one (due to overload, phase loss), the contacts of the thermal relay RT1 open and the power circuit of the electromagnetic starter coil breaks.

Thus, the thermal relay acts as a “Stop” button, and is in the same circuit, in series. Where to put it is not particularly important, it can be in the section of the L1 - 1 circuit, if it is convenient for installation.

However, a thermal relay does not protect against short circuits to the housing and between phases. Therefore, in such schemes a circuit breaker must be installed, as shown in Diagram 7:

7. Connection diagram of the starter with automatic buttons and thermal relay. PRACTICAL SCHEME

Attention! The control circuit (the circuit through which the KM starter coil is powered) must be protected by a circuit breaker with a current of no more than 10A. This circuit breaker is not shown in the diagram. Thanks to attentive readers!)

The current of the QF motor circuit breaker does not need to be selected as carefully as in scheme 3, since the RTL can handle the thermal overload. Enough for him.

Example. The motor is 1.5 kW, the current in each phase is 3A, the thermal relay current is 3.5 A. The motor power wires can be taken 1.5 mm2. They hold current up to 16A. And it seems like the machine can be set to 16A? However, there is no need to act clumsily. It’s better to put something in between – 6 or 10A.

Connection diagram of the magnetic starter from the controller

Over the past 10 years, controllers have been widely used in new industrial automation. The starter coils are also switched on from the controller outputs. And in this case, to protect against short circuits and thermal overheating, motor connection diagram number 8 is used:

8. Connection diagram for a starter controlled by a controller. PRACTICAL SCHEME

In the diagram, QF is an automatic motor, or motor protection circuit breaker, as in diagram 4. I just depicted it in a modern way. In this case, the starter connection diagram is “hidden” in the dotted line. There is a controller there that controls everything and turns on the engine according to the program embedded in it.

When the engine is overloaded, the automatic motor turns it off and opens its additional (fourth, signal) contact. This is only necessary to “inform” the controller about an accident. Often this contact simply enters and stops the entire machine.

Connection diagram for reversing magnetic starter

In fact, these are two magnetic starters, combined electrically and mechanically, more details below.

Reversible motor control

A reversing starter is needed when it is necessary for the motor to rotate alternately in both directions.

Right rotation (used most often) - when the engine rotates clockwise when looking at its rear. Left rotation - counterclockwise.

Changing the direction of rotation is realized in a well-known way - any two phases are swapped. Look at the motor reverse circuit diagram below:

9. Connection diagram for a 220V reversible magnetic starter with button control. PRACTICAL SCHEME

When the KM1 starter is turned on, it will be “right” rotation. When KM2 is turned on, the first and third phases change places, the engine will spin “to the left”. Switching on the starters KM1 and KM2 is realized by different buttons “ Start forward" And " Start back“, shutdown – with one, common button “ Stop”, as in circuits without reverse.

Pay close attention to the triangle between the power contacts KM1 and KM2. It means “foolproof.” It may happen that for some reason both starters turn on at once. A short circuit will occur between phases L1 and L3. You can say, “So what, we have a QF automatic engine, it will save us!” What if it doesn’t save you? And while he is saving, the contacts of the starters will burn out!

Therefore, the reversing starter must have mechanical protection against simultaneous switching on its two halves. And if it consists of two separate starters, a special mechanical interlock is placed between them.

Now look at the contacts KM2.4 and KM1.4, located in the power circuits of the starter coils. This - electrical protection from the same fool. For example, if KM1 is turned on, its NC contact KM1.4 is open, and if our fool, with all his foolishness, presses both “Start” buttons at once, nothing will happen - the engine will obey the button that was pressed earlier.

Mechanical and electrical protection must always be present in the connection diagram of the reversing starter; they complement each other. Do not put one or the other - bad manners among electricians.

To implement electrical interlocking of simultaneous switching on and self-retaining, each starter requires, in addition to power ones, one more NC (blocking) and NO (self-retaining). But since, as a rule, there is no fifth contact in starters, you have to install an additional one. contact. For example, for a PML type starter, the PKI prefix is ​​used. And if, as in scheme 8, a controller is used, self-retaining is not needed, and one NC contact for each direction of rotation is sufficient.

Reversible hydraulic control

And here is an example of reverse valve control, from an article about a hydraulic press:

Electrical circuit for hydraulic control

Push-button stations are used to operate an asynchronous motor. However, they can only be connected via magnetic starters. As a rule, adapters and contactors are used for this. However, it is important to consider the type of switch and the parameters of the starter. To understand the device connection in detail, you need to consider the standard diagram.

Connection diagram

The connection diagram for a magnetic starter via a push-button post involves the use of an analog adapter. There are blocks with three and four outputs. For connection, the direction of the cathode is determined. The starter contacts are connected via a switch. The trigger for this is a two-channel type. If we consider devices with automatic switches, then they use an electrode regulator. In this case, the blocks can be located on the controller. The most common are devices with broadband connectors.

Consideration of QF1 switches

The connection diagram for a magnetic starter via a push-button post has two controllers, which are connected through an expander. The output contacts must be mounted on the cover. The trigger for the devices is of the analog type. A normally closed contact of the first order is established at zero phase. The resistance on the magnetic starter must be at least 40 ohms. Before connecting the device, the switch is checked.

The current relay in the circuit is used only of the two-channel type. In this case, the controller must close in the first phase. The switch is set to the upper position. When connecting the expander, the contacts are cleaned and the protective plate is unscrewed. To stabilize the process, the rectifier is selected as an open type.

Scheme with irreversible starter

The connection diagram for a magnetic starter via a push-button post assumes the use of a low-impedance expander. In this case, the rectifiers are connected to the converter winding. The normally closed contact of the switch is installed in the first phase. It should also be noted that filters can be used with a grid triode.

The starter resistance is on average 55 Ohms. If we consider a circuit with a dipole adapter, then the regulator is installed on a pulse rectifier. The output contacts are closed directly on the dinistor. A tester is used to check the post. It should also be noted that there are variable converters. Starters with these elements can be connected via a controller via the zero phase. However, you will need a magnetic triode filter.

Application of reversing starters

The connection diagram for a magnetic starter via a push-button post is very simple. It involves the use of only one rectifier. And the filter can be used with a variable triode. Many models have two converters. In this case, the trigger is installed on three outputs. The normally open contact is connected to the post through the first phase. To check the element you will need a tester.

The resistance level of the magnetic starter is 50 Ohms. If we consider modifications with adjustable converters, then the dinistor can be selected on a binary filter. Some experts say that the outputs on the comparator need to be thoroughly cleaned. It should also be noted that the tetrode in the starters must be correctly positioned.

Instructions for PML-1100 series starters

The circuit has three adapters. The output contacts must be closed in the zero phase. The post is checked using a tester. Experts say that you should not use analog converters that have a low resistance level. If we consider simple switches, then the trigger is set to channel reception. The current relay is connected to the converter and closes on the first phase. If you have problems with overheating, you can try to reduce the load using a comparator.

Connecting a modular starter

The modular type starter circuit contains contact adapters. Many models are made with three connectors. They have a positive contactor that is connected through a converter. The trigger in this case is used with an operational filter. If we consider simple switches, then the modules are connected through the controller in the first phase. The closing contacts must be at the top.

It should also be noted that there are modifications for four outputs. Their triggers are installed with regulators. When connecting devices, it is important to thoroughly clean the contacts and check the device with a tester. For many models, the resistance value reaches a maximum of 40 ohms. posts are closed on the plate. Rectifiers are used with a positive direction. Dinistors are often installed on three adapters. A regular post is connected via the zero phase. If we talk about adjustable starters, then the trigger is of the analog type. In this case, only one switch is required. To do everything correctly, you will have to measure the maximum resistance in the circuit.

Open starters

An open type starter (manual) can be connected via a regular trigger. Controllers are most often used with four connectors. The output contacts are connected to the post via zero phase, and the resistance should be about 45 Ohms. Wired type controllers are connected to the converter. To check the phase, a tester is used. Starters with a dinistor are installed through an electrode adapter. Quite often rectifiers are used with low conductivity. The closing contacts must be connected on the top panel. To avoid problems with failures, it is important to check the insulation and take care of the rectifier.

Connecting enclosed starters

Starters of this type can be connected via a wired controller. In this case, the straightener is standardly used with a lining. Experts advise using only triode filters. If we consider posts for two switches, then the trigger is selected as a pulse type. In this case, the controller is connected first. Positive contacts are connected at zero phase. The resistance on the controller must be at least 45 ohms.

If we consider modifications on capacitive triggers, then they need a converter. The devices can only be used in a DC circuit. The filters in this case are installed with a triode. Many starters use only one comparator. A cover is used to protect the element. It should also be noted that experts recommend thoroughly cleaning the trigger contactors.

Connection via a unijunction trigger

Connection via a single-junction trigger can only be carried out in the first phase. It should also be noted that not all starters are suitable for this. Converters can only be used as wired type. Their resistance must be at least 55 ohms. Dinistors for starters are selected with an electrode triode. The contacts of the post are directly connected to the expander.

You can check the conductivity of the element using a tester. Experts do not recommend installing filters with high resistance. The standard scheme involves the use of two rectifiers. If we talk about adjustable starters for asynchronous motors, then they have a comparator that is connected through a converter.

Application of a two-junction trigger

Bijunction flip-flops can be used in a DC circuit. They have a high resistance parameter. And they are suitable for different types of starters. Converters in the standard circuit are of the duplex type. Quite often there are digital analogues that are available with two outputs. Many switches in devices are used with a rectifier. To connect the equipment, the first phase is determined. In this case, the resistance can be at least 45 ohms. With increased conductivity, the trigger with the plate changes.

Connection via dipole adapter

Dipole adapters are allowed to be connected only through a push-button station for two and “Stop”. Triggers are usually used of the low-resistance type. If we consider a simple post, then the upper contacts are closed first. It should also be noted that the controller can be connected through a converter, and its resistance is 55 Ohms. A dinistor is quite often used with analog filters, which significantly increase the conductivity coefficient. You must also remember that linear triggers are not suitable for this type of starter. The adapter can be connected to the expander. Thus, the overload from the starter is greatly removed. The filter in this case is installed behind the comparator.

Application of wired switch

A wired switch can be connected via a transceiver, but only in the first phase. Many controllers are used for two outputs. The expander in this case is used with one filter. The starter closes in the first phase. It should also be noted that the post should be installed behind the output contacts. If problems with breakdowns in the circuit are detected, the expander is checked.

Connection via module

Only electrode starters are allowed to be connected through the module. In this case, posts are selected of a two-button type. In some cases, modules are manufactured with three outputs. And they have one controller. In such a situation, a triode is used for connection. The closing contacts are aligned according to the first phase. It should also be noted that the expander is selected as a dipole type. If we talk about models with plates, then the closing contacts must be checked for maximum resistance. The expander outlets are thoroughly cleaned. It should also be noted that open contacts are set to zero phase.

Switches are used to supply power to various electrical appliances. Depending on the power of the electrical installation, the contacts of the switches are designed: the higher the current (power consumption), the greater the mass and contact area of ​​the metal. Accordingly, the clamping device (spring, steel plate) must provide greater pressing force. If the switch is manual (mechanical), its size will be too large and it will be inconvenient to use.

Such input devices have a number of disadvantages (in addition to dimensions):

• too much effort when turning on (off);
• contact groups are not designed for frequent switching: they wear out quickly;
• safety issues have not been resolved: too much time is wasted when emergency shutdown is necessary;
• “switches” must be placed near the work area (in close proximity to the electrical installation), this is not always convenient due to the same dimensions.

The only way out is to connect the motor (or other electrical appliance) through the starter.

Advantages of implementing such a connection scheme

In fact, such switching is a relay circuit.

How to connect a 220V starter with a button

The most common switching scheme is a single-phase consumer with a push-button start. Moreover, the buttons should be spaced apart: “start” separately, “stop” separately. To understand how to connect a magnetic starter, let’s draw a combined diagram showing the parts:

In our case, we use a single-phase power source (220 V), separated control buttons, a protective thermal relay, and the magnetic starter itself. The consumer is a powerful electric motor.

• The neutral cable (N) is connected simultaneously to the electric motor and the control circuit contacts.
• The “stop” button (Kn2) is normally closed: when released, electric current flows through it.
• The phase line (F) is controlled by a thermal relay (TP) protective circuit and is connected to the input operating contacts of the starter (PM1).
• The starting electrical circuit from the phase is connected to the winding of the starter solenoid (PM) through closed (without overheating) contacts of the thermal relay (TP-1).
• In parallel with the normally open “start” button (Kn1), the contacts of the service circuit of the magnetic starter (PM4) are connected.
• When the start button is pressed, electric current flows through the contactor solenoid. The contacts (PM1) - power supply to the electric motor and (PM4) - power supply to the starter solenoid close. After releasing the “start” button, the control and power circuits remain closed, the circuit is in the “on” mode.
• When the line overheats, the thermal relay (TP) is triggered, the normally closed contacts (TP1-) break the solenoid circuit, the contactor opens, and the consumer is switched off. You can turn it on again after the thermostat has cooled down.
• To force the consumer to de-energize, just touch the “stop” button (Kn2), the solenoid power circuit will open, and the consumer’s power will stop.

This key connection scheme for a 220 V magnetic starter allows you to safely use powerful electrical installations and provides additional protection in case of current line overheating. For example, if the motor shaft stops under load.

A simplified diagram (without protective devices and thermal relays) in the illustration:

In this case, the solenoid (and, accordingly, the power contact groups) is controlled manually using two buttons.

Information:

When organizing an electronic control station, the role of buttons is played by relays connected to the circuit or electrical systems (for example, on thyristors).

As a bonus, consider connecting using an outlet with a timer. In this case, the switching circuit works without a “stop” button. That is, in the presence of control voltage (from the timer), the electrical installation operates.

How to connect a three-phase motor via a magnetic starter

Power supply 380 V (three phases) is carried out in the same way, only there will be more power wires.

The contactor includes not one, but three phase lines. In this case, the control button is connected according to a similar circuit (as in the single-phase case).

The illustration shows a starter with a 380 V solenoid control coil. The control circuit is switched between any two phases. For safety, there is a thermal relay, the sensors of which can be located on one or several phase wires.

How to connect a 3-phase contactor with a 220 V starter winding? The circuit is similar, only the control circuit is switched between any of the phases and the neutral wire. The thermal relay works just as accurately, since its mechanism is tied to the temperature of the power cables.

How to change the direction of rotation of a motor using a starter

Three-phase electric motors make it possible to set the direction of rotation. There are many schemes for single-phase 220 V power supply. And for three-phase (380 V) switching, there is a connection diagram for a reversible magnetic starter.

The device consists of two independent circuits, with separate control of each group of contacts (pm1 and pm2). Each solenoid winding (PM1 and PM2) is controlled by its own button. In this case, there is only one stop key; it simply breaks the control circuit (as in a single starter). The connection of the input and output contacts of the second group is made with the so-called “phase shift”. In this case, the windings of the electric motor create torque on the shaft in the opposite direction.

The thermal relay is unchanged: their task is to open the starter in case of overload.

There is one feature:

To prevent a short circuit between phases, groups of contacts (pm1 and pm2) should not be closed at the same time. Therefore, they are mechanically placed on one rod, and purely physically cannot be connected to the power bus together. If you try to press the second button (while the first one is working), the power supply to the consumer will turn off.

Video on the topic

First of all, you need to understand what a switching device is and why it is needed. Then coping with the task of creating a circuit based on MP for lighting, heating, connecting pumps, compressors or other electrical equipment will become much easier.

Contactors or so-called magnetic starters (MP) are electrical equipment designed to control and distribute energy supplied to an electric motor. The presence of this device provides the following advantages:

• Protects against inrush currents.
• A well-designed circuit provides protection elements in the form of electrical interlocks, self-retaining circuits, thermal relays, etc.
• Control elements (buttons) are installed to allow the engine to start in reverse mode.

The contactor connection diagrams are quite simple, allowing you to assemble the equipment yourself.

Before connecting, you need to familiarize yourself with the operating principle of the device and its features. The MP contactor turns on the control pulse that comes from the start button after it is pressed. This is how voltage is supplied to the coil. According to the self-retaining principle, the contactor is held in connection mode. The essence of this process is to connect an additional contact in parallel to the start button, which supplies current to the coil, so there is no need to hold the start button pressed.

With the equipment of a shutdown button in the circuit, it becomes possible to break the control coil circuit, which turns off the MP. The control buttons of the device are called a push-button station. They have 2 pairs of contacts. The universalization of control elements is made to organize possible circuits with instant reverse.

The buttons are labeled with a name and color. Typically, the enabling elements are called "Start", "Forward" or "Start". Indicated by green, white or other neutral color. The opening element is called "Stop", a button of an aggressive, warning color, usually red.

The circuit must be switched with a neutral when using a 220 V coil in it. For options with an electromagnetic coil with an operating voltage of 380 V, the current taken from the other terminal is supplied to the control circuit. Supports operation in a network with alternating or direct voltage. The principle of the circuit is based on the electromagnetic induction of the coil used with auxiliary and working contacts.

There are two types of MP with contacts:

1. Normally closed - power supply to the load is turned off at the moment the starter operates.
2. Normally open - power is supplied only during MP operation.

The second type is used more widely, since most devices operate for a limited period, being mostly at rest.

Composition and purpose of parts

The design of a magnetic contactor is based on a magnetic circuit and an inductance coil. The magnetic core consists of metal elements divided into 2 parts in the shape of “W”, located mirror to each other inside the coil. Their middle part plays the role of a core, enhancing the induction current.

The magnetic core is equipped with a movable upper part with fixed contacts to which the load is supplied. Fixed contacts are fixed to the MP body, on which the supply voltage is established. A rigid spring is installed inside the coil on the central core, which prevents the contacts from connecting when the device is off. In this position, no power is supplied to the load.

Depending on the design, there are MFs of small ratings for 110 V, 24 V or 12 V, but they are more widely used with voltages of 380 V and 220 V. Based on the value of the supplied current, 8 categories of starters are distinguished: “0” - 6.3 A; “1” - 10 A; “2” - 25 A; “3” - 40 A; “4” - 63 A; “5” - 100 A; “6” - 160 A; "7" - 250 A.

Principle of operation

In the normal (off) state, the contacts of the magnetic circuit are opened by a spring installed inside, which lifts the upper part of the device. When connected to the MP network, an electric current appears in the circuit, which, passing through the turns of the coil, generates a magnetic field. As a result of the attraction of the metal parts of the cores, the spring is compressed, allowing the contacts of the movable part to close. After this, the current gets access to the motor, starting it to work.

IMPORTANT: For alternating or direct current supplied to the MP, it is necessary to maintain the rated values ​​specified by the manufacturer! As a rule, for direct current the voltage limit is 440 V, and for alternating current it should not exceed 600 V.

If the “Stop” button is pressed or the power to the MP is turned off in some other way, the coil stops generating a magnetic field. As a result, the spring easily pushes out the upper part of the magnetic circuit, opening the contacts, which leads to the cessation of power supply to the load.

Connection diagram for a starter with a 220 V coil

To connect the MP, two separate circuits are used - signal and working. The operation of the device is controlled via a signal circuit. The easiest way is to consider them separately to make it easier to understand the principle of organizing the circuit.

Power is supplied to the device through contacts located on the top of the MP housing. They are designated in diagrams A1 and A2 (in the standard version). If the device is designed to operate in a network with a voltage of 220 V, then this voltage will be supplied to the indicated contacts. There is no fundamental difference between connecting “phase” and “zero”, but usually “phase” is connected to pin A2, since this pin is duplicated in the lower part of the housing, which facilitates the connection process.

To supply the load from the power source, contacts located on the bottom side of the case and marked as L1, L2 and L3 are used. The type of current does not matter, it can be constant or alternating, the main thing is to comply with the nominal limit, limited to a voltage of 220 V. The voltage can be removed from the outputs designated T1, T2 and T3, which can be used to power a wind generator, battery and other devices.

The simplest scheme

When connecting a power cord to the contacts of the moving part of the MP, followed by supplying voltage of 12 V from the battery to outputs L1 and L3, and powering lighting devices to the outputs of the power circuit T1 and T3, then a simple circuit is organized to illuminate a room or space from Battery This scheme is one of the possible examples of using MP for domestic needs.

To power an electric motor, magnetic starters are used much more often. To organize this process, supply voltage from a 220 V network to outputs L1 and L3. The load is removed from contacts T1 and T3 of the same voltage rating.

These circuits are not equipped with a trigger mechanism, i.e. not used when organizing buttons. To stop the operation of the connected equipment via the MP, it is necessary to disconnect the plug from the network. When organizing a circuit breaker in front of the magnetic starter, you can control the time of current supply without the need for complete disconnection from the network. The circuit can be improved with a pair of buttons: “Stop” and “Start”.

Diagram with “Start” and “Stop” buttons

Adding control buttons to the circuit changes only the signal circuit, without affecting the power circuit. The overall design of the circuit will undergo minor changes after such manipulations. Control elements can be located in different housings or in one. The single-block system is called a “push-button post”. Each button has a pair of outputs and inputs. The contacts on the “Stop” button are normally closed, and on the “Start” button they are normally open. This allows you to organize power supply as a result of pressing the second one and break the circuit when the second one is initiated.

In front of the MP, these buttons are built in sequentially. First of all, it is necessary to set “Start”, which ensures that the circuit operates only as a result of pressing the first control button until it is held. When the switch is released, the power supply is interrupted, which may not require the organization of an additional interrupt button.

The essence of arranging a push-button post is the need to organize only pressing “Start” without the need for subsequent holding. To organize this, a coil is introduced that bypasses the start button, which is placed on self-feeding, organizing a self-retaining circuit. This algorithm is implemented by closing auxiliary contacts in the MP. To connect them, a separate button is used, and the moment of turning them on must be simultaneously with the “Start” button.

After pressing “Start” it is passed through the auxiliary power contacts, closing the signal circuit. There is no need to hold the start button, but to stop, you need to press the corresponding “Stop” switch, which initiates the return of the circuit to its normal state.

Connection to a three-phase network via a contactor with a 220 V coil

Three-phase power can be connected through a standard MP, which operates from a network with a voltage of 220 V. This circuit can be used for switching when working with asynchronous motors. The control circuit does not change; “zero” or one of the phases is supplied to the input contacts A1 and A2. A phase wire is passed through the “Stop” and “Start” buttons, and a jumper is equipped for the output normally open contacts.

Certain minor adjustments will be made for the power circuit. For three phases, the corresponding inputs L1, L2, L3 are used, where the three-phase load is output from the outputs T1, T2, T3. To prevent overheating of the connected motor, a thermal relay is built into the network, which operates at a certain temperature, opening the circuit. This element is installed in front of the engine.

Temperature control is carried out in two phases, which have the highest load. If the temperature in any of these phases reaches a critical value, an automatic shutdown occurs. It is often used in practice, noting its high reliability.

Reverse motor connection diagram

Some devices work with motors that can rotate in both directions. If you transfer the phases on the corresponding contacts, you can easily achieve this effect from any motor device. This can be organized by adding to the button post, in addition to the “Start” and “Stop” buttons, another one - “Back”.

The MP circuit for reverse is organized on a pair of identical devices. It is better to choose a pair equipped with normally closed contacts. These parts are connected in parallel to each other; when the reverse motion of the motor is organized, as a result of switching on one of the motors, the phases will change places. The load is applied to the outputs of both devices.

The organization of signal circuits is more complex. Both devices use a common “Stop” button followed by a “Start” control. The latter is connected to the output of one of the MPs, and the first - to the output of the second. For each control element, shunt circuits are organized for self-retaining, which ensures autonomous operation of the device after pressing “Start” without the need for subsequent holding. The organization of this principle is achieved through the installation of jumpers on normally open contacts on each MP.

An electrical interlock is installed to prevent power from being supplied to both control buttons at once. This is achieved by supplying power after the “Start” or “Forward” button to the contacts of another MP. The connection of the second contactor is similar, using its normally closed contacts in the first starter.

If there are no normally closed contacts in the MP, by installing the attachment you can add them to the device. With this installation, the work of the set-top box contacts is performed simultaneously with others due to the connection with the main unit. In other words, it is impossible to open the normally closed contact after turning on the Start or Forward button, which prevents reverse movement. To change direction, press the “Stop” button, and only after that the other one, “Back,” is activated. Any switching must be done via the "Stop" button.

Conclusion

A magnetic starter is a very useful device for any electrician. First of all, it makes it easy to work with an asynchronous motor. When using a 24 V or 12 V coil, powered by a conventional battery, subject to appropriate safety measures, it is even possible to start equipment designed for high currents, for example, with a load of 380 V.

To work with a magnetic starter, when drawing up a circuit, it is important to take into account the features of the device and carefully monitor the characteristics indicated by the manufacturer. It is strictly forbidden to supply a current of a higher voltage or strength to the outputs than indicated in the marking.