The electrical circuit of the magnetic starter. Magnetic starter connection diagram. Where to use the starter in everyday life

The name of this electrical device for 0.4 kV electrical installations contains two fundamental actions at once:

1. operation as an electromagnet from the passage of electric current through the coil winding;

2. start-up of the electric motor by power contacts.

Structurally, any magnetic starter consists of a permanently fixed part and a movable anchor moving along the skids. It is highlighted in blue in the picture.

How the electromagnetic system works

In a very simplified way, the starter can be represented as one button, on the body of which there are terminals with connected power circuits and stationary contacts. A contact bridge is mounted on the moving part. Its purpose:

1. providing a double break in the power circuit to turn off the power to the electric motor;

2. reliable electrical connection incoming and outgoing wires when the circuit is turned on.

With manual pressure on the anchor, the compression force of the built-in springs is well felt, which must be overcome by magnetic forces. When the armature is released, these springs push the contacts back to the off position.

This method of manual control of the starter during the operation of the circuit is not used, it is used during checks. During operation, starters are controlled only remotely due to the action of electromagnetic fields.

For this purpose, a coil winding with turns wound on it is placed inside the housing. It connects to a voltage source. When current is passed through the coils around the coil, a magnetic flux is created. To improve its passage, a laminated steel magnetic circuit was created, cut into two parts:

the lower half permanently fixed in the device body;

mobile, which is part of the anchor.

In a de-energized state, there is no magnetic field winding around the coil, the armature is thrown by the energy of the springs from the stationary part upwards. Under the influence of magnetic forces arising after the passage of electric current through the winding, the armature moves down.

Attracted to the fixed part of the magnetic circuit, its movable half creates in the complex a single structure with a minimum magnetic resistance. Its value during operation is affected by:

adjustment violations;

corrosion of steel parts of the magnetic circuit and its fastening;

surface wear;

technical condition of springs, their fatigue;

defects of the short-circuited coil of the magnetic circuit.

The movement of the anchor inside the hull is limited by two boundary values. In the lower tightened position, a reliable clamping of the contact system must be created. Its weakening leads to the burning of contacts, an increase in the value of the transition electrical resistance, excessive heating and subsequent burnout of the wires.

An increase in the magnetic resistance of the magnetic circuit for any reason is manifested by an increase in noise due to the appearance of vibrations, which lead to a weakening of the contact system pressure and, as a result, to failures in the operation of the magnetic starter.

How the power contact system works

Structurally, power contacts are designed for reliable and long-term operation. For this they:

made of technical silver alloys deposited by special methods on copper jumpers;

created with a margin of safety;

made in a shape that provides maximum electrical contact when turned on and well withstand the electric arc that occurs when the load is broken.

In three-phase circuits, magnetic starters are used with three power and several additional contacts that repeat the position of the armature and are used in motor control circuits. All of them are drawn on the diagrams in a position corresponding to the absence of current in the coil and the unclenched state of the springs.

The control contacts, when the starter is activated, close (called "make") or, conversely, open the circuit. They in the attracted position create a platform in the form of a point. To do this, the stationary part is made by a plane or a sphere (in critical nodes), and the movable part is made by a sphere.

Power contacts are more responsible, they must withstand increased loads. They are made to create a contact line consisting of many points. To this end, the stationary part is made by a plane or a cylinder, and the movable part is made only by a cylinder.

Magnetic starters manufactured by domestic manufacturers are classified according to their ability to work with loads of different capacities into 7 groups and are designated by increasing value from zero with a switching current up to 6.3 amperes inclusive and up to the sixth - (160 A).

Starters produced by foreign manufacturers are classified according to other criteria.

Electricians involved in the maintenance of magnetic starters and supervising their work are required to control the quality of the fit of the contact pads and their cleanliness. The current opinion is that “for modern starters, the contacts are made reliably and you don’t need to inspect them” not entirely correct.

Contact cleanliness depends on many factors, including:

load mode;

switching frequency;

environmental conditions.

They all show up differently on each specific device. Therefore, they must be periodically monitored and, at the first sign of contamination, washed with alcohol. When it's not there to fulfill similar works, then they use an ordinary school eraser, which, while cleaning the metal, leaves its crumbs on the outer surface, which have dielectric properties.

They are removed by rubbing surfaces with thin, dried wooden sticks from non-resinous tree varieties. Best suited for these purposes:

When wiping the contacts, hard wood species additionally polish the treated surfaces.

Minor burnouts of the contact surfaces are removed with homemade "crows". So in the language of electricians they call flat segments of strong metal plates (usually they are made from broken hacksaw blades for metal), the surface of which is slightly treated with the finest emery.

Such a tool allows you to remove a very thin layer of burnt metal and bring the contacts into working condition, preserving their original shape. It is impossible to use fine sandpaper and needle files for such purposes. You can quickly break the formed contact line. “Sandpaper” also clogs the treated surface with abrasive crumbs.

Schemes for switching on electric motors with magnetic starters

The easiest control

Such a motor connection can be made according to the picture below.

Three-phase power supply ≈380 through the power contacts K1-s is supplied to the electric motor, the temperature of the windings of which is controlled by a thermal relay kt. The control system is powered by any phase and zero. It is perfectly acceptable to replace the working zero with a ground loop.

In order to increase electrical safety, an isolation or step-down transformer TP1 is used. Its secondary winding must not be grounded.

The simplest fuse FU protects the control circuit from possible short circuits. When the operator presses the "Start" button, a circuit is created in the control circuit for the flow of current through the winding of the starter K1, which simultaneously closes its power contacts K1-s. How long the worker presses the button, so much the engine works. For the convenience of a person, such buttons are mounted with a trigger mechanism.

A running electric motor can be turned off when the button is pressed:

removing power from the power distribution board;

by pressing the "Stop" button;

operation of the thermal relay kt in case of motor overheating;

blown fuse.

Such schemes are used where, according to the conditions of technology, it is required to keep hands constantly on the equipment and not be distracted from production process. An example would be working with the press.

Scheme with holding the button by the contact of the starter

Adding only one make contact of the K1-y starter to the considered circuit allows you to set the "Start" button to be blocked by this addition and eliminates its constant pressing. Otherwise, the scheme completely repeats the previous algorithm.

Scheme with reverse

Many machine tool drives require changing the direction of rotation of the motor rotor during operation. This is done by changing the phases of the alternation of the power circuit - by switching the connection points of any two windings on the switched off engine. In the picture below, the windings of phases "B" and "C" are reversed. Phase "A" does not change.

Two magnetic starters No. 1 and No. 2 are already included in the circuit. The engine can rotate only from one of them clockwise or in the opposite direction. To do this, an opening contact for controlling the reverse rotation starter is introduced into the control circuit of each winding K1 and K2. It blocks both starters from being connected at the same time.

To change the direction of rotation of the motor, the operator must:

press the "Stop" button. The gap formed by it opens the control circuit and interrupts the flow of current through a working starter. In this case, the springs recline the armature, and the power contacts turn off the power supply from the electric motor;

wait for the rotor to stop rotating and press the "Start" button of the next starter. The current will flow through its coil, the button will be held by the closing contact, and the winding circuit of the reverse rotation starter will be broken by the opening contact.

Design features of various models

If earlier magnetic starters were supplied with power contacts and one or two of their position repeaters for closing or opening, then modern models are given additional structural elements, due to which they have more possibilities.

For example, complete products from leading manufacturers allow you to perform various control functions for three-phase electric motors, including reversing by integrating additional equipment into the starter. The consumer only needs to connect the electric motor and power wires to the purchased module, and the circuit itself has already been mounted and adjusted for certain loads.

A promising technical solution is a scheme that allows:

spin the motor rotor up to the rated speed by connecting its windings according to the "star" scheme;

turn on under load when switching to the "triangle".

Cases of magnetic starters can be open or protected from dust and / or moisture penetration by a special shell with seals.

Separate modern models of small capacities.

Powerful magnetic starters can be equipped with an arc extinguishing system that occurs when the current is turned off by power contacts.

Hello, dear visitors and guests of the Electrician's Notes website.

In the last article, I told you in detail, and even made a special video about.

Today I will continue to acquaint you with the magnetic starter, namely with its connection diagram.

For a more detailed and visual study of the connection diagram of a non-reversible type magnetic starter, we use the following electrical equipment:

• magnetic starter type PML-1100 (irreversible)
• push-button post with 3 buttons (for example, PKE 222-3U2)
• type AOL 22-4 with a power of 0.4 (kW)

Here, in fact, is the magnetic non-reversible starter of the PML-1100 type. You are already familiar with him.

PML-1100 refers to starters of the first magnitude, i.e. rated current its power (main) contacts is 12 (A) at a mains voltage of 220 (V) and 380 (V). Therefore, this starter can easily fit technical specifications to start our motor, whose rated current at is 1.97 (A). This can be seen on the tag, although not quite clearly, because the tag is varnished after the next engine repair.

Push-button post for connecting a magnetic starter

Button post PKE 222-3U2 has three buttons:

• red stop button
• black forward button
• black back button

I chose this type of button post, because. the other was not available at the time of writing. To connect a magnetic non-reversing starter, it is enough to purchase a push-button post with two buttons, for example, PKE 212-2U3.

It is also possible to purchase two single push-button posts of the PKE 222-1U2 type.

Now on sale there is a large selection of different buttons from IEK, EKF and other brands. So choose according to your "taste and color".

Let's look inside the PKE 222-3U2 push-button post I have chosen. To do this, unscrew the 6 fixing screws.

Each PKE 222-3U2 post button has two contacts:

• open (normally open) is marked (1-2)
• closed (normally closed) is marked (3-4)

For example, consider the Stop button.

Here is a photo of the closed (normally closed) contact of the Stop button:

And here is a photo of the open (normally open) contact of the Stop button:

Attention!!! When the button is pressed, the open (normally open) contact closes, and the closed (normally closed) contact opens.

So, we figured out the buttons. Now let's start assembling the magnetic starter circuit for starting a three-phase asynchronous motor AOL 22-4.

Example

1. The three-phase voltage source in my example is a test stand, which has a line-to-line voltage of ~220 (V). This means that the magnetic starter coil must have a rating of 220 (V).

Here is a diagram of connecting a magnetic starter through a push-button post to start an electric motor for my example:

If your line voltage of a three-phase circuit is not 220 (V), but 380 (V), then you have two choices.

In the first case, the starter coil must be selected with a rating of 380 (V) with the following connection diagram:

In the second case, the control circuit must be powered from one phase (phase-zero), while the value of the starter coil must be 220 (V).

In this article, I will assemble the magnetic starter circuit according to the first figure, i.e. at a three-phase network voltage of 220 (V) and a starter coil voltage of 220 (V).

I will assemble the circuit with a PV-1 copper wire with a cross section of 1 sq. mm.

2. First of all, we lay three phase wires from a three-phase power source (A, B, C) to the corresponding starter terminals: L1 (1), L2 (3), L3 (5).

3. Then we connect the wire on one side to the terminal L2 (3) of the starter, and on the other side to the closed contact of the Stop button marked (4).

Just now I noticed that the PKE 222-3U2 button post I have chosen does not have terminal markings. It's okay - after all, the contacts of the buttons are not hidden and they can be seen quite well. According to the text below, I will still indicate the marking, because. in other button posts it should be.

4. Now we install a jumper between the closed contact of the "Stop" button with the marking (3) and the open contact of the "Forward" button with the marking (2).

5. From the terminal (1) of the "Forward" button, lay the wire to the output of the starter coil (A1).

6. Parallel to the open contacts (1-2) of the "Forward" button, you need to connect an auxiliary open contact NO (13) - NO (14) of the PML-1100 magnetic starter.

Those. from the terminal (2) of the “Forward” button, we lay the wire to the NO auxiliary contact (13) of the magnetic starter.

7. From the auxiliary contact NO (14) of the PML-1100 magnetic starter, we make a jumper to the coil (A1).

It turned out that the open contact of the "Forward" button (1-2) and the auxiliary open contact NO (13) - NO (14) of the magnetic starter are connected in parallel.

8. And it remains to connect the output of the coil A2 of the magnetic starter to terminal L3 (5).

As a result, it turned out that only 3 wires come out of the PKE 222-3U2 button post, i.e. for installation it was possible to use a three-core cable.

9. Let's assemble a button post. Here's what we got.

10. The magnetic starter control circuit is ready. It remains to connect an asynchronous motor to terminals T1 (2), T2 (4), T3 (6) and check the circuit.

Here's what we ended up with.

This scheme is the simplest. In the following articles, we will consider more complex schemes for connecting magnetic starters, for example, with, interlocks, additional protection devices, etc.

Wiring diagram for connecting the starter PML-1100

Especially for you, I drew a wiring diagram for connecting the starter, which I collected in this article. Maybe it will make it easier for you to navigate the wires.

Principle of operation

The principle of operation of the magnetic starter circuit through a push-button post is very simple.

1. Turn on the three-phase voltage source on the test bench.

2. Press the "Forward" button.

The PML-1100 magnetic starter operates and closes its power (main) and auxiliary contacts:

• L1 (1) - T1 (2)
• L2 (3) - T2 (4)
• L3 (5) - T3 (6)
• NO(13) - NO(14)

The motor starts to rotate.

You do not need to hold the "Forward" button, because. when the magnetic starter is turned on, the contact of the “Forward” button is shunted by its own auxiliary closing contact NO (13) - NO (14). The starter coil is energized.

3. Press the red "Stop" button.

There is a break in the circuit (phase) of the power supply of the starter coil, respectively, the power (main) and auxiliary contacts of the starter open. The engine stops.

Everything that I demonstrated and told you in this article, I shot on video. See how the magnetic starter works:

P.S. This concludes the article on the connection diagram of a magnetic starter through a push-button post. If you have any questions about the material of the article, then feel free to ask them in the comments. Thank you for your attention!!!

Electromagnetic starter 220 V allows switching in AC (and DC) circuits. Typically, such devices are used when turning on powerful consumers - electric motors, heaters, etc. The need for it is justified in cases where it is necessary to turn the load on and off frequently.

The use of magnetic starters

Most often, electromagnetic starters are used to start, stop and reverse asynchronous electric motors. But since these devices are very unpretentious, they can be used to remote control lighting, in compressor installations, pumps, beam cranes, electric furnaces, conveyors, air conditioners. The scope of magnetic starters is very wide. But recently, starters have been supplanted by electromagnetic contactors. But, in fact, these two devices are not much different in design and characteristics. Even the wiring diagrams are the same.

How does a starter work?

The electromagnetic contactor works according to the following scheme:

1. Voltage is applied to the working coil of the electromagnetic starter.
2. A magnetic field appears around this coil.
3. The metal core, which is located next to the coil, is drawn inward.
4. Power contacts are attached to the core.
5. When the core is retracted, the power contacts are closed, current is supplied to the load.

In the simplest case, magnetic starters are controlled with just two buttons - "Start" and "Stop". If necessary, you can reverse - this is done by connecting two magnetic starters using a special circuit.

How is an electromagnetic starter arranged?

There are two main parts to this device:

1. Contact block.
2. Starter directly.

The contact block is mounted on top of the starter housing. It is intended to extend the functionality of the control circuit. With the help of an additional block, you can:

• Perform reverse movement of the electric motor.
• Power up the lamp that signals the operation of the motor.
• Turn on additional equipment.
• But the contact attachment is not always used, in most cases one starter is enough.

Contact prefix

This mechanism includes two pairs of normally open and the same number of normally closed contacts. On top of the starter there are skids and hooks, it is to them that the attachment is attached. As a result, this system is rigidly connected to the power contacts of the starter and works simultaneously with them.

By default, normally closed contacts connect circuit elements, and normally open ones break. When the magnetic starter is turned on, when the core closes the power elements, normally closed contacts open, and normally open ones close.

The design of the magnetic starter

In general, two parts can be distinguished - upper and lower. Above is a group of contacts, the movable part of the electromagnet connected to the power switches, as well as the arc chute. In the lower part there is a coil and a return spring, as well as the second half of the electromagnet.

With the help of a spring, the upper part returns to its original position after the voltage supply to the coil stops. In this case, the power contacts open. The electromagnet is assembled from W-shaped plates made of technical transformer steel. The coil is wound with copper wire, and the number of turns depends on what voltage it is designed for.

Sectors with symbols

The parameters are located on the starter, there are three sectors in total:

1. The first indicates where the magnetic starter can be used, as well as general information about him. Namely: frequency of alternating current, nominal value of current, conditional thermal current. For example, the designation AC-1 indicates that with the help of such mechanisms it is possible to switch the power circuits of heating elements, incandescent lamps, and other slightly inductive loads.
2. The second section indicates which maximum power loads can be switched with power contacts.
3. In the third sector, the device diagram is usually indicated: it includes power and auxiliary contacts, an electromagnet coil. In the event that a dotted line goes through all the contacts in the diagram from the coil, this means that they work synchronously.

Contact groups of starters

Power contacts are designated as follows:

• 1L1, 3L2, 5L3 are incoming, they are powered by AC or DC.
• 2T1, 4T2, 6T3 - outgoing power contacts that are connected to the load.

In fact, it does not matter at all where you connect the power source, and where the load is. It's just that such a scheme is generally accepted, and it must be used.

After all, if another person has to carry out repairs, he simply will not be able to immediately figure out what the installer was smart about. Auxiliary group of contacts 13NO-14NO is designed to carry out self-pickup. In other words, this pair is used so that when the electric motor is turned on, the start button is not constantly pressed.

stop button

Regardless of the type of electromagnetic starter used in the design, control is carried out using two buttons - "Start" and "Stop". Reverse may be enabled. The stop button differs from the others in that it has a red color. Normally closed contacts are mechanically connected to the button. Therefore, when the devices are operating, the current flows through them unhindered.

If the button is not pressed, then the metal bar closes two contacts under the action of the spring. If you need to stop the power supply of the device, you just need to press the button - the contacts will open. But there is no fixation, as soon as you release the button, the contacts will close again.

Therefore, to control the operation of electric motors, special circuits for switching on 220V electromagnetic starters are used. Such devices are installed on a DIN rail without problems, so they can be used even in the smallest mounting blocks.

start button

It is usually green or black in color and is mechanically connected to a normally open group of contacts.

As soon as you press the start button, the circuit closes and flows through the contacts electricity. The only difference from the stop button is that by default the contacts are in the open state. The spring holds the contact group in the open position and allows the button to return to its initial position after starting. This is the principle of operation of 220V electromagnetic starters used in large load control circuits.

Classic switching circuit

When implementing such a scheme, the following actions are performed:

1. When you press the "Start" button, the contacts close and voltage is applied to the load.
2. When the "Stop" button is pressed, the starter contacts open and the voltage supply stops.

As a load, you can connect heating elements, electric motors, and other devices. Normally open electromagnetic starter 220V can be used to turn on absolutely any load.

The power part of the circuit includes:

• Contacts for connecting three phases - "A", "B", "C".
• Circuit breaker. It is installed between the power source and the input of the electromagnetic starter 220V 25A. The fact is that 380V is an interphase voltage, and if you measure between zero and any of the phases, it will be equal to 220V.
• Load - a powerful consumer of electricity (motor, heating element).

The entire control circuit is connected to zero and phase "A". The circuit consists of the following components:

• Start and stop buttons.
• Coils.
• Auxiliary contact (switched on in parallel with the start button).

The work of the classical circuit

As soon as the circuit breaker is turned on, three phases appear on the upper contacts of the starter, the entire circuit is put into standby mode. The phase under the letter "A" passes through the circuit:

• Through the closed contacts of the stop button.
• On the contact of the start button.
• To an auxiliary contact group.

In this case, the scheme is fully prepared for work. As soon as the contacts close under the influence of the start button, voltage appears on the coil and its core is drawn in. In this case, the core pulls a group of contacts along with it, closing them.

At the bottom of the magnetic starter there are power contacts, on which voltage also appears, which then goes to the consumer of electricity. After releasing the start button, the power contacts will be closed due to the implementation of the "catch" circuit. In this case, the phase does not go through the contacts of the start button to the electromagnet, but through the auxiliary group.

Degree of protection

Best of all, devices with a degree of protection IP54 show themselves in work. They can be used in damp and very dusty environments. You can easily install it outdoors. But if the installation is carried out inside the cabinet, then it is sufficient to use devices with a degree of protection IP20. The higher the numerical index, the more severe the operating conditions of the device can be - this applies to any electrical device. The following factors must also be taken into account:

• The presence of a thermal relay, with the help of which the load is disconnected when the maximum consumption current is exceeded. The use of such a device in the control of electric motors is especially important.
• If there is a reverse function, then the design has two coils and six contacts. In fact, this is a pair of starters combined in one housing.
• It is imperative to take into account the wear resistance of the device, especially if the starter turns on and off the load very often.

Not the last place in the operation of any device, including the 220V electromagnetic starter, is occupied by the human factor. Unskilled workers are capable of breaking the entire control circuit, as they do not know how to operate the equipment correctly. If the thermal protection has tripped, it cannot be turned on immediately. And you can’t restart the engine - first you need to check if the motor is jammed, if there is a short circuit in the power circuit.

A magnetic starter is a switching device for electrical circuits with high currents. In everyday life, magnetic starters are used in country houses, for remote connection of street lighting or home craftsman's machines, powered by electric motors.

The device of the magnetic starter and its operation are tritely simple: a spring, a throttle and a moving armature. When current appears on the throttle, the armature closes the contacts of the starter and power is supplied to the installation. We interrupt the current through the choke, the armature opens the contacts of the starter, and the power of the installation is turned off. Under the installation we mean the receiver of electrical energy, which is switched by a magnetic starter (electric motor, street lighting).

Connecting a magnetic starter - wiring diagram

There are two fundamentally different schemes for connecting a magnetic starter:

1. simple non-reverse circuit (start and stop);
2. reverse motor connection diagram (start, forward, reverse).

In a simple (not reverse) connection scheme, the following elements “participate”:

• The starter is magnetic;
• Asynchronous electric motor with squirrel-cage rotor;
• Start and stop buttons;
• Thermal relay (optional, but desirable to protect the motor from current overloads).

Let's supplement this scheme with two working schemes:

Where to use the starter in everyday life

In a private house, through the starter, you need to connect all the electric motors available on the territory, street lighting and powerful household appliances, for example, heating elements. Engines, because it is supposed to be, and street lighting, because the starter will provide a remote, safe connection of street lighting from anywhere in the house. You can put the starter in the switchboard room, and the control buttons (turn on, turn off), where it is convenient.

Connecting a magnetic starter - an example

I will not talk about the internal design of the starter, about arcing chambers and an insulating traverse, this is on the video at the bottom of the article. I will show the practical connection of the electric motor, through a magnetic starter.

Let's prepare for work:

• Actuator;
• Thermal relay;
• Electrical cable. we calculate by the power of the electric motor;
• Push-button point for two buttons in one case;
• Electric motor installed in place.

Starter, pushbutton, motor

Electrical work installation magnetic starter

• From the three-phase (1 on the yellow diagram above), which we put to the starter, we bring the power cable to the starter;
• From the output of the starter we lay the cable to the push-button point;
• We lay the cable from the button to the electric motor.

Note: In this article, we restrict ourselves to connecting an asynchronous motor without reversing. That is, only start and stop.

To connect the magnetic starter according to the above diagram, you need to find and understand the purpose of the contacts on the starter and buttons. Therefore, we will analyze, first the button point, and then we will look at the starter.

Buttons (button point) for starter operation

For a simple, non-reversible connection of the starter, we need a push-button item for two buttons. For example, I took an old series in an ebonite case.

Buttons are designed to close and open the electrical circuit. To do this, the button device has closed and open contacts. Correctly called, open contacts are normally open, and closed contacts are normally closed.

For correct connection, it is important to identify open and closed contacts. Usually they are indicated by the numbers 1-2 and 3-4, respectively.

We understand that when the button is pressed, open contacts are closed, and open ones are closed. Now let's deal with the starter terminals.

Starter terminals required for connection

We put the starter in front of us and look at it with the naked eye, that is, we do not disassemble it.

• Starter input terminals. Input terminals for connecting phase wires: 1L1, 2L2, 3L3;
• Additional input terminal: 13NO (21NC);
• Output terminals. Phase wire terminals: 4T1, 5T2, 6T3.
• Additional (auxiliary) output terminal: 14NO (22 NC);

In the off state contact pairs: 1L1-4T1; 2L2-5T2; 3L3-6T3 are open. Visually we see that the traverse (orange plate in the middle of the device) is in the upper position.

• On the starter we see contact A2, this is the output of one contact of the starter inductor. There are starters (old models) with terminals A1 and A2 for outputting two contacts of the starter choke.

Terminal A2 starter coil
Terminals A1 and A2 of the starter coil

There are no other contacts on the case.

Connecting a starter with a push-button point

• We connect the incoming phase to terminal 1L1 of the starter;
• We connect the engine to terminals 4T1 and working zero, without a starter;
• From terminal 1L1 we connect with a loop the wire going to pin 1 of the "Start" button;
• From contact 2 of the "Start" button, we start up a loop to contact 3 of the "Stop" button;
• From terminal 4 of the "Stop" button, we launch a loop to contact A2 of the magnetic starter coil (it is on the case). If there is an A1 coil contact on the case, we connect zero to it;
• From the auxiliary contacts of the NO13 and NO14 starter, we throw wires to terminals 1-2 of the Start button;
• Before the starter, on the power supply side, you need to install a circuit breaker on the phase (phase) conductors;
• Parallel to the circuit breaker, a thermal relay must be installed up to terminals 1L1-3L3. It will protect the starter from overload;
• Connection completed. Turn on.

How a magnetic starter works and works

When turned on circuit breaker, the phase current is supplied to the contacts of the starter L and to terminal 1 of the start button.

To start the engine, press the "Start" button. The normally open contacts of the "Start" button are closed, the current is supplied to the starter coil, it closes the contact groups of the L-T starters.

Release the "Start" button. If there were no additional contacts in the starter, the motor would stop. But the additional contacts of the starter NO13 and NO14 are closed and when the "Start" button is released, they remain closed. This does not allow the starter coil supply circuit to open. We see that the traverse on the body is recessed, we hear a characteristic click.

When the "Stop" button is pressed, an elementary opening of the coil circuit occurs, and it is wrung out - the starter traverse rises, we hear a characteristic click.

Important! Important in connecting the starter are the additional contacts of the starter. It remains to be recalled that the additional contacts that pick up the functions of the Start button are located on the starter to the left of the input and output working contacts and are marked NO13 and NO14.

At the time of the birth of electrical engineering, 3-phase electric motors were switched on manually using ordinary knife switches. Knife switches did not create safe conditions, it was required to connect the control panel with power lines. During the further progress of the development of switching processes, scientists invented devices such as magnetic starters that did not have the disadvantages of a knife switch. This switching device provides connection of the load consumer remotely, makes it possible to control the operation of the equipment.

The design of the starter is simple, as well as its principle of operation. The starter consists of two types of contacts: fixed and moving. When these contacts are closed, the electric motor starts, and when the contacts are disconnected, it stops and turns off the power.

Varieties

Magnetic starters are mainly designed to control the operation of 3-phase electric motors at a remote level. The main operations carried out using magnetic starters are start, shutdown or reverse.

An auxiliary function of the starter, together with a thermal relay, is to protect the motor from excessive loads. There are starter circuits with voltage limiters based on semiconductor elements. According to the connection schemes, the loads are reversible and non-reversible.

According to the type of location, magnetic starters are classified:

• open type. They are located in protected cabinets, panels, and other places that are not accessible to moisture, dust and other harmful factors.
• Protected execution . They are mounted in rooms with a low content of dust in the air, excluding water access to the device.
• Waterproof design . They are mounted inside buildings, outside under equipped canopies from water and sun.

Auxiliary classification:

• Block with buttons on the body of the starter. Starters without reverse have two buttons: Start and Stop, devices with reverse are equipped with three buttons, two of them are the same as in the previous form, a Start back button has been added. Some versions of the devices provide a lamp that signals the inclusion.
• Devices with auxiliary contacts for signals and interlocks. They are used in various combinations, as closing or disconnecting. Contacts are built-in, or made on a separate stand. Sometimes auxiliary contacts are used in the general composition of the starter circuit. In devices with reversing, additional contacts perform electrical interlocking.
• The value of the voltage and current of the power winding.
• Thermal relay. Its property is the nominal current at which the relay does not operate at medium settings. This current value can be adjusted within certain limits from the nominal current value.

Some magnetic starters are equipped with voltage limiters and other interlocks.

Design features

The entire starter device is divided into two halves: upper and lower. The upper half contains the moving contacts along with the arc extinguishing chamber. The moving part of the magnet is also located there. It acts on power contacts.

The coil is located at the bottom along with the return spring. The property of the return spring is the return of the upper half to its original state after the power is turned off on the winding. This is how the power contacts are disconnected.

The arrangement of the two halves of the electromagnet includes W-shaped plates. They are made of electromagnetic steel. The coil uses copper wire with a calculated number of turns, which are designed to operate with a supply voltage of certain values, ranging from 24 volts to 380 volts. When voltage is applied to the winding, a magnetic field is generated. The two halves are trying to connect, a closed loop is formed. When the voltage is turned off, the magnetic field also disappears, the upper half moves back to its original place under the action of the spring.

Operating principle

The name of the device indicates how it works. It acts on the principle of an electromagnet, during the passage of current through the coil. After the contacts are attracted, the motor starts.

1 - Moving contacts
2 - Movable anchor
3 - Springs
4 - Coil
5 - Stationary core
6 - Movable core
7 - Stationary contacts

The general device consists of the main part and the anchor, which moves along the guides. It is easier to say that all magnetic starters are made in the form of a large button with power contact terminals and fixed contacts.

The moving part has a bridge with contacts, which provides a circuit break in two places, to turn off the voltage. Also, the bridge serves for high-quality connection of wires during the connection of the circuit into action. The system is checked manually. They press on the anchor and feel the force of the springs, which during operation is overcome by an electromagnet. When the anchor is released, the contacts are returned.

In operation, such control is not required, it is necessary for control. The remote form of connection is actually used electromagnetic field, which occurs in the winding from electric current. The laminated magnetic circuit provides good current conductivity.

When there is no electric current in the circuit, the magnetic field around the winding disappears, which leads to the withdrawal of the armature to its original position. When voltage is applied, the reverse process occurs. The working position of the armature, which is on, affects the operation of the device. In this position, there should be a high-quality connection of contacts. At the slightest weakening of the springs, the contacts begin to burn, heat up, and the ends of the wires burn out.

Installation and connection

For the possibility of high-quality operation of starters, their installation is carried out on a flat, fixed surface, vertically. Devices with a thermal relay must be installed so that there is no temperature difference with the external environment.

Mounting in violation leads to false alarms. Therefore, it is impossible to install magnetic starters in places with vibration, shock. Devices with a current rating of more than 150 amps vibrate and shake violently at startup.

The body of the thermal relay may become hot from other devices. This negatively affects the correct operation of the starter. Therefore, it is not recommended to place starters near hot equipment.

When connecting the wire to the contact of the starter, its end is bent in the form of a ring. This prevents misalignment of the spring washers in the clamp. When connecting two wires with the same cross section, they are placed on two opposite sides of the screw.

Before installation, the ends of the wires are tinned. In stranded wires, before tinning, the ends are twisted. The ends of aluminum wires are cleaned with a needle file, covered with a special paste. Moving contacts and parts of the starter must not be lubricated. Before starting, magnetic starters are inspected from the outside and check the serviceability of the parts. Freehand moving parts should be easy to move. The connection diagram is verified.

Maintenance

For high-quality care of the starter, you need to know the possible signs of device breakdowns. Usually this is a high case temperature, a strong buzz.

The high temperature of the device is most often associated with the short circuit of the winding between the turns. When inspecting the coil, there should be no cracks, soot, damage, melting. In such cases, the coil needs to be replaced. Excessive heating occurs due to an increase in the supply voltage above the nominal value, during overload, poor quality contacts, their strong wear. A strong starter hum can occur for several reasons. Most often you need to check the tightness of the anchor. Leakage may occur due to surface contamination. Another reason may be insufficient mains voltage, a decrease in it by more than 15 percent, as well as jamming of moving elements.

To prevent such breakdowns, constant care is needed. In general, magnetic starters do not need expensive work. Dirt, moisture and dust must not be allowed inside. It is necessary to regularly check the tightness and quality of the contacts. Compile a list of maintenance and repair work by electricians-repairmen.

Service Program

• External inspection for damage, body chips, removal of dirt. Chips and damage appear from prolonged vibration, improper installation, defects. If the housing is damaged to such an extent that it prevents its fastening to the surface, then the housing must be replaced. Particular attention is paid to the control of the presence of all springs and contacts.
• Revision of mechanical parts. The spring to break the contacts is subjected to control. It should not be soft or too tight. When checking the armature stroke, jamming is not allowed. The control of the course is carried out by hand.
• Contact cleaning - this event should not be carried out if the magnetic starter is in good condition. A layer with good conductivity on very thin contacts. With each cleaning with a needle file, the contacts will soon wear off. Cleaning is allowed only when soot occurs. When closing the contacts, there must be a snug fit, without inclinations, displacements. Otherwise, adjustment is needed.
• If there are metal parts in the starter housing, then you need to check that they are not connected to the power contacts. It is also necessary to ring all the power contacts among themselves for the absence of short circuits. To do this, use the tester. The insulation resistance must not be less than 0.5 Mohm.