Engine connection diagram via start-stop button. How to connect a magnetic starter

Magnetic starter (contactor) is a device designed for switching power electrical circuits. Most often used to start/stop electric motors, but can also be used to control lighting and other power loads.

What is the difference between a contactor and a magnetic starter?

Many readers may have been offended by our definition, in which we (deliberately) mixed the concepts of “magnetic starter” and “contactor”, because in this article we will try to emphasize practice rather than strict theory. But in practice, these two concepts usually merge into one. Few engineers will be able to give a clear answer as to how they really differ. The answers of various experts may agree on some points and contradict each other on others. We present to your attention our version of the answer to this question.

The contactor is a complete device that does not require the installation of additional modules. The magnetic starter can be equipped additional devices, for example, a thermal relay and additional contact groups. A magnetic starter can be called a box with two buttons “Start” and “Stop”. Inside there may be one or two interconnected contactors (or starters) that implement mutual interlocking and reverse.

The magnetic starter is designed to control three-phase motor, therefore it always has three contacts for switching power lines. The contactor is in general case may have a different number of power contacts.

The devices in these figures are more correctly called magnetic starters. The device number one suggests the possibility of installing additional modules, for example a thermal relay (Figure 2). In the third figure, a “start-stop” block for controlling the engine with overheating protection and an automatic pick-up circuit. This block device is also called a magnetic starter.

But the devices in the following figures are more correctly called contactors:

They do not require installation of additional modules on them. The device numbered 1 has 4 power contacts, the second device has two power contacts, and the third has three.

In conclusion, we will say: all the above-mentioned differences between a contactor and a magnetic starter are useful to know for general development and to remember just in case, however, you will have to get used to the fact that in practice no one usually separates these devices.

Design and principle of operation of a magnetic starter

The contactor device is somewhat similar to — it also has a coil and a group of contacts. However, the contacts of the magnetic starter are different. Power contacts are designed to switch the load controlled by this contactor; they are always normally open. There are also additional contacts designed to implement starter control (this will be discussed below). Auxiliary contacts can be normally open (NO) or normally closed (NC).

In general, the magnetic starter device looks like this:

When control voltage is applied to the starter coil (usually the coil contacts are designated A1 and A2), the moving part of the armature is attracted to the stationary part and this leads to the closure of the power contacts. Additional contacts (if any) are mechanically connected to the power ones, therefore, at the moment the contactor is triggered, they also change their state: normally open ones close, and normally closed ones, on the contrary, open.

Magnetic starter connection diagram

This is what it looks like simplest scheme connecting the motor through the starter. The power contacts of the KM1 magnetic starter are connected to the electric motor terminals. A QF1 circuit breaker is installed in front of the contactor for overload protection. The relay coil (A1-A2) is energized through a normally open “Start” button and a normally closed “Stop” button. When you press the “Start” button, voltage comes to the coil, the contactor is activated, starting the electric motor. To stop the engine, you need to press “Stop” - the coil circuit will break and the contactor will “disconnect” the power lines.

This scheme will only work if the “start” and “stop” buttons are latched.

Instead of buttons, there may be a contact of another relay or a discrete output of the controller:

The contactor can be turned on and off using the PLC. One discrete output of the controller will replace the “start” and “stop” buttons - they will be implemented by the controller logic.

Scheme of “self-recovery” magnetic starter

As already mentioned, the previous scheme with two buttons only works if the buttons are latched. In real life it is not used because of its inconvenience and unsafety. Instead, they use a circuit with automatic pickup (self-pickup).

This circuit uses an additional normally open contact of the starter. When you press the “start” button and the magnetic starter is triggered, the additional contact KM1.1 closes simultaneously with the power contacts. Now the “start” button can be released - it will be “picked up” by contact KM1.1.

Pressing the “stop” button will break the coil circuit and at the same time the additional circuit will open. contact KM1.1.

Connecting the motor via a starter with a thermal relay

The figure shows a magnetic starter with a thermal relay installed on it. When heated, the electric motor begins to consume more current - this is detected by a thermal relay. On the body of the thermal relay, you can set the current value, the excess of which will cause the relay to operate and close its contacts.

Fine closed contact The thermal relay uses the starter coil in the power supply circuit and breaks it when the thermal relay is activated, providing an emergency shutdown of the engine. The normally open contact of a thermal relay can be used in a signal circuit, for example, to light an “emergency” lamp when the electric motor is turned off due to overheating.

A reversible magnetic starter is a device with which you can start rotating a motor in forward and reverse directions. This is achieved by changing the phase sequence at the motor terminals. The device consists of two interlocking contactors. One of the contactors switches phases in order A-B-C, and the other, for example, A-C-B.

Mutual interlocking is necessary so that it is impossible to accidentally turn on both contactors at the same time and create a phase-to-phase short circuit.

The reversing magnetic starter circuit looks like this:

A reversible starter can change the phase sequence on the motor by switching the voltage supplying the motor through the contactor KM1 or KM2. Please note that the phase order of these contactors is different.

When you press the “Direct Start” button, the engine starts through the KM1 contactor. In this case, the additional contact of this starter KM1.2 opens. It blocks the start of the second contactor KM2, so pressing the “Reverse start” button will lead to nothing. In order to start the engine in the opposite (reverse) direction, you must first stop it with the “Stop” button.

When the “Reverse start” button is pressed, contactor KM2 is activated, and its additional contact KM2.2 blocks contactor KM1.

Automatic pickup of contactors KM1 and KM2 is carried out using normal open contacts KM1.1 and KM2.1, respectively (see section “Self-retaining magnetic starter circuit”).

In the operating circuits for controlling the operation of modern electric motors and similar units, switching devices of a special design, called contactors or magnetic starters, are necessarily installed. They are designed to safely turn on powerful equipment in the presence of strong inrush currents, accompanied by unwanted electrical surges. The connection diagram for a 220 volt magnetic starter is given below in the text.

Difference between contactor and starter

Both contactors and starters serve for switching power supply lines and are made on the basis of a powerful electromagnet, the activation of which is designed for various current modes. Before connecting the contactor to the load line, you should keep in mind that its main feature is its high switching power.

220V electromagnetic starters are designed for inrush currents of insignificant amplitude (no more than 10-15 Amperes) and can operate in circuits with direct and alternating voltage. Contactors are designed to work with very high currents (up to 100 Amperes or more) and are usually installed in phase alternating current circuits.

Regardless of their purpose, both devices are designed for standard operating voltages and contain the following mandatory elements:

• E/m coil, to which a control signal of insignificant power is supplied;
• Switching power contacts used to supply power voltage to the load;
• Protective thermal relays protecting switching lines from current overloads;
• A set of auxiliary contact pairs involved in signal circuits.

Important! Unlike starters, in 380-volt contactor circuits, special arc-extinguishing chambers are provided to localize the powerful current discharge created during its switching.

Thus, the difference in the operating parameters of these devices (the magnitude of switched currents) is manifested in the features of their design, which ultimately affects their dimensions and weight.

Types of magnetic starters

In accordance with the number of switched phases, all known types of these devices are divided into single-phase and three-phase, and according to the type of load connected to them - into reversible and non-reversible starters.

Classification of these devices according to the method of placement and protection from harmful effects allows you to distinguish them by the following characteristics:

• Open design, in which the three-phase device is mounted in closed cabinets that prevent the ingress of moisture, dust and small debris into them;
• Closed or protected design, in which devices can operate in conditions of high humidity and dust;
• A design option that allows you to protect them from dust, splashes and moisture; Moreover, they can also be installed outside (under specially equipped canopies that reliably shelter their working parts from sunlight and rain).

Based on the location of the push-button station, all known types of starters are divided into products equipped with a remote control panel, and into products with a built-in switching mechanism.

Additional information. IN latest models, as a rule, there is a built-in light indicating that the executive and control circuits are turned on.

Certain types of such devices contain thermal current limiters (relays) that are triggered when there is an overload in the switched circuit.

Features of connecting starters to three-phase networks

To connect to a 380 Volt power line, you will need three magnetic starters controlled from one common remote control. But this technique can only be considered theoretically, since the three-phase network is controlled by special switching devices - “powerful” contactors.

The diagram for connecting the contactor to the line is shown in the figure below.

It is clear from the diagram that in order to switch (switch) three “powerful” phases in 380V lines, it is enough to use one control panel designed for small currents.

Such remote controls can be located separately and at some distance from the starter itself, in a place convenient for putting the equipment into operation (a machine engine, for example).

Such a remote control must have two buttons, one of which is responsible for starting the final mechanism (electric motor), and the second for its start. To ensure that the power circuit does not open after releasing the start key, a special blocking contact is introduced into the starter operation control circuit, switching simultaneously with the contactors switching the power line.

The device of the starter and the principle of its operation

Before connecting a magnetic starter to the load switching circuit, you should understand its internal structure and also become familiar with the principle of operation.

The basis of the design of this device is an inductance coil placed on a special magnetic frame, which, in turn, consists of two parts: movable and stationary.

Pay attention! The shape of the two halves of the magnetic circuit resembles the letter “W”, each of which faces each other with its vertices.

Its fixed or lower part is fixed to the body of the device, and the upper part is spring-loaded and can move freely. The control coils of the magnetic starter are mounted in the slots of the fixed lower part, which can be designed for a discrete range of voltages (12, 24, 110, 220 and 380 Volts).

In the upper part of the body there are two groups of working contacts, one of which is fixed, and the second is connected to a movable magnetic core (see figure below).

The procedure for connecting the contactor to the line is established by the requirements of the PUE and involves the supply of phase voltages in the upper group, and their removal to the load from the lower ones. The general picture of their switching is as follows:

• When there is no control voltage on the coil, the spring-loaded part of the magnetic circuit is shifted upward, and the contact group associated with it is open. After applying supply voltage to it (the start button is closed), an e/m field is formed around the coil, attracting the upper half of the core along with the contacts;
• At the same time, they are connected, forming a closed circuit for powering the load;

Additional information. The starter connection diagram is designed in such a way that when the control button is pressed once, the system starts up.

• But the second time it is started, no changes occur in the starter circuit, since the push-button connection is blocked by a parallel-connected contact;
• Then, after pressing the “Stop” button, the control circuit is broken and the voltage on the coil disappears;
• This leads to a displacement of the moving part of the magnetic circuit to the lower position and opening of the working contacts of the starter.

Upon completion of the entire switching cycle, the launch station is again ready for use.

To all that has been said, it must be added that any type of voltage can be used to control the start and stop buttons: alternating or direct. The main thing is to ensure that its parameters correspond to the values ​​stated in the passport.

Checking the starter coil

To control the electric coil, one of the phases is most often used, supplied through a button to an electric motor or other load. For these purposes, the least loaded line is usually selected (most often this is phase “C”). But regardless of its choice, the coil constantly operates under significant current overloads and often burns out. In this regard, it makes sense to consider testing it under normal laboratory conditions.

To study the working node, you will need to assemble the diagram presented in the figure below.

The power supply used when testing the coil (in in this case This mains voltage is 220 Volts) is supplied to its terminals A1 and A2, located on top of the case. To do this, take any power cord with a regular plug, in which the mating parts of the wires are connected to the ends of the coil winding.

To check it, just plug the plug into the socket, and then make sure the contactor is activated (it should be accompanied by a loud bang with a metallic sound). To be completely sure that the coil is in good condition, you can ring any of the three contact chains of the starter, which will require a tester or multimeter turned on in the “Ringing” mode.

In the absence of a tester, you can use any working battery by connecting its plus and minus to the input contacts L1 and L2, for example. If you connect a light bulb at the appropriate voltage to the output terminals of the starter T1, T2, then when the plug is plugged into the network it should light up.

The absence of a characteristic click and the indicator light coming on with one hundred percent probability means a coil malfunction (winding breakage or burnout).

Pay attention! In some cases, the characteristic burnt smell can immediately suggest that it is not working, but it is still necessary to check it just in case.

In the final part, we note that to connect a 220 Volt magnetic starter, any of the circuits discussed above can be used. The main thing is that the voltage supplied to the coil matches the value indicated in its passport or label.

Video

Devices that are designed (their main purpose) to automatically turn on and off three-phase electric motors from the network, as well as their reversal are called magnetic starters. As a rule, they are used to control asynchronous electric motors with supply voltages up to 600 V. Starters can be reversible or non-reversible. In addition, a thermal relay is often built into them to protect electrical machines from long-term overcurrent.

Magnetic starters can be produced in various designs:

• Reversible;
• Not reversible;
• Protected type - installed in rooms where the environment does not contain large quantity dust;
• Dust-proof - installed in places where they will not be directly exposed to the sun, rain, snow (when placed outdoors, they are located under a canopy);
• Open type - designed for installation in places protected from foreign objects and dust (electrical cabinets and other equipment)

Magnetic starter device

The design of the magnetic starter is quite simple. It consists of a core on which the retractor coil is placed, an armature, a plastic case, mechanical power indicators, as well as main and auxiliary block contacts.

Let's take a look at the example shown below:

When voltage is applied to the starter coil 2, the current flowing in it will attract the armature 4 to the core 1, resulting in the closure of the power contacts 3, as well as the closure (or opening, depending on the version) of the auxiliary block contacts, which in turn signal to the system controls to turn the device on or off. When the voltage is removed from the coil of the magnetic starter under the action of the return spring, the contacts will open, that is, they will return to their initial position.

The operating principle of reversible magnetic starters is the same as non-reversible ones. The difference lies in the alternation of phases that are connected to the starters (A - B - C one device, C - B - A another device). This condition is necessary to reverse the AC motor. Also, when reversing magnetic starters, the simultaneous activation of devices is blocked to avoid short circuits.

Schemes for connecting magnetic starters

One of the simplest magnetic starter connection diagrams is shown below:

The operating principle of this circuit is quite simple: when the QF circuit breaker is closed, the power supply circuit for the magnetic starter coil is assembled. The PU fuse provides short circuit protection for the control circuit. Under normal conditions, the thermal relay contact P is closed. So, to start the asynchronous machine, we press the “Start” button, the circuit closes, current begins to flow through the coil of the magnetic starter KM, the core is retracted, thereby closing the power contacts of the KM, as well as the block contact BC. The block contact BC is needed in order to close the control circuit, since the button, after it is released, will return to its original position. To stop this electric motor, just press the “Stop” button, which will disassemble the control circuit.

In case of prolonged overload current, the thermal sensor P will be triggered, which will open contact P, and this will also lead to the machine stopping.

In the connection diagram given above, the nominal voltage of the coil should be taken into account. If the coil voltage is 220 V, and the motor (when connected to a star) is 380 V, then this diagram cannot be used, but can be used with a neutral conductor, and if the motor windings are connected by a delta (220 V), then this system quite viable.

Circuit with neutral conductor:

The only difference between these connection schemes is that in the first case, the power supply of the control system is connected to two phases, and in the second to a phase and a neutral conductor. At automatic control The starting system may switch on a contact from the control system instead of the “Start” button.

You can see how to connect a non-reversible magnetic starting device here:

The reversible connection circuit is shown below:

This circuit is more complex than when connecting a non-reversible device. Let's look at the principle of its operation. When you press the “Forward” button, all the actions described above occur, but as you can see from the diagram, a normally closed contact KM2 appears in front of the forward button. This is necessary to electrically block the simultaneous activation of two devices (avoiding short circuits). When you press the “Back” button while the electric drive is running, nothing will happen, since the KM1 contact in front of the “Back” button will be open. To reverse the machine, you must press the “Stop” button, and only after turning off one device can you turn on the second.

And a video of connecting the reversible magnetic starting device:

When installing magnetic starting devices with thermal relays, it is necessary to install with a minimum difference in ambient temperatures between the electric motor and the magnetic starting device.

It is undesirable to install magnetic devices in places subject to strong shocks or vibrations, as well as near powerful electromagnetic devices whose currents exceed 150 A, since they create quite large shocks and jolts when triggered.

For normal operation thermal relay, the ambient temperature should not exceed 40 0 ​​C. It is also not recommended to install it near heating elements (rheostats) and not install them in the most heated parts of the cabinet, for example at the top of the cabinet.

Comparison of magnetic and hybrid starters:

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

Connecting a magnetic starter - connection diagram

There are two fundamentally different schemes connecting a magnetic starter:

1. simple non-reverse circuit (start and stop);
2. reverse circuit for connecting the electric motor (start, forward, reverse).

In a simple (non-reverse) connection diagram, the following elements “participate”:

• Magnetic starter;
• 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 diagram with two working diagrams:

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. Motors, because it’s supposed to be so, and street lighting, because the starter will provide remote, safe connection of street lighting from anywhere in the house. You can place the starter in the switchboard room, and the control buttons (on, off) where convenient.

Connecting a magnetic starter - example

I won’t talk about the internal design of the starter, the arc-extinguishing chambers and the insulating cross-arm; that’s in the video at the bottom of the article. I will show you the practical connection of an electric motor through a magnetic starter.

For work we will prepare:

• Actuator;
• Thermal relay;
• Electrical cable. We calculate based on the power of the electric motor;
• Push-button point with two buttons in one housing;
• Electric motor installed on site.

Electrical installation work for installing a magnetic starter

• From the three-phase (1 in the yellow diagram above), which we place before the starter, we connect the power cable to the starter;
• From the starter output we lay a cable to the push-button point;
• We lay a cable from the button to the electric motor.

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

To connect a magnetic starter according to the above diagram, you need to find and understand the purpose of the contacts on the starter and buttons. Therefore, let’s look at the push-button point first, and then look at the starter.

Buttons (push-button point) for starter operation

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

Buttons are designed to make and break electrical circuit. For this purpose, the button structure has closed and open contacts. It is correct to say that open contacts are normally open, and closed contacts are normally closed.

For correct connection It is important to identify open and closed contacts. They are usually designated by numbers 1-2 and 3-4 respectively.

We understand that when you press a button, open contacts are closed, and open contacts are closed. Now let's look at the starter terminals.

Starter terminals required for connection

We place 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 output 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 (the 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 choke. There are starters (older models) with terminals A1 and A2 for outputting two contacts of the starter choke.

There are no more 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 motor to terminals 4T1 and working zero, without a starter;
• From terminal 1L1 we connect the wire going to pin 1 of the “Start” button with a cable;
• From contact 2 of the “Start” button we run a loop to contact 3 of the “Stop” button;
• From terminal 4 of the “Stop” button we run a cable to contact A2 of the magnetic starter coil (it’s on the body). If there is a coil contact A1 on the body, connect zero to it;
• From the auxiliary contacts of the starter NO13 and NO14 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 conductors;
• A thermal relay must be installed parallel to the switch, up to terminals 1L1-3L3. It will protect the starter from overload;
• The connection is complete. Turn it on.

How does a magnetic starter trigger and work?

When the circuit breaker is turned on, the phase current is supplied to the starter contacts 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 close, current is supplied to the starter coil, which closes the contact groups of the L-T starters.

Release the “Start” button. If there were no additional contacts in the starter, the engine would stop. But the additional starter contacts NO13 and NO14 are closed and remain closed when the “Start” button is released. This prevents the starter coil power supply from opening. We see that the traverse on the body is recessed, and we hear a characteristic click.

When you press the “Stop” button, the coil circuit simply opens, and it is pressed out - the starter cross-arm rises, and we hear a characteristic click.

Important! Additional contacts of the starter play an important role in connecting the starter. It remains to be recalled that additional contacts, which 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.

The times when switching of three-phase asynchronous electric motors was carried out using manual switches are long gone. They were replaced by more advanced devices - magnetic starters.

This device allows you to remotely control the working processes of electrical equipment, ensuring a high level of electrical safety.

IN lately starters are increasingly used for remote control powerful consumers of electricity: compressor units, pumps, air conditioning, ventilation systems, etc. One of the new applications is implementation in lighting and alarm control systems.

Structurally, modern magnetic starters consist of two parts:

1. A permanently fixed lower part and a contact block that moves along skids.
2. There are 4 contacts on the top of the device - 2 normally closed and 2 normally open.

The basis of any magnetic starter is a magnetic circuit and an inductor.

When voltage is turned on to the coil of the magnetic starter, the armature is instantly attracted to the core, thereby closing the power and auxiliary contacts, which send a signal to the control system to start or turn off the device.

By means of a return spring, when the voltage is removed from the coil, all contacts open (return to their original position). Starters can be used on both direct and alternating voltage. The most important thing is that it does not exceed the parameters recommended by the manufacturer.

The classic version of connecting a magnetic starter involves the use of two control buttons: the “Start” button and the “Stop” button, which are sequentially connected to the phase supply circuit to the magnetic coil connector. They can be placed either in separate housings or in a common housing (the so-called push-button post or push-button station).

This is what the simplest connection diagram looks like:

As can be seen from the connection diagram of the magnetic starter buttons, when the “Start” button is closed (pressed), the circuit is closed, as a result of which current begins to flow through the coil, drawing in the core and thereby closing the power and auxiliary contacts.

To stop managed device or equipment, just press the “Stop” button, which opens the circuit. Both buttons have a similar structure and differ only in that in the initial position the Start button is always in the open state.

Connect a magnetic starter with buttons Controlling Start and Stop with your own hands is quite simple. Now we'll tell you how to do this.

VIDEO REVIEW

Instructions - connecting a magnetic starter via a button

Let's look at the procedure for connecting a magnetic starter using the example of lighting control - turning on/off a regular lamp.

To do this you will need the following tools, devices and materials:

• magnetic starter;
• magnetic starter power button Start (it can be of two types - green or black);
• Stop button (red);
• installation box for buttons;
• two-core copper wire;
• socket with lamp;
• side cutters, knife, Phillips screwdriver.

To connect a push-button switch circuit, you need to do the following:

1. From the “plus” power is supplied to the Stop button and from it a wire is output to the power contact of our magnetic starter;
2. The output from the Stop button goes to the Start button and from it a “plus” is output to the auxiliary contact of the device, designated as 1L1;
3. The second output from the Start button goes to the base contact of the starter A1;
4. A jumper is connected to A1 from the 2T1 contact socket. This is necessary so that after releasing the “Start” button, the circuit does not open, and the phase continues to flow to the coil of the magnetic starter and self-holding is triggered when the start button is pressed once. IN otherwise for the device to operate, you will have to constantly keep the start button pressed;
5. The negative wire goes straight to connector A2, as well as to 5L3;
6. The controlled electrical device itself (in our case, a lamp) is connected to connectors 4T2 and 6L3.

VIDEO INSTRUCTIONS