Connecting a three-phase motor to a single-phase network. Connection diagram of a three-phase electric motor to a three-phase network

Three-phase motor connection diagrams - motors designed to operate from three-phase network, have a performance much higher than single-phase 220 volt motors. Therefore, if three phases are carried out in the workroom AC, then the equipment must be installed taking into account the connection to three phases. As a result, a three-phase motor connected to the network provides energy savings and stable operation of the device. No need to connect additional elements to start. The only condition for good operation of the device is error-free connection and installation of the circuit, in compliance with the rules.

Three-phase motor connection diagrams

Of the many circuits created by specialists, two methods are practically used for installing an asynchronous motor.

• Star diagram.
• Triangle diagram.

The names of the circuits are given according to the method of connecting the windings to the supply network. To determine on an electric motor which circuit it is connected to, you need to look at the specified data on a metal plate that is installed on the motor housing.

Even on old motor samples, it is possible to determine the method of connecting the stator windings, as well as the mains voltage. This information will be correct if the engine has already been in operation and there are no operational problems. But sometimes you need to make electrical measurements.

Star connection diagrams for a three-phase motor make it possible to start the motor smoothly, but the power is 30% less than the rated value. Therefore, in terms of power, the triangle circuit remains the winner. There is a feature regarding the current load. The current increases sharply during startup, which negatively affects the stator winding. The heat generated increases, which has a detrimental effect on the winding insulation. This leads to insulation failure and damage to the electric motor.

Many European devices supplied to domestic market, are equipped with European electric motors operating with voltages from 400 to 690 V. Such 3-phase motors must be installed in a 380 volt network of domestic voltage only according to the triangular pattern of the stator windings. Otherwise, the motors will immediately fail. Russian motors for three phases are connected in a star. Occasionally, a triangle circuit is installed to obtain from the engine highest power, used in special types of industrial equipment.

Manufacturers today make it possible to connect three-phase electric motors according to any circuit. If there are three ends in the mounting box, then the factory star circuit has been produced. And if there are six terminals, then the motor can be connected according to any circuit. When mounting in a star, you need to combine the three terminals of the windings into one unit. The remaining three terminals are supplied to phase power with a voltage of 380 volts. In a triangle circuit, the ends of the windings are connected in series in order to each other. Phase power connects to the node points of the ends of the windings.

Checking the motor connection diagram

Let's imagine the worst case scenario for connecting the windings, when the wire terminals are not marked at the factory, the circuit assembly is carried out in the inside of the motor housing, and one cable is brought out. In this case, it is necessary to disassemble the electric motor, remove the covers, disassemble the internal part, and deal with the wires.

Stator phase determination method

After disconnecting the lead ends of the wires, use a multimeter to measure the resistance. One probe is connected to any wire, the other is brought in turn to all wire terminals until a terminal belonging to the winding of the first wire is found. Do the same for the other terminals. It must be remembered that marking the wires in any way is mandatory.

If there is no multimeter or other device available, then use homemade probes made from a light bulb, wires and batteries.

Winding polarity

To find and determine the polarity of the windings, you need to apply some techniques:

• Connect pulsed direct current.
• Connect variable source current

Both methods operate on the principle of applying voltage to one coil and transforming it along the magnetic circuit of the core.

How to check the polarity of the windings with a battery and a tester

A voltmeter with increased sensitivity is connected to the contacts of one winding, which can respond to a pulse. Voltage is quickly connected to the other coil with one pole. At the moment of connection, the deviation of the voltmeter needle is monitored. If the arrow moves to the positive, then the polarity coincides with the other winding. When the contact opens, the arrow will go to minus. For the 3rd winding the experiment is repeated.

By changing the terminals to another winding when the battery is turned on, it is determined how correctly the markings of the ends of the stator windings are made.

AC test

Any two windings are connected in parallel with their ends to the multimeter. The voltage is turned on to the third winding. They look at what the voltmeter shows: if the polarity of both windings matches, then the voltmeter will show the voltage value, if the polarities are different, then it will show zero.

The polarity of the 3rd phase is determined by switching the voltmeter, changing the position of the transformer to another winding. Next, control measurements are made.

Star diagram

This type of three-phase motor connection circuit is formed by connecting the windings in different circuits, united by a neutral and a common phase point.

Such a circuit is created after the polarity of the stator windings in the electric motor has been checked. A single-phase voltage of 220V is supplied through a machine to the beginning of 2 windings. Capacitors are inserted into the gap into one: working and starting. The neutral power wire is connected to the third end of the star.

The capacitance value of capacitors (working) is determined by the empirical formula:

C = (2800 I) / U

For the starting circuit, the capacity is increased by 3 times. When the motor is operating under load, it is necessary to control the magnitude of the winding currents by measurements, and adjust the capacitance of the capacitors according to the average load of the mechanism drive. Otherwise, the device will overheat and an insulation breakdown will occur.

It is best to connect the motor to operation through the PNVS switch, as shown in the figure.

It already contains a pair of closure contacts, which together supply voltage to 2 circuits by means of the “Start” button. When the button is released, the circuit breaks. This contact is used to start the circuit. Complete shutdown power supply is done by clicking on “Stop”.

Triangle diagram

The diagram for connecting a three-phase motor with a delta is a repetition of the previous version in startup, but differs in the method of connecting the stator windings.

The currents passing in them are greater than the values ​​of the star circuit. The operating capacitances of capacitors require increased rated capacitances. They are calculated using the formula:

C = (4800 I) / U

The correct choice of capacitances is also calculated by the ratio of currents in the stator coils by measuring with a load.

Motor with magnetic starter

A three-phase electric motor operates through a similar circuit with a circuit breaker. This circuit additionally has an on and off block, with Start and Stop buttons.

One phase, normally closed, connected to the motor, is connected to the Start button. When it is pressed, the contacts close and current flows to the electric motor. It must be taken into account that when the Start button is released, the terminals will open and the power will turn off. To prevent this situation from happening, the magnetic starter is additionally equipped with auxiliary contacts, which are called self-retaining. They block the chain and prevent it from breaking when the Start button is released. You can turn off the power using the Stop button.

As a result, a 3-phase electric motor can be connected to the network three-phase voltage absolutely different methods, which are selected according to the model and type of device, operating conditions.

Connecting a motor from a machine

A general version of this connection diagram looks like in the figure:

Shown here is a circuit breaker that turns off the power supply to the electric motor in case of excessive current load and short circuit. The circuit breaker is a simple 3-pole circuit breaker with a thermal automatic load characteristic.

For rough calculation and evaluation required current thermal protection, it is necessary to double the rated power of a motor designed to operate on three phases. The rated power is indicated on a metal plate on the motor housing.

Such connection diagrams for a three-phase motor may well work if there are no other connection options. The duration of the work cannot be predicted. This is the same if you twist an aluminum wire with a copper one. You never know how long it will take for the twist to burn out.

When using a connection diagram for a three-phase motor, you need to carefully select the current for the machine, which should be 20% greater than the operating current of the motor. Select the thermal protection properties with a reserve so that the blocking does not work during startup.

If, for example, the engine is 1.5 kilowatts, highest current 3 amperes, then the machine needs at least 4 amperes. The advantage of this motor connection scheme is low cost, simple design and maintenance.

If the electric motor is in one number and works a full shift, then there are the following disadvantages:

• It is impossible to adjust the thermal current of the circuit breaker. To protect the electric motor, the protective shutdown current of the machine is set to 20% greater than the operating current of the motor rating. The motor current needs to be through certain time measure with clamps, adjust the thermal protection current. But a simple circuit breaker does not have the ability to adjust the current.
• You cannot turn the electric motor off and on remotely.

The operation of three-phase electric motors is considered much more efficient and productive than single phase motors, designed for 220 V. Therefore, if there are three phases, it is recommended to connect the appropriate three-phase equipment. As a result, connecting a three-phase motor to a three-phase network provides not only economical, but also stable work devices. The connection diagram does not require the addition of any starting devices, since immediately after starting the engine, a magnetic field is formed in its stator windings. The main condition for the normal operation of such devices is the correct connection and compliance with all recommendations.

Connection diagrams

The magnetic field created by the three windings ensures the rotation of the electric motor rotor. Thus, electrical energy transforms into mechanical.

The connection can be made in two main ways - star or triangle. Each of them has its own advantages and disadvantages. Star circuit provides more soft start unit, however, the engine power drops by about 30% of the nominal. In this case, the delta connection has certain advantages, since there is no loss of power. However, this also has its own peculiarity associated with the current load, which increases sharply during startup. This condition has negative impact for wire insulation. The insulation may be broken and the motor may fail completely.

Particular attention should be paid to European equipment equipped with electric motors designed for voltages of 400/690 V. They are recommended for connection to our 380 volt networks only using the delta method. If connected with a star, such motors immediately burn out under load. This method Applicable only to domestic three-phase electric motors.

Modern units have a connection box into which the ends of the windings are led out. Their number can be three or six. In the first case, the connection diagram is initially assumed to be a star method. In the second case, the electric motor can be connected to a three-phase network in both ways. That is, with a star circuit, the three ends located at the beginning of the windings are connected into a common twist. The opposite ends are connected to the phases of the 380 V network from which power is supplied. With the triangle option, all ends of the windings are connected in series to each other. The phases are connected to three points at which the ends of the windings are connected to each other.

Using a star-delta circuit

A combined connection diagram known as “star-delta” is used relatively rarely. It allows for a smooth start with a star circuit, and during the main operation a triangle is turned on, providing maximum power unit.

This connection diagram is quite complex, requiring the use of three windings installed in the connections at once. The first MP is connected to the network and with the ends of the windings. MP-2 and MP-3 are connected to opposite ends of the windings. The delta connection is made to the second starter, and the star connection is made to the third. Simultaneous activation of the second and third starters is strictly prohibited. This will cause a short circuit between the phases connected to them. To prevent such situations, an interlock is installed between these starters. When one MP turns on, the contacts of the other open.

The entire system operates according to the following principle: simultaneously with MP-1 being turned on, MP-3, connected by a star, is turned on. After a smooth start of the engine, after a certain period of time set by the relay, the transition to normal operating mode occurs. Next, MP-3 is turned off and MP-2 is turned on according to a triangle diagram.

Three-phase motor with magnetic starter

Connecting a three-phase motor using a magnetic starter is carried out in the same way as through a circuit breaker. This circuit is simply supplemented with an on/off block with corresponding START and STOP buttons.

One normally closed phase connected to the motor is connected to the START button. When pressed, the contacts close, after which current flows to the motor. However, it should be noted that if the START button is released, the contacts will be open and no power will be supplied. To prevent this, the magnetic starter is equipped with another additional contact connector, the so-called self-retaining contact. It functions as a locking element and prevents the circuit from breaking when the START button is turned off. The circuit can only be completely disconnected using the STOP button.

In this way, connecting a three-phase motor to a three-phase network can be done in various ways. Each of them is selected in accordance with the unit model and specific operating conditions.

For a variety of work electrical devices Asynchronous motors are used, which are simple and reliable in operation and installation - you can easily install them yourself. The connection of a three-phase motor to a single-phase and three-phase network is carried out by star and delta.

General information

An asynchronous three-phase motor consists of the following main parts: windings, a moving rotor and a stationary stator. The windings can be connected to each other, and to them open contacts the main power supply of the network is connected either in series, i.e. the end of one winding is connected to the beginning of the next.

The connection can be made to a single-phase, two-phase and three-phase network, while the motors are mainly designed for two voltages - 220/380 V. Switching the type of winding connection allows you to change the rated voltage. Despite the fact that, in principle, it is possible to connect the motor to a single-phase network, it is rarely used, since the capacitor reduces the efficiency of the device. And the consumer receives approximately 60% of the rated power. But if there is no other option, then you need to connect it using a delta circuit, then the motor overload will be less than with a star.

Before connecting the windings in a single-phase network, it is necessary to check the capacitance of the capacitor that will be used. For this you need a formula:

C µF = P W /10

If the initial parameters of the capacitor are unknown, then it is recommended to use a starting model that can “adapt” to the operation of the engine and control its speed. Also, a current relay or a standard magnetic starter is often used to operate a device with a squirrel-cage rotor. This detail of the circuit allows for complete automation of the workflow. Moreover, for household models (with a power from 500 V to 1 kW), you can use a starter from a washing machine or refrigerator, further increasing the capacitor capacity or changing the relay winding.

Video: how to connect a three-phase 220V motor

Connection methods

With a single-phase network, it is necessary to shift the phase using special parts, most often a capacitor. But in some conditions it will be replaced by a thyristor. If you install a thyristor switch in the motor housing, then in the closed position it not only shifts the phases, but also significantly increases the starting torque. This helps to increase efficiency up to 70%, which is an excellent indicator for such a connection. Using only this part, you can avoid using a fan and the main types of capacitors - starting and running.

But this connection is not ideal either. When operating an electric motor with a thyristor, 30% more electric current is consumed than with capacitors. Therefore, this option is used only in production or in the absence of a choice.

Let's consider how a three-phase asynchronous motor is connected to a three-phase network if a triangle circuit is used.

The drawing shows two capacitors - starting and working, a start button, a diode signaling the start of work and a resistor system for braking and stopping completely. Also in in this case A switch is used that has three positions: “hold”, “start”, “stop”. When the handle is installed in the first position, the contacts begin to receive electric current. It is important here to switch to the “start” mode immediately after the engine starts, otherwise the windings may catch fire due to overload. At the end of the working process, the handle is fixed at the “stop” point.

Sometimes, when connected in phase, it is more convenient to stop a three-phase motor using the energy stored in the capacitor. Sometimes electrolytes are used instead, but this is a more complex option for installing the device. In this case, the parameters of the capacitor are very important, in particular, its capacity - braking and the time to completely stop the moving parts depend on it. This circuit also uses rectifying diodes and resistors. They will help, if necessary, stop the engine faster. But their technical specifications should look like this:

1. The resistor's resistance should not exceed 7 kOhm;
2. The capacitor must withstand voltages of 350 volts and above (depending on the mains voltage).

Having at hand a circuit that stops the motor, you can use a capacitor to connect it in reverse. The main difference from the previous drawing is the modernization of the three-phase two-speed motor with a double switch and a magnetic start relay. The switch, like in previous versions, has several main positions, but is fixed only to “start” and “stop” - this is very important.

Reversing motor connection is also possible via a magnetic starter. In this case, it is necessary to change the order of the stator phases, then it will be possible to ensure a change in the direction of rotation. To do this, immediately after pressing the “Forward” starter button, press the “Back” button. After this, the blocking contact will turn off the forward coil and transfer the power to reverse - the direction of rotation will change. But you need to be careful when connecting the starter - if the contacts are swapped, then during the transition there will not be a reversal, but a short circuit.

One more in an unusual way How you can connect a three-phase motor is the option of using a four-pole RCD. Its feature is the ability to use the network without zero.

1. In most cases, ED only requires 3 phases and 1 ground wire, zero is not necessary, since the load is symmetrical;
2. The connection principle is as follows: we take the power phases to the circuit breaker, and connect the zero directly to the RCD terminal - N, after which we do not connect it to anything;
3. From the machine, the cables are also connected to the RCD in the same way. We ground the engine and that's it.

Many owners, especially owners of private houses or cottages, use equipment with 380 V motors operating from a three-phase network. If an appropriate power supply circuit is connected to the site, then no difficulties arise with their connection. However, quite often a situation arises when a section is powered by only one phase, that is, only two wires are connected - phase and neutral. In such cases, you have to decide how to connect a three-phase motor to a 220 volt network. This can be done in various ways, but it should be remembered that such intervention and attempts to change parameters will lead to a drop in power and a decrease in the overall efficiency of the electric motor.

Connecting a 3-phase 220 motor without capacitors

As a rule, circuits without capacitors are used to start low-power three-phase motors in a single-phase network - from 0.5 to 2.2 kilowatts. Start-up time is spent approximately the same as when operating in three-phase mode.

These circuits are used under the control of pulses with different polarities. There are also symmetrical dinistors that supply control signals to the flow of all half-cycles present in the supply voltage.

There are two options for connecting and starting. The first option is used for electric motors with a speed of less than 1500 per minute. The windings are connected in a triangle. A special chain is used as a phase-shifting device. By changing the resistance, a voltage is generated across the capacitor, shifted by a certain angle relative to the main voltage. When the capacitor reaches the voltage level required for switching, the dinistor and triac are triggered, causing activation of the power bidirectional switch.

The second option is used when starting engines whose rotation speed is 3000 rpm. This category also includes devices installed on mechanisms that require a large moment of resistance during startup. In this case, it is necessary to provide a large starting torque. To this end, modifications were made to the previous circuit, and the capacitors required for the phase shift were replaced by two electronic keys. The first switch is connected in series with the phase winding, leading to an inductive shift of the current in it. The connection of the second switch is parallel to the phase winding, which contributes to the formation of a leading capacitive current shift in it.

This connection diagram takes into account the motor windings, which are displaced in space by 120 0 C. When setting, the optimal angle of current shift in the phase windings is determined, ensuring reliable starting of the device. When performing this action, it is quite possible to do without any special equipment.

Connecting a 380V to 220V electric motor via a capacitor

For a normal connection, you should know the principle of operation of a three-phase motor. When connected to the network, current begins to flow alternately through its windings at different times. That is, in a certain period of time, the current passes through the poles of each phase, also creating a rotating magnetic field in turn. It exerts an influence on the rotor winding, causing rotation by pushing in different planes at certain times.

When such a motor is connected to a single-phase network, only one winding will participate in the creation of rotating torque and the impact on the rotor in this case occurs only in one plane. This force is completely insufficient to shift and rotate the rotor. Therefore, in order to shift the phase of the pole current, it is necessary to use phase-shifting capacitors. Normal operation three-phase electric motor largely depends on the right choice capacitor.

Calculation of a capacitor for a three-phase motor in a single-phase network:

• With an electric motor power of no more than 1.5 kW, one operating capacitor will be sufficient in the circuit.
• If the engine power is over 1.5 kW or it experiences heavy loads during startup, in this case, two capacitors are installed at once - a working one and a starting one. They are connected in parallel, and the starting capacitor is needed only for starting, after which it is automatically turned off.
• The operation of the circuit is controlled by the START button and the power off toggle switch. To start the engine, press the start button and hold it until it is fully turned on.

If necessary, ensure rotation in different sides, an additional toggle switch is installed that switches the direction of rotation of the rotor. The first main output of the toggle switch is connected to the capacitor, the second to the neutral, and the third to the phase wire. If such a scheme promotes or weak recruitment rpm, in this case it may be necessary to install an additional starting capacitor.

Connecting a 3-phase motor at 220 without loss of power

The simplest and in an efficient way It is considered to connect a three-phase motor to a single-phase network by connecting a third contact connected to a phase-shifting capacitor.

Greatest output power, which can be obtained at home, is up to 70% of the nominal value. Such results are obtained when using the “triangle” scheme. Two contacts in the distribution box are directly connected to the wires of the single-phase network. The connection of the third contact is made through a working capacitor with any of the first two contacts or wires of the network.

In the absence of loads, a three-phase motor can be started using only a run capacitor. However, if there is even a small load, the speed will increase very slowly, or the engine will not start at all. In this case you will need additional connection starting capacitor. It turns on for literally 2-3 seconds so that the engine speed can reach 70% of the nominal speed. After this, the capacitor is immediately turned off and discharged.

Thus, when deciding how to connect a three-phase motor to a 220 volt network, all factors must be taken into account. Particular attention should be paid to capacitors, since the operation of the entire system depends on their action.

1. Connecting a three-phase electric motor - general diagram

When an electrician gets a job at any industrial enterprise, he must understand that he will have to deal with a large number three-phase electric motors. And any self-respecting electrician (I’m not talking about those who do wiring in an apartment) should clearly know the wiring diagram for a three-phase motor.

I immediately apologize that in this article I often call a contactor a starter, although I have already explained in detail that. What can you do, I'm tired of this name.

The article will discuss the connection diagrams for the most common asynchronous electric motor through a magnetic starter.

Various electric motor connection diagrams, their pros and cons. From simple to complex. Schemes that can be used in real life, designated: PRACTICAL DIAGRAM. So let's begin.

Connecting a three-phase motor

Meaning asynchronous electric motor, winding connection - star or triangle, connection to 380V network.

For the engine to operate, the working neutral conductor N (Neutral) is not needed, but the protective conductor (PE, Protect Earth) must be connected for safety reasons.

In the most general case, the diagram will look like this, as shown at the beginning of the article. Indeed, why not turn on the engine like a regular light bulb, only the switch will be a “three-key”?

2. Connecting the engine through a switch or circuit breaker

But no one even turns on a light bulb just like that; the lighting network and, in general, any load is always turned on only through circuit breakers.

Diagram of connecting a three-phase motor to the network via a circuit breaker

Therefore, in more detail, the general case will look like this:

3. Connecting the motor via a circuit breaker. PRACTICAL SCHEME

Diagram 3 shows a circuit breaker that protects the motor from overcurrent (“rectangular” bending of the supply lines) and from short circuit(“round” bends). By circuit breaker I mean a regular three-pole circuit breaker with a load thermal characteristic of C or D.

Let me remind you that in order to approximately select (estimate) the required thermal current of the thermal protection setting, you need to multiply the rated power of the three-phase motor (indicated on the nameplate) by 2.

Circuit breaker for turning on the electric motor. The current is 10A, through which you can turn on a 4 kW motor. No more and no less.

Scheme 3 has the right to life (due to poverty or ignorance of local electricians).

It works great, just like it has for many years. And one “fine” day the twist will burn out. Or the engine will burn out.

If you use such a circuit, you need to carefully select the current of the machine so that it is 10-20% greater than the operating current of the motor. And select the characteristic of the thermal release D so that the machine does not trip when starting.

For example, a 1.5 kW engine. We estimate the maximum operating current - 3A (real operating current may be less, we need to measure it). This means that the three-pole circuit breaker must be set to 3 or 4A.

The advantage of this motor connection diagram is the price and ease of execution and maintenance. For example, where there is one engine, and it is turned on manually for the entire shift. The disadvantages of such a scheme with switching on via an automatic machine are:

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1. Inability to regulate the thermal current of the machine. In order to reliably protect the engine, the shutdown current of the circuit breaker must be 10-20% greater than the rated operating current of the engine. The motor current must be periodically measured with clamps and, if necessary, the thermal protection current must be adjusted. But a regular machine does not have the ability to adjust (.
2. Inability to remotely and automatically turn on/off the engine.

These shortcomings can be eliminated; the diagrams below will show how.

A manual starter or automatic motor is a more advanced device. It has “Start” and “Stop” buttons, or an “On-Off” knob. Its advantage is that it is specially designed for starting and protecting the engine. The start is still manual, but the operating current can be adjusted within certain limits.

4. Connecting the motor via a manual starter. PRACTICAL SCHEME

Since motors usually have a high starting current, motor circuit breakers (automatic motors) usually have a thermal protection characteristic of type D. That is it can withstand short-term (starting) overloads of approximately 10 times the nominal value.

Here's what's on the side:

Motor circuit breaker - characteristics on the side wall

Setting current (thermal) – from 17 to 23 A, set manually. Cut-off current (trigger during short circuit) – 297 A.

In principle, a manual starter and an automatic motor are the same device. But the starter shown in the photo can switch the power supply to the engine. And the automatic motor constantly supplies power (three phases) to the contactor, which, in turn, switches the power to the motor. In short, the difference is in the connection diagram.

An advantage of the scheme is that you can adjust the thermal current setting. The downside is the same as in the previous scheme, there is no remote activation.

Motor connection diagram via 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 simple machines it is 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.

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 ).

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”.

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.

Since the topic of magnetic starters is very extensive, it is included in a separate article. The article has been significantly expanded and supplemented. Everything is covered there - connection of various loads, protection (thermal and short-circuit), reversible circuits, control from different points, etc. The numbering of the schemes has been preserved. I recommend it.

Connecting a three-phase motor via electronic devices

All methods of starting the engine described above are called Starting by direct voltage supply. Often, in powerful drives, such a start-up is a difficult test for the equipment - belts burn, bearings and fasteners break, etc.

Therefore, the article would be incomplete if I did not mention current trends. Nowadays, electronic starters are increasingly used to connect a three-phase motor instead of electromagnetic starters. power devices. By this I mean:

1. Solid State Relays ( solid state relay) – in them the power elements are thyristors (triacs), which are controlled input signal from a button or from a controller. There are both single-phase and three-phase. .
2. Soft (soft) starters (soft starters, soft starters) are advanced solid state machines. You can set the protection current, acceleration/deceleration time, turn on reverse, etc. And on this topic. Practical Application soft starters – .Connecting two-speed asynchronous motors. Keywords– Rarity, Retro, USSR.

   I’ll end here, thank you for your attention, I couldn’t cover everything, write questions in the comments!