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Connection diagram for a motor via a capacitor. Three-phase motor in a single-phase network. Connection diagram for a three-phase motor How to power a three-phase motor from 220

Most often, our houses, plots, and garages are supplied with a single-phase 220 V network. Therefore, equipment and all homemade products are made so that they work from this power source. In this article we will look at how to correctly connect a single-phase motor.

Asynchronous or collector: how to distinguish

In general, you can distinguish the type of engine by a plate - a nameplate - on which its data and type are written. But this is only if it has not been repaired. After all, anything can be under the casing. So if you are not sure, it is better to determine the type yourself.

How do collector motors work?

You can distinguish between asynchronous and commutator motors by their structure. The collectors must have brushes. They are located near the collector. Another mandatory attribute of this type of engine is the presence of a copper drum, divided into sections.

Such motors are produced only as single-phase ones; they are often installed in household appliances, as they allow one to obtain a large number of revolutions at the start and after acceleration. They are also convenient because they easily allow you to change the direction of rotation - you just need to change the polarity. It is also easy to organize a change in the rotation speed by changing the amplitude of the supply voltage or its cutoff angle. That is why such engines are used in most household and construction equipment.

The disadvantages of commutator motors are high operating noise at high speeds. Think of a drill, grinder, vacuum cleaner, washing machine, etc. The noise during their operation is decent. At low speeds, commutator motors are not so noisy (washing machine), but not all tools operate in this mode.

The second unpleasant point is that the presence of brushes and constant friction leads to the need for regular maintenance. If the current collector is not cleaned, contamination with graphite (from brushes being worn out) can cause adjacent sections in the drum to become connected and the motor simply stops working.

Asynchronous

An asynchronous motor has a stator and a rotor, and can be single or three-phase. In this article we consider connecting single-phase motors, so we will only talk about them.

Asynchronous motors are characterized by a low noise level during operation, therefore they are installed in equipment whose operating noise is critical. These are air conditioners, split systems, refrigerators.

There are two types of single-phase asynchronous motors - bifilar (with a starting winding) and capacitor. The whole difference is that in bifilar single-phase motors the starting winding works only until the motor accelerates. Afterwards it is turned off by a special device - a centrifugal switch or a start-up relay (in refrigerators). This is necessary, since after overclocking it only reduces efficiency.

In capacitor single-phase motors, the capacitor winding runs all the time. Two windings - main and auxiliary - are shifted relative to each other by 90°. Thanks to this, you can change the direction of rotation. The capacitor on such engines is usually attached to the housing and is easy to identify by this feature.

You can more accurately determine the bifilar or capacitor motor in front of you by measuring the winding resistance. If the resistance of the auxiliary winding is twice as large (the difference can be even greater), most likely this is a bifilar motor and this auxiliary winding is a starting winding, which means that a switch or starting relay must be present in the circuit. In capacitor motors, both windings are constantly in operation and connecting a single-phase motor is possible through a regular button, toggle switch, or automatic machine.

Connection diagrams for single-phase asynchronous motors

With starting winding

To connect a motor with a starting winding, you will need a button in which one of the contacts opens after switching on. These opening contacts will need to be connected to the starting winding. In stores there is such a button - this is PNDS. Its middle contact closes for the holding time, and the two outer ones remain in a closed state.

Appearance of the PNVS button and the state of the contacts after the “start” button is released.”

First, using measurements, we determine which winding is working and which is starting. Typically the output from the motor has three or four wires.

Consider the option with three wires. In this case, the two windings are already combined, that is, one of the wires is common. We take a tester and measure the resistance between all three pairs. The working one has the lowest resistance, the average value is the starting winding, and the highest is the common output (the resistance of two windings connected in series is measured).

If there are four pins, they ring in pairs. Find two pairs. The one with less resistance is the working one, the one with more resistance is the starting one. After this, we connect one wire from the starting and working windings, and bring out the common wire. A total of three wires remain (as in the first option):

• one from the working winding is working;
• from the starting winding;
• general.

With all these

connecting a single-phase motor

We connect all three wires to the button. It also has three contacts. Be sure to place the starting wire on the middle contact(which is closed only during start-up), the other two are extremelyie (arbitrary). We connect a power cable (from 220 V) to the extreme input contacts of the PNVS, connect the middle contact with a jumper to the working one ( note! not with the general). That's the whole circuit for switching on a single-phase motor with a starting winding (bifilar) through a button.

Condenser

When connecting a single-phase capacitor motor, there are options: there are three connection diagrams and all with capacitors. Without them, the engine hums, but does not start (if you connect it according to the diagram described above).

The first circuit - with a capacitor in the power supply circuit of the starting winding - starts well, but during operation the power it produces is far from rated, but much lower. The connection circuit with a capacitor in the connection circuit of the working winding gives the opposite effect: not very good performance at start-up, but good performance. Accordingly, the first circuit is used in devices with heavy starting (for example), and with a working capacitor - if good performance characteristics are needed.

Circuit with two capacitors

There is a third option for connecting a single-phase motor (asynchronous) - install both capacitors. It turns out something between the options described above. This scheme is implemented most often. It is in the picture above in the middle or in the photo below in more detail. When organizing this circuit, you also need a PNVS type button, which will connect the capacitor only during the start time, until the motor “accelerates”. Then two windings will remain connected, with the auxiliary winding through a capacitor.

Connecting a single-phase motor: circuit with two capacitors - working and starting

When implementing other circuits - with one capacitor - you will need a regular button, machine or toggle switch. Everything connects there simply.

Selection of capacitors

There is a rather complex formula by which you can calculate the required capacity accurately, but it is quite possible to get by with recommendations that are derived from many experiments:

• The working capacitor is taken at the rate of 70-80 uF per 1 kW of engine power;
• starting - 2-3 times more.

The operating voltage of these capacitors should be 1.5 times higher than the network voltage, that is, for a 220 volt network we take capacitors with an operating voltage of 330 V and higher. To make starting easier, look for a special capacitor for the starting circuit. They have the words Start or Starting in their markings, but you can also use regular ones.

Changing the direction of motor movement

If, after connecting, the motor works, but the shaft does not rotate in the direction you want, you can change this direction. This is done by changing the windings of the auxiliary winding. When assembling the circuit, one of the wires was fed to the button, the second was connected to the wire from the working winding and the common one was brought out. This is where you need to switch the conductors.

The need to use a three-phase asynchronous electric motor yourself most often arises when home-made equipment is installed or designed. Typically, at dachas or in garages, craftsmen want to use homemade sanding machines, concrete mixers, and sharpening and trimming devices.

Using a three-phase asynchronous electric motor yourself

This is where the question arises: how to connect an electric motor designed for 380 to a 220-volt network. In addition, it is important to both connect the electric motor to the network and ensure the required coefficient of performance (COP) and maintain the efficiency and operability of the unit.

Features of the engine design

Each motor has a plate or nameplate containing technical data and a winding twist diagram. The Y symbol represents a star connection and ∆ represents a triangle connection. In addition, the plate indicates the mains voltage for which the electric motor is intended. The wiring for connecting to the network is located on the terminal block, where the winding wires are led out.

To designate the beginning and end of the winding, the letters C or U, V, W are used. The first designation was in practice earlier, and English letters began to be used after the introduction of GOST.

It is not always possible to use a motor designed for a three-phase network for operation. If there are 3 pins on the terminal block, and not 6 as usual, then connection is possible only with the voltage indicated in the engineering specifications. In these units, the delta or star connection is already made inside the device itself. Therefore, it is not possible to use a 380 Volt electric motor with 3 leads for a single-phase system.

You can partially disassemble the motor and convert 3 pins to 6, but this is not so easy.

There are different schemes on how best to connect devices with parameters of 380 Volts to a single-phase network. To use a three-phase electric motor in a 220 Volt network, it is easier to use one of 2 connection methods: “star” or “delta”. Although it is possible to start a three-phase motor with 220 without capacitors. Let's consider all the options.

The figure shows how this type of connection is made. When operating an electric motor, you should additionally use phase-shifting capacitors, which are also called starting capacitors (Down capacitors) and running capacitors (Run capacitors).

Connection type “Star”

In a star connection, all three ends of the winding are connected. For this, a special jumper is used. Power is supplied to the terminals from the beginning of the windings. In this case, the beginning of winding C1(U1) through parallel connected capacitors is supplied to the beginning of winding C3(U3). Next, this end and C2 (U2) must be connected to the network.

In this type of connection, as in the first example, capacitors are used. In order to connect according to this twisting scheme, 3 jumpers are required. They will connect the beginning and end of the winding. The terminals coming from the beginning of winding C6C1 through the same parallel circuit as in the case of a star connection are connected to the terminal coming from C3C5. Then the resulting end and pin C2C4 should be connected to the network.

Connection type “Triangle”

If the nameplate indicates 380/220VV, then connection to the network is only possible via a “triangle”.

How to calculate capacity

For the working capacitor, the formula is used:

Operating = 2780xI/U, where
U – rated voltage,
I – current.

There is another formula:

Work = 66xP, where P is the power of the three-phase electric motor.

It turns out that 7 μF capacitor capacity is designed for 100 W of its power.

The value for the capacitance of the starting device should be 2.5-3 orders of magnitude greater than the working one. Such a discrepancy in capacitance values ​​for capacitors is required because the starting element is turned on for a short time when the three-phase motor is running. In addition, when turned on, the highest load on it is much greater; it is not worth leaving this device in the operating position for a longer period, otherwise, due to the current imbalance in the phases, after some time the electric motor will begin to overheat.

If you are using an electric motor with a power of less than 1 kW, then a starting element is not required.

Sometimes the capacity of one capacitor is not enough to start working, then the circuit is selected from several different elements connected in series. The total capacitance for a parallel connection can be calculated using the formula:

Ctot=C1+C1+…+Cn.

In the diagram, such a connection looks like this:

It will be possible to understand how correctly the capacitor capacitances are selected only during use. Because of this, a circuit of several elements is more justified, because with a larger capacity the engine will overheat, and with a smaller one, the output power will not reach the desired level. It is better to start selecting a capacity with its minimum value and gradually increase it to the optimal value. In this case, you can measure the current using current clamps, then choosing the best option will become easier. A similar measurement is made in the operating mode of a three-phase electric motor.

Which capacitors to choose

To connect an electric motor, paper capacitors (MBGO, KBP or MPGO) are most often used, but they all have small capacitive characteristics and are quite bulky. Another option is to choose electrolytic models, although here you will have to additionally connect diodes and resistors to the network. In addition, if the diode breaks down, and this happens quite often, alternating current will begin to flow through the capacitor, which can lead to an explosion.

In addition to capacity, it is worth paying attention to the operating voltage in the home network. In this case, you should select models with technical indicators of at least 300W. For paper capacitors, the calculation of the operating voltage for the network is slightly different, and the operating voltage for this type of device should be higher than 330-440VV.

Network connection example

Let's see how this connection is calculated using the example of an engine with the following characteristics on the nameplate.

Engine characteristics

So, let's take a three-phase asynchronous motor with a connection diagram for a 220 Volt network with a “triangle” and a “star” for 380 Volts.

In this case, the power of the electric motor taken as an example is 0.25 kW, which is significantly less than 1 kW, a starting capacitor is not required, and the general circuit will look like this.

To connect to the network, you need to find the capacity of the working capacitor. To do this, you need to substitute the values ​​into the formula:
Operating = 2780 2A/220V = 25 µF.

The operating voltage of the device is selected above 300 Volts. Based on this data, the corresponding models are sorted. Some options can be found in the table:

Dependence of capacitance and voltage on capacitor type

Connection with a thyristor switch

A three-phase electric motor designed for 380 Volts is used for single-phase voltage using a thyristor switch. In order to start the unit in this mode, you will need this diagram:

Three-phase electric motor diagram for single-phase voltage

Used in this work:

• transistors from the VT1, VT2 series;
• MLT resistors;
• silicon diffusion diodes D231
• thyristors KU 202 series.

All elements are designed for a voltage of 300 Volts and a current of 10A.
The thyristor switch, like other microcircuits, is assembled on a board.

Anyone who has basic knowledge of creating microcircuits can make such a device. When the electric motor power is less than 0.6-0.7 kW, when connected to the network, heating of the thyristor switch is not observed, so additional cooling is not required.

This connection may seem overly complicated, but it all depends on what elements you have to convert the motor from 380W to single phase. As you can see, using a three-phase motor for 380 via a single-phase network is not as difficult as it seems at first glance.

Connection. Video

The video talks about safely connecting the emery machine to a 220 V network and shares tips on what is needed for this.

For any asynchronous motor to operate, it is necessary to have a rotating electromagnetic field. When connected to a three-phase electrical network, this condition is easily met: three phases, shifted relative to each other by 120°, create a field whose strength within the stator space changes cyclically.

However, the overwhelming majority of household networks are single-phase - with a voltage of 220 volts. It is no longer so easy to create a rotating electromagnetic field in such a network, which is why single-phase asynchronous motors are not as common in use as their three-phase counterparts.

However, single-phase “asynchronous” systems are quite successfully used in household fans, pumps and other installations. Since the power of a household single-phase network is usually not at all large, and the energy indicators and characteristics of single-phase motors in general lag significantly behind the characteristics of three-phase motors, a single-phase asynchronous motor rarely has a power exceeding one kilowatt.

The rotor of single-phase asynchronous motors is squirrel-cage, since due to the low power of these machines there is no need for regulation along the rotor circuit.

The stator circuit consists of two windings connected to the network in parallel. One of them is working and it ensures operation of the engine in a 220 volt network, and the second can be considered auxiliary, or starting.

An element is included in the circuit of the second winding that provides a current difference in the windings. necessary to create a rotating field. In the vast majority of cases, this element is a capacitor, but there are single-phase motors that contain inductance or a resistor for these purposes.

Capacitor electric motors are structurally divided into the following motors:

1) with starting; 2) with starting and working; 3) with a working capacitor.

In the first and most common case, the additional winding and capacitor are connected to the network only during the start-up period, and at the end of the start-up they are taken out of service.

This scheme is implemented using a relay or simply a button pressed by the operator during startup. In the case of a working capacitor, it, together with its winding, is constantly connected to the circuit.

Electrical machines with a starting capacitor have a good starting torque with small current surges during starting. However, during operation in nominal mode, the performance of such motors decreases sharply due to the fact that the field of one working winding is not circular, but elliptical.

Motors with a running capacitor, on the contrary, provide good operating ratings with mediocre starting parameters. Motors that have a starting and running capacitor in their design are a compromise between the two previous solutions and have average performance both during starting and during operation.

In general, circuits with a starting capacitor are preferred for heavy starting, and circuits with a running capacitor are preferred if there is no need for good starting torque.

It is worth noting that when connecting a single-phase motor, the user almost always has a choice of which circuit to give preference to, since all the motor leads: from the capacitor, from the auxiliary winding and from the main winding are assembled in a terminal box (bar).

If there is no capacitor, or if it is necessary to redo the circuit, you can select a working capacitor at the rate of 0.7-0.8 µF per kilowatt of power, and a starting capacitor - 2.5 times more.

You can determine the working and starting stator windings in the box by the cross-section of the wires: at the starting one it will be smaller. Often, the starting and operating windings are connected directly in the motor housing and brought out to the outside with one common terminal.

The possibility of reversing when controlling such an electric machine is not possible, since it is impossible to swap the ends of the starting winding.

And it is possible to determine which of the three power terminals is common, which is the starting terminal and which is the working terminal, only by ringing them relative to each other. The greatest resistance will be between the starting and working terminals, and the resistance between the common and starting terminals will be greater than the resistance between the working and common terminals.

Asynchronous motors are designed for connection to a three-phase network of 380V and 220V. Below, as an example, there are two tags that show:

- engine's type
— type of current — alternating (three-phase)
— frequency — (50Hz)
— power — (0.25kW)
— revolutions per minute — (1370 rpm)
- possibility of connecting windings - delta / star
— rated motor voltage – 220V/380V
— rated motor current — 2.0/1.16A

I'm paying attention!
The indicated power on the electric motor tag is not electrical, but mechanical power on the shaft. Now I’ll try to explain the power of three-phase current using the formula.

P = 1.73 * 220 * 2.0 * 0.67 = 510 (W) for voltage 220V
P = 1.73 * 380 * 1.16 * 0.67 = 510.9 (W) for voltage 380V

We conclude:
The result of the solution shows that the electrical power is greater than the mechanical power. This is natural, since the engine must have a power reserve to compensate for losses due to the creation of a rotating magnetic field and voltage loss in the wires.

This tag shows that the windings of the electric motor can be connected either with a triangle (220V) or with a star (380V). There are six pins on the motor terminal
(C1, C2, C3, C4, C5, C6).

And on this label the windings are already connected inside the engine - by a star.
There are only three terminals on the terminal (C1, C2, C3).

The figure shows a diagram of a star connection of the windings of an asynchronous motor. (380V/220V)

The diagram shows with red arrows the voltage distribution in the motor windings, that one phase voltage of 220V is distributed to one winding, and the voltage of two windings is the sum of the phase-to-phase (linear) voltage of 380V.

From this follows a recommendation on how to adapt a three-phase motor to a single-phase 220V network. You need to look at the motor label to see what voltage its windings are designed for; it is possible to connect the windings with a star and a delta.

If it is possible to change the connection diagram of the windings at the terminal, we change it, connecting the windings with a triangle - 220V, in this case the engine will lose less power, since the voltage distribution for each winding will be the same 220V.

Star connection of the windings at the terminal. The beginning of the windings - (C1; C2; C3;) are connected to the network, and the ends - (C6; C4; C5;) of the windings are connected in place with a jumper.

Connection of windings at the terminal with a triangle. Jumpers are installed between the terminals (C1 - C6); (C2 – C4); (C3 - C5), and the outputs are connected to the network - (C1; C2; C3;).

Scheme for connecting an asynchronous motor to a single-phase network through capacitors. Connection of windings in a triangle with connection of working and starting capacitors.

There is a motor whose windings are designed to connect to a 220V/127V network. In the star connection of the windings, it is connected to a three-phase 220V network, and in the triangle connection of the windings, it is connected to a 127V three-phase network.

Table 1. Technical characteristics of some capacitors.

The most common way to start an engine:
This is a phase shifting capacitor.
In this case, engine power will be lost.
The useful power of the electric motor will be 50.60% of its power.

Let's get started:
What capacitors do we use?
Selecting oil capacitors
voltage, at least 300 - 400V.

To gain the capacity of working capacitors you need to:
connect capacitors in parallel.

Parallel connection of a capacitor

Now you need to select the capacity of the starting capacitors:
— the starting capacitance of the capacitors should be three times greater than the working capacitors.

Starting capacitors are only needed when starting the engine.
What happens if the starting capacitors are not disconnected from the circuit while the engine is running?
It is unacceptable. When the engine reaches rated speed, the starting capacitors will induce a large current imbalance in the motor windings,
This will cause overheating of the motor windings.

There is an e-book “Crib for the Master”, which explains in simple accessible language the connection of motors, magnetic starters, etc.

How to connect a three-phase electric motor if there is only 220 volts?

The most common drives of various electrical machines in the world are asynchronous motors. They were invented back in the 19th century and very quickly, due to the simplicity of their design, reliability and durability, are widely used both in industry and in everyday life.

However, not all consumers of electrical energy are provided with three-phase power supply, which makes it difficult to use reliable human assistants - three-phase electric motors. But there is still a way out, quite simply implemented in practice. You just need to connect the motor using a special circuit.

But first, it’s worth learning a little about the operating principles of three-phase electric motors and their connection.

How will an asynchronous motor operate when connected to a two-phase network?

On the stator of an asynchronous motor there are three windings, which are designated by the letters C1, C2 - C6. The first winding belongs to the terminals C1 and C4, the second to C2 and C5, and the third to C3 and C6, with C1-C6 being the beginning of the windings, and C4-C6 being their end. In modern engines, a slightly different marking system has been adopted, designating the windings with the letters U, V, W, and their beginning and end are indicated by the numbers 1 and 2. For example, the beginning of the first and C1 windings corresponds to U1, the end of the third C6 corresponds to W2, and so on.

All winding terminals are mounted in a special terminal box, which is found in any asynchronous motor. The plate that should be on each engine indicates its power, operating voltage (380/220 V or 220/127 V), as well as the possibility of connecting in two circuits: “star” or “delta”.

It is worth considering that the power of an asynchronous machine when connected to a single-phase network will always be 50-75% less than when connected to a three-phase network.

Connection diagram to a single-phase 220 volt network

If you simply connect a three-phase motor to a 220 volt network by simply connecting the windings to the supply network, then the rotor will not move for the simple reason that there is no rotating magnetic field. In order to create it, it is necessary to shift the phases on the windings using a special circuit.

From the course of electrical engineering it is known that a capacitor included in an alternating current electrical circuit will shift the phase of the voltage. This is due to the fact that during its charging there is a gradual increase in voltage, the time of which is determined by the capacitance of the capacitor and the amount of current flowing.

It turns out that the potential difference at the terminals of the capacitor will always be late in relation to the supply network. This effect is used to connect three-phase motors to a single-phase network.

The figure shows a diagram of connecting a single-phase motor using different methods. Obviously, the voltage between points A and C and also B and C will increase with a delay, which will create the effect of a rotating magnetic field. The capacitor rating in delta connections is calculated by the formula: C=4800*I/U, where I is the operating current and U is the voltage. The capacitance in this formula is calculated in microfarads.

In connections using the “star” method, which is least preferably used in single-phase networks due to the lower power output, a different formula is used: C = 2800 * I/U. Obviously, capacitors require lower ratings, which is explained by lower starting and operating currents.

Connecting high-power devices to a single-phase network

The diagram presented above is only suitable for those three-phase electric motors whose power does not exceed 1.5 kW. With higher power, it will be necessary to use a different circuit, which, in addition to the performance characteristics, is guaranteed to ensure the engine starts and reaches operating mode. Such a diagram is presented in the following figure, where it is additionally possible to reverse the engine.

Capacitor Cp ensures engine operation in normal mode, and Cp– needed when starting and accelerating the engine, which is done within a few seconds. Resistor R discharges the capacitor after starting and opening the pushbutton switch Kn. a switch S.A. serves for reverse.

The capacitance of the starting capacitor is usually used twice as large as the capacitance of the running capacitor. In order to gain the required capacity, assembled batteries from capacitors are used. It is known that parallel connection of capacitors sums up their capacitance, and series connection is inversely proportional.

When choosing capacitor ratings, they are guided by the fact that their operating voltage must be at least one step higher than the network voltage, and this will ensure their reliable operation during startup.

The modern element base allows the use of high-capacity capacitors with small dimensions, which greatly simplifies the connection of three-phase motors to a single-phase 220 volt network.

• Asynchronous machines can also be connected to single-phase 220 volt networks using phase-shifting capacitors, the rating of which is calculated based on their operating voltage and current consumption.

connecting a single-phase motor

We connect all three wires to the button. It also has three contacts. Be sure to place the starting wire on the middle contact(which is closed only during start-up), the other two are extremelyie (arbitrary). We connect a power cable (from 220 V) to the extreme input contacts of the PNVS, connect the middle contact with a jumper to the working one ( note! not with the general). That's the whole circuit for switching on a single-phase motor with a starting winding (bifolar) through a button.

Condenser

When connecting a single-phase capacitor motor, there are options: there are three connection diagrams and all with capacitors. Without them, the engine hums, but does not start (if you connect it according to the diagram described above).

Connection diagrams for a single-phase capacitor motor

The first circuit - with a capacitor in the power supply circuit of the starting winding - starts well, but during operation the power it produces is far from rated, but much lower. The connection circuit with a capacitor in the connection circuit of the working winding gives the opposite effect: not very good performance at start-up, but good performance. Accordingly, the first circuit is used in devices with heavy starting (concrete mixers, for example), and with a working condenser - if good performance characteristics are needed.

Circuit with two capacitors

There is a third option for connecting a single-phase motor (asynchronous) - install both capacitors. It turns out something between the options described above. This scheme is implemented most often. It is in the picture above in the middle or in the photo below in more detail. When organizing this circuit, you also need a PNVS type button, which will connect the capacitor only during the start time, until the motor “accelerates”. Then two windings will remain connected, with the auxiliary winding through a capacitor.

Connecting a single-phase motor: circuit with two capacitors - working and starting

When implementing other circuits - with one capacitor - you will need a regular button, machine or toggle switch. Everything connects there simply.

Selection of capacitors

There is a rather complex formula by which you can calculate the required capacity accurately, but it is quite possible to get by with recommendations that are derived from many experiments:

• The working capacitor is taken at the rate of 0.7-0.8 µF per 1 kW of engine power;
• starting - 2-3 times more.

The operating voltage of these capacitors should be 1.5 times higher than the network voltage, that is, for a 220 V network we take capacitors with an operating voltage of 330 V and higher. To make starting easier, look for a special capacitor in the starting circuit. They have the words Start or Starting in their markings, but you can also use regular ones.

Changing the direction of motor movement

If, after connecting, the motor works, but the shaft does not rotate in the direction you want, you can change this direction. This is done by changing the windings of the auxiliary winding. When assembling the circuit, one of the wires was fed to the button, the second was connected to the wire from the working winding and the common one was brought out. This is where you need to switch the conductors.

What it might look like in practice

How to connect an asynchronous motor

How to connect a three-phase motor to an AC network with a voltage of 220 V - you ask. After all, the engine itself has 3 phases and the network has 2 wires. Let's try to figure this out.

Appearance of an asynchronous motor

Asynchronous motors they are called because they have different rotation frequencies of the magnetic field of the stator and rotor. It turns out that the rotor is trying to catch up or equalize these frequencies. This is how rotation occurs.

Connection diagram of the stator windings of an asynchronous motor

The stator windings, of which there are 3, have 2 connection methods:

• star connection;
• triangle connection.

There are pins on the engine cover that are designated C1-C6. C1-C3 are the ends of the windings, and C4-C6 are their beginnings. How the windings are connected to one or another configuration is shown in the figures below.

How does an asynchronous motor work?

The operating principle of such motors is based on the well-known law of electromagnetic induction. The motor stator has 3 windings; voltage is applied to them alternately. An electric current arises in the windings, which also appears alternately in these windings.

Electric current is known to create an alternating magnetic field “around” itself. And according to the law of electromagnetic induction, an alternating magnetic field induces an electric current in the metal. As a result, an electric current is induced in the rotor winding. This current creates its own magnetic field that interacts with the magnetic field of the stator. It turns out a kind of analogue of two magnets that interact with each other. I don’t think it’s worth explaining how magnets repel and attract.

No electric current is supplied to the rotor - this is worth understanding. The rotor windings are connected to each other using a block of variable resistances. Variable resistance is used in this case to regulate the engine speed. By changing the rotor current with it, the force of interaction between the rotor and stator changes.

Connection diagram for an asynchronous motor to a 220V network

In order to connect an asynchronous motor, we need to connect the two winding terminals through a capacitor to each other and draw a conclusion. When connecting our asynchronous machine to a 220V network according to the diagram presented above, the power it produces will be 0.7 of the rated one. This happens because we connect a 3-phase motor to a single-phase network. To calculate capacity, you can use an approximate formula:

C - capacitance in microfarads

P - engine power in W

The operating voltage of the capacitor must be greater than the mains voltage. The diagram also shows a starting capacitor; its capacitance rating should be 3-4 times greater than the working capacitance. A starting capacitor is necessary to compensate for significant starting currents at the moment of starting the engine, since significant self-induction voltages arise at the moment of starting.

Quite often it happens that you don’t have the required container at hand. To get out of this situation, you need to use a parallel connection of capacitors.

Asynchronous three-phase motors are common in production and everyday life. The peculiarity is that they can be connected to both three-phase and single-phase networks. In the case of single-phase motors, this is impossible: they only operate when powered by 220V. What are the ways to connect a 380 Volt motor? Let's look at how to connect stator windings depending on the number of phases in the power supply using illustrations and a training video.

There are two basic schemes (video and diagrams in the next subsection of the article):

• triangle,
• star.

The advantage of a delta connection is that it operates at maximum power. But when the electric motor is turned on, high starting currents are produced in the windings, which are dangerous for equipment. When connected by a star, the motor starts smoothly, since the currents are low. But it will not be possible to achieve maximum power.

In connection with the above, motors when powered by 380 Volts are connected only by a star. Otherwise, high voltage when switched on by a delta can develop such inrush currents that the unit will fail. But under high load, the output power may not be enough. Then they resort to a trick: they start the engine with a star for safe inclusion, and then switch from this circuit to a delta for gaining high power.

Triangle and star

Before we look at these diagrams, let's agree:

• The stator has 3 windings, each of which has 1 beginning and 1 end. They are brought out in the form of contacts. Therefore, for each winding there are 2 of them. We will designate: winding - O, end - K, beginning - N. In the diagram below there are 6 contacts, numbered from 1 to 6. For the first winding, the beginning is 1, the end is 4. According to the accepted notation, this is HO1 and KO4. For the second winding - NO2 and KO5, for the third - HO3 and KO6.
• There are 3 phases in the 380 Volt electrical network: A, B and C. Let’s leave their symbols the same.

When connecting the windings of an electric motor with a star, first all ends are connected: HO1, HO2 and HO3. Then KO4, KO5 and KO6 are respectively supplied with power from A, B and C.

When connecting an asynchronous electric motor with a triangle, each beginning is connected to the end of the winding in series. The choice of the order of winding numbers is arbitrary. It may turn out: NO1-KO5-NO2-KO6-NO3-KO2.

Star and delta connections look like this:

The 380V to 220V electric motor is connected via a capacitor. For such a connection you must use paper (or starting) capacitors, wherein IMPORTANT to rated capacitor voltage was greater than or equal to the mains voltage(it is recommended that the capacitor voltage be 2 times the mains voltage). The following brands (types) of capacitors can be used:

MBGO, MBGCh, MBGP, MBGT, MBGV, KBG, BGT, OMBG, K42-4, K42-19, etc.

The capacitance of the capacitor can be determined using the formulas given below, or using .

The first thing you need to do is to correctly connect the leads of the motor windings. As is already known from the article: the windings of an electric motor can be connected along (denoted - Y) or along (denoted - Δ), while, as a rule, to connect a 220V electric motor, a “triangle” circuit is used, in order to determine the connection diagram of the windings you need to look at label attached to it:

The entry: “Δ/ Y 220/380V” means that to connect this electric motor to 220V, you need to connect its windings according to the diagram, and to connect to 380V, according to the diagram, how to do it.

The second thing you need to decide is how the electric motor will be started, under load (when at the moment of starting the electric motor a load is applied to its shaft and it cannot rotate freely) or without load (when the electric motor shaft rotates freely at the moment of starting, for example, emery , fan, circular saw, etc.).

When starting the engine without load, 1 capacitor is used, which is called a working capacitor, and if it is necessary to start the engine under load, in addition to the working one, a second capacitor is additionally used in the circuit, which is called a starting capacitor, it is turned on only at the moment of starting.

Let's look at the connection diagrams for a 380 by 220 electric motor for both cases:

1. Schemes for connecting an electric motor through a capacitor.

1) Connecting the electric motor through a capacitor in a delta pattern, starting without load:

The capacity of the working capacitor for connecting an electric motor with a star connection of the windings is calculated by the formula:

CR=2800 * In/ UWith; ICF

Where: In- rated current of the electric motor in Amperes (accepted in accordance with the passport data of the electric motor); UWith— network voltage in Volts.

If a 380 to 220 Volt engine starts under load, a starting capacitor must additionally be used in the circuit, otherwise the torque on the electric motor shaft will not be enough to spin it up and the engine will not be able to start.

The starting capacitor is connected in parallel with the working capacitor and should be turned on only when the engine starts; after the engine picks up speed it must be turned off.

Start capacitor capacity should be 2.5 - 3 times more than the worker.

CP= (2,5…3) * CR; ICF

With this scheme, to start the electric motor, you must press and hold the SB button, then apply voltage by turning on the circuit breaker; as soon as the engine starts, the SB button must be released. You can also use a regular switch as a button.

However, the best option for connecting a 380 to 220 electric motor is to use PNVS-10 (push-type starter with starting contact):

The “start” buttons in these starters have 2 contacts, one of them, when the “start” button is released, opens, turning off the starting capacitor, and the second remains closed and through it voltage is supplied to the electric motor through the working capacitor; the shutdown is performed by the “stop” button.

1. Reverse of an electric motor connected to 220 Volts through a capacitor.

So, from the diagrams above it follows that with any method of connecting the windings (star or delta), there are three points left in the motor terminal box for connecting it to the network, conditionally: zero is connected to the first terminal, phase is connected to the second, and phase is supplied to the third through a capacitor, but what to do if the engine starts to rotate in the wrong direction when starting? To change the direction of rotation of a motor connected through a capacitor, you simply need to switch the phase wire from one terminal of the electric motor to another, while leaving the neutral wire at the same terminal, i.e. conditionally: leave zero on the first terminal, apply the phase to the third, and apply the phase to the second through a capacitor.

Because switching the terminals in the terminal box takes a certain time, then if it is necessary to frequently change the direction of rotation of the capacitor motor, it is better to use a connection diagram via a single-pole packet switch in 2 directions:

With this scheme, in the package switch position “0” the engine will be turned off, and in positions “1” and “2” it will start clockwise or counterclockwise.

1. Using a group (block) of capacitors.

When connecting an electric motor through a capacitor, it is very important to select its capacitance as accurately as possible. The closer the value of the actual capacitor capacitance is to the calculated one, the more optimal the shift of the voltage vector relative to the current vector will be, which in turn will give higher torque on the motor shaft and its efficiency.

For example: according to the calculation, the required capacitance of the working capacitor was 54 µF, but it is not possible to find a capacitor of suitable capacitance; in this case, the most appropriate option is to use a group of parallel-connected capacitors (capacitor block).

As you know, when connecting capacitors in parallel, their capacitance is summed up, so to get the 54 µF we need, you can use 2 parallel-connected capacitors - 40 and 14 µF (40 + 14 = 54), or any other number of capacitors whose total capacitance will give the desired value, for example 30, 20 and 4 µF.