A torque quite sufficient to start the indicated electric motors from a single-phase 220 V/50 Hz network can be obtained by shifting the currents in phase in the phase windings of the electric motor, using for this purpose bidirectional electronic switches, which are turned on at a certain time.

The first circuit (Fig. 1) is intended for starting electric motors with a rated rotation speed equal to or less than 1500 rpm, the windings of which are connected in a triangle. This scheme was based on the diagram, which was simplified to the limit. In this circuit, an electronic switch (triac VS1) provides a current shift in the winding “C9raquo; at a certain angle (50. 70°), which provides sufficient torque.

The second circuit (Fig. 2) is intended for starting electric motors with a rated rotation speed of 3000 rpm, as well as for electric motors operating mechanisms with a high resistance moment during starting. In these cases, a significantly larger starting torque is required. Therefore, an “open star” connection scheme for the EM windings was used (Fig. 14, c), which provides maximum starting torque. In the indicated circuit, the phase-shifting capacitors are replaced by two electronic switches. One switch is connected in series with the phase winding “A9raquo; and creates in it “inductive9raquo; (lagging)

Capacitorless starting of three-phase electric motors from a single-phase network Capacitorless starting of three-phase electric motors from a single-phase network
current shift, the second is connected in parallel to the phase winding “B9raquo; and creates a “capacitive” in it (leading) current shift. Here it is taken into account that the EM windings themselves are displaced in space by 120 electrical degrees relative to each other.
Voltage is supplied to the electric motor by a manual push-button starter. type PNVS-10, through the middle pole of which a phase-shifting chain is connected. The middle pole contacts are closed only when the “Start” button is pressed.
By pressing the “Start” button, by rotating the trimmer resistance R2, the required starting torque is selected. This is what you do when setting up the circuit shown in Fig. 2.
When setting up the circuit in Fig. 1, due to the passage of large starting currents, the electric motor hums and vibrates strongly for some time (before turning around). In this case, it is better to change the value of R2 in steps when the voltage is removed, and then, by briefly applying voltage, check how the EM starts. If the voltage shift angle is far from optimal, then the ED hums and vibrates very strongly. As it approaches the optimal angle, the engine “tries9raquo; rotate in one direction or the other, and when optimal it starts quite well.
The author debugged the circuit shown in Fig. 1 on an electric motor of 0.75 kW 1500 rpm and 2.2 kW 1500 rpm, and the circuit shown in Fig. 2 on an electric motor 2.2 kW 3000 rpm .

220 V. By changing the value of R, you need to set the voltage on the lamp to 170 V (for the circuit in Fig. 1) and 100 V (for the circuit in Fig. 2). These voltages were measured by a pointer device of the magnetoelectric system, although the voltage shape across the load is not sinusoidal.

tmp5A24-4

V.V. Burloko, Moriupol
Literature
1. // Signal. - 1999. - No. 4.

As is known, for starting a three-phase electric motor(ED) with a squirrel-cage rotor from a single-phase network, a capacitor is most often used as a phase-shifting element. In this case, the capacity of the starting capacitor should be several times greater than the capacity of the working capacitor. For electric motors most often used in households (0.5 - 3 kW), the cost of starting capacitors is comparable to the cost of an electric motor. Therefore, it is desirable to avoid the use of expensive starting capacitors that only work for a short time. At the same time, the use of workers that are constantly on phase shifting capacitors can be considered appropriate, since they allow you to load the engine at 75. 85% of its power when switched on 3-phase (without capacitors its power is reduced by about 50%).

Based on this, to launch 3-phase electric motors from a single-phase network, the author developed and debugged two simple circuits. Both schemes were tested on an electric motor with a power of 0.5. 2.2 kW and showed very good results (start-up time is not much longer than in three-phase mode). The circuits use triacs controlled by pulses of different polarities and a symmetrical dynistor, which generates control signals during each half-cycle of the supply voltage.

The first circuit (Fig. 1) is intended for starting electric motors with a rated rotation speed equal to or less than 1500 rpm, the windings of which are connected in a triangle. This scheme was based on the diagram, which was simplified to the limit. In this circuit, an electronic switch (triac VS1) ensures a current shift in winding “C” by a certain angle (50. 70°), which provides sufficient torque.

The phase shifting device is an RC circuit. By changing resistance R2, a voltage is obtained on capacitor C that is shifted relative to the supply voltage by a certain angle. A symmetrical dinistor VS2 is used as a key element in the circuit. At the moment when the voltage on the capacitor reaches the switching voltage of the dinistor, it will connect the charged capacitor to the control terminal of the triac VS1 and turn on this bidirectional power switch.

The second circuit (Fig. 2) is intended for starting electric motors with a rated rotation speed of 3000 rpm, as well as for electric motors operating mechanisms with a high resistance moment during starting. In these cases, a significantly larger starting torque is required. Therefore, an “open star” connection scheme for the EM windings was used (Fig. 14, c), which provides maximum starting torque. In the indicated circuit, the phase-shifting capacitors are replaced by two electronic switches. One switch is connected in series with the winding of phase “A” and creates an “inductive” (lagging) in it.

current shift, the second is connected in parallel to the winding of phase “B” and creates a “capacitive” (advanced) current shift in it. Here it is taken into account that the EM windings themselves are displaced in space by 120 electrical degrees relative to each other.

The adjustment consists of selecting the optimal shift angle of the currents in the phase windings, at which the electric motor is reliably started. This can be done without the use of special devices. It is performed as follows.

Voltage is supplied to the electric motor by a push-type “manual” starter PNVS-10, through the middle pole of which a phase-shifting chain is connected. The middle pole contacts are closed only when the “Start” button is pressed.

By pressing the “Start” button, by rotating the trimmer resistance R2, the required starting torque is selected. This is what you do when setting up the circuit shown in Fig. 2.

When setting up the circuit in Fig. 1, due to the passage of large starting currents, the electric motor hums and vibrates strongly for some time (before turning around). In this case, it is better to change the value of R2 in steps when the voltage is removed, and then, by briefly applying voltage, check how the EM starts. If the voltage shift angle is far from optimal, then the ED hums and vibrates very strongly. As it approaches the optimal angle, the engine “tries” to rotate in one direction or another, and at the optimal angle it starts quite well.

At the same time, it has been experimentally established that it is possible to select the values of R and C of the phase-shifting chain corresponding to the optimal angle in advance. To do this, you need to connect a 60 W incandescent lamp in series with a key (triac) and plug them into the network

220 V. By changing the value of R, you need to set the voltage on the lamp to 1 70 V (for the circuit in Fig. 1) and 1 00 V (for the circuit in Fig. 2). These voltages were measured by a pointer device of the magnetoelectric system, although the voltage shape across the load is not sinusoidal.

It should be noted that optimal current shift angles can be achieved with various combinations of values of R and C of the phase-shifting chain, i.e. By changing the capacitance value of the capacitor, you will have to select the corresponding resistance value.

Experiments were carried out with triacs TS-2-10 and TS-2-25 without radiators. They worked very well in this scheme. You can also use other triacs with bipolar control for the corresponding operating currents and voltage class not lower than 7. When using imported triacs in a plastic case, they should be installed on radiators.

The symmetrical DB3 dinistor can be replaced with the domestic KR1125. It has a slightly lower switching voltage. Perhaps this is better, but this dinistor is very difficult to find on sale.

Capacitors C are any non-polar, designed for an operating voltage of at least 50 V (preferably 100 V). You can also use two polar capacitors connected in back-to-back series (in the circuit in Fig. 2, their nominal value should be 3.3 μF each).

The appearance of the electric drive of the grass chopper with the described start-up circuit and 2.2 kW 3000 rpm motor is shown in photo 1.

V.V. Burloko, Moriupol

1. // Signal. - 1999. - No. 4.

2. S.P. Fursov Use of three-phase

electric motors in everyday life. - Chisinau: Cartea

How to connect a 380V to 220V electric motor

Before starting work, understand the design of the IM (induction motor).

The device consists of two elements - a rotor (moving part) and a stator (fixed unit).

The stator has special grooves (recesses) into which the winding is placed, distributed in such a way that the angular distance is 120 degrees.

The windings of the device create one or more pairs of poles, the number of which determines the frequency with which the rotor can rotate, as well as other parameters of the electric motor - efficiency, power and other parameters.

When an asynchronous motor is connected to a three-phase network, current flows through the windings at different time intervals.

A magnetic field is created that interacts with the rotor winding and causes it to rotate.

In other words, a force appears that turns the rotor at different time intervals.

If you connect the IM to a network with one phase (without performing preparatory work), the current will appear in only one winding.

The torque generated will not be enough to move the rotor and keep it spinning.

That is why, in most cases, the use of starting and operating capacitors is required to ensure the operation of a three-phase motor. But there are other options.

How to connect an electric motor from 380 to 220V without a capacitor?

As noted above, to start an electric motor with a squirrel-cage rotor from a single-phase network, a capacitor is most often used.

It is this that ensures the device starts at the first moment after the single-phase current is supplied. In this case, the capacity of the starting device should be three times higher than the same parameter for the working capacity.

For motors with a power of up to 3 kilowatts and used at home, the price of starting capacitors is high and sometimes comparable to the cost of the motor itself.

Consequently, many are increasingly avoiding containers used only at the moment of start-up.

The situation is different with working capacitors, the use of which allows you to load the motor at 80-85 percent of its power. If they are absent, the power indicator may drop to 50 percent.

However, capacitorless starting of a 3-phase motor from a single-phase network is possible thanks to the use of bidirectional switches that operate for short periods of time.

The required torque is provided by the displacement of phase currents in the windings of the IM.

Today, two schemes are popular, suitable for motors with power up to 2.2 kW.

It is interesting that the start-up time of the IM from a single-phase network is not much lower than in the usual mode.

The main elements of the circuit are triacs and symmetrical dinistors. The first are controlled by multi-polar pulses, and the second by signals coming from the half-cycle of the supply voltage.

Suitable for 380 Volt electric motors up to 1,500 rpm with delta windings.

The RC circuit acts as a phase-shifting device. By changing the resistance R2, it is possible to achieve a voltage across the capacitor that is shifted by a certain angle (relative to the household network voltage).

The main task is performed by the symmetrical dinistor VS2, which at a certain point in time connects a charged capacitance to the triac and activates this switch.

Suitable for electric motors with a rotation speed of up to 3000 rpm and for motors with increased resistance at start-up.

Such motors require more starting current, so an open star circuit is more relevant.

A special feature is the use of two electronic switches that replace phase-shifting capacitors. During the adjustment process, it is important to ensure the required shift angle in the phase windings.

This is done as follows:

Voltage is supplied to the electric motor through a manual starter (it must be connected in advance).
After pressing the button, you need to select the starting moment using resistor R

When implementing the considered schemes, it is worth considering a number of features:

For the experiment, radiatorless triacs (types TS-2-25 and TS-2-10) were used, which showed excellent results. If you use triacs on a plastic case (imported), you cannot do without radiators.
A symmetrical DB3 type dinistor can be replaced with a KP. Despite the fact that the KP1125 is made in Russia, it is reliable and has a lower switching voltage. The main drawback is the scarcity of this dinistor.

How to connect via capacitors

First, decide which circuit is assembled on the ED. To do this, open the bar cover where the blood pressure terminals are output, and see how many wires come out of the device (most often there are six).

The designations are as follows: C1-C3 are the beginnings of the winding, and C4-C6 are its ends. If the beginnings or ends of the windings are combined with each other, this is a “star”.

The most difficult situation is if six wires simply come out of the housing. In this case, you need to look for the corresponding designations on them (C1-C6).

To implement a scheme for connecting a three-phase electric motor to a single-phase network, two types of capacitors are required - starting and working.

The first ones are used to start the electric motor at the first moment. As soon as the rotor spins to the required number of revolutions, the starting capacitance is excluded from the circuit.

If this does not happen, there may be serious consequences, including engine damage.

The main function is performed by working capacitors. Here it is worth considering the following points:

Working capacitors are connected in parallel;
The rated voltage must be at least 300 Volts;
The capacity of the working capacitors is selected taking into account 7 µF per 100 W;
It is desirable that the type of working and starting capacitor be identical. Popular options are MBGP, MPGO, KBP and others.

If you take these rules into account, you can extend the life of the capacitors and the electric motor as a whole.

Capacity calculations must be made taking into account the rated power of the electric motor. If the motor is underloaded, overheating is inevitable, and then the capacity of the working capacitor will have to be reduced.

If you choose a capacitor with a capacitance less than acceptable, the efficiency of the electric motor will be low.

Remember that even after the circuit is turned off, the voltage remains on the capacitors, so it is worth discharging the device before starting work.

Also note that connecting an electric motor with a power of 3 kW or more to conventional wiring is prohibited, as this can lead to the machines turning off or the plugs burning out. In addition, there is a high risk of insulation melting.

To connect ED 380 to 220V using capacitors, proceed as follows:

Connect the containers to each other (as mentioned above, the connection should be parallel).
Connect the parts with two wires to the electric motor and a single-phase alternating voltage source.
Turn on the engine. This is done in order to check the direction of rotation of the device. If the rotor moves in the desired direction, no additional manipulations are needed. Otherwise, the wires connected to the winding should be swapped.

With a capacitor, an additional simplified one is for a star circuit.

With a capacitor, an additional simplified one is for a triangle circuit.

How to connect with reverse

There are situations in life when you need to change the direction of rotation of the motor. This is also possible for three-phase electric motors used in a household network with one phase and zero.

To solve the problem, it is necessary to connect one terminal of the capacitor to a separate winding without the possibility of breaking, and the second - with the possibility of transferring from the “zero” to the “phase” winding.

To implement the circuit, you can use a switch with two positions.

The wires from “zero” and “phase” are soldered to the outer terminals, and the wire from the capacitor is soldered to the central terminal.

How to connect in a star-delta connection (with three wires)

For the most part, domestically produced EDs already have a star circuit assembled. All that is required is to reassemble the triangle.

The main advantage of the star/delta connection is the fact that the engine produces maximum power.

Despite this, such a scheme is rarely used in production due to the complexity of implementation.

To connect the motor and make the circuit operational, three starters are required.

The current is connected to the first (K1), and the stator winding is connected to the other. The remaining ends are connected to starters K3 and K2.

When the K3 starter is connected to the phase, the remaining ends are shortened and the circuit is converted into a “star”.

Please note that simultaneous activation of K2 and K3 is prohibited due to the risk of a short circuit or knocking out of the AV supplying the ED.

To avoid problems, a special interlock is provided, which means turning off one starter when turning on the other.

The operating principle of the circuit is simple:

When the first starter is connected to the network, the time relay starts and supplies voltage to the third starter.
The engine starts working in a star configuration and starts working with more power.
After some time, the relay opens contacts K3 and connects K2. In this case, the electric motor operates in a “triangle” pattern with reduced power. When it is necessary to turn off the power, K1 turns on.

As can be seen from the article, it is possible to connect a three-phase electric motor to a single-phase network without loss of power.

At the same time, for home use, the simplest and most affordable option is using a starting capacitor.

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How to start a three-phase motor from 220 volts

As a rule, to connect a three-phase electric motor, three wires and a supply voltage of 380 volts are used. There are only two wires in a 220 volt network, so in order for the engine to work, voltage must also be applied to the third wire. For this purpose, a capacitor is used, which is called a working capacitor.

The capacitor capacity depends on the engine power and is calculated by the formula:
C=66*P, where C is the capacitance of the capacitor, μF, P is the power of the electric motor, kW.

That is, for every 100 W of engine power it is necessary to select about 7 µF of capacitance. Thus, a 500-watt motor requires a capacitor with a capacity of 35 µF.

The required capacity can be assembled from several capacitors of smaller capacity by connecting them in parallel. Then the total capacity is calculated using the formula:
Ctotal = C1+C2+C3+…..+Cn

It is important to remember that the operating voltage of the capacitor should be 1.5 times the power supply to the electric motor. Therefore, with a supply voltage of 220 volts, the capacitor should be 400 volts. Capacitors can be used of the following types: KBG, MBGCh, BGT.

To connect the motor, two connection schemes are used - “triangle” and “star”.

If in a three-phase network the motor was connected according to a delta circuit, then we connect it to a single-phase network according to the same circuit with the addition of a capacitor.

The star connection of the motor is carried out according to the following diagram.

To operate electric motors with a power of up to 1.5 kW, the capacity of the working capacitor is sufficient. If you connect a higher power engine, then such an engine will accelerate very slowly. Therefore it is necessary to use a starting capacitor. It is connected in parallel with the run capacitor and is used only during engine acceleration. Then the capacitor is turned off. The capacitor capacity to start the engine must be 2-3 times greater than the operating capacity.

After starting the engine, determine the direction of rotation. Typically you want the motor to rotate clockwise. If the rotation occurs in the desired direction, you do not need to do anything. To change direction, it is necessary to remount the engine. Disconnect any two wires, swap them and reconnect. The direction of rotation will change to the opposite.

When performing electrical installation work, follow safety regulations and use personal protective equipment against electric shock.

How to connect a three-phase motor to a 220 volt network

Connecting a 3-phase 220 motor with a capacitor
Video

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 use triacs. 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, changes were made to the previous circuit, and the capacitors required for the phase shift were replaced by two electronic switches. 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 a three-phase 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 rotational 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. The normal operation of a three-phase electric motor largely depends on the correct choice of 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 more than 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 it is necessary to ensure rotation in different directions, 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 circuit causes a drop in power or a weak increase in speed, 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 most effective way is to connect a three-phase motor to a single-phase network by connecting a third contact connected to a phase-shifting capacitor.

The highest output power that can be obtained in domestic conditions is up to 70% of the rated one. 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, an additional connection of a starting capacitor will be required. 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.

Attention, TODAY only!

In various amateur electromechanical machines and devices, in most cases three-phase asynchronous motors with a squirrel cage rotor are used. Alas, a three-phase network in everyday life is a very rare phenomenon, therefore, to power them from an ordinary electrical network, amateurs use a phase-shifting capacitor, which does not allow the full power and starting properties of the motor to be realized.

Asynchronous three-phase electric motors, namely them, due to their widespread use, often have to be used, consist of a stationary stator and a moving rotor. Winding conductors are laid in the stator slots with an angular distance of 120 electrical degrees, the beginnings and ends of which (C1, C2, C3, C4, C5 and C6) are brought out into the junction box.

Delta connection (for 220 volts)

Star connection (for 380 volts)

Three-phase motor junction box with jumper positions for star connection

When a three-phase motor is turned on to a three-phase network, a current begins to flow through its windings at different times in turn, creating a rotating magnetic field that interacts with the rotor, forcing it to spin. When the motor is connected to a single-phase network, no torque capable of moving the rotor is created.

If you can connect the engine on the side to a three-phase network, then determining the power is not difficult. We place an ammeter at the break in one of the phases. Let's launch. We multiply the ammeter readings by the phase voltage.

In a good network it is 380. We get the power P=I*U. We subtract 10-12% for efficiency. You get the actually correct result.

There are mechanical instruments for measuring revolutions. Although it is also possible to determine by ear.

Among the various methods of connecting three-phase electric motors to a single-phase network, the most common is connecting the third contact through a phase-shifting capacitor.

Connecting a three-phase motor to a single-phase network

The rotational speed of a three-phase motor operating from a single-phase network remains almost the same as when it is connected to a three-phase network. Alas, this cannot be stated about power, the losses of which reach significant values. Clear values of power loss depend on the switching circuit, operating conditions of the motor, and the capacitance value of the phase-shifting capacitor. Approximately, a three-phase motor in a single-phase network loses within 30-50% of its own power.

Not many three-phase electric motors are ready to perform well in single-phase networks, but most of them cope with this task completely satisfactorily - except for power loss. Mainly, for operation in single-phase networks, asynchronous motors with a squirrel-cage rotor (A, AO2, AOL, APN, etc.) are used.

Asynchronous three-phase motors are designed for 2 rated network voltages - 220/127, 380/220, and so on. Electric motors with an operating voltage of windings of 380/220V (380V for star, 220 for delta) are more common. The highest voltage is for the "star", the lowest - for the "triangle". In the passport and on the motor plate, in addition to other characteristics, the operating voltage of the windings, their connection diagram and the likelihood of its change are indicated.

Three-phase motor labels

The designation on plate A states that the motor windings can be connected both as a “triangle” (at 220V) and a “star” (at 380V). When connecting a three-phase motor to a single-phase network, it is better to use a delta circuit, since in this case the motor will lose less power than when switched on as a star.

Plate B informs you that the motor windings are connected in a star configuration, and the junction box does not take into account the possibility of switching them to delta (there are no more than 3 terminals). In this case, all that remains is to either come to terms with a large loss of power by connecting the motor in a star configuration, or, having penetrated the electric motor winding, try to bring out the missing ends in order to connect the windings in a delta configuration.

If the operating voltage of the motor is 220/127V, then the motor can only be connected to a single-phase 220V network using a star circuit. When you turn on 220V in a delta circuit, the engine will burn out.

Beginnings and ends of windings (various options)

Probably the main difficulty in connecting a three-phase motor to a single-phase network is to understand the electrical wires going into the junction box or, in the absence of one, simply leading out of the motor.

The most common option is when the windings in an existing 380/220V motor are already connected in a delta circuit. In this case, you simply need to connect the current-carrying electrical wires and the working and starting capacitors to the motor terminals according to the connection diagram.

If the windings in the motor are connected by a “star”, and there is a possibility of changing it to a “triangle”, then such a case also cannot be classified as labor-intensive. You just need to change the winding connection circuit to a “triangle” one, using jumpers for this.

Determination of the beginnings and ends of the windings. The situation is more difficult if 6 wires are brought out into the junction box without indicating their belonging to a specific winding and marking the beginnings and ends. In this case, it comes down to solving two problems (Although before doing this, you should try to search the Internet for some documentation for the electric motor. It may describe what electrical wires of different colors refer to.):

identifying pairs of wires related to one winding;

finding the beginning and end of the windings.

The first problem is solved by “ringing” all the wires with a tester (measuring resistance). When there is no device, it is possible to solve it using a light bulb from a flashlight and batteries, connecting the existing electrical wires into the circuit alternately with the light bulb. If the latter lights up, it means that the two ends being tested belong to the same winding. This method identifies 3 pairs of wires (A, B and C in the figure below) related to 3 windings.

Determination of pairs of wires belonging to one winding

The second task is to determine the beginnings and ends of the windings; here it will be somewhat more complicated and you will need a battery and a pointer voltmeter. Digital is not suitable for this task due to inertia. The procedure for determining the ends and beginnings of the windings is shown in diagrams 1 and 2.

Finding the beginning and end of the windings

A battery is connected to the ends of one winding (for example, A), and a pointer voltmeter is connected to the ends of the other (for example, B). Now, when you break the contact of wires A with the battery, the voltmeter needle will swing in some direction. Then you need to connect a voltmeter to winding C and do the same operation with breaking the battery contacts. If necessary, changing the polarity of winding C (switching ends C1 and C2) it is necessary to ensure that the voltmeter needle swings in the same direction as in the case of winding B. Winding A is checked in the same way - with a battery connected to the winding C or B.

Ultimately, all manipulations should result in the following: when the battery contacts break with any of the windings, an electric potential of the same polarity should appear on the other two (the device arrow swings in one direction). Now all that remains is to mark the conclusions of the 1st bundle as the beginning (A1, B1, C1), and the conclusions of the other as the ends (A2, B2, C2) and connect them according to the desired pattern - “triangle” or “star” (when the motor voltage is 220 /127V).

Extracting missing ends. Probably the most difficult option is when the engine has a fusion of windings in a star configuration, and there is no ability to switch it to a delta (no more than 3 electrical wires are brought into the distribution box - the beginning of the windings C1, C2, C3).

In this case, to turn on the motor according to the “triangle” circuit, you need to bring the missing ends of the windings C4, C5, C6 into the box.

Schemes for connecting a three-phase motor to a single-phase network

Triangle connection. In the case of a home network, based on the belief of obtaining greater output power, single-phase connection of three-phase motors in a delta circuit is considered more suitable. With all this, their power can reach 70% of the nominal. 2 contacts in the junction box are connected directly to the electrical wires of a single-phase network (220V), and the 3rd - through the working capacitor Cp to any of the first 2 contacts or the electrical wires of the network.

Ensuring launch. It is possible to start a three-phase motor without a load using a working capacitor (more details below), but if the electric motor has some kind of load, it either will not start or will pick up speed extremely slowly. Then, for a quick start, you need an auxiliary starting capacitor Sp (calculation of the capacitor capacity is described below). The starting capacitors are turned on only for the duration of the engine startup (2-3 seconds, until the speed reaches approximately 70% of the nominal), then the starting capacitor must be disconnected and discharged.

It is convenient to start a three-phase motor using a special switch, one pair of contacts of which closes when the button is pressed. When it is released, some contacts open, while others remain on - until the "stop" button is pressed.

Switch for starting electric motors

Reverse. The direction of rotation of the motor depends on which contact ("phase") the third phase winding is connected to.

The direction of rotation can be controlled by connecting the latter, through a capacitor, to a two-position switch connected by its two contacts to the first and 2nd windings. Depending on the position of the switch, the engine will rotate in one direction or the other.

The figure below shows a circuit with a starting and running capacitor and a reverse button, which allows for comfortable control of a three-phase motor.

Connection diagram for a three-phase motor to a single-phase network, with reverse and a button for connecting a starting capacitor

Star connection. A similar diagram for connecting a three-phase motor to a network with a voltage of 220V is used for electric motors whose windings are designed for a voltage of 220/127V.

Capacitors. The required capacity of working capacitors for operating a three-phase motor in a single-phase network depends on the connection circuit of the motor windings and other characteristics. For a star connection, the capacitance is calculated using the formula:

Cp = 2800 I/U

For a triangle connection:

Cp = 4800 I/U

Where Cp is the capacitance of the working capacitor in microfarads, I is the current in A, U is the network voltage in V. The current is calculated by the formula:

I = P/(1.73 U n cosph)

Where P is the electric motor power kW; n - engine efficiency; cosф - power factor, 1.73 - coefficient that determines the correspondence between linear and phase currents. The efficiency and power factor are indicated in the passport and on the motor plate. Traditionally, their value is located in the spectrum of 0.8-0.9.

In practice, the capacitance value of the working capacitor when connected in a triangle can be calculated using the simplified formula C = 70 Pn, where Pn is the rated power of the electric motor in kW. According to this formula, for every 100 W of electric motor power, you need about 7 μF of working capacitor capacity.

The correct selection of capacitor capacity is checked by the results of engine operation. If its value is greater than required under these operating conditions, the engine will overheat. If the capacity is less than required, the power output of the motor will become very low. It makes sense to look for a capacitor for a three-phase motor, starting with a small capacitance and gradually increasing its value to a rational one. If possible, it is much better to choose a capacitance by measuring the current in the electrical wires connected to the network and to the working capacitor, for example, with a current clamp. The current value should be closer. Measurements should be made in the mode in which the engine will operate.

When determining the starting capacity, we first proceed from the requirements for creating the required starting torque. Do not confuse the starting capacitance with the capacitance of the starting capacitor. In the above diagrams, the starting capacitance is equal to the sum of the capacitances of the working (Cp) and starting (Sp) capacitors.

If, due to operating conditions, the electric motor starts without load, then the starting capacitance is traditionally assumed to be the same as the working capacitance, in other words, a starting capacitor is not needed. In this case, the connection diagram is simplified and cheaper. To simplify this and generally reduce the cost of the circuit, it is possible to organize the possibility of disconnecting the load, for example, by making it possible to quickly and comfortably change the position of the motor to drop the belt drive, or by making the belt drive a pressing roller, for example, like the belt clutch of walk-behind tractors.

Starting under load requires the presence of an additional tank (Sp) that is connected temporarily to start the engine. An increase in the switchable capacitance leads to an increase in the starting torque, and at a certain specific value, the torque reaches its maximum value. A further increase in capacitance leads to the opposite effect: the starting torque begins to decrease.

Based on the condition of starting the engine under a load closest to the rated load, the starting capacitance must be 2-3 times greater than the working capacitance, that is, if the capacity of the working capacitor is 80 µF, then the capacitance of the starting capacitor must be 80-160 µF, which will provide the starting capacitance (sum of the capacitance of the working and starting capacitors) 160-240 µF. Although, if the engine has a small load when starting, the capacitance of the starting capacitor may be less or may not exist at all.

Starting capacitors operate for a short time (only a few seconds during the entire connection period). This makes it possible to use cheaper starting electrolytic capacitors, specially designed for this purpose, when starting the engine.

Note that for a motor connected to a single-phase network through a capacitor, operating in the absence of a load, the winding fed through the capacitor carries a current 20-30% higher than the rated one. Therefore, if the engine is used in an underloaded mode, the capacity of the working capacitor should be minimized. But then, if the engine was started without a starting capacitor, the latter may be required.

It is much better to use not 1 large capacitor, but several much smaller ones, partly due to the ability to select a good capacitance, connecting additional ones or disconnecting unnecessary ones, the latter are used as starting ones. The required number of microfarads is obtained by connecting several capacitors in parallel, based on the fact that the total capacitance in a parallel connection is calculated using the formula:

Determination of the beginning and end of the phase windings of an asynchronous electric motor

When operating or manufacturing this or that equipment, it often becomes necessary to connect an asynchronous three-phase motor to a regular 220 V network. This is quite realistic and not even particularly difficult, the main thing is to find a way out of the following possible situations if there is no suitable single-phase motor, and a three-phase one is lying without business, and also if there is three-phase equipment, but in the workshop there is only a single-phase network.

To begin with, it makes sense to recall the diagram for connecting a three-phase motor to a three-phase network.

Connection diagram for a 220 V three-phase electric motor according to the “Star” and “Triangle” circuits

For ease of understanding, the magnetic starter and other switching units are not shown. As can be seen from the diagram, each motor winding is powered by its own phase. In a single-phase network, as its name suggests, there is only one “phase”. But it is also enough to power a three-phase electric motor. Let's take a look at an asynchronous motor connected to 220 V.

How to connect a three-phase electric motor 380 V to 220 V through a capacitor according to the “Star” and “Triangle” circuit: diagram.

Here, one winding of a three-phase electric motor is directly connected to the network, the other two are connected in series, and voltage is supplied to their connection point through the phase-shifting capacitor C1. C2 is the starting button and is turned on by button B1 with self-return only at the moment of starting: as soon as the engine starts, it must be released.

Several questions immediately arise:

How effective is this scheme?
How to ensure engine reverse?
What capacities should capacitors have?

In order to make the motor rotate in the other direction, it is enough to “reverse” the phase arriving at the connection point of windings B and C (Triangle connection) or to winding B (Star circuit). The circuit, which allows you to change the direction of rotation of the rotor by simply clicking the SB2 switch, will look like this.

Reversing a 380 V three-phase motor operating on a single-phase network

It should be noted here that almost any three-phase motor is reversible, but you need to select the direction of rotation of the motor before starting it. It is impossible to reverse the electric motor while it is running! First you need to de-energize the electric motor, wait for it to stop completely, select the desired direction of rotation with the SB1 toggle switch, and only then apply voltage to the circuit and briefly press button B1.

Capacitances of phase-shifting and starting capacitors

To calculate the capacity of a phase-shifting capacitor, you need to use a simple formula:

C1 = 2800/(I/U) - for inclusion according to the “Star” circuit;
C1 = 4800/(I/U) - for switching on according to the “Triangle” scheme.

Here:

C1 is the capacity of the phase-shifting capacitor, μF;
I is the rated current of one motor winding, A;
U is the voltage of a single-phase network, V.

But what to do if the rated current of the windings is unknown? It can be easily calculated by knowing the motor power, which is usually printed on the device nameplate. To calculate we use the formula:

I = P/1.73*U*n*cosф, where:

I—current consumption, A;
U—mains voltage, V;
n - efficiency;
cosф - power factor.

The symbol * denotes the multiplication sign.

The capacity of the starting capacitor C2 is selected 1.5–2 times greater than the capacity of the phase-shifting one.

When calculating a phase-shifting capacitor, you need to keep in mind that an engine operating at less than full load may overheat at the design capacitor capacity. In this case, its denomination must be reduced.

Efficiency

Unfortunately, a three-phase motor, when powered by one phase, will not be able to develop its rated power. Why? In normal mode, each of the motor windings develops a power of 33.3%. When the motor is turned on, for example, in a “triangle” mode, only one winding C operates in normal mode, and at the point of connection of windings B and C, with a correctly selected capacitor, the voltage will be 2 times lower than the supply voltage, which means the power of these windings will drop 4 times - i.e. only 8.325% each. Let's do a simple calculation and calculate the total power:

33,3 + 8,325 + 8,325 = 49.95%.

So, even theoretically, a three-phase motor connected to a single-phase network develops only half of its rated power, and in practice this figure is even less.

A way to increase the power developed by the motor

It turns out that it is possible to increase engine power, and significantly. To do this, you don’t even have to complicate the design, but just connect a three-phase motor according to the diagram below.

Asynchronous motor - 220 V connection using an improved circuit

Here windings A and B are already operating in nominal mode, and only winding C delivers a quarter of the power:

33,3 + 33,3 + 8,325 = 74.92%.

Not bad at all, isn't it? The only condition for this connection is that windings A and B must be turned on in antiphase (marked with dots). Reversing such a circuit is done in the usual way - by switching the polarity of the capacitor-winding C circuit.

One final note. In place of the phase-shifting and starting capacitor, only non-polar paper devices can operate, for example, MBGCH, which can withstand a voltage one and a half to two times higher than the supply voltage.

If you have a three-phase electric motor, you know it doesn't come cheap. Therefore, if you need to use a single-phase motor, the thought of buying new equipment will only come to you when you do not know how to make an electric motor at home. We will tell you how to convert an electric motor from 380 to 220 Volts with your own hands.

Low-power 380 Volt electric motors are suitable for conversion: up to 3 kW. Theoretically, powerful motors are also reconnected. But this will additionally entail the installation of a separate circuit breaker in the electrical panel and special wiring. And this work becomes meaningless if it suddenly turns out that the input cable cannot carry such a load.

Even if your network carries high loads, and you managed to convert a 3 kW motor from 380 to 220 Volts, you will be upset the first time you put it into operation. The launch will be difficult. You will decide that the work was in vain. Therefore, if you redo it, then it will be low-power models.

Remodeling stages

To convert an electric motor from 380 volts to 220, first open the motor cover to see how many ends there are on the stator windings. There can be 6 or 3 of them. If there are 6, then it is possible to change the connection diagram: if there was a “star”, you can switch to a “triangle”, and vice versa.

If there are only 3 ends, it means that inside the box the windings are already connected either by a “star” or a “triangle” (there are 6 ends in total, which are connected in pairs by terminals, there will be 3 of them, since there are 2 ends for each terminal). In this case, you will have to leave the previous scheme.

Attention! If you decide to change the connection diagram of the stator windings with three ends outside, you will have to open the motor housing with your own hands. It's labor intensive, but possible.

Winding connection

Star;
Triangle.

The windings are usually connected with a star if the motor will be powered from a 380 V network. Thanks to this, the start becomes smooth, although a third of the power is lost. The triangle is recommended when powered from 220 Volts. Inrush currents are not so high compared to those that arise from three-phase power. But the power is equal to that provided by a “star” connection if the motor is connected to 380 V.

See the diagrams below. The difference is that in the first case, all the beginnings are connected so that a three-pointed star is obtained. And in the second, the end of one winding is connected to the beginning of the next so that a figure with three vertices (a triangle) is formed.

Calculation of capacitors

When the ends of the windings are connected in a star or triangle, there are 3 places where they are joined. Terminals are placed at these places. When powered by 380 Volts, a phase is supplied to each of them. But our task, having the same 3 contacts, is to supply only 1 phase 220 Volts and zero. This can be done with your own hands, compensating for the lack of three-phase power supply with capacitors. The launcher will be active only for the duration of the launch, and the worker will be active permanently.

In order for an electric motor to start and operate well, you need to choose the right capacitor capacity. For a working drive it depends on the connection scheme. If it is a star, then the formula works:

If it is a triangle, then the formula changes its form:

Wed is the required capacity of the working storage element. U – network voltage (220 Volts). I is the current strength, which is found by the formula:

P – power, U – voltage already known to us, ƞ – efficiency, cosine “phi” – power factor. All these values can be found in the technical data sheet of your three-phase motor.

Calculating the capacitance of the starting capacitor (Cn) is simple: multiply Cp by 1.5 or 2. If Cp = 50 µF, then Cp will be from 75 to 100 µF. Alternately place one container, then another, starting the motor each time. Listen to the sound of the move: if there is no hum, then everything is in order.

Attention! Capacitors must be paper. For rebuilding an engine with your own hands, MBGP or MBGO work well. If you don’t find a drive of the required capacity, then connect several in parallel.

Assembly according to the diagram

The diagram above shows how to correctly connect the stator windings with capacitors and wires of a 220 V network with your own hands. You need to connect storage elements parallel to each other to one of the vertices of the triangle or star (provide a key to manually turn off the starting drive after overclocking). Then they are brought either to phase or to zero: it doesn’t matter. Only the direction of rotation of the shaft will depend on this.

How to change the direction of rotation

If you need to change the direction only once, then this can be done at the rework stage. To do this, it is enough to swap any two stator windings. The same goal is achieved by transferring a branch of capacitors from zero to phase, or vice versa. But if you need to frequently reverse a three-phase converted motor, a switch is needed. By assembling the electric motor according to the diagram below, you will free yourself from changing the windings every time you need to set the direction of rotation of the shaft in the opposite direction.

There is nothing difficult about converting a three-phase electric motor to a single-phase network with your own hands. The greatest difficulty will be only the calculation of the capacitance of the working capacitor and the experimental selection of the capacitance from the calculated range for the starting accumulator. But this becomes easy if you haven’t lost your technical passport and have a calculator at hand.

There are often cases when it is necessary to connect an electric motor to a 220 volt network - this happens when you try to adapt the equipment to your needs, but the circuit does not meet the technical characteristics specified in the passport of such equipment. In this article we will try to analyze the main methods for solving the problem and present several alternative circuits with a description for connecting a single-phase electric motor with 220 volt condensate.

Why is this happening? For example, in a garage you need to connect a 220-volt asynchronous electric motor, which is designed for three phases. At the same time, it is necessary to preserve the efficiency (efficiency factor), this is done if an alternative (in the form of an engine) simply does not exist, because in a three-phase circuit a rotating magnetic field is easily formed, which ensures the creation of conditions for the rotation of the rotor in the stator. Without this, the efficiency will be lower compared to a three-phase connection diagram.

When there is only one winding in single-phase motors, we see a picture where the field inside the stator does not rotate, but pulsates, that is, the starting push does not occur until the shaft is untwisted with one’s own hand. In order for rotation to occur independently, we add an auxiliary starting winding. This is the second phase, it is moved 90 degrees and pushes the rotor when turned on. In this case, the motor is still connected to a single-phase network, so the name single-phase is retained. Such single-phase synchronous motors have working and starting windings. The difference is that the starter is active only when the rotor is turned on, working for only three seconds. The second winding is on all the time. In order to determine which is which, you can use a tester. In the figure you can see their relationship with the circuit as a whole.

Connecting a 220-volt electric motor: the motor starts by supplying 220 volts to the working and starting windings, and after reaching the required speed, you must manually turn off the starting winding. In order to shift the phase, ohmic resistance is necessary, which is provided by inductive capacitors. There is resistance both in the form of a separate resistor and in part of the starting winding itself, which is performed using the bifilar technique. It works like this: the inductance of the coil is maintained, but the resistance becomes greater due to the elongated copper wire. Such a diagram can be seen in Figure 1: connecting a 220 volt electric motor.

Figure 1. Connection diagram for a 220 volt electric motor with a capacitor

There are also motors in which both windings are continuously connected to the network; they are called two-phase, because the field inside rotates, and a capacitor is provided to shift the phases. To operate such a circuit, both windings have a wire with a cross-section equal to each other.

Connection diagram for a 220 volt commutator motor

Where can you find it in everyday life?

Electric drills, some washing machines, hammer drills and grinders have a synchronous commutator motor. It is capable of operating in single-phase networks even without triggers. The scheme is as follows: a jumper connects ends 1 and 2, the first originates in the armature, the second in the stator. The two tips that remain must be connected to a 220 volt power supply.

Connecting a 220 volt electric motor with a starting winding

Attention!

This scheme excludes the electronics unit, and therefore, the motor will immediately operate at full power from the moment of start - at maximum speed, when starting, literally breaking off with force from the starting electric current, which causes sparks in the collector;
There are electric motors with two speeds. They can be identified by the three ends in the stator coming out of the winding. In this case, the speed of the shaft during connection decreases, and the risk of insulation deformation at start increases;
The direction of rotation can be changed by swapping the ends of the connection in the stator or armature.

Connection diagram for a 380 to 220 volt electric motor with a capacitor

There is another option for connecting an electric motor with a power of 380 Volts, which starts moving without load. This also requires a capacitor in working order.

One end is connected to zero, and the other to the output of the triangle with serial number three. To change the direction of rotation of the electric motor, it is worth connecting it to a phase, and not to zero.

Connection diagram for a 220 volt electric motor through capacitors

In the case when the engine power is more than 1.5 Kilowatts or when it starts working immediately with a load, it is necessary to install a starting capacitor in parallel with the working capacitor. It serves to increase the starting torque and turns on for only a few seconds during the start. For convenience, it is connected with a button, and the entire device is powered via a toggle switch or a button with two positions, which has two fixed positions. In order to start such an electric motor, you need to connect everything through a button (toggle switch) and hold the start button until it starts. When it starts, simply release the button and the spring opens the contacts, turning off the starter

The specificity is that asynchronous motors are initially designed to be connected to a three-phase network of 380 V or 220 V.

Important! In order to connect a single-phase electric motor to a single-phase network, you need to read the motor data on the tag and know the following:

P = 1.73 * 220 V * 2.0 * 0.67 = 510 (W) calculation for 220 V

P = 1.73 * 380 * 1.16 * 0.67 = 510.9 (W) calculation for 380 V

According to the formula, it becomes clear that electrical power exceeds mechanical power. This is the necessary reserve to compensate for power losses during start-up - the creation of a rotating moment of the magnetic field.

There are two types of winding - star and delta. Based on the information on the motor tag, you can determine which system is used in it.

This is a star winding circuit

Red arrows are the voltage distribution in the motor windings, indicating that a single phase voltage of 220 V is distributed on one winding, and a linear voltage of 380 V is distributed on the other two windings. Such a motor can be adapted for a single-phase network according to the recommendations on the tag: find out for which windings are created, they can be connected in a star or triangle.