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Connecting a three-phase electric motor to a 220 V network, starting with a capacitor. Your electrician

However, quite often a situation arises when the power supply of the site is carried out by only one phase, that is, only two wires are connected. phase and zero. 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, however, it should be remembered that such an intervention and attempts to change the parameters will lead to a drop in power and a decrease in the overall efficiency of the electric motor.

Connection of 3 phase 220 volt motor without capacitors

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

In these circuits, triacs are used, under the control of pulses with different polarity. There are also symmetric dinistors that feed control signals into the stream of all half-cycles in the supply voltage.

By changing the resistance, a voltage is generated on the capacitor, shifted by a certain angle relative to the main voltage.

When the voltage level necessary for switching in the capacitor is reached, the dinistor and triac are triggered, causing the activation of a power bidirectional switch.

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 current shift in it.

Connecting the second key is parallel to the phase winding, which contributes to the formation of a leading capacitive current shift in it.

This connection scheme takes into account the motor windings offset in space between themselves by 1200C. When setting, the optimal angle of current shift in the phase windings is determined, which ensures reliable start-up of the device. When performing this action, it is quite possible to do without any special devices.

Connection of an electric motor 380v to 220v through 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 flows through its windings at different points in time.

That is, in a certain period of time, the current passes through the poles of each phase, creating the rotation magnetic field in the same way.

It affects the winding of the rotor, causing rotation by pushing in different planes at certain points in time.

When you turn on such an engine in a single-phase network, only one winding will participate in the creation of the rotating moment, and the impact on the rotor in this case occurs only in one plane.

Such an effort is completely insufficient for the shear and rotation of 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 the capacitor for a three-phase motor in a single-phase network:

With an electric motor power of not more than 1.5 kW, one working capacitor will be sufficient in the circuit.
If the engine power is more than 1.5 kW or it experiences heavy loads during start-up, in this case two capacitors are installed at once. a working one and a starting one. Their connection is carried out in parallel, and the starting capacitor is needed only for starting, after which it automatically shuts off.
The operation of the circuit is controlled by the START button and the power switch. To start the engine, the start button is pressed and held until it is fully turned on.

If necessary, to provide rotation in different directions, an additional toggle switch is installed, which 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 zero, and the third to the phase wire.

If such a circuit contributes to a drop in power or a weak set of revolutions, in this case, the installation of an additional starting capacitor may be required.

Connection of a 3-phase 220 V motor 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 maximum output power that can be obtained in domestic conditions is up to 70% of the nominal. Such results are obtained when using the "triangle" scheme. Two contacts in the junction box are directly connected to the wires of a single-phase network. The third contact is connected through a working capacitor to any of the first two contacts or wires of the network.

In this case, an additional connection of the starting capacitor will be required. It turns on literally for 2-3 seconds, so that the engine speed can reach 70% of the nominal.

After that, the capacitor immediately turns off and discharges.

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.

Wiring diagram of a three-phase electric motor for 220 connection and circuit power

2017-04-07 Electrotechnology Natalya S 4467

Asynchronous electric motors widely used in production are connected by a "triangle" or "star". The first type is mainly used for continuous start-up and operation motors.

Joint connection is used to start high-power electric motors. The “star” connection is used at the start of the start, then moving to the “triangle”.

A connection scheme for a three-phase 220 volt electric motor is also applied.

When connected to 220v, high inrush currents act on the motor, reducing its service life. In industry, a triangle connection is rarely used. Powerful electric motors are connected with a "star".

There are several options for switching from the connection scheme of the electric motor 380 to 220, each of which has advantages and disadvantages.

Reconnecting from 380 volts to 220

It is very important to understand how a three-phase electric motor is connected to a 220v network. To connect a three-phase motor to 220v, we note that it has six terminals, which corresponds to three windings. Using a tester, the wires are dialed to find coils. We connect their ends in two. the connection is a "triangle" (and three ends).

For starters, we connect the two ends of the network wire (220 V) to any two ends of our “triangle”. The remaining end (the remaining pair of twisted coil wires) is connected to the end of the capacitor, and the remaining capacitor wire is also connected to one end of the network wire and coils.

From whether we choose one or the other, it will depend in which direction the engine starts to rotate. Having done all these steps, we start the engine, applying 220 V to it.

If, when turned on, the motor hums, but does not spin, it is necessary to additionally install a capacitor (via a button). It will at the moment of start give the engine a boost, making it spin.

Video: How to connect an electric motor from 380 to 220

Ringing i.e. resistance measurement, carried out by a tester. If this is absent, you can use the battery and a conventional lamp for a flashlight: in a circuit, in series with the lamp, connect the detected wires. If the ends of one winding are found, the lamp lights up.

It is much harder to find to determine the beginning and ends of the windings. You can’t do without a voltmeter with an arrow.

Breaking the contact of the wire with the battery, observe whether the arrow deviates and in which direction. The same actions are carried out with the remaining windings, changing, if necessary, the polarity. Achieve that the arrow deviates in the same direction as in the first measurement.

Star triangle pattern

In domestic engines, often the “star” is already assembled, and the triangle must be implemented, i.e. connect three phases, and assemble the star from the remaining six ends of the winding. Below is a drawing to make it easier to understand.

Nevertheless, such a connection is “loved” by amateurs, but is not often used in production, since the connection scheme is complex.

For it to work, three starters are needed:

The stator winding is connected to the first of them, K1, on the one hand, and current, on the other. The remaining ends of the stator are connected to the starters K2 and K3, and then, to obtain a "triangle", the winding from K2 is also connected to the phases.

By connecting to the K3 phase, the remaining ends are slightly shortened to obtain a "star" scheme.

How the circuit works

When K1 is turned on with a time relay, K3 is turned on. The three-phase motor switched on according to the "star" scheme works with more power than usual. After some time, the contacts of the K3 relay open, but K2 starts. Now the motor circuit is a “triangle”, and its power becomes less.

When a power outage is required, K1 starts. The pattern is repeated in subsequent cycles.

Other motor connections

often than the option described, a capacitor circuit is used that will significantly reduce power. One of the contacts of the working capacitor is connected to zero, the second to the third output of the electric motor. As a result, we have a low power unit (1.5 W). With a large engine power, a starting capacitor will be required in the circuit. With a single-phase connection, it simply compensates for the third output.
It is not difficult to connect an induction motor with a star or a triangle when switching from 380v to 220. There are three windings for such motors. To change the voltage, it is necessary to exchange the outputs going to the tops of the connections.
When connecting electric motors, it is important to carefully study passports, certificates and instructions, because in imported models there is often a “triangle” adapted to our 220V. Such motors, when ignored and turned on by a star, simply burn out. If the power is more than 3 kW, the motor cannot be connected to the household network. This is fraught with a short circuit and even the failure of an RCD machine.

The inclusion of a three-phase motor in a single-phase network

The rotor connected to the three-phase circuit of the three-phase motor rotates due to the magnetic field created by the current flowing at different times through different windings.

But, when connecting such an engine to a single-phase circuit, there is no torque that could rotate the rotor.

The easiest way to connect three-phase motors to a single-phase circuit is to connect its third contact through a phase-shifting capacitor.

Included in a single-phase network, such a motor has the same speed as when operating from a three-phase network. But this cannot be said about power: its losses are significant and they depend on the capacity of the phase-shifting capacitor, the operating conditions of the motor, and the selected connection scheme. Losses approximately reach 30-50%.

Chains can be two-, three-, six-phase, but the most used are three-phase. A three-phase circuit is understood to mean a set of electrical circuits with the same frequency of a sinusoidal EMF, which differ in phase, but are created by a common energy source.

Although most motors can handle single-phase operation, not all can work well. Better than others in this sense, asynchronous motors, which are designed for a voltage of 380/220 V (the first for a star, the second for a triangle).

This operating voltage is always indicated in the passport and on the plate attached to the engine. It also shows the connection diagram and options for changing it.

If “A” is present, this indicates that both the “triangle” scheme and the “star” can be used. "B" reports that the windings are connected by a "star" and cannot be connected in any other way.

The result should be: when the contacts of the winding with the battery break, the electric potential of the same polarity (i.e. the arrow deviates in the same direction) should appear on the two remaining windings. The conclusions of the beginning (A1, B1, C1) and the end (A2, B2, C2) are marked and connected according to the scheme.

Using a magnetic starter

The application of the connection circuit of the electric motor 380 through the starter is good because the start can be done remotely. The advantage of the starter over the switch (or other device) is that the starter can be placed in the cabinet, and the controls are put into the working area, the voltage and currents are minimal, therefore, the wires will fit a smaller cross section.

In addition, the connection using the starter ensures safety in case the voltage “disappears”, since the power contacts open, when the voltage reappears, the starter will not feed the equipment without pressing the start button.

Wiring diagram for an electric induction motor starter 380v:

On contacts 1,2,3 and start button 1 (open) voltage is present at the initial moment. Then it is fed through the closed contacts of this button (when you click on "Start") to the contacts of the starter K2 of the coil, closing it. A magnetic field is created by the coil, the core is attracted, the contacts of the starter are closed, driving the motor.

At the same time, the NO contact closes, from which the phase is supplied to the coil through the “Stop” button. It turns out that when the "Start" button is released, the coil circuit remains closed, as do the power contacts.

By pressing “Stop”, the circuit is broken, returning the power contacts. The voltage disappears from the supply wires to the motor and NO.

Video: Connecting an induction motor. Determination of engine type.

Condenser-free start-up of three-phase electric motors from a single-phase network

home electronics

As you know, to start 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 capacitance of the starting capacitor should be several times larger than the capacity of the working capacitor. For ED most often used in households (0.5. 3 kW), the cost of starting capacitors is commensurate with the cost of an electric motor.

Therefore, it is desirable to avoid the use of expensive starting capacitors that operate only for a short time.

At the same time, the use of working, constantly switched on phase-shifting capacitors can be considered expedient, since they allow loading the engine at 75. 85% of its power with 3-phase switching on (without capacitors, its power decreases by about 50%).

A torque that is quite sufficient to start the specified ED from a single-phase 220 V / 50 Hz network can be obtained by shifting the currents in phase in the phase windings of the ED, using bidirectional electronic keys for this, which are turned on at a certain time.

Based on this, the author developed and debugged two simple circuits for starting 3-phase electric motors from a single-phase network. Both circuits were tested on ED 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).

In the circuits, triacs are used, controlled by pulses of different polarity, and a symmetric dinistor, which generates control signals during each half-cycle of the supply voltage.

The first circuit (Fig. 1) is designed to start the electric motor with a nominal speed equal to or less than 1500 rpm, the windings of which are connected in a triangle. The basis of this scheme was taken scheme [1], which is simplified to the limit. In this circuit, an electronic switch (triac VS1) provides a current shift in the “C” winding by a certain angle (50. 70 °), which provides sufficient torque.

The phase shifting device is an RC chain. By changing the resistance R2, a voltage is obtained on the capacitor C, shifted relative to the supply voltage by a certain angle.

As a key element in the circuit, a symmetric VS2 dinistor is used.

At the moment when the voltage across the capacitor reaches the switching voltage of the dinistor, it will connect the charged capacitor to the control terminal of the triac VS1 i will turn on this bi-directional power switch.

The second circuit (Fig. 2) is intended for starting EDs with a nominal speed of 3000 rpm, as well as for electric motors operating on mechanisms with a large moment of resistance during start-up. In these cases, a significantly larger starting torque is required.

Therefore, the connection scheme of the windings of the ED “open star” ([2], Fig. 14, c), which provides the maximum starting torque, was applied.

In this scheme, phase-shifting capacitors are replaced by two electronic keys. One key is connected in series with the phase “A” winding and creates an “inductive” (lagging) one in it

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

The adjustment consists in selecting the optimal angle of current shift in the phase windings, at which a reliable start-up of the electric motor occurs. This can be done without the use of special devices. It is performed as follows.

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

By pressing the "Start" button, by rotating the tuning resistance R2 engine, the necessary starting moment is selected. This is what happens when setting up the circuit shown in Fig. 2.

When adjusting the circuit of Fig. 1, due to the passage of large inrush currents for some time (before the turn), the ED strongly buzzes and vibrates.

In this case, it is better to change the value of R2 in steps with the voltage removed, and then, by applying a short-time voltage supply, check how the ED starts up. If at the same time the angle of the voltage shift is far from optimal, then the ED buzzes and vibrates very much.

As you approach the optimal angle, the engine "tries" to rotate in one direction or another, and at the optimum it starts quite well.

The author debugged the circuit shown in Fig. 1 on an electric motor of 0.75 kW 1,500 rpm and 2.2 kW 1,500 rpm, and the circuit shown in Fig. 2 on an electric motor of 2.2 kW 3,000 rpm.

At the same time, it was experimentally established that it is possible to select the values of R and C of the phase-shifting chain corresponding to the optimal angle.

To do this, you need to connect a 60 W incandescent lamp in series with the key (triac) and turn them on

220 V. By changing the value of R, it is necessary to set the voltage on the lamp of 170 V (for the circuit of Fig. 1) and 100 V (for the circuit of Fig. 2).

These voltages were measured with a pointer instrument of the magnetoelectric system, although the shape of the voltage at the load is not sinusoidal.

It should be noted that it is possible to achieve optimal current shear angles with various combinations of the values of R and C of the phase-shifting chain, i.e. changing the value of the capacitance of the capacitor, you will have to choose the corresponding resistance value.

The experiments were conducted with triacs TS-2-10 and TS-2-25 without radiators. In this scheme, they worked very well. You can 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 by domestic KR1125. It has a slightly lower switching voltage. This may be 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 (better. 100 V). You can also use two polar capacitors connected in series-counter (in the circuit of Fig. 2, their nominal value should be 3.3 μF each).

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

V.V. Burloko, Moriupol

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

2. S.P. Fursov Using Three Phase

electric motors in everyday life. Chisinau: Cartya

Independent connection of a three-phase motor to a single-phase network is difficult, but feasible

Homegrown "kulibins" use what is handy for electromechanical crafts. When choosing an electric motor, three-phase asynchronous ones usually come across. This type is widespread due to its successful design, good balance and economy.

This is especially true in powerful industrial units. Outside a private house or apartment, there are no problems with three-phase power. And how to organize the connection of a three-phase motor to a single-phase network, if your meter has two wires?

Consider the standard connection

Three-phase motor, has three windings at an angle of 120 °. Three pairs of contacts are output to the terminal block. A connection can be organized in two ways:

Star and delta connection

Connection according to the "star" scheme. Each winding at one end is connected to two other windings, forming the so-called neutral. The remaining ends are connected to three phases. Thus, 380 volts are supplied to each pair of windings:

In the distribution block, jumpers are connected accordingly, it is impossible to mix up the contacts. There is no concept of polarity in alternating current, so it does not matter which phase, which wire to feed.

Connection according to the "triangle". With this method, the end of each winding is connected to the next, the result is a vicious circle, more precisely a triangle. Each winding has a voltage of 380 volts.

Accordingly, jumpers on the terminal block are installed differently. Similarly with the first option, polarity is absent as a class.

For each group of contacts, current flows at a different moment in time, following the concept of “phase shift”. Therefore, the magnetic field sequentially carries the rotor along, creating continuous torque. This is how the engine works with its “native” three-phase power supply.

And if you got the engine in excellent condition, and you need to connect it to a single-phase network? Do not be upset, the connection diagram of a three-phase motor has long been worked out by engineers. We will share with you the secrets of several popular options.

Connecting a three-phase motor to a 220 volt network (single phase)

At first glance, the operation of a three-phase motor when connected to one phase is no different from the correct inclusion. The rotor rotates, practically without losing speed, no jerks and decelerations are observed.

However, it is impossible to achieve the nominal power with such power. This is a necessary loss, there is no way to fix it, we have to reckon with this. Depending on the control circuit, power reduction ranges from 20% to 50%.

In this case, energy is consumed in the same way as if you are using all the power. To choose the most profitable option, we suggest you familiarize yourself with various methods:

Capacitor switching method

Since we need to ensure the same “phase shift”, we use the natural capacities of capacitors. We have two lead wires, we connect them respectively to both points of the standard terminal block.

There remains the third contact, to which the current from one of the already connected ones is turned on. And not directly (otherwise the engine will not start rotation), but through a capacitor circuit. Two capacitors are used (they are called phase-shifting).

The above diagram shows that one capacitor is turned on constantly, and the second through a fixed button. The first element is working, its task is to simulate a regular phase shift for the third winding.

The second tank is designed for the first rotation of the rotor, then it rotates by inertia, each time falling between the false "phases". The starting capacitor cannot be left turned on continuously, as it will add to the confusion in the relatively harmonious rhythm of rotation.

Attention! The above scheme for connecting a three-phase motor to a single-phase network is theoretical. For real work, it is necessary to correctly calculate the capacitance of both elements, and choose the type of capacitors.

The formula for calculating the working "capacitor":

When connected by a "star" C = (2800I) / U;
When connected with a "triangle" C = (4800I) / U;

C is the obtained value of the capacitance in microfarads.

2800 (4800) physical constant, without unit.

I. rated current of each phase when connected correctly.

It must be clarified when purchasing a motor or recognized using clamp meters. To do this, you will have to start the engine from three phases at least once.

U is the mains voltage for a single-phase connection. Typically 220 volts.

If it is not possible to measure or find out the working three-phase current (as a rule, it will), it is possible to calculate the capacitance by a simplified formula. The value will be with a small error, but this will not greatly affect the operation of the engine.

C is the obtained value of the capacitance in microfarads. 66 is a physical constant.

P. engine power when operating from three-phase power. It is indicated on the nameplate.

The capacitance of the starting capacitor is calculated without a formula. It should be 3 times the value of the work item.

Important! Be sure to install the button without locking to disable the starting capacitance. Some "masters" mount a switch, which they then forget to open.

As a result, the rotor speed becomes unstable, and the stator windings become very hot.

Now it remains to find suitable capacitors.

Since we strive to get shareware equipment (the engine, as a rule, was purchased for a couple of bottles of hot water), the capacitors are selected according to a similar principle.

Usually in the workshop there are several paper capacitors in an iron case, such as PGM or KBP. This is just what you need. They have good reliability and you can find specimens with an operating voltage of 300-600 volts.

There is one drawback. such capacitors have a small capacity and large dimensions. Therefore, you will have to type a whole battery, which must be placed somewhere. This is a fee for the “free” design. If you want to do it carefully, or if it’s not possible to install a surround trigger mechanism, use modern radio elements.

If you have assembled a home-made circular saw with a motor with a power of 5-8 kW, then there is a place for a battery of paper capacitors. But a small grinder with a 500-watt motor requires compact placement.

Connecting a three-phase motor to a single-phase power supply can be anything: a star and a triangle. This does not fundamentally affect the quality of work. Usually they leave the same scheme that was used normally. However, sometimes, in order to save on capacitors (when connecting with a "star" they need less), they change the way the windings are switched.

Tip: With this connection method, you can change the direction of rotation of the three-phase motor.

This can be convenient when working with a grinding or drilling machine.

It is necessary to add a switching switch with a central point to the circuit.

By switching the circuit from the third winding and the capacitor group to one or the other contact of a single-phase connection, you can make the rotor rotate in the right direction.

Attention! Switching can only be carried out with the rotor stopped and the power disconnected.

Reverse connection of a three-phase motor through a magnetic starter

For the convenience of working with a powerful motor, and creating a safe connection, use a magnetic starter. Three-phase installations are connected just like that, the control button has compact dimensions and is designed for low currents. And the power cable is switched by powerful contacts of the starter.

Connecting a three-phase motor to a single-phase network makes it possible to use the reverse mode. We covered technology in the previous chapter.

To build the circuit, we need the following components:

Actually an electric motor;
Two identical three-phase starters. Important! Since the power is single-phase, the working coil must be at 220 volts;
Button post (two closing buttons, one opening, to stop);
Input circuit breaker;
Phase-shifting working capacitor with calculated capacity.

Let’s define the terminology. Assign the contacts of the three-phase starters the names "A", "B" and "C".

Putting together a control scheme. We start the phase from the machine through the opening button in parallel to the conditional working contacts “A” of both starters.

We connect the zero wire to the working inputs “C” of both starters, and in parallel we connect again with both coils of magnets. On this, the input part of the control circuit is assembled. Contacts “B” remain idle.

We rotate the starter block 180 °. To protect against short circuit when you accidentally press two reverse buttons at once, set the lock. To do this, we connect the control coils of the starters crosswise. Now, while one coil is closed, the second simply will not turn on. This is achieved due to the presence of normally closed and open contacts of the starter.

Next, connect the button post. Connection scheme: We connect the normally open contacts of the coils of two starters to each other. On normally closed contacts we connect buttons, each to its own starter.

The result is a reverse inclusion of coils. each button closes the contact group of its starter, and the stop button de-energizes both coils, and the entire module is switched off immediately, regardless of the starter number.

We check the correct assembly of the block without load. When the start buttons are pressed, the corresponding starter should be activated. When you press the second button at the same time, nothing happens. This means that the circuit is assembled correctly, and you can connect the motor and phase-shifting capacitor.

At the output contacts, phase “A” of the first starter is connected to phase “A” of the second. This part of the switching should be performed especially carefully. At the input, both power cables are connected in parallel. And at the output it is necessary to provide cross-switching.

We connect the phase "B" of the first starter with the phase "C" of the second starter. Accordingly, the phase "C" No. 1 is connected to the phase "B" No. 2. In parallel to the contacts “B” and “C” of the second magnet, we connect a phase-shifting capacitor.

Now, when you press the buttons, we get the desired direction of rotation.

Bottom line: Depending on the availability of parts, you can use any of the proposed options. It all depends on the amount you wish to spend.

And in conclusion, watch the video. connecting a three-phase motor to a single-phase 220 volt network.

Independent connection of a three-phase motor to a single-phase network is difficult, but feasible Link to main publication

Starting a 3-phase motor from 220 volts

Often there is a need for a farm to connect a three-phase electric motor, and there is only a single-phase network (220 V). Nothing, the matter is fixable. Just have to connect a capacitor to the engine, and it will work.

Figure 1. The principal (a) and mounting (b) schemes for connecting a three-phase electric motor to a single-phase network according to the "triangle" scheme

A three-phase electric motor is also connected according to the "star" scheme (Fig. 2).

Fig. 2. The principal (a) and mounting (b) schemes for connecting a three-phase electric motor to a single-phase network according to the "star" scheme

To make a star connection, you need to connect two phase motor windings directly to a single-phase network (220 V), and a third. through a working capacitor (Cp) to any of the two wires of the network.

To start a three-phase electric motor of small power, usually only a working capacitor is enough, but with a power of more than 1.5 kW, the electric motor either does not start, or very slowly picks up speed, therefore it is necessary to use a starting capacitor (Cn). The capacitance of the starting capacitor is 2.5-3 times greater than the capacity of the working capacitor. As starting capacitors, electrolytic capacitors of the EP type or the same type as the working capacitors are best used.

The connection diagram of a three-phase electric motor with a starting capacitor Sp is shown in Fig. 3.

Fig. 3. Scheme of connecting a three-phase electric motor to a single-phase network according to the "triangle" scheme with a starting capacitor Sp

You need to remember: starting capacitors are turned on only for the duration of starting a three-phase motor connected to a single-phase network for 2-3 s, and then the starting capacitor is turned off and discharged.

First determine the affiliation of the wires to the individual phases of the stator winding.

To do this, take any of the 6 external terminals of the electric motor and connect it to some power source, and connect the second terminal of the source to the control lamp and use the second wire from the lamp to alternately touch the remaining 5 terminals of the stator winding until the lamp lights up. A light bulb means that 2 pins belong to the same phase. Conditionally mark with tags the beginning of the first wire C1, and its end. C4. Similarly, we find the beginning and end of the second winding and designate them C2 and C5, and the beginning and end of the third. C3 and C6.

The next and main stage will be the determination of the beginning and end of the stator windings. To do this, we use the selection method, which is used for electric motors with power up to 5 kW.

We connect all the beginnings of the phase windings of the electric motor according to the previously connected tags to one point (using the "star" circuit) and turn on the motor in a single-phase network using capacitors.

If the motor without strong buzz immediately picks up the nominal speed, this means that all the beginnings or all ends of the winding are in a common point.

If, when you turn on the engine, it is very humming and the rotor cannot gain the rated speed, then in the first winding, swap the terminals C1 and C4.

If this does not help, return the ends of the first winding to its original position and now change the outputs C2 and C5. Do the same for the third pair if the engine continues to hum.

When determining the beginnings and ends of the phase windings of the stator of an electric motor, strictly adhere to safety rules. In particular, touching the clamps of the stator winding, hold the wires only by the insulated part. It is also necessary to do this because the electric motor has a common steel magnetic circuit and high voltage can appear on the terminals of other windings.

To change the direction of rotation of the rotor of a three-phase electric motor included in a single-phase network according to the "triangle" scheme (see Fig. 1), it is sufficient to connect the third phase stator winding (W) through the capacitor to the terminal of the second phase stator winding (V).

Video: Engine Angle Grinder Hums And Turns On Shortly

To change the direction of rotation of a three-phase electric motor included in a single-phase network according to the "star" scheme (see. Fig.

2b), the third phase stator winding (W) needs to be connected through a capacitor to the terminal of the second winding (V).

The direction of rotation of a single-phase motor is changed by changing the connection of the ends of the starting winding P1 and P2 (Fig. 4).

The reason for this may be the poor condition of the bearings: the treadmills are covered with rust, deep scratches and dents, individual balls and the cage are damaged. In all cases, it is necessary to inspect the electric motor in detail and eliminate the existing malfunctions.

In case of minor damage, it is enough to flush the bearings with gasoline, lubricate them, and clean the engine housing from dirt and dust.

To replace damaged bearings, remove them with a screw puller from the shaft and rinse the bearing seat with gasoline. Heat the new bearing in an oil bath to 80 ° C.

Press the metal pipe, the inner diameter of which slightly exceeds the diameter of the shaft, into the inner ring of the bearing and with light blows of the hammer through the pipe, push the bearing onto the motor shaft. After that, fill the bearing 2/3 of the volume with grease.

Assemble in the reverse order. In a properly assembled electric motor, the rotor should rotate without knocking and vibration.

Fig. 4. Changing the direction of rotation of the rotor of a single-phase motor by switching the starting winding

Connecting a 220 volt induction motor without capacitor

In the article you will learn how to connect a 380-volt motor to 220 V. In a household network, the voltage is single-phase 220 V. And most of the asynchronous motors are designed for 380 V and three phases. And in the manufacture of home-made drilling machines, concrete mixers, emery and others, it becomes necessary to use a powerful drive. The motor from the angle grinder, for example, cannot be used. it has many revolutions, and the power is small, it is necessary to use mechanical gearboxes, which complicate the design.

Design features of asynchronous three-phase motors

Asynchronous AC machines are just a godsend for any host. But just connecting them to a household network is problematic. But you can still find a suitable option, using which the power loss will be minimal.

Before you connect the 380 to 220 engine, you need to understand its design. It consists of the following elements:

A squirrel cage rotor.
Stator with three identical windings.
Terminal box

Be sure to have a metal nameplate on the engine. all parameters are written on it, even the year of manufacture. The wires from the stator exit into the terminal box. Using three jumpers, all wires are connected to each other. And now let’s look at what motor connection schemes exist.

Star Connection

Each winding has a beginning and an end. Before you connect the 380 to 220 motor, you need to find out where the ends of the windings are. To connect according to the "star" scheme, it is enough to install jumpers in such a way that all ends are closed. Three phases must be connected to the beginning of the windings. When starting the engine from a three-phase network, it is advisable to use this particular circuit, since high currents are not induced during operation.

But it is unlikely to achieve high power, therefore, hybrid schemes are used in practice. They start the motor with the windings turned on according to the "star" scheme, and when they reach the established mode, they switch to the "triangle".

The connection diagram of the "triangle" windings

The disadvantage of using such a circuit in a three-phase network is that large currents are induced in the windings and wires. This leads to damage to electrical equipment. But when working in a 220 V household network, such problems are not observed. And if you are thinking how to connect a 380 to 220 V induction motor, the answer is obvious. only using the “triangle” circuit. In order to make a connection in this way, you need to connect the beginning of each winding to the end of the previous one. You need to connect power to the vertices of the resulting triangle.

Connecting a motor using a frequency converter

This method is at the same time the most simple, progressive and expensive. Although, if you need functionality from an electric drive, you will not regret any money. The cost of the simplest frequency converter is about 6000 rubles. But with it, it is not difficult to connect the 380 engine to 220 V. But you need to choose the right model. First, you need to pay attention to which network is allowed to connect the device. Secondly, pay attention to how many outputs he has.

For normal operation in a domestic environment, you need a frequency converter connected to a single-phase network. And the output should be three phases. It is recommended to carefully study the operating instructions so as not to make a mistake with the connection, otherwise the powerful transistors that are installed in the device may burn.

Using capacitors

When using a motor with power up to 1500 W, only one capacitor can be installed. a working one. To calculate its power, use the formula:

I. operating current, U. voltage, P. motor power.

To simplify the calculation, you can do otherwise. for every 100 watts of power you need 7 microfarads of capacitance. Therefore, for a 750 W motor, 52-55 uF is needed (you need to experiment a bit to achieve the desired phase shift).

Starting capacitor is necessary when using engines with a power exceeding 1.5 kW. The starting capacitor only works in the first seconds of switching on to give a “push” to the rotor. It is switched on via a button parallel to the worker. In other words, with its help, the phase shifts more strongly. Only in this way can a 380 to 220 motor be connected via capacitors.

The essence of using a working capacitor is to get the third phase. The first two are zero and phase, which is already on the network. Problems with connecting the motor should not arise, most importantly. hide the capacitors away, preferably in a sealed, sturdy case. If an element fails, it can explode and cause harm to others. The voltage of the capacitors must be at least 400 V.

Connection without capacitors

But you can even connect a 380 to 220 motor without capacitors, you don’t even have to buy a frequency converter for this. It is enough to rummage in the garage and find several main components:

Two transistors type KT315G. The cost on the radio market is about 50 kopecks. apiece, sometimes even less.
Two thyristors of the KU202N type.
Semiconductor diodes D231 and KD105B.

You will also need the presence of capacitors, resistors (constant and one variable), a zener diode. The whole structure is enclosed in a housing that can protect against electric shock. Elements used in the design must operate at voltages up to 300 V and currents up to 10 A.

It is possible to carry out both surface mounting and printing. In the second case, foil material and the ability to work with it will be required. Please note that domestic thyristors of the KU202N type are very hot, especially if the drive power is above 0.75 kW. Therefore, install the elements on aluminum radiators, if necessary, use additional airflow.

Now you know how to independently connect the 380 engine to 220 (in the household network). There is nothing complicated in this, there are many options, so you can choose the most suitable for a specific purpose. But it is better to spend money once and purchase a frequency converter, it increases the number of drive functions many times over.

Connecting a three-phase motor to a single-phase circuit is an urgent issue. Such inclusion is useful in ensuring the operation of the equipment at home. For example, a circular saw, a drilling machine or a grain grinder.

Single-phase three-phase motor: frequency converter

The most progressive method of this inclusion is the frequency converter. With its help, the most significant factors are obtained during the operation of an asynchronous electric motor. smooth starting and soft braking. This eliminates multiple excesses of the rated starting voltage, which increases the durability of the engine. In addition, the frequency converter reduces energy consumption by almost half. The principle of its operation is based on double voltage conversion. But the cost of the inverter is determined, high, so it is a little scary.

DIY step-by-step assembly instructions for the frequency converter

In order to save money, you can assemble the frequency converter yourself. Introducing step-by-step instructions for assembling an inverter at home.

Step No. 1. Inverter circuit

Begin the assembly of any electronic device you need from the circuit. On the Internet, there are a lot of such schemes. Therefore, before starting work, it will be useful to delve into and find out the working model chosen or not. In our case, this is a repeatedly tested and used circuit.

She looks like this. The circuit is designed for engines with power up to 4 kW, during operation protection against overload, heating and short circuit works. An unpleasant moment happened, a short circuit in the brno engine, but the protection worked clearly, neither the engine nor the frequency converter burned out.

Step No. 2. Converter housing

As the case, the case was chosen from the computer system unit. You can use something more compact, but at that moment it was just such a block case that seemed acceptable. No need to spend money on the acquisition or manufacture of something new.

Step No. 3. Power Supply

You can make a simple power supply with your own hands according to the proposed scheme.

But in our case, it was purchased in a finished version at 24 V.

Step No. 4. Installation of the power unit

Next, a set of capacitors, relays,

the diode bridge with reverse diodes G4PH50UD is removed, IGBT field effect transistors are used.

Step No. 5. Cooling device

And also mounted cooling coolers to prevent heating of the radiator.

When testing a circuit on a 4kW motor, heating may occur. Checking the converter on electric machines up to 3.0 kW of heating did not reveal.

Therefore, in order to prevent dust from accumulating during cooler operation, the converter is planned to be used in the workshop, a thermal relay has been installed that will turn on cooling only if the radiator overheats to 36º C or more. over, after the temperature drops to the specified values, the cooler will turn off again.

Step number 6. Installing the shunt

Install the shunt for 4kW, as shown in the photo.

Step No. 7. Installation of the main converter board, installation and firmware of the controller

At the bottom of the case, the frequency converter board is mounted directly,

she goes to pic 16F628A microcontroller.

Step number 8. Upgrading the inverter to adjust the engine speed

This design of the frequency converter is sufficient for a smooth start-up of a three-phase electric motor and its operation in a single-phase network.

If the task is to adjust the engine speed, then it needs to be slightly complicated by installing another pic 16F648A microcontroller,

two capacitors for its 30PF strapping,

and a knob for adjusting engine speed.

It should be noted that the cost of parts for a frequency converter results in approximately 2,700 hryvnias or 6,700 rubles, if you purchase a device with the same parameters, but factory-made, the price will be about 7,000 hryvnias or 17,400 rubles.

The main advantage of having a frequency converter is the ability to connect all three-phase electric motors up to 4kW available on the farm.

Single-phase three-phase motor: capacitors

Another most acceptable way to connect a three-phase electric motor to a single-phase network is capacitors. If you do not have the means to purchase expensive equipment or the question rests on a one-time connection of one electric motor, then it is advisable to use capacitors. This is quite simple to do using the step-by-step instructions from our article.

Step-by-step instructions for using capacitors for connecting an induction motor to a single-phase network

Step No. 1. Calculation of the required capacitance of capacitors

You need to start connecting the electric motor with the selection of capacitors. The capacitance of the capacitors when connected by a triangle is the ratio of the product of the magnitude of the current and the scalar coefficient of 4 800 to the rated voltage.

In the case of a star connection, the scalar index is 2 800.

The magnitude of the current is determined as the ratio of the electric motor power to the product of the scalar coefficient 1.73, the nominal voltage U, the power factor cosφ and the efficiency η.

The data for calculating the current strength are indicated on the nameplate of each specific motor.

The capacitance of the starting capacitor is taken to be two to three times the working capacitor.

Step No. 2. Connection diagram

The connection diagram of three-phase motors and a single-phase network looks like this.

Step # 3. Connection of conclusions

First, we determine the number of pins in the brno electric machine. To connect with a triangle, there must be six of them. If there are only three conclusions. It is necessary to remove the motor covers and find the ends of the windings. Then solder the wires to them and bring them to Brno. Using the scheme to connect the windings with a triangle.

Step No. 4. Application of a starting capacitor

If the number of revolutions of the electric motor exceeds 1500 rpm, then a separate special capacitor should be used for starting.

The simplest connection of a starting capacitor to the network is made using a non-latching button. When automating the process, a current relay is used.

Electric motors with power up to 0.5 kW can be turned on using a relay from the refrigerator, after replacing the contact plate and disabling the protection against heating. To avoid sticking it can be made from a graphite brush. For motors from 0.5 to 1.1 kW, the relay is usually rewound with a wire of a larger diameter, and if the engine power is higher than the specified value,

then you can make a current relay yourself.

Step No. 5. Connecting a capacitor bank of the required capacity

For a 1.1 kW engine, a capacitor with a capacity of 80 microfarads is enough. In our case, we use 4 pieces of 20 microfarads. Connect them into one, soldering jumpers. They will fulfill the function of launching and further work.

Step No. 6. Power Connection

We connect the power, see photo. Be sure to carefully prepare the end of the wires. Then, if problems arise, a poor-quality connection, as a cause, can be immediately eliminated.

Step number 7. Connecting a capacitor bank

Connect the capacitors directly. The engine is ready for operation.

Another connection method is the inclusion of a three-phase electric motor in a single-phase network without capacitors, using two-sided switching keys, the activation of which is carried out in a specific time period.

Three-phase motor in a single-phase network without capacitors: wiring diagrams

Schematic diagram of the device

Faced with this scheme on the Internet, a person will be very happy. By the way, this decision was first published in the distant 1967.

This scheme theoretically has the right to life, but in practice, basically, it does not work. Perhaps more careful tuning is needed. It is impossible to say unequivocally or to give guarantees. Most members of the forum consider the assembly of such a device a waste of time, although some argue the opposite.

The following conclusions can be drawn from this dispute:

the circuit can run on an engine up to 2.2 kW and a speed of 1,500 rpm;
large power loss on the motor shaft;
the circuit requires a careful option of the C1R7 driving circuit, which must be adjusted so that the voltage across the capacitor opens and closes the key, in all likelihood the transistors of the switch are in non-working mode, for this it is necessary to replace the resistor R6 or one of R3R4;
more reliable ways to connect a three-phase motor to a single-phase network are capacitors or a frequency converter.

The scheme was modernized in 1999. To start a three-phase motor in a single-phase network without capacitors, two simplest circuits were debugged.

Both were tested on electric motors with capacities from 0.5 to 2.2 kW and showed pretty good results (the start-up time is not much longer than in the three-phase mode).

For financial savings, you can connect a three-phase motor according to modern working schemes.

These circuits use triacs, which are controlled by pulses of different polarity, as well as a symmetrical dinistor, which generates control signals into the stream of each half-cycle of the supply voltage.

Scheme No. 1 for low-speed electric motors

It is designed to start an electric motor with a nominal speed of rotation, which is equal to or less than 1500 revolutions per minute. The windings of these motors are connected in a triangle. The phase shifting device in this circuit is a special chain.

Changing the resistance, we obtain a voltage on the capacitor, which is shifted relative to the main supply voltage by a certain angle.

The key element in this circuit is a symmetrical dinistor. When the voltage on the capacitor reaches the level at which the dinistor makes a switch, a charged capacitor is connected to the control terminal of the triac.

At this moment, a bi-directional power switch is activated.

Scheme No. 2 for high-speed electric machines

It is needed to start electric motors with a nominal speed of 3000 rpm, as well as for engines that operate on mechanisms with a considerable moment of resistance at startup.

In these cases, a larger starting torque is required. That is why the connection circuit of the motor windings, which creates the maximum starting torque, has been replaced. In this circuit, phase-shifting capacitors are replaced by a pair of electronic keys.

The first switch is connected to the system in series with the phase winding and forms an inductive current shift in it. The second one is connected parallel to the phase winding, and forms a leading capacitive current shift in it.

With this scheme, the windings of electric motors are taken into account, which are offset in space by 120 electrical degrees relative to each other.

The adjustment consists in determining the optimal angle of the current shift in the phase windings, at which the engine is reliably started.

This action can be performed without the use of special devices.

The implementation of this process is as follows. The voltage is supplied to the engine by the PNVS-10 manual push-type starter, through the central pole of which a phase-shifting chain is connected.

The contacts of the middle pole are in the circuit only when the start button is pressed.

Pressing this button, by rotating the tuning resistance motor, select the desired starting torque. They also do when setting up other schemes.

An example of operating an 380 V asynchronous motor in a 220 V household network without capacitors

Video connecting a three-phase motor to a single-phase network without capacitors: without power loss

Matched for you:

Home craftsmen often use a three-phase motor to turn on home-made machines that operate from 220-volt household wiring inside a garage or workshop. To start them, the capacitor circuit is most often used.

The article contains tips on how to connect such an electric motor to a single-phase network without using a capacitor bank or a frequency converter due to a current pulse from an electronic switch. They are supplemented by diagrams and a video.

The principle of operation of the electronic key

If you assemble the windings of an asynchronous electric motor according to the triangle scheme and connect 220 volts to the voltage of a single-phase network, then the same currents will flow through them, as shown in the graph below.

The angular displacement of any winding relative to others is 120 degrees. Therefore, the magnetic fields from each of them will add up, eliminate the mutual influence.

The resulting stator magnetic field created will not affect the rotor: it will remain at rest.

In order for the electric motor to begin rotation, it is necessary to pass currents shifted by 120 ° through its windings, as is done in a normal three-phase power system or by connecting a frequency converter. Then the engine will generate power with minimal losses, having the greatest efficiency.

Widespread industrial schemes for starting a three-phase motor in a single-phase network allows it to work, but with less efficiency and large losses, which, most often, is quite acceptable.

Optimal circuits are considered for connecting the windings to a star or a triangle for starting and working with a block of capacitors.

Alternative methods are:

The mechanical rotation of the rotor, for example, due to the manual winding of the cord on the shaft and its sharp jerking at a given voltage;
The supply of a phase-shifting current pulse with an electronic key into one or two motor windings.

Since the first method “wound and pulled” does not cause difficulties, we immediately analyze the second.

The upper diagram shows the electronic key “k” connected in parallel to the winding B. This rather conventional designation is accepted to explain the principle of operation of the electric motor due to the formation of a current pulse.

When the moment of maximum amplitude of the voltage at winding A is reached, it is turned on and a phase-shifting current pulse is thrown into the phase B winding.

Due to this pulse, a phase shift of the current occurs inside this winding. It will unbalance the magnetic moments acting on the rotor, creating its rotation.

The angle of phase shift φ necessary to start the engine, it is enough to withstand in the range of 50 ÷ 70O, although the ideal option is 120.

The design of the phase-shifting electronic key can be assembled from different parts. The most suitable devices for domestic purposes, as they become more complex, are presented below.

Motor start-up circuit up to 2 kW

Its description can be found in No. 6 of Radio magazine for 1996. The author of the article, Golik, proposes the construction of a bi-directional (positive and negative half-harmonic) electronic key on two diodes and thyristors with transistor block control.

Power diodes VD1 and VD2 together with thyristors VS1, VS2 form a bridge, which is controlled by forward and reverse bipolar transistors. The position of the tuning resistor R7 affects the opening voltage VT1, VT2.

When the transistor switch is opened, at each half-wave of voltage, current is applied to the control electrodes of the thyristors and one of them is injected with the corresponding powerful current pulse into the connected winding of a three-phase electric motor.

Due to the applied moment of magnetic forces to the rotor, the latter starts rotation. Its energy is constantly replenished at each half-wave with the next impulse.

The author made an electronic key on a fiberglass board and placed it in an insulated case with the ability to connect input and output circuits through contact pins. The variant of execution of the scheme by mounted installation also has the right to implementation.

For the operation of electric motors of low power, it is permissible to place power diodes and thyristors without radiators. But to ensure good heat dissipation from them and reliable operation is better in advance by including these elements in the design of the electronic key.

The ratings of the electronic components are indicated directly on the diagram.

In order to ensure safety, it is necessary to properly insulate the case of the electronic unit, to exclude accidental contact with its parts during operation: they are all under voltage of 220 volts.

The slider of the resistor R7 "Mode" has two extreme positions:

minimum;
and maximum resistance.

In the first case, the electronic switch is open and creates the maximum pulse of the current shift in the winding, and in the second it is closed: the rotation of the rotor is excluded.

Starting a three-phase motor is carried out at the maximum allowable phase shift of the current inside the winding. Then position R7 set its operating speed and power.

Proven Models

The author tested the circuit on engines with:

the speed of 1360 and the power of 370 watts (AAAM63V4SU1);
1380 rpm, 2 kW.

The results of the experiments suit him.

Instead of the recommended power diodes and thyristors, you can use any other semiconductor elements. But, you should pay attention to their working current of at least 10 amperes and a reverse voltage of 300 volts.

Two circuits on triacs

The following 2 electronic key designs were described in Burlaco in 1999. They are published in the journal Signal No. 4.

Light motor start

The device is designed for engines with power up to 2.2 kW, has a minimum set of electronic parts.

Capacitor C, possessing capacitive resistance, under the action of voltage applied to its plates, shifts the current vector forward by 90 degrees, directing it to control the VS2 dinistor.

The potential difference on the capacitor is regulated by the total resistance R1, R2. The dynistor pulse is fed to the control electrode of the triac VS1, which injects current into the motor winding.

Engine starting diagram under load

For machines and mechanisms that create a great deal of opposition to the spinning of the rotor, we can recommend switching the windings to an open-star circuit with the creation of two untwisting moments.

The polarity of the motor windings is indicated by dots in the diagram. Phase shifting chains of current pulses operate according to the same technology as in previous cases. Denominations of electrical parts are affixed next to their graphic designations.

The author Burlako applied voltage to the engine with a three-phase PN1 starter PNVS-10, which was equipped with old activator washing machines.

All three contacts of this starter, when you press the "Start" button, close simultaneously, and when released:

two extreme remain in a closed state;
middle. breaks, disconnecting the starting winding circuit.

Through this middle contact, in both circuits a current pulse is supplied from the phase-shifting circuit. It works only for the time necessary to spin up the engine, after which it is taken out of operation and disconnected from the supply voltage.

The engine starting moment in each circuit is selected after applying voltage by changing the resistance R2. In this case, large currents pass in the triangle until the rotor is spinning, causing strong vibration of the structure. To reduce them, it is recommended to select a phase-shifting pulse in steps, rather than smoothly.

With an optimal R2 position, the engine starts without vibrations.

For low-power engines, it is possible to install triacs without cooling radiators, but the latter nevertheless increase the reliability of the circuit.

My opinion on the method

I recommend paying attention to the following conclusion.

In the three considered circuits, the operating mode current flows through all connected windings. The full expenditure of applied energy is not being spent economically. Only about 30% of its power is generated by the rotation of the rotor. The rest of the order of 70% is irretrievable losses.

If someone is comfortable with starting a three-phase motor in a single-phase network according to this scheme, then this is your choice. I did a review of these schemes to show their positive and negative sides, without imposing my own opinion.

The creators of videos on YouTube began to use this topic in large numbers, gaining the number of views and subscribers, like YUKA LAHT, in their video “Without the capacitor starting a three-phase motor”.

Make a choice consciously, and if you have questions about the topic, now it’s convenient for you to ask them in the comments.

Three-phase motor in a single-phase network without capacitor starting

The principle of operation of the electronic key

The angular displacement of any winding relative to others is 120 degrees. Therefore, the magnetic fields from each of them will add up, eliminate the mutual influence.

The resulting stator magnetic field created will not affect the rotor: it will remain at rest.

In order for the electric motor to start rotation, it is necessary to pass currents shifted by 120 ° through its windings, as is done in a normal three-phase power system or by connecting a frequency converter. Then the engine will generate power with minimal losses, having the greatest efficiency.

Widespread industrial schemes for starting a three-phase motor in a single-phase network allows it to work, but with less efficiency and large losses, which, most often, is quite acceptable.

Optimal circuits are considered for connecting the windings to a star or a triangle for starting and working with a block of capacitors.

Alternative methods are:

The mechanical rotation of the rotor, for example, due to the manual winding of the cord on the shaft and its sharp jerking at a given voltage;
The phase shift of the currents due to the short-term use of an electronic switch that commutes the electrical resistance of one winding.

Since the first method “wound and pulled” does not cause difficulties, we immediately analyze the second.

How does the engine start

The stator windings are connected according to the triangle circuit. One of them (A) is supplied with a voltage of 220 volts. In parallel with it, another chain of two consecutive windings (BC) is connected.

According to Ohm’s law, the mains voltage creates currents in them. Their value depends on the resistance. All windings are the same. Therefore, in (A) the current is greater, and (BC) is 2 times smaller in magnitude. over, they coincide in phase. In this situation, they are not able to create a rotating magnetic field sufficient to start the rotor.

Parallel to the winding (B), an electronic circuit is connected, designated as key K. It is in the open state, but it closes briefly when the maximum voltage on the winding C is reached.

The electronic switch shorts the winding B and the voltage drop across the winding C jumps twice, which ultimately ensures a phase shift of the currents in the windings A and C. It is important to note that the current in the windings (A) and (BC) at this moment is zero.

The phase angle φ necessary for starting the engine is sufficient to maintain in the range of 50 ÷ 70 °, although the ideal option is 120.

The design of the phase-shifting electronic key can be assembled from different parts. The most suitable devices for domestic purposes, as they become more complex, are presented below.

Motor start-up circuit up to 2 kW

Technology Description

The operation of the transistor switch provides a short-term phase shift of the currents in the windings and the creation of a rotating magnetic field, spinning the rotor.

Due to the applied moment of magnetic forces to the rotor, the latter starts rotation. Its energy is constantly replenished at each half-wave with the next impulse.

Mounting Features

The ratings of the electronic components are indicated directly on the diagram.

Setup Principles

The slider of the resistor R7 "Mode" has two extreme positions:

minimum;
and maximum resistance.

In the first case, the electronic switch is open and creates the maximum pulse of the current shift in the winding, and in the second it is closed: the rotation of the rotor is excluded.

Starting a three-phase motor is carried out at the maximum allowable phase shift of the current inside the winding. Then position R7 set its operating speed and power.

Proven Models

The author tested the circuit on engines with:

the speed of 1360 and the power of 370 watts (AAAM63V4SU1);
1380 rpm, 2 kW.

The results of the experiments suit him.

Two circuits on triacs

The following 2 electronic key designs were described in Burlaco in 1999. They are published in the journal Signal No. 4.

Light motor start

The device is designed for engines with power up to 2.2 kW, has a minimum set of electronic parts.

Capacitor C, possessing capacitive resistance, under the action of voltage applied to its plates, shifts the current vector forward by 90 degrees, directing it to control the VS2 dinistor.

Engine starting diagram under load

Setup Features

The author Burlako applied voltage to the engine with a three-phase PN1 starter PNVS-10, which was equipped with old activator washing machines.

All three contacts of this starter, when you press the "Start" button, close simultaneously, and when released:

two extreme remain in a closed state;
middle. breaks, disconnecting the starting winding circuit.

Through this middle contact, a current pulse is applied in both circuits. The circuit only works for the time required to spin up the engine, after which it is taken out of operation and disconnected from the supply voltage.

With an optimal R2 position, the engine starts without vibrations.

For low-power engines, it is possible to install triacs without cooling radiators, but the latter nevertheless increase the reliability of the circuit.

My opinion on the method

I recommend paying attention to the following conclusion.

Make a choice consciously, and if you have questions about the topic, now it’s convenient for you to ask them in the comments.

Connecting 3 phase motors to 220

Connection of 3 phase 220 volt motor without capacitors
Connection of 3 phase 220 V motor with capacitor
Connection of a 3-phase 220 V motor without loss of power
Video

Many owners, especially owners of private houses or summer cottages, use equipment with 380 V motors operating from a three-phase network. If an appropriate power scheme is connected to the site, then there are no difficulties with their connection. However, quite often a situation arises when the power supply of the site is carried out by only one phase, that is, only two wires are connected. phase and zero. 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, however, it should be remembered that such an intervention and attempts to change the parameters will lead to a drop in power and a decrease in the overall efficiency of the electric motor.

Connection of 3 phase 220 volt motor without capacitors

In these schemes triacs are used. under the control of pulses with different polarity. There are also symmetric dinistors that feed control signals into the stream of all half-cycles 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 connection of the windings is made in a triangle. As a phase shifter, a special chain is used. By changing the resistance, a voltage is generated on the capacitor, shifted by a certain angle relative to the main voltage. When the voltage level necessary for switching in the capacitor is reached, the dinistor and triac are triggered, causing the activation of a power bidirectional switch.

The second option is used when starting engines with a rotation speed of 3000 rpm. The same category includes devices mounted on mechanisms that require a large moment of resistance during startup. In this case, it is necessary to ensure 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 current shift in it. Connecting the second key is parallel to the phase winding, which contributes to the formation of a leading capacitive current shift in it.

This connection scheme takes into account the motor windings offset in space between themselves by 120 0 C. When setting up, the optimal angle of the current shift in the phase windings is determined, which ensures reliable start-up of the device. When performing this action, it is quite possible to do without any special devices.

Connection of an electric motor 380v to 220v through 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 flows through its windings at different points in time. That is, in a certain period of time, the current passes through the poles of each phase, creating the rotation magnetic field in the same way. It affects the winding of the rotor, causing rotation by pushing in different planes at certain points in time.

When you turn on such an engine in a single-phase network, only one winding will participate in the creation of the rotating moment, and the impact on the rotor in this case occurs only in one plane. Such an effort is completely insufficient for the shear and rotation of 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 the capacitor for a three-phase motor in a single-phase network:

With an electric motor power of not more than 1.5 kW, one working capacitor will be sufficient in the circuit.
If the engine power is more than 1.5 kW or it experiences heavy loads during start-up, in this case two capacitors are installed at once. a working one and a starting one. Their connection is carried out in parallel, and the starting capacitor is needed only for starting, after which it automatically shuts off.
The operation of the circuit is controlled by the START button and the power switch. To start the engine, the start button is pressed and held until it is fully turned on.

If necessary, to provide rotation in different directions, an additional toggle switch is installed, which 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 zero, and the third to the phase wire. If such a circuit contributes to a drop in power or a weak set of revolutions, in this case, the installation of an additional starting capacitor may be required.

Connection of a 3-phase 220 V motor 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.

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

Radio circuits for motorists

Starting a 3-phase motor from 220 volts

Often there is a need for a farm to connect a three-phase electric motor. but there is only a single-phase network (220 V). Nothing, the matter is fixable. Just have to connect a capacitor to the engine, and it will work.

Figure 1. The principal (a) and mounting (b) schemes for connecting a three-phase electric motor to a single-phase network according to the "triangle" scheme

A three-phase electric motor is also connected according to the "star" scheme (Fig. 2).

Fig. 2. The principal (a) and mounting (b) schemes for connecting a three-phase electric motor to a single-phase network according to the "star" scheme

To start a three-phase electric motor of low power, usually only a working capacitor is enough, but with a power of more than 1.5 kW, the electric motor either does not start, or very slowly picks up speed, therefore it is necessary to use a starting capacitor (Cn). The capacitance of the starting capacitor is 2.5-3 times greater than the capacity of the working capacitor. As starting capacitors, electrolytic capacitors of the EP type or the same type as the working capacitors are best used.

The connection diagram of a three-phase electric motor with a starting capacitor Sp is shown in Fig. 3.

Fig. 3. Scheme of connecting a three-phase electric motor to a single-phase network according to the "triangle" scheme with a starting capacitor Sp

Typically, the findings of the stator windings of electric motors are marked with metal or cardboard tags with a designation of the beginnings and ends of the windings. If, for some reason, the tags do not appear, proceed as follows. First determine the affiliation of the wires to the individual phases of the stator winding. To do this, take any of the 6 external terminals of the electric motor and connect it to some power source, and connect the second terminal of the source to the control lamp and use the second wire from the lamp to alternately touch the remaining 5 terminals of the stator winding until the lamp lights up. A light bulb means that 2 pins belong to the same phase. Conditionally mark with tags the beginning of the first wire C1, and its end. C4. Similarly, we find the beginning and end of the second winding and designate them C2 and C5, and the beginning and end of the third. C3 and C6.

The next and main stage will be the determination of the beginning and end of the stator windings. To do this, we use the selection method, which is used for electric motors with power up to 5 kW. We connect all the beginnings of the phase windings of the electric motor according to the previously connected tags to one point (using the "star" circuit) and turn on the motor in a single-phase network using capacitors.

If the motor without strong buzz immediately picks up the nominal speed, this means that all the beginnings or all ends of the winding are in a common point. If, when you turn on the engine, it is very humming and the rotor cannot gain the rated speed, then in the first winding, swap the terminals C1 and C4. If this does not help, return the ends of the first winding to its original position and now change the outputs C2 and C5. Do the same for the third pair if the engine continues to hum.

To change the direction of rotation of a three-phase electric motor included in a single-phase network according to the “star” scheme (see Fig. 2, b), it is necessary to connect the third phase stator winding (W) through the capacitor to the terminal of the second winding (V). The direction of rotation of a single-phase motor is changed by changing the connection of the ends of the starting winding P1 and P2 (Fig. 4).

When checking the technical condition of electric motors, it is often possible to notice with chagrin that after prolonged operation there is extraneous noise and vibration, and it is difficult to rotate the rotor manually. The reason for this may be the poor condition of the bearings: the treadmills are covered with rust, deep scratches and dents, individual balls and the cage are damaged. In all cases, it is necessary to inspect the electric motor in detail and eliminate the existing malfunctions. In case of minor damage, it is enough to flush the bearings with gasoline, lubricate them, and clean the engine housing from dirt and dust.

To replace damaged bearings, remove them with a screw puller from the shaft and rinse the bearing seat with gasoline. Heat the new bearing in an oil bath to 80 ° C. Press a metal pipe, the inner diameter of which slightly exceeds the diameter of the shaft, into the bearing inner ring and with light hammer blows through the pipe, push the bearing onto the motor shaft. After that, fill the bearing 2/3 of the volume with grease. Assemble in the reverse order. In a properly assembled electric motor, the rotor should rotate without knocking and vibration.

Fig. 4. Changing the direction of rotation of the rotor of a single-phase motor by switching the starting winding

How to start a three-phase motor from 220 volts

As a rule, three wires and a supply voltage of 380 volts are used to connect a three-phase electric motor. There are only two wires in the 220 volt network, therefore, in order for the engine to work, the third wire also needs to be supplied with voltage. To do this, use a capacitor, which is called a working capacitor.

The capacitance of the capacitor depends on the engine power and is calculated by the formula: C = 66P, 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, you need to pick up about 7 microfarads of capacitance. Thus, a 500 watt capacitor is needed for a 500-watt motor.

The necessary capacity can be assembled from several capacitors of a smaller capacity, connecting them in parallel. Then the total capacity is calculated according to the formula: Ctot = C1C2C3.Cn

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

To connect the engine, two connection schemes are used. this is a "triangle" and a "star".

If in a three-phase network the motor was connected according to the “triangle” scheme, then we connect to a single-phase network according to the same scheme with the addition of a capacitor.

Connecting the engine with a star is performed as follows.

For the operation of electric motors, power up to 1.5 kW is enough capacity of the working capacitor. If you connect a larger engine, then such an engine will accelerate very slowly. Therefore, it is necessary to use a starting capacitor. It is connected in parallel to the working capacitor and is used only during acceleration of the engine. Then the capacitor is turned off. The capacity of the capacitor to start the engine should be 2-3 times greater than the capacity of the worker.

After starting the engine, determine the direction of rotation. It is usually necessary for the motor to rotate clockwise. If the rotation is in the right direction, nothing needs to be done. To change the direction, it is necessary to re-mount the engine. Disconnect any two wires, swap them and reconnect. The direction of rotation will be reversed.

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

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