Among the different methods of starting three-phase electric motors into a single-phase network, more common is based on the connection of the third winding through the phase shift condenser. The desired power developed by the engine in this case is 50 ... 60% of its power in three-phase inclusion. Not all three-phase electric motors, however, work well when connected to a single-phase network. Among such electric motors can be allocated, for example, with a double section of the short-circuited rotor of the MA series. In this regard, when choosing three-phase electric motors to work in a single-phase network, the engines of the series A, AO, AO2, APN, UAD, and others should be preferred.

For the usual operation of the electric motor with condenser, it is necessary that the capacity of the applied capacitor varies depending on the number of revolutions. In practice, this condition is difficult enough, therefore they use two-stage control of the engine. When the motor starts, two capacitors are connected, and after overclocking, one condenser is turned off and only the working capacitor leaves.

1.2. Calculation of characteristics and parts of the electric motor.

If, for example, its electric motor passport indicates the voltage of its 220/380, the engine is included in the single-phase network according to the diagram shown in Fig. one

Turning on the three-phase electric motor in 220 V network

With p - working capacitor;
With P - starting capacitor;
P1 - Batch Switch

After switching on the P1 packet switch, the contacts of P1.1 and P1.2 are closed, after which it is necessary to immediately press the "acceleration" button. After a set of revolutions, the button is released. The reversing of the electric motor is carried out by switching the phase on its winding switch SA1.

The capacity of the working condenser CP in the case of connecting the motor windings to the "triangle" is determined by the formula:

where


U -Nature in the network, in

And in the case of connecting the winding of the motor in the "star" is determined by the formula:

where
CP - the capacity of the working capacitor in the ICF;
I - electric motor consumed in a;
U -Nature in the network, in

The electric motor consumed in the above formulas, with a known power of the electric motor, can be calculated from the following expression:

where
P - Motor power in W, marked in his passport;
h - kpd;
COS J - power factor;
U -Nature in the network, in

The capacitance of the JV starting capacitor is selected at 2..2.5 times the capacity of the working capacitor. These capacitors must be calculated on the voltage of 1.5 times the network voltage. For the network 220 to better use condensers of the MBGO type, MBPG, IBGC with an operating voltage of 500 V and above. Subject to short-term inclusion, electrolytic capacitors of type K50-3, EGC-M, KE-2 with an operating voltage of more than 450 V can be used for greater reliability. Electrolytic capacitors are connected alternately, connecting their minus conclusions. (Fig. 2)

The diagram of connecting electrolytic capacitors to use them as starting capacitors.

The total container of the connected capacitors will be (C1 + C2) / 2.

In practice, the magnitude of the containers of workers and starting capacitors is chosen depending on the power of the motor in the table. one

Table 1. The value of the capacity of the working and starting capacitors of the three-phase electric motor depending on its power when it is turned on into a network of 220 V.

It is necessary to emphasize that the electric motor with the condenser starting in idling over the winding, powered through the capacitor, flows the current by 20 ... 30% superior nominal. In this regard, if the engine is often used in short-sufficient mode, either inhabitant, then in this case the capacitance of the CP capacitor should be reduced. It may happen that during overloading the electric motor has braked, then the starting capacitor is connected again to start it, removing the load completely either dropping it to a minimum.

The capacitance of the JV starting capacitor can be reduced by starting electric motors at idle or with a small load. For inclusion, for example, an AO2 electric motor with a capacity of 2.2 kW per 1420 rpm, a working capacitor with a capacity of 230 μF can be used, and start-up - 150 μF. In this case, the electric motor confidently starts with a small load on the shaft.

1.3. Portable universal block to start three-phase electric motors with a capacity of about 0.5 kW from the 220 V network.

To start electric motors of different series, with a capacity of about 0.5 kW, from a single-phase network without reversing, you can collect a portable universal starting unit (Fig. 3)

A portable universal block diagram for starting three-phase electric motors with a capacity of about 0.5 kW from the 220 V network without reverse.

When you press the SB1 button, the magnetic dousekl. KM1 (SA1 switch is closed) and the KM 1.1's own contact system, km 1.2 connects the M1 electric motor to the network 220 V. Immediately with this 3rd contact group KM 1.3 closes the SB1 button. After a complete overclocking of the motor, the SA1 switch is disabled with a C1 starting capacitor. The motor stop is performed by pressing the SB2 button.

1.3.1. Details.

The device uses an A471A4 (AO2-21-4) electric motor with a capacity of 0.55 kW per 1420 rpm and a PML magnetic starter, designed for alternating current by voltage of 220 V. Buttons SB1 and SB2 - Paired type PKE612. The T2-1 switch is used as SA1 toggle. In the device, a constant resistor R1 is a wire, type PE-20, and a R2 resistor of the MLT-2 type. CONDENSERS C1 and C2 type MBGH to voltage 400 V. Capacitor C2 is composed of parallel connected capacitors of 20 μF 400 V. Lamp HL1 type km-24 and 100 mA.

The starting device is mounted in an iron case with a size of 170x140x50 mm (Fig. 4)

1 - housing
2 - handle for carrying
3 - Signal Lamp
4 - Switch shutdown starting capacitor
5 - "Run" and "Stop" buttons
6 - Modified Electroville
7 - panel with connector sockets

On the top of the housing panel, the "Run" and "Stop" button are displayed - a warning lamp and a switch to disable starting capacitor. A connector for connecting an electric motor is on the front panel of the device.

To disable starting capacitor, you can use an additional relay K1, then the need for SA1 toggle switch disappears, and the condenser will be turned off with automata (Fig. 5)

Starting Diagram with automatic shutdown of the starting capacitor.

When you press the SB1 button, the K1 relay and the contact pair K1.1 turns on the Magnetic Rams 21, and K1.2 - the starting capacitor of the joint venture. The Magnetic Master of KM1 itself is blocked using its own contact pair of KM 1.1, and contacts km 1.2 and km 1.3 connect the electric motor to the network. The "Run" button is kept until complete overclocking of the motor, and then release. The relay K1 is de-energized and disables the starting capacitor, which is discharged through the R2 resistor. At this time, the magnetic starter of KM 1 remains on and provides power to the electric motor in operation. To stop the electric motor, press the "Stop" button. In an improved starting device according to Fig. 5 scheme, you can use the MKU-48 type relay or similar to it.

2. The introduction of electrolytic capacitors in the motors start circuits.

When you turn on three-phase asynchronous electric motors into a single-phase network, simple paper capacitors usually use. But practice has shown that instead of massive paper capacitors, oxide (electrolytic) capacitors, which have the smallest dimensions and more accessible in terms of purchase can be used. The equivalent replacement scheme of a conventional paper capacitor is given in Fig. 6.

Scheme of the rear of a paper capacitor (A) electrolytic (B, B).

A positive alternating current half-wave passes through a chain VD1, C2, and negative VD2, C2. Based on this, you can use oxide capacitors with a permissible voltage twice as the smallest than for conventional capacitors of the same container. For example, if a paper capacitor for a voltage of 400 V is used in a voltage of 400 V in a single-phase voltage of 220 V, then with its substitution, according to the above scheme, you can use an electrolytic capacitor to voltage 200 V. in the above circuit diagram of both capacitors similar and selected similarly to the selection technique Paper capacitors for starting device.

2.1. The inclusion of a three-phase motor into a single-name network with the introduction of electrolytic capacitors.

A three-phase motor inclusion scheme into a single-phase network with the introduction of electrolytic capacitors is shown in Fig. 7.

The circuit for the inclusion of a three-phase motor into a single-phased network with electrolytic capacitors.

In the Scheme, SA1 - Motor Rotation Torler, SB1 - Motor Overclock Button, C1 and C3 Electrolytic Capacitors are used to start the motor, C2 and C4 during operation.

Selection of electrolytic capacitors in the fig. 7 Better to create with current ticks. Define currents at points A, B, C and reaches equality of currents at these points by the method of stepwise selection of capacitors. Measurements are carried out with a loaded engine in the mode, in which its operation is meant. VD1 and VD2 diodes for network 220 V are selected with a revolving very permissible voltage of more than 300 V. The largest direct current of the diode is depending on the power of the motor. For electric motors with a capacity of up to 1 kW, d245, d245a, D246, D246A d247 d247 d247 d24s are suitable for a larger motor power from 1 kW to 2 kW. It is necessary to take large diodes with a suitable direct current, or put some smaller diodes in parallel, setting them on radiators.

You should draw ATTENTION That when the diode is overloaded, it may be sampled and an alternating current will flow through an electrolytic capacitor, which can lead to heating and an explosion.

3. Inclusion of powerful three-phase engines into a single-phase network.

The condenser circuit on the inclusion of three-phase engines into a single-phase network allows you to get less than 60% of the rated power from the motor, while the power limit of the electrified device is limited to 1,2 kW. This is obvious not enough for the operation of the electrolablan or electric saws, which are required to have a power of 1.5 ... 2 kW. In this case, it can be solved in the introduction of an electric motor of greater power, for example, with a capacity of 3 ... 4 kW. Such type of engine is designed to voltage 380 V, the windings are connected by the "star" and in the terminal box contains only 3 outputs. The inclusion of such a motor into the network 220 V leads to a decrease in the rated power of the motor 3 times and by 40% when working in a single-phase network. Such a decrease in the power makes the engine inappravert not applicable to work, but can be applied to the promotion of the rotor, either with a low load. Practice indicates that most of the electric motors confidently accelerates to nominal revolutions, and in this case, starting currents do not exceed 20 A.

3.1. Refinement of a three-phase motor.

You can easily translate a powerful three-phase motor into the working mode if it is recycled to a single-name operation mode, obtaining with all this 50% of the rated power. Switching the motor into single-phase mode requires its refinement. Open the terminal box and determine which side of the motor housing cover fit the windings conclusions. Turn the cover bolts of the cover and take it out of the motor housing. The connections of 3 windings are found at a common point and fall to a common point an additional conductor with a cross section, suitable cross section of the winding wire. A twitch with a subfall conductor is isolated by a tape or a polyvinyl chloride tube, and the additional output is stretched into the terminal box. After that, the housing cover is installed in place.

The switching circuit of the electric motor in this case will be viewed in Fig. eight.

The switching circuit of the three-phase motor windings for inclusion in a single-phase network.

During the overclocking of the motor, the "star" winding connection is used with the connection of the SP phasoscient condenser. In operating mode, only one winding remains on the network, and the rotation rotation is maintained by a pulsating magnetic field. After switching the windings, the CD condenser is discharged through the RR resistor. The work of the submitted scheme was tested with the AIR-100S2Y3 type engine (4 kW, 2800 rpm) installed on a homemade woodworking machine and showed its effectiveness.

3.1.1. Details.

In the switching circuit in the motor windings, the SA1 switching device should use a batch toggle switch for a working current more than 16 A, for example, a Tubler type PP2-25 / H3 (two-pole with neutral, for current 25 A). The SA2 toggle switch can be any type, but for current more than 16 A. If the motor reverse is not required, then this SA2 toggle switch can be excluded from the scheme.

A disadvantage of the proposed circuit for including a powerful three-phase electric motor into a single-phase network can be considered the sensitivity of the motor to overloads. If the load on the shaft reaches half the power of the motor, then the shaft rotation speed can occur right until its complete stop. In this case, the load from the motor shaft is removed. The toggle switch is translated at first to the "overclocking" position, and later to the "work" position and continue to work.

It happens that a three-phase electric motor falls into the hands. It is from such engines that homemade circular saws, emers and various kinds of choppers are manufactured. In general, a good owner knows what you can do with it. But the trouble, the three-phase network in private homes is very rare, and it is not always possible to spend it. But there are several ways to connect such a motor to the 220V network.

It should be understood that the power of the engine with such a connection, no matter how hard you try, will noticeably fall. Thus, the connection of the "triangle" uses only 70% of the power of the engine, and the "star" and is less - only 50%.

In this regard, the engine is desirable to have more powerful.

Important! Connecting the engine, be extremely careful. Do not rush. By changing the circuit, disconnect the power supply and discharge the capacitor with an electrolympo. Works for at least two.

So, in any connection scheme used condensers. In essence, they fulfill the role of the third phase. Thanks to him, the phase to which is connected one condenser withdrawal, shifts exactly as much as necessary to simulate the third phase. Moreover, one capacity (working) is used to run the engine, and for launch, one more (launcher) in parallel with the working. Although it is not always necessary.

For example, for a lawn mower with a knife in the form of a sharpened web, there will be a 1 kW unit and condensers only workers, without the need of tanks for launch. It is due to this by the fact that the engine at startup runs at idle and it is enough to unwind the shaft.

If you take a circular saw, a hood or other device that gives an initial load on the shaft, then without additional cans of capacitors to start not do. Someone can say: "Why not connect the maximum capacity so that it was not enough?" But not everything is so simple. With such a connection, the motor will be strongly overheated and can fail. Do not risk equipment.

Important! Whatever capacity has condensers, their working voltage should be no less than 400V, otherwise they will not work for a long time and can explode.

Consider first how the three-phase engine is connected to the 380V network.

Three-phase engines are like with three conclusions - to connect only on the "star" and with six connections, with the possibility of choosing a scheme - a star or a triangle. The classic scheme can be seen in the figure. Here in the picture on the left depicted a star connection. In the photo on the right, it is shown as it looks like a real brno motor.

It can be seen that this requires to install special jumpers for the desired output. These jumpers are included with the engine. In the case when there is only 3 outputs, the connection to the star has already been made inside the motor hull. In this case, it is impossible to change the connection scheme of the windings.

Some say that they did so that the workers do not negate the aggregates at home for their needs. Anyway, such versions of the engines can be successfully used for garage purposes, but their power will be significantly lower than the connected triangle.

Connection diagram of the 3-phase motor to the 220V connected network.

As can be seen, the voltage is 220V is distributed into two successively connected windings, where each is designed for such a voltage. Therefore, the power is lost almost twice, but this engine can be used in many low-power devices.

The maximum engine power to 380V in the 220V network can be achieved only using a connection to a triangle. In addition to minimum power losses, the number of engine speed remains unchanged. Here, each winding is used to its operating voltage, hence the power. Connection diagram of such an electric motor is shown in Figure 1.

In Fig. 2, depicted Brno with a terminal for 6 conclusions to connect a triangle. Three of the resulting output, served: phase, zero and one condenser condenser. From where the second condenser withdrawal is connected - phase or zero, the direction of rotation of the electric motor depends.

In the photo: the electric motor is only with working capacitors without tanks for launch.

If the starting load is on the shaft, you must use condensers to start. They are connected to parallel with workers using a button or switch at the time of inclusion. As soon as the engine dials the maximum turnover, the launch capacity must be disconnected from the workers. If this is a button, simply release it, and if the switch is turned off. The engine uses only working capacitors. This connection is depicted in the photo.

How to choose condensers for a three-phase engine using it in a 220V network.

The first thing you need to know - capacitors must be non-polar, that is, not electrolytic. It is best to use the brand containers - MBGO. They were successfully used in the USSR and in our time. They have perfectly withstand tension, current jumps and destroying environmental impact.

They also have eyelets for fastening, helping without any problems to arrange them anywhere in the body of the apparatus. Unfortunately, to get them now problematic, but there are many other modern capacitors no worse than the first. The main thing is that, as mentioned above, their working voltage was not less than 400V.

Calculation of capacitors. Capacity of the working capacitor.

In order not to refer to long formulas and torment your brain, there is an easy way to calculate the engine for 380V engine. For every 100 W (0.1 kW) takes - 7 μF. For example, if the engine is 1 kW, then calculate this: 7 * 10 \u003d 70 μF. Such a container in one bank is extremely difficult, and even expensive. Therefore, most often the tank is connected to the parallel, gaining the desired container.

Starting capacitor capacity.

This value is taken at the rate of 2-3 times more than the capacity of the working capacitor. It should be borne in mind that this container is taken in the amount of working, that is, for the engine of 1 kW, the worker is 70 μF, multiply it by 2 or 3, and we obtain the necessary value. This is 70-140 ICF additional capacity - launcher. At the time of inclusion, it connects to the working and in the amount, it turns out - 140-210 μF.

Features of the selection of capacitors.

Capacitors both workers and launchers can be selected by the method from smaller to more. So picking up the average capacity, you can gradually add and follow the engine mode, so that it does not overheat and have enough power on the shaft. Also, the starting capacitor is selected by adding until it is started smoothly without delay.

In electrical engineering, there are often options when the electric motor is connected, assembled for a start-up of 380 volts to the household network. Capacity drives are used to start electrical motors.

Capacitors may differ from the type of execution and purpose, not every container drive is applied in the starting start of the electric motor in the network 220. For these reasons, it is necessary to understand how to make a start-up capacitor, what type of starting drive must be selected than they differ in the operation of an electric motor with Network 220 volts. Consider what is the capacitive drive.

Appointment of condenser

When the question is that such a starting capacitor is recommended, it is recommended to consider the principle of operation of the container drive, why do you need capacitors to start an electric motor. In its design, the property of conductors is applied - polarization, when located close one from another conductor is charged. Plates are used to remove the charge in the condenser design, they are located opposite each other, a dielectric is installed between them.

Modern manufacturers of capacitive drives offer "Condenser" of different modifications, with different values \u200b\u200bfor different applications. The buyer remains only to choose a drive for the scheme.

In the electrical motors, capacitors are used for electric motors that run from 220 volts. The starting capacitor is needed to promote the electric motor shaft, often under load.

Capacitors in their design have features, it is:

• as a dielectric, there is a different material, in electrolytic products of the STB brand - an oxide film that is applied to one of the built-in electrodes;
• polar containers are small sizes, but are able to accumulate a large container;
• non-polar Condenser (diagram element) has large dimensions, but is included in the circuit without taking into account polarity, is characterized by a high cost.

In the system of starting an electric motor in the network on a 220, the working capacity of the capacity and the starting capacitor is used, the starting drive works only at the time of the motor start, while the rotor does not get the revolutions required for the operation. The launcher in the chain determines the following factors:

1. The power supply of the electric charge brings the electric field at the time of starting to the circular field of the electric motor;
2. Makes it possible to significantly increase the parameters of the magnetic flux;
3. Increases the starting point, improves the operation of the electric motor.

When a three-phase motor starts, a three-phase motor start from a household power grid and further operation, the presence of a container in the start circuit extends the duration of the efficient use of the motor, since often the calculated load is on the shaft. Non-polar capacitors have a greater operating voltage.

Electromotor for 3 phases in 220V power grid

There are different types of electromotors of industrial use in 220 volts in power grid, but launching capacitors are used more often for the start of the electric motor. This method is based on the inclusion of the third stator winding into the power circuit through the Condenser, shifting the phase.

Important! When using an electric motor of 3 phase execution in a single-phase network, its power from the nominal parameters of the 380 volt network drops to 60%. In addition, not each brand of the electric motor operates satisfactorily from 220 volts - these are MA engines. It is recommended for switching the operation of electric motors from a network of 380 to 220 volts to use the electric motor stamps: APN, A, removal and other engines.

To start the engine with a condenser start, it is necessary that the container of the drive can change from the engine speed, which is almost impossible to implement. For this reason, specialists are recommended to control the electric motor in two steps: when the electric motor starts, there are two capacitance drives, reaching the engine speeds, the starting drive is turned off, only the working capacitor remains.

How to make condensers

The proper use of inclusion is indicated in the passport data of the electric motor. If there is shown that the engine can operate from the power supply 380 / 220V, then for 220 it is necessary to apply the condenser for the motor and connect it according to the following scheme.

The scheme works as follows: including switch P1, closing its contacts P1.1, as well as p1.2. At this point, you need to immediately click on the "acceleration" button when the electric motor will type the necessary revs, it is released. Reverse, or reverse rotation of the electric motor, in this connection can be implemented using the SA1 switch, but after the engine is completely stopped.

The selection of the CP capacity drive is distinguished when the electromotor winding is connected according to the scheme Δ - a triangle, formula is calculated:

Calculation of the CP capacity drive when the electric motor windings are connected by the Y - Star circuit formula is calculated:

• drive (Capacitors) worker (CP), is measured (ICF);
• current, electric motor (I), is measured (a);
• network voltage (U) is measured (B).

Current consumption by electric motor is calculated by the formula:

According to the formula:

• the engine power can be viewed in passport data or on a signboard, fixed on the electromotor housing (P), is measured in watts (W);
• Efficiency (efficiency coefficient) - H;
• electrical motor coefficient - COS J;
• network voltage (U) is measured in volts (b).

Note! The starting capacitor must be chosen in two or 2.5 times higher on the capacity of the worker drive, as they are calculated not by the voltage of the network, but 1.5 times higher than it. So for a single-phase network of 220 volts, it is recommended to use capacitive storage storage devices: MBGH or MBGO, in which the operating voltage is 500 volts. A tangible difference, which of these capacitors choose, will not, they both have proven themselves well.

For short-term use, you can use electrolytic storage capacitors, K50-3 or KE stamps, voltage working more than 450 volts as starting capacitors.

It should be noted when electrolytic containers are applied, they are recommended to be connected in series for reliability and use diode shunt.

(C commonly.) \u003d C1 + C2 / 2.

In fact, it is easier to use the condenser selection tables for the power of the electric motor.

Important! Choosing the "capacitors" of the electric motor, it is necessary to take into account that at idle course, the capacity of the capacitance included in the winding passes the electric current to 30% higher than the nominal. This must be taken into account, based on the mode of operation of the electric motor. When it often works without a load or with incomplete load, the container (CP) is selected with a lower nominal value, and when the engine is overloaded and stopping, it is necessary to start starting again.

Portable block

In practice, a portable unit is often used to start three-phase low power electric motors within 500 watts, without reverse conditions.

The operation of the portable block occurs as follows:

• pressing the button (SB1), feeding the Magnetic Starter (km1), the switch (SA1) in the "Closed" position;
• a group of contacts of the magnetic starter (km1.1 and km1.2) connects at this moment the electric motor (M1) to the electrical network of 220 volts voltage;
• at the same time, the next contact group of the magnetic starter (km3.1) performs the closure of the button (SB1);
• when the electric motor dialed the desired number of revolutions with the button (SA1), turn off the starting Capacitors (C1);
• the electric motor stops by pressing the button (SB2).

A portable block is implemented and with automatic shutdown of the capacitance start-up drive, for this you need to enter an additional device, the relay that will replace the operation of the toggler (SA1). Differences in the application of the block and the connection of the same engine is that the block is easy to operate with multiple engines.

Condenser start

It should be noted that a capacitor starter is applied to start a single-phase engine. The difference between this type of engines from three-phase electric motors is that they do not lose power, but since the launch moment is low, the launcher of the container is needed.

Electric motors of this species have two stator windings in their design, they use the same launch scheme using a condenser for a single-phase motor. In this case, the total capacity of the container can be calculated from a simple proportion. If you do not know how to choose a condenser, every 0.1 kilowatt of the engine power is 1 microfrace of the container.

Important! In this calculation, the simplified calculation of the capacitance of the start of a single-phase motor, the resulting result must be taken as a common container, which develops from the launcher and working capacity of the drives.

Experts analyzed many options for connecting asynchronous electric motors, having a standard power supply from the network 380 V and switching to work from a 220 V network, and they made the following conclusions:

1. When a 220 volt connection is being connected to the engine, it loses 50% of its power. Recommendation - To reduce power loss, make switching windings with Y to compound δ. Such switching also reduces power, but not 50%, and by 30% of the rated power of the electric motor;
2. Selecting capacitors to the main chain (working or starting), it is necessary to take into account their working voltage, which should be above the network voltage one and a half times, preferably from 400 volts;
3. The circuit of the electric motor of the feed from 220/127 volts is distinguished, it is necessary to include a "Star" diagram, another type of connection Δ "Triangle" will burn the electric motor;
4. When it is not possible to find a start-up and working capacitor for the operation and start of the engine, you can collect a chain of parallel connected tank drives. In this case: with common. \u003d The sum of all capacitors (C1 + C2 + C3 ...);
5. If the motor is heated in the work, you can undress the parameters of the working Condenser included in the winding of the electric motor. In the event that the engine is not powerless, it is necessary to experimentally raise the parameters of the working Condenser, the container.

For home purposes, a three-phase electric motor can be used, which is used in the industry, but consider the factor that there will be losses in power. The following brands of condensers are popular among lovers of alterations:

• SWV-60 is a metallized polypropylene capacity of the container, its cost - 300 rubles;
• brand of capacitors of the NTS - film, which cost a little cheaper, 200 rubles;
• capacitive E92 drives worth up to 150 rubles;
• the use of metal brand storage storage devices of the MBGO brand container is widespread.

There are cases when the starting capacitor is not required. This is possible when the electric motor is launched without load. But if the electric motor has a greater power of 3 kW and more, the condenser for starting the engine is necessary.

Video

Connecting a three-phase motor into a single-phase chain - the question is relevant. Such an inclusion is useful when equipping the equipment at home. For example, a circular saw, drilling machine or grain crust.

Three-phase motor in a single-phase network: frequency converter

The progressive method of such an inclusion is the frequency converter. With it, it is obtained by the most significant factors in the process of operation of an asynchronous electric motor - smoothness of start-up and softness of braking. This eliminates the multiple excess of the nominal starting voltage than increases the durability of the engine. In addition, the frequency converter almost twice reduces power consumption. The principle of its work is based on double voltage conversion. But the value of the inverter is defined, great, so it scares a little.

Step-by-step instruction of the assembly of the frequency converter do it yourself

For the purpose of saving, you can collect the frequency converter with your own hands. Introducing step-by-step instructions for assembling inverter at home.

Step number 1. Inverter scheme

Start assembling any electronic device need from the scheme. On the Internet of the Internet there are a large set of such schemes. Therefore, before you start work, it will be useful to dig and find out the working selected model or not. In our case, this is repeatedly tested and used scheme.

She looks like that. The scheme is calculated for the engines with a capacity of up to 4 kW, during operation, protection against overload, heating and KZ is running. An unpleasant moment happened, a short circuit in Brno engine, but the defense worked clearly, nor the engine nor frequency movement.

Step # 2. Converter Case

A housing was selected as a case from the computer system unit. You can apply something more compact, but at this moment it is this block-hull seemed acceptable. No need to spend money on the purchase or manufacture of something new.

Step number 3. Power supply

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

But in our case, he was acquired in the finished execution at 24 V.

Step No. 4. Installing the Power Part

the diode bridge with reverse diodes G4PH50UD is made, IGBT field transistors are applied.

Step number 5. Cooling device

Cooling coolers are mounted to prevent radiator heating.

When testing the circuit on the 4kW engine, it may be heating. Checking the converter on electrical machines up to 3.0 kW of heating did not reveal.

Therefore, so that the dust is not stuffed during the work of the coolers, the converter is planned to be used in the workshop, installed the thermaller, which will turn on the cooling only in the case of overheating of the radiator to 36º C and more. Moreover, after the temperature drops to the specified indicators, the cooler will be disconnected again.

Step number 6. Installing Shunts

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

Step number 7. Installation of the main converter board, installation and firmware of the controller

At the bottom of the housing is mounted directotens board directly,

it goes to the microcontroller Pic 16F628A.

Step number 8. Modernization of the converter to adjust the engine speed

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

If there is a task of adjusting the engine speed, then it is necessary to complicate it slightly by installing another PIC 16F648A microcontroller,

quartz 20 MHz,

two capacitors for his strapping 30pf,

and the handle for adjusting the engine speed.

It should be noted that the cost of parts for the frequency converter is poured about in the amount of 2,700 hryvnia or 6,700 rubles, but if you purchase the device with the same parameters, but the factory manufacture, the price will be about 7,000 hryvnias or 17,400 rubles.

The main advantage of the presence of a frequency converter in the possibility of connecting all three-phase electric motors to 4kW, which is available in the economy.

Three-phase motor in a single-phase network: capacitors

Another most acceptable way to connect a three-phase electric motor to a single-phase network are capacitors. If you do not have a funds for the purchase of expensive equipment or the question rests on the unite connection of one electric motor, then it is advisable to apply capacitors. It is completely easy to do, using a step-by-step instruction from our article.

Step-by-step instructions for using capacitors for connecting an asynchronous motor into a single-phase network

Step No. 1. Calculation of the required capacitance capacitors

You need to start connecting the electric motor with the selection of capacitors. The working capacity of the capacitors when the triangle is connected equals the ratio of the product of the current force and the scalar coefficient 4 800 to the nominal voltage.

In the case of the connections, the star scalar indicator is 2 800.

The value of the current force is defined as the ratio of the power of the electric motor to the product of the scalar coefficient of 1.73, the rated voltage U, the coefficient of power Cosφ and the efficiency η.

I \u003d p / 1,73uηcosφ

Data for calculating the current strength is indicated on the nameplate of each specific motor.

The capacitance of the starting capacitor is taken in two to three times the larger working condenser.

Step # 2. Connection Scheme

Connection diagram of three-phase engines A single-phase network looks like this.

Step No. 3. Connection Connections

First, determine the number of conclusions in the Brno electric machine. To connect a triangle, it is necessary for them six. If the conclusions are only three. You need to remove the covers of the electric motor and find the ends of the windings. After that, solder the wires and bring to Brno. Using the scheme to connect the windings with a triangle.

Step No. 4. Application of a starting capacitor

If the speed of the electric motor exceeds 1500 rpm, a separate special condenser should be applied to start.

The simplest switching on the network capacitor network is performed using an uncomply button. When automation of the process, current relays apply.

Electric motors with a capacity of up to 0.5 kW can be included using a relay from a refrigerator, after replacing the contact plate and turning off the protection against heating. To avoid sticking it can be made from a graphite brush. For engines from 0.5 to 1.1 kW, the switch is usually rewind the relay with a larger diameter, and if the engine power is higher than the specified value,

you can make a current relay yourself.

Step number 5. Battery connection of the capacitors of the required capacity

For an engine with a capacity of 1.1 kW, a sufficient condenser with a capacity of 80 μF. In our case, we use 4 pieces of 20 μF. Connect them to one whole, paving the jumpers. They will execute the function of launch and further work.

Step number 6. Power Connection

Connect food, see photo. Be sure to carefully prepare the end of the wires. Then, if problems occur, a poor quality connection, as a cause, it will be possible to immediately exclude.

Step number 7. Connecting the capacitors battery

Connect directly capacitors The engine is ready for operation.

Another way to connect is the inclusion of a three-phase electric motor into a single-phase network without capacitors, with the help of two-stage switching keys, the activation of which is performed in a specific time cut.

Three-phase motor in a single-phase network without capacitors: Connection schemes

Device concept

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.

Expenditures are small, why not try and not create a device that provides a trouble-free connection of an asynchronous three-phase engine into a single-phase network. But before you arm your soldering iron, read reviews and comments.

This scheme theoretically has the right to life, but in practice, mostly does not work. Perhaps need more thorough configuration. It is impossible to say unequivocally or guarantees. Most members of the forum considers the assembly of such a device in vain spending time, although some approve the opposite.

From this dispute you can draw the following conclusions:

• the scheme can operate on an engine up to 2.2 kW and rotation frequency of 1,500 rpm;
• large power loss on the motor shaft;
• the scheme requires a thorough option of the C1R7 chain, which you want to adjust in such a way that the voltage on the condenser opens and closes the key, in all likelihood the key transistors hit the open mode, for this it is necessary to replace the R6 resistor or one of R3R4;
• more reliable ways of connecting a three-phase motor into a single-phase network are capacitors or frequency converter.

The scheme was existence in 1999. To start a three-phase motor in a single-phase network without capacitors, two simple schemes were debugged.

Both are tested on electric motors of power from 0.5 to 2.2 kW and showed quite good results (startup time not many more than in three-phase mode).

For financial savings, you can connect a three-phase engine for working modern schemes.

In these schemes, simistors are used, which are controlled by pulses of different polarity, as well as a symmetrical dynistor, which forms control signals into the stream of each power supply voltage.

Scheme number 1 for low robust electric motors

It is designed to start the electric motor with a rated frequency of revolutions, which is equal to or less than 1,500 revolutions per minute. Engine data winding are connected to a triangle. The phase shifting device in this scheme is a special chain.

By changing the resistance, we obtain a voltage on the condenser, which is shifted relative to the main supply voltage to a certain angle.

The key element in this scheme is a symmetric dynistor. At the time of reaching the voltage on the level condenser, in which the dinister will switch, the charged condenser will connect to the conclusion of the Simistor control.

At this point, the power bidirectional key is activated.

Scheme number 2 for high-breeding electrical machines

It is needed to start electric motors with a nominal speed of rotation of 3000 revolutions per minute, as well as for engines that work on mechanisms with a considerable moment of resistance at startup.

In these cases, a larger starting point is required. That is why the engine winding circuit has been replaced, which creates the maximum starting point. In this scheme, condensers, shifting phases, are replaced by a pair of electronic keys.

The first key is included in the system sequentially with the winding of the phase and forms an inductive shift shift in it. The second is attached parallel to the phase winding, and forms an advanced capacitive current shift in it.

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

Adjustment is to determine the optimal angle of current shift in phase windings, which produces a reliable engine start.

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

The execution of this process is made as follows. The voltage supply to the engine is performed by a manual pressure type of PNVS-10, through the central pole of which the phase shifting chain is connected.

Contacts of the middle pole are in closure only when the start button is stuck.

By pressing this button, by rotating the engine of trimmed resistance, select the desired starting point. Also enter and when adjusting other schemes.

An example of using an asynchronous electric motor 380 V in the household network 220 V without capacitors

Video connections of a three-phase motor into a single-phase network without capacitors: without power loss

Pick out for you:

In different amateur electromechanical machines and devices, in most cases, three-phase asynchronous motors with a short-circuited rotor are used. Alas, a three-phase use in everyday life - a phenomenon is very rare, because for their nutrition from an ordinary electrical network, amateurs use a phase-shifting capacitor, that it allows in full to embody the power and starting properties of the motor.

Asynchronous three-phase electric motors, and specifically it is precisely them, as a result of widespread distribution, it is often necessary to apply, consist of a fixed stator and a movable rotor. In the grooves of the stator with an angular distance of 120 electric degrees, the conductors of the windings, the beginning and the ends of which are laid (C1, C2, C3, C4, C5 and C6) are removed in the junction box.

Connection "Triangle" (for 220 volts)

Connect "Star" (for 380 volts)

Distribution box of the three-phase motor with the position of the jumper for connecting the star scheme

When the three-phase motor is turned on to the three-phase network over its windings at various times, in turn, the current is starting to go, creating a spinning magnetic field, which leads to the rotor, forcing it to spin it. When the motor is connected into a single-phase network, the torque that can move the rotor is not created.

If you can connect the engine on the side to the three-phase network, then the power is not hard. In the gap of one of the phases, we put an ammeter. Run. Ampmeretary readings Multiply on the phase voltage.

In a good network it is 380. We obtain the power P \u003d I * U. Taken% 10-12 on the efficiency. Get actually true result.

For measuring revolutions there are fur-fir devices. Although the rumor is also possible to determine.

In the middle of various methods for including three-phase electric motors into a single-phase network, the most common is the inclusion of the third contact through the phase shifting capacitor.

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

The speed of rotation 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, it is impossible to declare the power whose losses achieve significant values. The clear values \u200b\u200bof the loss of force are dependent on the inclusion scheme, the operating conditions of the motor, the magnitude of the container of the phasigating capacitor. Approximately, the three-phase engine in a single-phase network loses up 30-50% of its own strength.

Not many three-phase electric motors are ready to act well in single-phased networks, but most of them coped with this task completely satisfactory - if not counting power loss. In the main to work in single-phased networks, asynchronous engines with a short-circuited rotor (A, AO2, AOL, APN, etc.) are used.

Asynchronous three-phase engines are designed for 2 rated voltages of the network - 220/127, 380/220, and so on, electric motors with an operating voltage of windings 380 / 220V (380V - for "Stars", 220 - for the "triangle"). The highest voltage for the "star", the smallest - for the "triangle". In the passport and on the sign of the engines, not counting the other characteristics indicate the working voltage of the windings, the diagram of their connection and the likelihood of its change.

Tablets of three-phase electric motors

The designation on the plate A says that the motor windings have every chance of being connected both "triangle" (by 220V) and "star" (for 380V). When connecting a three-phase motor into a single-name network, it is better to use a "triangle" scheme, since in this case the engine is less power than when the "star" is turned on.

The name B informs that the motor windings are connected according to the "Star" scheme, and the probability of switching them to the "triangle" is not taken into account (there is no more than 3 outputs). In this case, it remains either to compete with a large loss of power, connecting the engine according to the "Star" scheme, or, embedded in the winding of the electric motor, try to output the missing ends to connect the windings according to the triangle scheme.

In the event that the operating voltage of the motor is 220 / 127V, then it is possible to connect to a single-phase network to a 220V engine only according to the "Star" scheme. When you turn on 220V according to the "Triangle" scheme, the engine is burning.

Starts and ends of the windings (various options)

Probably, the main complexity of the inclusion of a three-phase motor into a single-phase network is to understand the electrical pipelines overlooking the junction box or, if the latter is lather, simply derived from the outward motor.

The most common option when the winding is already connected via the "triangle" in the existing engine to 380 / 220V. In this case, it is necessary to simply connect the current electrical pipes and the working and starting capacitors to the motor terminals according to the connection scheme.

If the winding engine is connected by the "star", and there is a chance to change it on the "triangle", then such a case can also be attributed to time consuming. It is necessary to simply change the scheme for turning the windings to the "triangle" using for this jumper.

Definition began and ends of the windings. The situation is more difficult, if 6 wires are displayed in the junction box without specifying their belonging to a specific winding and designation started and ends. In this case, the case comes down to solving 2 tasks (although it is necessary to try to search for some documentation for the electric motor in the network. It may be described what the electric pipes of various colors refer to:):

definition of pair of wires related to one winding;

finding the beginning and end of the windings.

The 1st task is solved by the "nickname" of all wires with a tester (measuring resistance). When the device is not, it is possible to solve it with a light bulb from a flashlight and batteries, connecting the existing electrical pipes into the chain alternately with a light bulb. If the latter lights up, it means that the two checked end belong to the same winding. This method defines 3 pairs of wires (A, B and C in Figure below) with a ratio of 3 windings.

Definition of pair of wires related to one winding

The second task, you need to determine the starts and ends of the windings, it will be somewhat more complicated and the availability of a battery and an arrow voltmeter will be necessary. Digital for this task is not suitable due to inertia. The procedure for determining the ends and began the windings is shown in Schemes 1I 2.

Finding the start and end of the windings

To the ends of the same winding (for example, a) the battery is connected, to the ends of others (for example, b) - the arrow voltmeter. Now, when to break the contact of the wires and with the battery, the arrow of the voltmeter swam in some side. Then you need to connect the voltmeter to the winding C and make the same operation with the breakup of the battery contacts. As needed by changing the polarity of the winding with (changing the ends of C1 and C2), it is necessary to ensure that the booming arrow swung in the same direction, as in the case of the winding of B. In the same way, the winding A - with a battery connected to the winding C or B.

Ultimately, all manipulations should come out the following: when the battery contacts are breaking with at least some of the windings on 2 others, the electrical potential of the same polarity should appear (the device arrow swings in one direction). The conclusions of the 1st beam as the beginning (A1, B1, C1) remains to be labeled (A1, B1, C1), and the conclusions of the other - as the ends (A2, B2, C2) and connect them along the desired scheme - the "triangle" either "star" (when motor voltage 220 / 127B).

Removing the absence ends. Probably the most difficult version - when the engine has a merger of the windings according to the "Star" scheme, and there is no ability to switch it to the "triangle" (no more than 3 electric pipes are displayed in the junction box - the start of the windings C1, C2, C3).

In this case, to turn on the motor according to the "Triangle" scheme, you must display the missing ends of the C4, C5, C6 windings.

Three-phase motor inclusion circuits in single-phase network

Enable according to the "Triangle" scheme. In the case of a home network, based on the beliefs of obtaining a larger output power, one-phase inclusion of three-phase motors according to the "Triangle" scheme is considered more appropriate. With all this, their capacity has the ability to reach 70% of the nominal. 2 contacts in a splitting box are connected directly to the electrical pipelines of a single-phase network (220V), and 3-ie - through the working capacitor CP to at least some of the 2nd contacts or network electrical wires.

Provide launch. Running a three-phase motor without load can be made from the working capacitor (more below below), but if the email has some load, it either does not start, or it will become extremely slow. Then, for quick launch, auxiliary running capacitor of the joint venture is needed (the calculation of the capacitance capacitance is described below). Starting capacitors are driving only during the time of the motor startup (2-3 seconds, the turnover is not accomplished by approximately 70% of the nominal), then the starting capacitor must be turned off and discharge.

It is comfortable to start a three-phase motor using a special switch, one pair of which is closed when the button is pressed. When it is released, alone contacts are blocked, while others remain on - the "Stop" button will not be pressed.

Switch to start electric motors

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

The direction of rotation is possible to control, connecting the last, through the condenser, to the two-position switch connected by two contacts with the first and 2nd windings. Depending on the position of the switch, the engine will turn into one or the other side.

The figure below shows a diagram with a start-up and working capacitor and the reverse key, allowing to make comfortable control of the three-phase motor.

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

Connection according to the "Star" scheme. Such a diagram of connecting a three-phase motor to a 220V voltage network is used for electric motors, in which the windings are designed for voltage 220 / 127V.

Capacitors. The desired capacity of the working capacitors for the operation of a three-phase motor in a single-phase network is depending on the inclusion circuit on the motor windings and other characteristics. To connect the "star" the capacity is calculated by the formula:

CP \u003d 2800 I / U

For a triangle connection:

CP \u003d 4800 I / U

Where CP is the capacity of the working capacitor in the ICF, I - current in A, U - the voltage of the network in V. The current is calculated by the formula:

I \u003d p / (1.73 u n cosf)

Where P is the power of the electric motor kW; n - motor efficiency; COSF - power coefficient, 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 value of the capacity of the working capacitor when connecting the "triangle" it is possible to consider the facilitated formula C \u003d 70 PN, where the PN is the rated power of the electric motor in kW. According to this formula, about 7 μF of the working capacitor capacity is needed for each 100 W.

The correctness of the selection of the capacitor capacity is checked by the results of the engine operation. In the event that its value is greater than, it will be necessary under these operating conditions, the engine will be overweight. If the container was less required, the output power of the electric motor will become very low. It has a reason to look for a condenser for a three-phase motor, starting with a small capacity and evenly increasing its value to rational. In the event that it is possible, it is much better to select the capacity to measure the current in the electrical pipelines attached to the network and to the working condenser, for example with current-measuring ticks. The current value must be closer. Measurements should be performed during the mode, in which engine will act.

When determining the starting capacity, first come from the requirements of creating the desired starting point. Do not confuse the starting capacity with the container capacity. On the above schemes, the starting capacity is equal to the sum of the containers of the working (CP) and starting (SP) capacitors.

In the event that, under the working conditions, the launch of the electric motor happens without load, the starting capacity is traditionally accepted the same working, in other words, the starting capacitor is not needed. In this case, the connection scheme simplifies and is reduced. For such a simplification and the main reduction of the scheme, it is possible to organize the likelihood of turning off the load, for example, making it possible to quickly and comfortably change the position of the motor to drop the belt transmission, or by making the removal of the pressing roller, for example, like a motor-block belt clutch.

Starting under load requires the presence of a fair capacity (SP) of the connected temporary engine start. The increase in the disconnected container leads to an increase in the starting point, and with a certain particular value of its value reaches its own greatest value. Further increase in the capacity leads to the opposite effect: the starting point begins to decrease.

Stripping from the engine starting condition under the load closest to the nominal, the starting capacity is obliged to be 2-3 times more working, that is, if the capacity of the working capacitor is 80 μF, then the capacitance of the starting capacitor is required to be 80-160 microfa, which will provide a starting capacity (The sum of the capacity of working and starting capacitors) 160-240 μF. Although if the engine has a small load at startup, the capacitance of the trigger capacitor may be less or necessary for it at all.

Starting capacitors operate short-term time (just a few seconds for the entire connection period). This makes it possible to use cheaper key electrolytic capacitors when starting the engine, specially created for this purpose.

Note that the engine attached to a single-phase network through a condenser operating in the absence of a load, on the winding, powered through the capacitor, is followed by 20-30% superior nominal. Therefore, in case the engine is used in short-sufficient mode, the capacity of the working capacitor should be minimized. But then, in case the engine started without a starting capacitor, the latter has the ability to be required.

It is much better to apply not 1 great condenser, but somewhat much smaller, partially due to the ability to select a good capacity, connecting the added or shutting down the inadequate, the latter are used as a launcher. The required number of microfarades is typed parallel to the compound of several capacitors, repulsted from the fact that the total capacity at a parallel connection is calculated by the formula:

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