What is the difference between connecting a motor with a star and a delta? Star or triangle. Optimal connection of an asynchronous motor

The asynchronous electric motor is powered from a three-phase AC network. Such a motor, with a simple connection diagram, is equipped with three windings located on the stator. Each winding is shifted relative to each other by an angle of 120 degrees. A shift at such an angle is intended to create rotation of the magnetic field.

The ends of the phase windings of the electric motor are brought out to a special “block”. This was done for ease of connection. In electrical engineering, two main methods are used for connecting asynchronous electric motors: the “delta” connection method and the “star” method. When connecting the ends, jumpers specially designed for this purpose are used.

Differences between "star" and "triangle"

Based on the theory and practical knowledge of the basics of electrical engineering, the “star” connection method allows the electric motor to operate smoother and softer. But at the same time, this method does not allow the engine to reach the full power presented in the technical specifications.

By connecting the phase windings in a delta pattern, the motor is able to quickly reach maximum operating power.

This allows you to use the full efficiency of the electric motor, according to the technical data sheet. But this connection scheme has its own drawback: large inrush currents. To reduce the value of currents, a starting rheostat is used, allowing for a smoother start of the engine.

Star connection and its advantages

Each of the three working windings of the electric motor has two terminals - the beginning and the end, respectively. The ends of all three windings are connected to one common point, the so-called neutral.

If there is a neutral wire in the circuit, the circuit is called 4-wire, otherwise, it will be considered 3-wire.

The beginning of the terminals is connected to the corresponding phases of the supply network. The applied voltage on such phases is 380 V, less often 660 V.

The main advantages of using the star scheme:
Stable and long-term non-stop operation of the engine;
Increased reliability and durability by reducing equipment power;
Maximum smooth start-up of the electric drive;
Possibility of exposure to short-term overload;

There is equipment with internal connection of the ends of the windings. Only three pins will be output to the block of such equipment, which does not allow the use of other connection methods. Electrical equipment made in this form does not require competent specialists for its connection.

Triangle connection and its advantages

The principle of the “triangle” connection is to connect in series the end of the winding of phase A with the beginning of the winding of phase B. And then, by analogy, the end of one winding with the beginning of another. As a result, the end of the phase C winding closes the electrical circuit, creating an unbroken circuit. This scheme could be called a circle, if not for the mounting structure. The triangle shape is given by the ergonomic placement of the winding connection.

When connected by a “triangle” on each of the windings, there is a linear voltage equal to 220V or 380V.

The main advantages of using the triangle scheme:

Increasing the power of electrical equipment to the maximum value;
Using a starting rheostat;
Increased torque;
Large traction forces.

Flaws:

Increased starting current;
When running for a long time, the engine gets very hot.

The “triangle” method of connecting motor windings is widely used when working with powerful mechanisms and the presence of high starting loads.

A large torque is created due to an increase in the self-induction EMF caused by large flowing currents.

Star-delta connection type

In complex mechanisms, a combined star-delta circuit is often used. With this switching, power increases sharply, and if the engine, according to its technical characteristics, is not designed to operate using the “delta” method, it will overheat and burn out.

Motors with increased power have high starting currents, and as a result, when starting, they often cause fuses to blow and circuit breakers to turn off. To reduce the line voltage in the stator windings, autotransformers, universal chokes, starting rheostats or a star connection are used.

As a result, using this combination, we will obtain maximum reliability and effective productivity of the electrical equipment used, without fear of damaging it.

Star-delta switching is permissible for electric motors with a light starting mode. This method is not applicable if it is necessary to reduce the starting current and at the same time not reduce the high starting torque. In this case, a wound-rotor motor with a starting rheostat is used.

Main advantages of the combination:

Increased service life. Smooth start allows you to avoid uneven load on the mechanical part of the installation;
Possibility of creating two power levels.

At the moment of starting the electric motor, its starting current is 7 times the operating current.
1.5 times more power when connected windings using the delta method.
To create a smooth start and protect against engine overloads, frequency wires are often used.
When using the star connection method, special attention is paid to the absence of “phase imbalance”, otherwise the equipment may fail.
Line and phase voltages with a delta connection– are equal to each other, as are the linear and phase currents in a star connection.
To connect the motor to a household network, they often use phase shifting capacitor.

Each stator of a three-phase electric motor has three coil groups (windings) - one for each phase, and each coil group has 2 terminals - the beginning and end of the winding, i.e. There are only 6 pins that are signed as follows:

C1 (U1) is the beginning of the first winding, C4 (U2) is the end of the first winding.
C2 (V1) is the beginning of the second winding, C5 (V2) is the end of the second winding.
C3 (W1) is the beginning of the third winding, C6 (W2) is the end of the third winding.

Conventionally, in the diagrams, each winding is depicted as follows:

The beginnings and ends of the windings are brought out into the terminal box of the electric motor in the following order:

The main winding connection diagrams are triangle (denoted by Δ) and star (denoted by Y), which we will analyze in this article.

Note: In the terminal box of some electric motors you can only see three outputs- this means that the motor windings are already connected inside its stator. As a rule, the windings inside the stator are connected when repairing an electric motor (if the factory windings are burned out). In such motors, the windings are usually connected in a star configuration and are designed for connection to a 380 Volt network. To connect such a motor, you simply need to supply three phases to its three outputs.

Connection diagram of electric motor windings according to the “triangle” diagram

To connect the windings of an electric motor according to the “triangle” diagram, it is necessary: connect the end of the first winding (C4/U2) to the beginning of the second (C2/V1), the end of the second (C5/V2) to the beginning of the third (C3/W1), and the end of the third windings (C6/W2) - with the beginning of the first (C1/U1).

Voltage is applied to terminals “A”, “B” and “C”.

In the terminal box of the electric motor, the connection of the windings according to the “triangle” diagram has the following form:

A, B, C—connection points for the power cable.

Connection diagram of electric motor windings according to the “star” scheme

To connect the windings of an electric motor in a star configuration, it is necessary to connect the ends of the windings (C4/U2, C5/V2 and C6/W2) to a common point, while voltage is applied to the beginning of the windings (C1/U1, C2/V1 and C3/W1 ).

Conventionally, this is depicted in the diagram as follows:

In the terminal box of the electric motor, the star connection of the windings has the following form:

Definition of winding terminals

Sometimes situations arise when, after removing the cover from the terminal box of an electric motor, you are horrified to discover the following picture:

In this case, the winding terminals are not labeled, what should I do? Don't panic, this issue can be completely resolved.

The first thing to do is to divide the leads into pairs, each pair should have leads related to one winding, this is very easy to do, we will need a tester or a two-pole voltage indicator.

If using a tester, set its switch to the resistance measurement position (underlined by a red line); when using a bipolar voltage indicator, before use, it is necessary to touch the live parts under voltage for 5-10 seconds to charge it and check its functionality.

Next, you need to take any one terminal of the winding, conditionally take it as the beginning of the first winding and accordingly sign it “U1”, then touch the “U1” terminal we signed with one tester or voltage indicator probe, and touch with the second probe any other terminal from the remaining five unsigned ends. If, having touched the second terminal with the second probe, the tester readings have not changed (the tester shows one) or in the case of the voltage indicator - not a single light comes on - we leave this end and touch the other terminal of the remaining four ends with the second probe, and touch the ends with the second probe to until the tester readings change, or, in the case of a voltage indicator, until the “Test” light comes on. Having found the second terminal of our winding in this way, we accept it conditionally as the end of the first winding and sign it “U2” accordingly.

We proceed in the same way with the remaining four pins, also dividing them into pairs and signing them respectively as V1, V2 and W1, W2. You can see how this is done in the video below.

Now that all the pins are divided into pairs, it is necessary to determine the actual beginnings and ends of the windings. This can be done in two ways:

The first and simplest method is the selection method, which can be used for electric motors with a power of up to 5 kW. To do this, we take our conditional ends of the windings (U2, V2 and W2) and connect them, and briefly, preferably no more than 30 seconds, apply three-phase voltage to the conditional beginnings (U1, V1 and W1):

If the engine starts and runs normally, then the beginnings and ends of the windings are determined correctly; if the engine hums a lot and does not develop the proper speed, then there is an error somewhere. In this case, you just need to swap any two terminals of one winding, for example U1 with U2, and start again:

If the problem persists, return U1 and U2 to their places and swap the following two pins - V1 with V2:

If the engine works normally, the pins are identified correctly, the work is finished, if not, return V1 and V2 to their places and swap the remaining pins W1 with W2.

Second method: We connect the second and third windings in series, i.e. we connect together the end of the second winding with the beginning of the third (terminals V2 with W1), and apply to the first winding to terminals U1 and U2 reduced variable voltage(no more than 42 Volts). In this case, voltage should also appear at terminals V1 and W2:

If voltage does not appear, then the second and third windings are connected incorrectly, in fact, two beginnings (V1 with W1) or two ends (V2 with W2) are connected together, in this case we just need to change the inscriptions on the second or third winding, for example V1 with V2. Then check the first winding in a similar way, connecting it in series with the second, and applying voltage to the third. This method is presented in the following video:

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The main methods of connecting three-phase electric motors are star or delta. These are special cases when three-phase loads are connected through a circuit breaker. In most cases, a universal motor connection is made - star-delta. At the same time, a three-phase electric motor can be connected to ordinary electrical wiring.

Connection methods: star and delta

Connecting the motor alternately in two ways, that is, star and triangle, is done by simply switching jumpers installed on the terminal block between the winding terminals.

The motor winding contacts are connected to the terminal box contacts. This electrical connection, in turn, is with the motor windings and power phases. Special jumpers are installed in the terminal box to allow switching from the “triangle” position to the “star” position. Power is supplied to the ends of the triangle, which are formed by the windings of the electric motor. When connecting in a star, the jumper is set in such a position that all three windings are connected at one point.

In a "triangle", on the contrary, each winding is connected to another, corresponding winding. Since the load in all windings is equal, there is no need for a neutral wire. In modern conditions, connection diagrams are very often used to switch from star to delta mode. At the same time, the starting mode of the electric motor is significantly softened. However, the connection of the contactor itself does not change the general circuit at all; it’s just that an additional power device appears between the electric motor and the machine, which includes several contactors at once.

Switching from different positions

When the electric motor switches from the "triangle" position to the "star" position, its power decreases by almost three times. If the switch is performed in the opposite direction, then the engine power, on the contrary, increases very sharply. At the same time, it should be remembered that if the electric motor is not designed to operate in these conditions, it may simply burn out.

Motor connection - "star-delta" is used to reduce the starting current, the value of which is several times higher than the operating current of the motor. For high-power electric motors, the starting current is so high that its action can cause serious consequences and lead to a voltage drop. During the starting process, the rotation speed of the electric motor increases and the current decreases. After this, the windings switch to delta mode.

The asynchronous motor is powered by a three-phase alternating current network. A delta and star connection can be used for operation. In order for everything to work stably, it is necessary to use special jumpers created for this, be it a star or triangle connection. These are the most convenient options for connection and, accordingly, have a high degree of reliability.

Connection differences

First you need to find out what the difference is between a star and a triangle. If we approach this issue from the point of view of electrical engineering, then the first option allows the engine to operate more smoothly and softly. But there is one point: the engine will not be able to reach full power, which is presented in the technical specifications.

The delta connection allows the engine to quickly reach maximum power. Therefore, the efficiency of the device is applied to its full power. However, there is a serious drawback, which is large inrush currents.

The fight against such phenomena as high starting currents consists of connecting a starting rheostat to the circuit. This makes it possible to start the engine much smoother and improve its performance.

Star connection

A star connection is where the ends of all 3 windings are reunited at a common point called the neutral. If there is a neutral wire, then such a circuit is considered to be four-wire; if it is absent, it is three-wire.

The beginning of the terminals is fixed to certain phases of the power supply network. The voltage applied to these phases is 380 volts or 660 volts . The main advantages of this scheme include:

Non-stop engine operation for a long time and with stability.
By reducing the power of the equipment, the reliability and operating time of the star circuit are increased.
Thanks to this connection, the start-up of an electric drive is more smooth.
There is a possibility for the parameters to be influenced by a short-term overload.
During operation, the housing of the equipment will not become accessible to overheating.

There is equipment with winding connections inside. Since only three terminals are placed on the block of such equipment, other connection methods cannot be used. This implementation does not require the presence of qualified specialists.

Triangle diagram

Instead of a star circuit, you can use a delta connection, the essence of which is to connect the ends and beginnings of the windings in a series manner. The end at the phase C winding closes the circuit and creates a whole circuit. Due to this shape, the resulting circuit will be more ergonomic.

Each winding has a line voltage of 220 or 380 volts. The main advantages of the scheme are::

The power of electric motors reaches its highest level.
Use of an appropriate rheostat for a smoother start.
Significantly increased torque.
High traction rates.

The triangle is used in mechanisms that require significant starting loads and energy for powerful mechanisms. A significant torque is achieved by increasing the self-induction EMF. This phenomenon is caused by large flow currents.

Star and triangle combination

If the design is of a complex type, then use a combined star and triangle method. Using this method leads to a significant increase in power. But in the case where the engine cannot meet the technical specifications, everything will overheat and burn out.

To reduce the linear voltage in the stator windings, a star circuit should be used. After the flowing current decreases, the frequency will begin to increase. The relay type circuit helps to switch delta to star.

It is this combination that provides the greatest reliability and significant productivity of the equipment used without fear of failure. This circuit is effective for engines that use a lightweight starting circuit. But if the starting current decreases and the torque remains constant, it should not be used. An alternative is a wound rotor with a rheostat for starting.

The current during engine starting is 7 times higher than the operating current. Power is one and a half times higher when connected in a triangle, a highly smooth start is obtained using frequency-type wires.

The star reconnection method requires taking into account the fact that phase imbalances need to be corrected, otherwise there is a risk of equipment failure.

Linear and phase voltages in a triangle are equal to each other. If you want to connect the motor to a household network, then you need a phase-shifting capacitor. Thus, Whether a delta or star circuit is used depends on the engine design and household network requirements. Therefore, you should carefully look at the engine performance and the necessary parameters that need to be increased for more efficient operation of the structure.

When creating any device, it is important not only to select the necessary parts, but also to connect them all correctly. And within the framework of this article we will talk about the connection with a star and a triangle. Where is this applied? What does this action look like schematically? These, as well as other questions, will be answered within the article.

What is a three-phase power supply system?

It is a special case of multiphase systems for constructing electrical circuits for alternating current. They operate using sinusoidal EMFs created using a common energy source and having the same frequency. But at the same time they are shifted relative to each other by a certain phase angle. In a three-phase system it is equal to 120 degrees. The six-wire (often also called multi-wire) design for alternating current was invented at one time by Nikola Tesla. Also, a significant contribution to its development was made by Dolivo-Dobrovolsky, who was the first to propose making three- and four-wire systems. He also discovered a number of advantages that three-phase designs have. What are switching circuits?

Star diagram

This is the name for a connection in which the ends of the phases of the generator windings are connected to a common point. It is called neutral. The ends of the phases of the consumer windings are also connected to one common point. Now to the wires that connect them. If it is located between the beginning of the consumer and generator phases, it is called linear. The wire that connects the neutrals is designated as neutral. The name of the chain also depends on it. If there is a neutral, the circuit is called four-wire. Otherwise it will be three-wire.

Triangle

This is a type of connection in which the beginning (H) and end (K) of the circuit are at the same point. So, K of the first phase is connected to H of the second. Her K connects to the third N. And its end is connected to the beginning of the first. Such a scheme could be called a circle, if not for the peculiarity of its installation, when placement in the form of a triangle is more ergonomic. To find out all the features of the connection, check out the types of connections below. But before that, a little more information. What is the difference between a star and delta connection? The difference between them is that the phases are connected differently. There are also certain differences in ergonomics.

Kinds

As can be understood from the figures, there are quite a few options for implementing the inclusion of parts. The resistances that arise in such cases are called load phases. There are five types of connections through which the generator can be connected to the load. This:

Star-star. The second is used with a neutral wire.
Star-star. The second is used without a neutral wire.
Triangle-triangle.
Star-triangle.
Triangle-star.

What are these reservations in the first and second paragraphs? If you have already asked yourself this question, read the information that comes with the star diagram: there is an answer there. But here I would like to make a small addition: the beginnings of the generator phases are indicated using capital letters, and the loads are indicated in capital letters. This is relative to the schematic representation. Now, based on the experience of use: when choosing the direction of current flow, in the linear wires they make it so that it is directed from the generator to the load. With the zeros they do the exact opposite. See what a star-delta connection diagram looks like. The drawings very well clearly show how and what should be. The star/delta winding connection diagram is presented from different angles, and there should be no problems understanding them.

Advantages

Each EMF operates in a certain phase of the periodic process. To designate conductors, the Latin letters A, B, C, L and numbers 1, 2, 3 are used. Speaking about three-phase systems, their advantages are usually highlighted:

Cost-effective when transmitting electricity over long distances, which provides a star-delta connection.
Low material consumption of three-phase transformers.
Balance of the system. This point is one of the most important, since it allows you to avoid uneven mechanical load on the power generating installation. This results in a longer service life.
Power cables have low material consumption. Thanks to this, with the same power consumption, the currents required to maintain a star-delta connection are reduced compared to single-phase circuits.
It is possible, without significant effort, to obtain a circular rotating magnetic field, which is necessary for the operation of an electric motor and a number of other electrical devices that operate on a similar principle. This is achieved due to the possibility of creating a simpler and at the same time effective design, which, in turn, follows from the efficiency indicators. This is another significant advantage that the star and delta connection has.
In one installation you can obtain two operating voltages - phase and linear. It is also possible to make two power levels when there is a delta or star connection.
You can dramatically reduce the flickering and stroboscopic effect of lamps operating on fluorescent lamps by following the path of placing devices powered from different phases in it.

Thanks to the above seven advantages, three-phase systems are now the most common in modern electronics. The star/delta connection of the transformer windings allows you to select the optimal options for each specific case. In addition, the ability to influence the voltage transmitted through networks to residents’ homes is invaluable.

Conclusion

These connection systems are the most popular due to their efficiency. But it should be remembered that the work is carried out with high voltage, and extreme caution must be taken.