What is better to connect a star or triangle. What is the difference between the compounds of asynchronous engines: star and triangle? Connection of three-phase chains according to the scheme "Star"

Electrical connection circuits. Star, Triangle, Star - Triangle.

Asynchronous engines, having a number of such indisputable advantages, as reliability in operation, high performance, the ability to withstand large mechanical overloads, unpretentiousness and low cost of maintenance and repair, due to the simplicity of design, have, of course, their certain shortcomings.

In practice, the main methods of connecting to the three-phase electric motors are used: "Connect the star" and "Triangle Connection".

When the three-phase electric motor is connected, the ends of its stator windings are connected together, the compound occurs at one point, and at the beginning of the windings, a three-phase voltage is supplied (Fig. 1).

When the three-phase electric motor is connected by the "triangle" circuit, the winding of the electric motor is connected in series in such a way that the end of one winding is connected by the next and so on (Fig. 2).

Without going into the technical and theoretical foundations of electrical engineering, it is known that the electric motors in which the windings connected by the star work more smoothly and softer than the electric motors with the connected windings of the triangle, it should be noted that when the windings connect the star, the motor cannot develop the full power. When connecting the windings according to the triangle scheme, the electric motor operates on a full passport power (which is 1.5 times more in power than when connected by the star), but it has very large values \u200b\u200bof starting currents.

In this regard, to reduce starting currents, it is advisable (especially for electric motors with greater power) Connection according to the star scheme - a triangle; Initially, the launch is carried out according to the "Star" scheme, after that (when the electric motor "scored turns") occurs automatic switching According to the "Triangle" scheme.

Control scheme:

Another version of the engine control scheme

Connecting the supply voltage through the contact NC (normally closed) Time relay K1 and contact NC K2, in the circuit of the K3 starter coil.

After switching on the K3 starter, the circuit of the K2 contact coil circuit is opened with its normal-closed contacts, and contact K3 contacts, in the power supply chain of the magnetic starter coil K1, which is combined with the time relay contacts.

When the starter is turned on, the contacts of the K1 in the circuit of the magnetic starter coil circuit circuit occurs and the time relay is simultaneously turned on, the contact relay contact is swapped into the K3 starter chain, closes the Time Relay Contact K1 in the C2 Ravenger circuit.

Turning off the winding of the K3 startup, contact K3 in the circuit of the coil of the magnetic starter K2 is closed. After the switching on the K2 starter, opens with its contacts K2 in the circuit of the power rebel C3.

(Status windings start: U1; V1; W1. End of windings: U2; V2; W2. On the terminal board, the studs of the beginning and ends of the windings are located in a strict sequence: W2; U2; V2; Under them are located: u1; V1; W1. When the engine is connected to the Triangle, the studs are connected by jumpers: W2-U1; U2-V1; V2-W1.)

At the beginning of the windings U1, V1 and W1 through the power contacts of the magnetic starter K1, three-phase voltage is supplied. When the magnetic starter is triggered by K3 using its contacts K3, a closure occurs, connecting the ends of the windings U2, V2 and W2 with each other engine winding connected by the star.

After some time, the time relay is triggered by the K1 starter, shutting down the K3 starter and at the same time, including K2, the power contacts K2 are closed and the voltage to the ends of the motor windings U2, V2 and W2 occurs. Thus, the electric motor is turned on by a triangle scheme.

To start the engines according to the Star-triangle scheme, the so-called launch relays are produced different manufacturers, they can have different "starting time relays", the "start-delta" relay, etc., but the appointment is the same:

Typical diagram with starting time relay ("Star / Triangle" relay) To manage the start of a three-phase asynchronous engine:

Output : To reduce starting currents, start the engine is necessary in the following sequence: first included according to the "Star" scheme on low revs, then switch to "triangle".
Run first triangle creates a maximum moment, and already switching to a star (starting moment 2 times less) with further work in the nominal mode, when the electric motor "scored turns", automatically switching to the triangle scheme, it is worth considering how the load on the shaft before launching, After all, the torque at the star is weakened, so this method of launch is hardly suitable for very loaded engines, may fail.

Today, asynchronous electric motors are popular due to reliability, excellent performance and relatively low cost. Engines of this type have a design capable of withstanding strong mechanical loads. To start the unit successfully, it must be connected correctly. To do this, use the link type and triangle type, as well as their combination.

Types of compounds

The design of the electric motor is quite simple and consists of two main elements - fixed stator and located inside rotating rotor. Each of these parts has its own windings conductive. Stator is laid in special grooves with a compulsory compliance with a distance of 120 degrees.

The principle of operation of the engine is simple - after turning on the starter and the voltage supply to the stator occurs a magnetic field forcing the rotor to rotate. Both tip of the windings are displayed in the junction box and are located in two rows. Their conclusions are marked with the letter "C" and receive a digital designation ranging from 1 to 6.

To connect them, you can use one of three ways:

"Star";
"Triangle";
"Triangle Star".

However, the combined diagram cannot be used if it is necessary to reduce the starting current indicator, but at the same time requires a large torque. In this case, an electromotor with a phase rotor equipped with a retail should be used.

If we talk about the benefits of a combination of two connection methods, you can mark two:

Thanks to the smooth start, the service life increases.
You can create two levels of power of the unit.

Today, electromotors designed to work in networks at 220 and 380 volts are most widely used. It is from this that the selection of the connection scheme depends. Thus, the "triangle" is recommended to be used at a voltage of 220 V, and "Star" - at 380 V.

Content:

The design of the three-phase electric motor is an electrical machine, for the normal operation of which three-phase networks are necessary. alternating current. The main parts of such a device are the stator and the rotor. The stator is equipped with three windings shifted by 120 degrees. When three-phase voltage appears in the windings, the formation of magnetic streams occurs on their poles. Due to these streams, the engine rotor begins to rotate.

In industrial production and in everyday life, the wide use of three-phase asynchronous engines is practiced. They can be one-speed when the star and the triangle of the electric motor winding or multi-speed, with the possibility of switching from one circuit to another.

Coupling star and triangle windings

All three-phase motors of the winding are connected according to the star or triangle scheme.

When connecting the windings by the star scheme, their ends are connected at one point in the zero node. Therefore, another additional zero conclusion is obtained. Other ends of the windings are connected to the network phases 380 V.

The connection of the triangle is sequential connection windings. The end of the first winding is connected to the initial end of the second winding and so on. Ultimately, the end of the third winding is connected to the beginning of the first winding. The supply of three-phase voltage is carried out in each connections node. Connection according to the triangle scheme is distinguished by the absence of zero wire.

Both types of compounds received approximately the same distribution and have no significant distinctive features among themselves.

There is a combination connection when both options are used. This method is used quite often, its goal is the smooth start of the electric motor, which can not always be achieved in conventional connections. At the time of direct start, the windings are in the star position. Next, the relay is used, which ensures switching to the triangle position. Due to this, the starting current is reduced. The combined scheme is most often used during the start of electric motors with high power. For such engines, a significantly greater starting current is required, exceeding the nominal value of about seven times.

Electric motors can be connected in other ways when a double or triple star is applied. Such connections are used for engines with two or more adjustable speeds.

Starting a three-phase electric motor with switching from a star to a triangle

This method is used to reduce the starting current, which can be approximately 5-7 times higher than the rated current of the electric motor. The aggregates with too high power have such a start-up current at which the fuses are easily cut, automata and, large, the voltage is significantly reduced. With such a decrease in voltage, incandescent lamps decreases, there is a decrease in the torque of other electric motors, contactors are spontaneously disconnected. Therefore, applied different methods, in order to reduce the start current.

Common for all methods is the need to reduce voltage in the stator windings during the immediate start. To reduce the starting current, the stator chain at the start time can be supplemented with a throttle, a row or automatic transformer.

The highest distribution received the switching of the winding from the star to the triangle position. In the star position, the voltage becomes 1.73 times less than the nominal, so the current will be less than with full voltage. During start, the frequency of rotation of the electric motor increases, the current is reduced and the windings are switched to the triangle position.

Such switching is allowed in electric motors with a lightweight start mode, as the starting torque decreases, by about twice. This method is switched to those engines that can be constructively connected to a triangle. They should have windings capable of working at.

When you need to switch from a triangle in a star

When you want to connect the star and the triangle of the motor windings, you should remember the possibility of switching from one view to another. The main option is the shift circuit of the triangle star. However, if necessary, the reverse option is also possible.

Everyone knows that electric motors loaded not completely, the power factor decreases. Therefore, such engines are desirable to replace devices with less power. However, if it is impossible to replace and large power, the triangle-star switch is shifted. The current in the stator circuit should not exceed the nominal, otherwise the electric motor will occur.

Powering an asynchronous electric motor comes from a three-phase network with alternating voltage. Such an engine, with a simple connection scheme, is equipped with three windings located on the stator. Each winding has a shift relative to each other at an angle of 120 degrees. Shift to such an angle is designed to create a magnetic field rotation.

The ends of the phase windings of the electric motor are derived to a special "block". This is done for the convenience of connecting. In the electrical engineering use the main 2 connection methods asynchronous electric motors: Connection method "Triangle" and "Star" method. When connecting, the ends are used specifically designed for this jumper.

Differences between the "Star" and "Triangle"

Based on the theory and practical knowledge of the foundations of electrical engineering, the method of connecting the "star", allows the electric motor to work smarter and softer. But at the same time this method Does not leave the engine for the entire power presented in the specifications.

By connecting the phase windings according to the "Triangle" scheme, the engine is able to quickly go to the maximum operating power. This allows the use of an electric motor in full efficiency, according to the technical transport. But this compound scheme has its drawback: large launchers. To reduce the values \u200b\u200bof the currents, the launcher is used, allowing you to make a smoother engine launch.

Connection "star" and its advantages

Each of the three operating windings of the electric motor has two outputs - respectively, the beginning and end. 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 scheme is called 4-wired, otherwise it will be considered a 3-wire.

The beginning of the conclusions are attached to the corresponding phases of the supply network. The applied voltage at such phases is 380 V, less often 660 V.

The main advantages of applying the "Star" scheme:

Stable and long mode of non-stop engine operation;
Increased reliability and durability, by reducing the capacity of the equipment;
Maximum smooth start of an electrical drive;
The possibility of impact of short-term overload;
During operation, the equipment case does not overheat.

There is equipment with the internal connection of the ends of the windings. Only three conclusions will be displayed on the block of such equipment, which does not allow to apply other connection methods. The electrical equipment performed in this form, it does not require competent specialists for its connection.

Connection "Triangle" and its advantages

The principle of connection "Triangle" lies in a sequential connection of the end of the phase and with the beginning of the phase V. and further by analogy - the end of one winding with the beginning of another. As a result, the end of the phase winding with closes electric chain, creating an inextant contour. This schema It can be called around, if it were not for the mounting structure. The shape of the triangle betrays ergonomic placement of the connection of the windings.

When connecting a "triangle" on each of the windings, there is a linear voltage equal to 220V or 380V.

The main advantages of applying a triangle scheme:

An increase to the maximum power of electrical equipment;
Use of launchers;
Increased rotating moment;
Large traction effort.

Disadvantages:

Increased start current;
With long-term operation, the engine is greatly heated.

The method of connecting the engine windings "Triangle" is widely used when working with powerful mechanisms and the presence of high starting loads. A large torque is created by increasing self-induction EMF indicators caused by leaking large currents.

Type of Connection "Star-Triangle"

In complex mechanisms, the combined "Star-Triangle" scheme is often used. With this switching, the power grows sharply, and if the engine according to technical specifications is not designed to work according to the "triangle" method, it will overheat and burn.

Motors S. increased power They have large starting currents, and as a result, when starting, the fuses are often caused by the automata shutdown. To reduce linear voltage Autotransformers, universal chokes, launchers or connection of the Star type are used in the stator windings.

In this case, the voltage on the connection of each winding will be 1.73 times less, therefore, it will be less and flowing during this period. The frequency increases, and continue to reduce the current reading. Then applying a relay-contact diagram, switching from the "Star" to the "Triangle" will be switched.

As a result, using this combination, we obtain the maximum reliability and efficient productivity of the electrical equipment used, without fearing to bring it out of order.

Switching "Star-Triangle" is permissible for electric motors with a lightweight start mode. This method is not applicable if it is necessary to lower the start current and at the same time do not reduce the big starting point. In this case, an engine with a phase rotor with a start-up retail is used.

The main advantages of the combination:

Increase service life. Smooth start allows you to avoid uneven load on the mechanical part of the installation;
The ability to create two power levels.

At the time of starting the electric motor, its start current is 7 times more operating current.
Power 1.5 times more when connected Winding by the "triangle" method.
To create a smooth start and protection against engine overloadsoften used frequency wires.
When using the junction method "Star"Special attention is paid to the absence of "skewing phase", otherwise the equipment may fail.
Linear and phase voltages when connecting "Triangle" - equal to each other, like linear and phase currents in the "Star" connection.
To connect the engine to the household network, it is often used Fazos-shifting capacitor.

Asynchronous three-phase engines are more efficient compared to single-phase and received much greater distribution. Electrical devices, working on a propulsion, most often equipped with three-phase electric motors.

The electric motor consists of two parts: a rotator rotor and a fixed stator. The rotor is located inside the stator. Both elements have conductive windings. The stator winding is laid in the groove of the magnetic pipeline with a distance of 120 electrical degrees. The starts and ends of the windings are bred in and fixed in two rows. Contacts are marked with a literary with, each assigned a digital designation from 1 to 6.

Phases of stator windings when connected to the supply network are connected by one of the schemes:

"Triangle" (Δ);
"Star" (Y);
combined "Star-Triangle" scheme (Δ / Y).

Connecting to combined scheme Used for engines with a capacity of over 5 kW.

« Star»Call the connection of all the ends of the stator windings at one point. Powering is supplied to the beginning of each of them. With a sequential connection of the windings in a closed cell forms " triangle" Contacts with terminals are placed in such a way that the ranks are shifted relative to each other, on the contours of the output C6 is C1, etc.

The supply voltage supply from the three-phase network to stator windings creates a rotating magnetic field, which leads the rotor in motion. The rotational torque arising after the launch is not enough. To increase the torque, the network includes additional items.

The easiest and most common way to connect to household networks is a connection using a phasigating condenser.

When the supply voltage is filled from both types of power grid, the rotor speed of an asynchronous motor will be almost the same. At the same time, power in three-phase networks higher than in similar single-phase. Accordingly, the connection of a three-phase electric motor into a single-phase network is inevitably accompanied by a noticeable power loss.

There are electromotors that are originally not designed to connect to the household network. By purchasing an electric motor for use in domestic conditions, it is better to immediately look for models with a short-circuited rotor.

Connecting the engine "star" and "triangle" in networks with different rated voltage

In accordance with the nominal supply voltage of asynchronous three-phase motors of domestic production are divided into two categories: to work on networks 220/127 V and 380/220 V. Engines designed to work from the network 220/127 B have a small capacity - today their use. Strongly limited.

Electromotors, calculated on the rated voltage of 380/220 in distributed everywhere.

Regardless of the rated voltage when the motor is installed, a rule is used: lower voltage values \u200b\u200bare used when connected to a "triangle", high - exclusively in stator windings connections according to the "Star" scheme.

That is, voltage in 220 B. Served on " triangle», 380 B. - on the " star."Otherwise, the motor will quickly braid.

Maintenance specifications The unit, including the recommended connection scheme, and the possibility of its change is displayed on the motor tag and its technical passport. The presence of a type of type Δ / y indicates the ability to connect the windings and the "star", and the "triangle". To minimize power losses, inevitable when working from single-phase household networks, the motor of this type is better to connect the "triangle".

The Y sign indicates the engines where the possibility of connecting to the "triangle" is not provided. In the distribution box of such models, instead of 6 contacts are only three, the connection of the three others is performed under the case.

Connecting three-phase with a nominal supply voltage of 220/127 to standard single-phase networks is performed only by the type "Stars". Connecting an aggregate designed for a low power supply voltage in a triangle will quickly lead it into disrepair.

Features of the electric motor when connecting in different ways

Connecting the electric motor "Triangle" and "Star" is characterized by a certain set of its advantages and disadvantages.

The connection of the engine windings in the "star" provides a softest launch. In this case, there is a significant loss of the power of the unit. This scheme also connects all electric motors of domestic origin to 380V.

Connection "Triangle" provides output power Up to 70% of nominal, but starting currents reach significant values \u200b\u200band the engine can fail. This scheme is the only correct option for connecting to the Russian electricity networks of imported electric motors of the European production, calculated on the rated voltage of 400/690.

Starting function for the "Star" switching schemes is used only for engines with Δ / Y, in which the possibility of both connection options is implemented. Starting the engine is produced when the "star" is connected to reduce the starting current.

When the engine is accelerated, switching to the "triangle" to get the maximum possible output power.

The use of the combined method is inevitably connected with current jumps. At the moment the current supply circuits stops, the rotor speed is reduced, in some cases there is a sharp decline. After some time, the rotational speed is restored.