Star triangle engine difference. Star or triangle. Optimal connection of an asynchronous electric motor. Method for reducing starting currents of an electric motor
Asynchronous motors offer many operational advantages. This is reliability, high power, good performance. Connecting the electric motor with star and delta ensures its stable operation.
There are two main parts to an electric motor: a rotating rotor and a static stator. Both have a set of conductive windings in their structure. The electrical windings of the stationary element are located in the grooves of the magnetic wire at a distance of 120 degrees. All ends of the windings are output to the electrical distribution block and are fixed there. Contacts are numbered.
Motor connections can be star, delta, as well as all kinds of switching. Each connection has its own advantages and disadvantages. Motors connected in a star configuration have smooth, soft operation; the action of the electric motor is limited by power compared to a triangle, since its value is one and a half times greater.
An association V one general point: star connection
The ends of the stator windings are connected together at one point. Three-phase voltage is supplied to the beginning of the windings. The value of inrush currents when connecting a triangle is more powerful. A star connection means a connection between the ends of the stator winding. Voltage is supplied to the beginning of each winding.
The windings are connected in a series closed cell, forming a triangular connection. The rows of contacts with terminals are located parallel to each other. For example, the beginning of pin 1 is opposite the end of 1. Network power is supplied to the stator windings, creating a rotation of the magnetic field, leading to the movement of the rotor. The torque generated after connecting a three-phase electric motor is insufficient for starting. An increase in the rotating element is achieved by using an additional element. For example, a three-phase frequency converter connected to an asynchronous motor in the figure below.
Connection drawing of a classic frequency converter with a star
According to this scheme, domestic 380 volt motors are connected.
Mixed way
The combined connection type is applicable for electric motors with a power of 5 kW or more. The star-delta circuit is used when it is necessary to reduce the starting currents of the unit. The principle of operation begins with a star, and after the engine reaches the required speed, it automatically switches to a triangle.
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This scheme is not suitable for devices with overloads, as a weak torque occurs, which can lead to breakdown.
Principle work
The power supply starts using the second and relay contact. Then the third starter is triggered on the stator, thereby opening the circuit formed by the coil of the third element, and a short circuit occurs in it. Next, the first stator winding begins to work. Then a short circuit occurs in the magnetic starter, a temporary thermal relay is triggered, which closes at the third point. Next, the contact of the temporary thermal relay in the electrical circuit of the second stator winding is observed to close. After disconnecting the windings of the third element, the contacts in the chain of the third element are closed.
To the beginning of the windings, current passes in three phases. It enters through the power contacts of the magnet of the first element. The contacts of the third starter turn it on and close the ends of the windings, which are connected by a star.
Then the time relay of the first starter is turned on, the third is turned off, and the second is turned on. Contacts K2 are closed, voltage is supplied to the ends of the windings. This is the inclusion of a triangle.
Various manufacturers make the start relay needed to start an electric motor. They differ in appearance and name, but perform the same function.
Typically, the connection to network 220 occurs with a phase-shifting capacitor. Power comes from any electrical network and rotates the rotor at the same frequency. Of course, the power from a three-phase network will be greater than from a single-phase one. If a three-phase motor operates from a single-phase network, power is lost.
Some types of motors are not designed to operate from a household network. Therefore, when choosing a device for your home, preference should be given to motors with squirrel-cage rotors.
Based on rated power, domestic electric motors are divided into two types: 220 - 127 volts and 380 - 220 volts. The first type of low-power electric motors is used infrequently. The second devices are widespread.
When installing an electric motor of any power, a certain principle applies: devices with low power are connected in a triangle, and devices with high power are connected in a star. The 220 power supply goes to the delta connection, the 380 voltage goes to the star connection. This will ensure long and high-quality operation of the mechanism.
The recommended diagram for connecting the motor is listed in the technical document. The △ icon means a connection in the same form. The letter Y indicates the recommended star connection. The characteristics of numerous elements are indicated by colors, due to their small dimensions. For example, the denomination or resistance can be read by color. If both signs are present, then the connection is possible by switching △ and Y. When there is one specific marking, for example, Y, then the connection available will only be in a star configuration.
Circuit △ provides output power up to 70 percent, the value of inrush currents reaches the maximum value. And this can ruin the engine. This circuit is the only option for operating foreign asynchronous motors with a power of 400 - 690 volts from Russian electrical networks.
Therefore, choosing the correct connection or switching must take into account the characteristics of the electrical network and the power of the electric motor. In each case, you should familiarize yourself with the technical characteristics of the motor and the equipment for which it is intended.
How to connect a motor according to the “Star-Delta” scheme
There is plenty written about star-delta motor connection diagrams. But every article contains inaccuracies and errors. The authors simply copy from each other. I suspect that most of them have never connected a motor in their lives, and the name of the circuit for them is just geometric figures. Therefore, I decided to follow the popular wisdom “if you want something done well, do it yourself,” and write this article.
I am telling you based on my experience and understanding of the issue. As always, I will give the theory and show what it looks like in practice.
To begin with, if someone is completely out of the loop, what area of knowledge is this all from? We are talking about one of the common methods of connecting a three-phase asynchronous electric motor, in which the motor windings are first connected to the supply network in a star circuit, and then in a delta circuit. In young inquisitive minds the question will immediately arise - “Why is this necessary?” OK.
Why do we need a “Star-Triangle” scheme?
The root of the problem lies in the starting currents and excessive loads that the motor experiences when power is applied directly to it. What about the engine - the entire drive grinds and shudders when starting!
IMPORTANT! If you've read this far, . There is a lot of detail about where they come from, how to recognize them, count and measure them.
This is especially critical where there is no reduction gear - a gearbox or a belt on pulleys.
This is especially important where something massive is mounted on the engine shaft - an impeller or a centrifuge.
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This is especially significant where the engine power is more than 5 kW and the rotation speed is high (3000 rpm).
These are the pigs that don’t like being connected directly to the network
The drive is different from the engine, like a wheel is from a tire and like.
So, in order to reduce the power on the motor shaft during start-up, it is first turned on at a reduced voltage, it slowly accelerates, and then turned on at full, rated power. This is implemented not by changing the voltage with rheostats and transformers, but in a more cunning way. But in order.
“Star” and “Triangle” schemes
Any classic three-phase motor has three stator windings. They may have different configurations in space, additional conclusions, but there are three of them.
Diagram of stator windings with leads for a three-phase asynchronous motor
How to connect all these 6 pins if our power supply only has 3 phases?
In short, here is the simplest diagram:
Star-Delta control circuit with time relay. The simplest theoretical
In contacts with a time delay, everyone is constantly confused. I have it right)
You already know what KM1, KM2, KM3 are, but KA1 is a time relay with a delay when turned on. The relay can be anything, be it electronic or pneumatic, such as PVL. The main thing is that the contacts switch from the initial state after a delay time after power is applied to KA1.
You can supply power to the circuit (start the engine) by any means - even with a toggle switch, at least.
The disadvantage of this scheme is that there is a danger of conflict between KM2 and KM3. That's why I don't really like this scheme, because... it operates “on the edge”, and its failure-free operation is highly dependent on the mechanics and design of the contactors. Because of this, the contacts may burn out, or the input machine may be knocked out. Therefore, locking is required (electrical and preferably mechanical):
Practical star-delta circuit with interlocking
The blocking is implemented on NC contacts, more about this and more. A mechanical interlock is shown between the coils, not to be confused with the “Triangle” circuit!
This is a real scheme, you can apply it. If something is not clear, ask.
By the way, instead of KA1.1 you can install a NO contact with a Shutdown delay. That is, it turns on immediately after power is applied, and turns off after a while. But for this you need two separate time relays with different operating principles, which must be synchronized to guarantee a pause. This is exactly what is implemented in specialized “Star-Triangle” time relays.
Yes, one more note. Sometimes the power supply to the general contactor KM1 is turned on not directly, but through the NO contact of the “Star” KM2, then KM1 becomes self-retaining through its NO contact. This is necessary for additional testing of the functionality of the time relay KA1.
Timing diagrams of the Star-Delta circuit operation
With reference to my control circuit, contactor switching diagrams:
Star-delta control timing diagrams
Everything seems clear here, but there is one important note. Again. A small gap (pause) is required between the green and red areas. It may not exist (pause = 0), but these areas can overlap each other if contactors with a DC coil (=24 VDC) are used. Especially when using a reverse-connected diode (and it is required!), the turn-off time can be 7-10 times longer than the turn-on time!
What I mean is that I once suffered with such a scheme; it periodically knocked out the input machine. We installed a special relay with a pause, the problem was solved!
Real circuit example
Here is a real example of such a circuit on an electronic time relay:
Photo of a star-delta circuit with timer control and galvanic isolation on a transformer.
From left to right in the bottom row: KM1, KM2, KM3, KA1.
And here is an example of a circuit controlled by a controller:
Star-delta, compressor, controlled by controller program
Video of how the contactors click in this circuit:
Here's how beautifully the Germans designed the circuit in their compressor:
Star-Triangle compressor circuit
There are three wires at the input of the circuit, and six at the output. Everything fits)
How to switch the engine circuit to “Star” and “Triangle” manually
If no automation is needed, and the engine operates constantly in “Star” or “Triangle”, then using an open-end wrench, you can switch the winding connection diagram manually.
Motor nameplate 220 / 380 V 0.37 kW
On the back of the boron cap, as usual, there is a diagram:
Connection diagram 220 – 380 on the engine cover
The motor was powered directly from a three-phase 380 V network through a contactor and was assembled into a “Star:
The motor terminals are connected in a star connection
Unscrew the M4 nuts, remove the jumpers and power wires:
We disassemble the circuit, remove the wires
We assemble the circuit into a triangle, for a reduced voltage of 220 V:
Assembling a triangular circuit for 220 V
The alteration was necessary due to the fact that it was necessary to change the engine rotation speed, and to do this, use a frequency converter. And frequency generators for such power are usually single-phase. As a result, let's go!
By the way, I’m planning a series of articles on frequencies, subscribe!
Features of working at Zvezda
In accordance with GOST 28173 (IEC 60034-1), motors can be operated with a voltage deviation of ± 5% or
frequency deviation ± 2%. In this case, the motor parameters may differ from the nominal ones, and the temperature rise of the windings may be 10 °C higher than the limit according to GOST 28173 (IEC 60034-1).What am I talking about? The fact is that during startup, when the engine is running in “Star” mode, it does not work in the mode (the voltage differs by 70%!), which can lead to overheating if this lasts for a long time. Be careful to protect the engine from overheating and overload! But that's a completely different story)
Video
The entire load in three-phase circuits is connected according to a star or delta circuit. Depending on the type of electricity consumers and the voltage in the electrical network, the appropriate option is selected. If we talk about electric motors, then the choice of winding connection option determines the possibility of its operation in a specific network with nominal characteristics. In the article we will look at the difference between a star and a triangle in an electric motor, what they influence and what is the principle of connecting wires in the terminal block of a three-phase motor.
Theory
As already mentioned, star and delta connection diagrams are typical not only for an electric motor, but also for transformer windings, heating elements (for example, electric boiler heating elements) and other loads.
To understand why these connection diagrams for the elements of a three-phase circuit are called that way, you need to modify them somewhat.
In a “star”, the load of each phase is connected to each other by one of the terminals, this is called the neutral point. In a “triangle”, each of the load terminals is connected to opposite phases.
Let's consider this issue using the example of connecting the windings of a three-phase transformer or a three-phase motor (in this context it does not matter).
In this figure, the differences are more noticeable; in a “star,” the beginnings of the windings are connected to the phase conductors, and the ends are connected together; in most cases, the neutral wire from the supply generator or transformer is connected to the same load point.
The dots indicate the beginning of the windings.
That is, in a “triangle” the end of the previous winding and the beginning of the next are connected, and the supply phase is connected to this point. If you confuse the end and the beginning, the connected machine will not work.
What is the difference
If we talk about connecting single-phase consumers, let’s briefly look at the example of three electric heaters, then in a “star”, if one of them burns out, the remaining two will continue to work. If two out of three burn out, none of them will work at all, since they are connected in pairs to line voltage.
In a triangle circuit, even if 2 heating elements burn out, the third one will continue to work. There is no neutral wire in it, there is simply nowhere to connect it. And in the “star” it is connected to the neutral point, and it is needed to equalize the phase currents and their symmetry in the case of different loads across the phases (for example, in one of the branches there is 1 heating element connected, and in the rest there are 2 in parallel).
But if with such a connection (with different loads in phases) the zero burns out, then the voltages will be unequal (where the load is greater, it will sag, and where it is less, it will increase). We wrote more about this in the article about
It should be taken into account that it is impossible to connect ordinary single-phase devices (220V) between phases at 380V. Either the devices must be designed for such power, or the network must be with Ulinear 220V (as in electrical networks from some specific objects, for example, ships).
But, at , zero is often not connected to the midpoint of the star, since this is a symmetrical load.
Formulas for power, current and voltage
Let's start with the fact that in a star circuit there are two different voltages - linear (between linear or phase wires) and phase (between phase and zero). Ulinear is 1.73 (root of 3) times greater than Uphase. In this case, the linear and phase currents are equal.
That is, they are correlated in such a way that with linear 380V, phase is equal to 220V.
In a “triangle”, Ulinear and Uphase are equal, and the currents differ by a factor of 1.73.
In both cases, they are calculated using the same formulas:
- full S = 3*Sф = 3*(Uл/√3)*I = √3*Uл*I;
- active P = √3*Uл*I*cos φ;
- reactive Q = √3*Uл*I*sin φ.
When connecting the same load to the same Uphase and Ulinear, the power of the connected devices will differ by 3 times.
Let's say there is a motor that operates from a three-phase network of 380/220V, and its windings are designed for a star connection to an electrical network with a linear voltage of 660V. Then, when connected in a “triangle”, the supply Ulinear should be 1.73 times less, that is, 380V, which is suitable for connecting to our network.
Let us present calculations to show what differences will occur for the motor when switching the windings from one circuit to another.
Let’s assume that the stator current when connected in a triangle to a 380V network was 5A, then its total power is equal to:
S=1.73*380*5=3287 VA
Let's switch the electric motor to a "star" and the power will decrease by 3 times, since the voltage on each winding has decreased by 1.73 times (it was 380 per winding, and now it is 220), and the current is also 1.73 times: 1.73 * 1 .73=3. This means that taking into account the reduced values, we will calculate the total power.
S=1.73*380*(5/3)=1.73*380*1.67=1070 VA
As you can see, the power has dropped by 3 times!
But what will happen if there is another electric motor and it worked in a “star” in a 380V network and the stator current is the same 5A, respectively, and the windings are designed to be connected to a “triangle” at 220V (3 phases), but for some reason they connected exactly in a “triangle” and connected to 380V?
In this case, the power will increase 3 times, since the voltage on the winding has now, on the contrary, increased by 1.73 times and the current by the same amount.
S=1.73*380*5*(3)=9861 VA
The engine power has become more than rated by these same 3 times. So it will just burn out!
Therefore, you need to connect the electric motor according to the winding connection diagram that corresponds to their rated voltage.
Practice - how to choose a scheme for a specific case
Most often, electricians work with a 380/220V network, so let’s look at how to connect an electric motor, star or delta, to such a three-phase electrical network.
In most electric motors, the winding connection diagram can be changed; for this purpose, there are six terminals in the Brno, they are located in such a way that with the help of a minimum set of jumpers you can assemble the circuit you need. In simple words: the terminal of the beginning of the first winding is located above the end of the third, the beginning of the second, above the end of the first, the beginning of the third above the end of the second.
You can see how to distinguish the two options for connecting an electric motor in the figure below.
Let's talk about which scheme to choose. The connection diagram of the electric motor coils does not have a particular influence on the operating mode of the engine, provided that the nominal parameters of the engine comply with the supply network. To do this, look at the nameplate and determine what voltages your particular electrical machine is designed for.
Typically the marking looks like:
It deciphers like this:
If the phase-to-phase voltage is 220, assemble the windings in a triangle, and if 380, assemble them in a star.
To simply answer the question “How to connect the windings of a motor?” We have made a connection diagram selection table for you:
Star-delta changeover for smooth starting
When starting the electric motor, high starting currents are observed. Therefore, to reduce the starting currents of asynchronous motors, a starting circuit is used with switching the windings from star to delta. In this case, as mentioned above, the electric motor must be designed to be connected in a “triangle” and work under the Ulinear of your network.
Thus, in our three-phase electrical networks (380/220V), for such cases we use motors with a nominal “380/660” Volt, for “Δ/Y”, respectively.
When starting, the windings are switched on as a star to a reduced voltage of 380V (relative to the nominal 660V), the engine begins to pick up speed and at a certain point in time (usually by a timer, in more complicated versions - by a signal from current and speed sensors) the windings switch to delta and operate already at its nominal 380 volts.
The illustration above describes this method of starting engines, but a changeover switch is shown as an example; in practice, two additional contactors (KM2 and KM3) are used; although it is more complicated than the usual electric motor connection diagram, this is not its drawback. But it has a number of advantages:
- Less load on the electrical network from inrush currents.
- Accordingly, there are smaller voltage drops and the likelihood of stopping related equipment is reduced.
- Soft start of the engine.
There are two main drawbacks to this solution:
- It is necessary to lay two three-core cables from the location of the contactors directly to the motor terminals.
- The starting torque drops.
Conclusion
As such, there are no differences in performance characteristics when connecting the same electric motor in a star or delta configuration (it will simply burn out if you make the wrong choice). Just as there are no advantages or disadvantages of any of the schemes. Some authors argue that there is less current in the star. But with the same power of two different motors, one of which is designed to be connected in a “star” and the second in a “delta” to a network, for example, 380V, the current will be the same. And the same engine cannot be switched “at random” and “for unknown reasons”, as it will simply burn out. The main thing is to choose the option that matches the supply voltage.
We hope that now you have become more clear about what a star and delta circuit is in an electric motor, what the difference is in connecting in each method, and how to choose a circuit for a particular case. We hope the information provided was useful and interesting for you!
Materials
Today, asynchronous electric motors are popular due to their reliability, excellent performance and relatively low cost. Motors of this type are designed to withstand strong mechanical loads. In order for the unit to start up successfully, it must be connected correctly. For this purpose, star and delta connections are used, as well as a combination of them.
Types of connections
The design of the electric motor is quite simple and consists of two main elements - a stationary stator and an internal rotating rotor. Each of these parts has its own windings that conduct current. The stator one is placed in special grooves with a mandatory distance of 120 degrees.
The principle of operation of the engine is simple - after turning on the starter and applying voltage to the stator, a magnetic field appears, causing the rotor to rotate. Both ends of the windings are brought out into the distribution box and are arranged in two rows. Their conclusions are marked with the letter “C” and receive a numerical designation ranging from 1 to 6.
To connect them, you can use one of three methods:
- "Star";
- "Triangle";
- "Star-triangle".
If all ends of the stator winding are connected at one point, then this type of connection is called “star”. If all ends of the winding are connected in series, then it is a “triangle”. In this case, the contacts are arranged so that their rows are shifted relative to each other. As a result, opposite terminal C6 is terminal C1, etc. This is one of the answers to the question of what is the difference between star and delta connections.
In addition, in the first case, smoother operation of the motor is ensured, but maximum power is not achieved. If a delta circuit is used, then large inrush currents arise in the windings, which negatively affect the service life of the unit. To reduce them, you have to use special rheostats that make the start as smooth as possible.
If a 3-phase motor is connected to a 220 volt network, then the torque is not enough to start. To increase this indicator, additional elements are used. In domestic conditions, the optimal solution would be a phase-shifting capacitor. It should be noted that the power of three-phase networks is higher in comparison with single-phase ones. This suggests that connecting a 3-phase motor to a single-phase electrical network will certainly lead to a loss of power. It is impossible to say exactly which of these methods is better, since each has not only advantages, but also disadvantages.
Pros and cons of "star"
The common point at which all ends of the winding are connected is called neutral. If there is a neutral conductor in the electrical circuit, then it will be called four-wire. The beginning of the contacts is connected to the corresponding phases of the power supply network. The connection diagram of the electric motor windings “star” has a number of advantages:
- Ensures long-term non-stop operation of the electric motor.
- Due to the reduction in power, the service life of the unit increases.
- A smooth start is achieved.
- During operation, there is no significant overheating of the engine.
There is equipment that has an internal connection of the ends of the winding and only three contacts are brought into the box. In such a situation, using a connection scheme other than “star” is not possible.
Advantages and disadvantages of the “triangle”
Using this type of connection allows you to create an unbroken circuit in the electrical circuit. The circuit received this name because of its ergonomic shape, although it can also be called a circle. Among the advantages of the “triangle” it is worth noting:
- The maximum power of the unit is achieved during operation.
- A rheostat is used to start the motor.
- Significantly increases torque.
- A powerful traction force is created.
Among the disadvantages, one can note only high values of starting currents, as well as active heat generation during operation. This type of connection is widely used in powerful mechanisms that contain large load currents. It is due to this that the EMF increases, affecting the power of the torque. It should also be said that there is another connection diagram called “open delta”. It is used in rectifier installations designed to produce triple-frequency currents.
Combining circuits
In highly complex mechanisms, a combined star and delta connection of a three-phase motor is often used. This allows you not only to increase the power of the unit, but also to extend its service life if it is not designed to work using the “triangle” method. Since the starting currents in high-power motors are high, when the equipment starts, fuses often fail or circuit breakers turn off.
To reduce the linear voltage in the stator winding, various additional devices are actively used, for example, autotransformers, rheostats, etc. As a result, a voltage reduction of more than 1.7 times is achieved. After the motor has been successfully started, the frequency begins to gradually increase and the current decreases. The use of a relay contact circuit in such a situation makes it possible to switch the star-delta connection of the electric motor. In this situation, the smoothest possible start of the power unit is ensured.
The 380V to 220V electric motor is connected via a capacitor. For such a connection you must use paper (or starting) capacitors, wherein IMPORTANT to rated capacitor voltage was greater than or equal to the mains voltage(it is recommended that the capacitor voltage be 2 times the mains voltage). The following brands (types) of capacitors can be used:
MBGO, MBGCh, MBGP, MBGT, MBGV, KBG, BGT, OMBG, K42-4, K42-19, etc.
The capacitance of the capacitor can be determined using the formulas given below, or using .
The first thing you need to do is to correctly connect the leads of the motor windings. As is already known from the article: the windings of an electric motor can be connected along (denoted - Y) or along (denoted - Δ), while, as a rule, to connect a 220V electric motor, a “triangle” circuit is used, in order to determine the connection diagram of the windings you need to look at label attached to it:
The entry: “Δ/ Y 220/380V” means that to connect this electric motor to 220V, you need to connect its windings according to the diagram, and to connect to 380V, according to the diagram, how to do it.
The second thing you need to decide is how the electric motor will be started, under load (when at the moment of starting the electric motor a load is applied to its shaft and it cannot rotate freely) or without load (when the electric motor shaft rotates freely at the moment of starting, for example, emery , fan, circular saw, etc.).
When starting the engine without load, 1 capacitor is used, which is called a working capacitor, and if it is necessary to start the engine under load, in addition to the working one, a second capacitor is additionally used in the circuit, which is called a starting capacitor, it is turned on only at the moment of starting.
Let's look at the connection diagrams for a 380 by 220 electric motor for both cases:
Schemes for connecting an electric motor through a capacitor.
1) Connecting the electric motor through a capacitor in a delta pattern, starting without load:
The capacity of the working capacitor for connecting an electric motor with a “triangle” winding connection diagram is calculated by the formula:
CR=4800 * In/ UWith; mkf
Where: In- rated current of the electric motor in Amperes (taken in accordance with); UWith— network voltage in Volts.
In the circuit, a single-pole circuit breaker is used to turn on the electric motor, but its use is not necessary; you can turn on the electric motor directly to the network through an outlet using a regular plug or, for example, turn it on through a regular light switch.
2) Connecting the electric motor via a capacitor in a star configuration, starting without load:
The capacity of the working capacitor for connecting an electric motor with a star connection of the windings is calculated by the formula:
CR=2800 * In/ UWith; mkf
Where: In- rated current of the electric motor in Amperes (accepted in accordance with the passport data of the electric motor); UWith— network voltage in Volts.
If a 380 to 220 Volt engine starts under load, a starting capacitor must additionally be used in the circuit, otherwise the torque on the electric motor shaft will not be enough to spin it up and the engine will not be able to start.
The starting capacitor is connected in parallel with the working capacitor and should be turned on only when the engine starts; after the engine picks up speed it must be turned off.
Start capacitor capacity should be 2.5 - 3 times more than the worker.
CP= (2,5…3) * CR; mkf
With this scheme, to start the electric motor, you must press and hold the SB button, then apply voltage by turning on the circuit breaker; as soon as the engine starts, the SB button must be released. You can also use a regular switch as a button.
However, the best option for connecting a 380 to 220 electric motor is to use PNVS-10 (push-type starter with starting contact):
The “start” buttons in these starters have 2 contacts, one of them, when the “start” button is released, opens, turning off the starting capacitor, and the second remains closed and through it voltage is supplied to the electric motor through the working capacitor; the shutdown is performed by the “stop” button.
Reverse of an electric motor connected to 220 Volts through a capacitor.
So, from the diagrams above it follows that with any method of connecting the windings (star or delta), there are three points left in the motor terminal box for connecting it to the network, conditionally: zero is connected to the first terminal, phase is connected to the second, and phase is supplied to the third through a capacitor, but what to do if the engine starts to rotate in the wrong direction when starting? To change the direction of rotation of a motor connected through a capacitor, you simply need to switch the phase wire from one terminal of the electric motor to another, while leaving the neutral wire at the same terminal, i.e. conditionally: leave zero on the first terminal, apply the phase to the third, and apply the phase to the second through a capacitor.
