How does three-phase voltage differ from single-phase? Why there are two phases in the socket: we find out the reasons for the appearance and fix it ourselves The socket shows 2 phases

30.06.2023

Used at the beginning of the 20th century in electrical distribution networks alternating current. They used two circuits, the voltages in which were shifted in phase relative to each other by (90 electrical degrees). Typically, four lines were used in the circuits - two for each phase. Less commonly used was one common wire, which had a larger diameter than the other two wires. Some of the earliest two-phase generators had two full rotors with windings physically rotated 90 degrees.

The idea of using two-phase current to create torque was first proposed by Dominic Arago in 1827. The practical application was described by Nikola Tesla in his patents from 1888, around the same time he developed the design of a two-phase electric motor. These patents were then sold to the Westinghouse company, which began developing two-phase networks in the United States. Later, these networks were supplanted by three-phase networks, the theory of which was developed by the Russian engineer Mikhail Osipovich Dolivo-Dobrovolsky, who worked in Germany at the AEG company. However, due to the fact that Tesla's patents contained general ideas for the use of polyphase circuits, the Westinghouse company was able to hold back their development for some time through patent litigation.

The advantage of two-phase networks was that they allowed simple, soft starting of electric motors. In the early days of electrical engineering, these networks with two separate phases were easier to analyze and design. At that time, the method of symmetrical components had not yet been created (it was invented in 1918), which subsequently gave engineers convenient mathematical tools for analyzing asymmetrical load modes of multiphase electrical systems.

Scott transformer circuit

Two-phase circuits typically use two separate pairs of current-carrying conductors. Three conductors can be used, however, the vector sum of phase currents flows through the common wire, and therefore the common wire must have a larger diameter. In contrast, in three-phase networks with a symmetrical load, the vector sum of the phase currents is zero, and therefore in these networks it is possible to use three lines of the same diameter. For electrical distribution networks, the requirement of three conductor lines is better than the requirement of four, since this results in significant savings in the cost of conductor lines and in installation costs.

Two-phase voltage can be obtained by connecting single-phase transformers using the so-called Scott circuit. A symmetrical load in such a three-phase system is exactly equivalent to a symmetrical three-phase load.

In some countries (for example, Japan), the Scott scheme is used for nutrition railways electrified using a single-phase alternating current system of industrial frequency. In this case, only two phases alternate in the contact network, and not three. On double-track roads, tracks of different directions can each be powered throughout its entire length from its own phase of a two-phase network, which makes it possible to get rid of the alternation of phases along the train and the installation of neutral inserts (although this complicates the operation of stations). In Russia, such a system has not become widespread.

Two-phase electric current

A two-phase electric current is a combination of two single-phase currents shifted in phase relative to each other by an angle π 2 (\displaystyle (\frac (\pi )(2))), or 90°:

I 1 = I m sin ⁡ ω t (\displaystyle i_(1)=I_(m)\sin \omega t) ;

I 2 = I m sin ⁡ (ω t − π 2) (\displaystyle i_(2)=I_(m)\sin(\omega t-(\frac (\pi )(2)))) .

Φ 1 = Φ m sin ⁡ ω t (\displaystyle \Phi _(1)=\Phi _(m)\sin \omega t) ;

Φ 2 = Φ m sin ⁡ (ω t − π 2) (\displaystyle \Phi _(2)=\Phi _(m)\sin(\omega t-(\frac (\pi )(2)))) .

Two-phase electrical networks were used in the early 20th century in AC electrical distribution networks. They used two circuits, the voltages in which were shifted in phase relative to each other by 90 degrees. Typically, 4 lines were used in the circuits - two for each phase. Less commonly used was one common wire, which had a larger diameter than the other two wires. Some of the earliest two-phase generators had two full rotors with windings physically rotated 90 degrees.

The first ideas for using two-phase current to create torque were expressed by Dominic Arago in 1827. The practical application was described by Nikola Tesla in his patents from 1888, around the same time he developed the design of a corresponding electric motor. These patents were then sold to the Westinghouse company, which began developing two-phase networks in the United States. Later, these networks were supplanted by three-phase networks, the theory of which was developed by the Russian engineer Mikhail Osipovich Dolivo-Dobrovolsky, who worked in Germany at the AEG company. However, due to the fact that Tesla's patents contained general ideas for the use of polyphase circuits, the Westinghouse company was able to hold back their development for some time through patent litigation.

Electric current is especially dangerous for humans, and it is also invisible. When installing wiring, wires of different colors are used for safe and fast work; letters and numbers indicate the wire cross-section. Color and symbolic designations are prescribed in the standards; you should not violate them, so as not to endanger your own and others’ lives.

Color coding of core insulation

Visually, the wires differ from each other not only in color and diameter, but also in the number and type of cores. Depending on this characteristic, single-core and multi-core electrical wires are distinguished. Their variety finds its application in alternating current circuits, both in industrial three-phase networks with a voltage of 380V, and in a home single-phase network of 220V. DC power circuits use the same standard of electrical wiring.

Single-phase two-wire network 220V

This type of network includes an outdated type of wiring, where aluminum wires in a single white braid, popularly known as “noodles,” are used as cores. One core of the electrical wire is a phase conductor, the second core is a neutral conductor. A single-phase two-wire network is used for ordinary household needs: simple sockets and switches.

The problem when installing single-color wiring is that it is difficult to determine the phase and neutral wires. The presence of additional measuring equipment will help to cope with the task; you can use a multimeter or a special screwdriver with an indicator, a probe, a tester, or a “continuity tester”.

The design of a single-phase two-wire network is permitted by GOST for premises with a small load on the electrical network and low safety requirements. In such cases, two single-core wires or one two-core wire with wires of different colors are used.

When using a solid wire, one core is brown, the other blue or cyan. According to generally accepted markings, the brown conductor is a phase, and the blue conductor is a neutral conductor; it is strictly not recommended to violate this order. In practice, there are phase wires in colors other than brown: black, gray, red, turquoise, white, pink, orange, but not blue.

The use of two independent single-core wires also requires marking. You can use a wire colored along the entire length, for example, blue for zero, red for phase. It is permissible to mark wires of the same color with electrical tape or heat-shrinkable tubing of different colors, placing the marking on both ends of each wire.

The use of a tube does not involve wrapping the ends, but putting it on the wire and exposing it to hot air in order to fix the heat shrink on the wire. For home use, you can use any colors of marking materials that are accessible and understandable to the wiring installer.

Single-phase three-wire network 220V

Modern requirements for the installation of electrical wiring dictate the presence of a third wire - grounding. This is the difference and main advantage of a single-phase three-wire network.

Three electrical conductors perform the corresponding functions: phase, neutral and grounding, protection against injury from alternating current. The marking of the phase wire remains brown, the neutral wire remains blue or light blue, and the ground wire must be braided in a yellow-green color.

Household appliances that comply with European safety standards require connection to earthed sockets. Such sockets have a special contact to which a yellow-green wire is connected. It is strictly not recommended to use this color to mark phase and neutral wires in order to avoid possible unpleasant consequences.

Three-phase network 380V

A three-phase network, just like a single-phase one, can be with or without grounding. Depending on this, a three-phase four-wire electrical network with a voltage of 380V and a three-phase five-wire network are divided.

A four-wire network consists of three phase conductors and one neutral working conductor; there is no protective grounding conductor here. In a five-wire network, in addition to three phase conductors and one neutral, there is also a grounding conductor.

Similarly with two-phase marking of conductors, a blue or cyan conductor is used for the neutral conductor, yellow-green for the grounding conductor. Phase A is brown, phase B is black, phase C is marked gray. There may be exceptions to the rules for phase conductors; their color marking allows the use of other colors, but not blue and yellow-green, which already have their own function.

When distributing single-phase loads into groups or connecting three-phase loads, four-core and five-core wires are used.

DC network

Net direct current differs from an alternating current network in that it contains two conductors: plus and minus. The core of the positive conductor is marked in red, and the core of the negative conductor is marked in blue.

The practice of color separation of wires is familiar to professionals and amateurs; it is actively used in electrical engineering, but still you should not blindly trust the markings. Backing up with a measuring device is a thoughtful and balanced move when installing electrical networks; you should not neglect it.

If you are an electrician, we would appreciate your feedback on this article. Please write your comment below.

The average consumer encounters electricity in their daily lives.
light and plugging this or that device into an outlet. Switches
They differ little from each other, but with sockets everything is much more
more difficult. Let's try to figure out how the socket works.
Let's start with the one that was manufactured and installed years ago
10-15 ago. It is connected to only two wires. Insulation
one of the wires must have a bluish or
blue color. This is how the working neutral conductor is determined.
The current through it does not come from the source, but from the consumer. This
the wire is quite harmless, and if you grab it without touching
to the second, then nothing bad or terrible will happen.
And here is the second wire, the color of which can be any color, except
blue, light blue, yellow-green striped and black, more
dangerous and treacherous. It is called a phase conductor.
By touching this wire, you can get a nice
discharge. And this is no joke, since the AC voltage of the household network
current 220 V, and any current whose voltage is over 50 V,
kills a person in a few seconds. Presence of voltage on phase
conductors can be determined by special indicators.

Single-phase three-phase alternating current Many have heard such mysterious words as one phase, three
phase, neutral, grounding, or earth, and know that these are important concepts
in the world of electricity. However, not everyone understands what they mean.
However, it is necessary to know this. Without going into technical
details that are not needed home handyman, Can
say that a three-phase network is a method of transmitting electrical
current, when alternating current flows through three wires, and through
one returns back. The above needs some clarification.
Any electrical circuit consists of two wires. One by one
the current goes to the consumer (for example, to a kettle), and in another way -
comes back. If you open such a circuit, then the current flows
will not be. That's all the description of a single-phase circuit. The wire through which
current flows is called phase or simply phase, and along which
returns - null or null. The three-phase circuit consists
of three phase wires and one return. Is it possible
because the phase of the alternating current in each of the three wires is shifted
in relation to the adjacent wire by 120°. More
A textbook on electromechanics will help answer this question in detail.
The transmission of alternating current occurs precisely with the help of
three-phase networks. This is economically beneficial - no need yet
two neutral wires. Approaching the consumer, the current is divided into
three phases, and each of them is given a zero. In this form he usually
and gets into apartments and houses, although sometimes the three-phase network starts
straight to the house. As a rule, we are talking about the private sector, and such
the situation has its pros and cons.
A three-phase system consists of three sources
electricity and three circuits connected by common wires
transmission lines.
The energy source for all phases is a three-phase generator.
Sequence of connection of three-phase motors
as a load turns out to be essential for establishing
the direction of their rotation, then to ensure this unambiguity
The following color conventions are accepted:
phases: A - yellow insulation; B - green; C - red and neutral
- black.

Single phase three phase alternating current. When connecting with a star, in addition to equal voltage at the terminals
each of the phases (phase voltage between phase and common
wire - Uph), there is also voltage between different phases,
called linear voltage - Ul. Line voltage
in this case, √3 times more than the phase value.
If the current in all phases is the same (such a load
called symmetrical; an example would be a three-phase
motor), then there is no current in the neutral wire and this
no wire needed. But other connected loads are asymmetrical,
therefore, a neutral wire is necessary for them.

Slightly less common than star connection in three-phase networks
use a triangle connection. Source phase windings
electromotive force are connected so that the end
one connects to the beginning of the next, etc.
The advantage of connecting the phases with a triangle is that
that even with an asymmetrical load there is no need to use
fourth wire.
Note that the connection of loads in case of supply
voltage from the source using the triangle method can be produced
both triangle and star.

Sometimes an interesting fault occurs in electrical wiring that leaves the inexperienced electrician or amateur in a difficult situation. Such a malfunction is the occurrence second phase in the socket, which appears in the place of zero there, which makes you think a lot.

In fact, the same phase is present on both sockets of the socket, since in a single-phase electrical network The 220V alternating voltage is formed by one phase and one neutral conductor, and there cannot be a second phase there. But it is precisely this understanding that causes some bewilderment when a phase is detected in place of the standard zero.

If there really was a second phase in the socket, then the voltage between both phases would be 380V and all switched on household appliances would have to be taken to a repair shop.

A little theory.

Without going into technical details, we can say that a single-phase electrical network is a method of transmitting electric current when alternating current flows to the consumer (load) through one wire, and returns from the consumer through another wire.

Let's take for example closed an electrical circuit consisting of a source AC voltage, two wires and an incandescent lamp. From the voltage source to the lamp, current flows through one wire and, having passed through the filament of the lamp, making it hot, the current returns to the voltage source through another wire. So, the wire through which current flows to the lamp is called phase or simply phase (L), and the wire through which the current returns from the lamp is called zero or simply zero (N).

When, for example, a phase wire breaks, the circuit opens, the flow of current stops and the lamp goes out. In this case, the section of the phase wire from the voltage source to the break point will be under current or phase voltage(phase). The rest of the phase and neutral wires will be de-energized.

If the neutral wire breaks, the flow of current will also stop, but now the phase wire, both terminals of the lamp and part of the neutral wire extending from the lamp base to the break point will be under phase voltage.

You can use an indicator screwdriver to make sure there is a phase on both terminals of the lamp and on the neutral wire coming from the lamp. But if you measure the voltage on the same terminals and wire with a voltmeter, it will not show anything, since in this part of the circuit there is the same phase, which cannot be measured relative to itself.

Conclusion: There is no voltage between the same phase. There is voltage only between the neutral and phase wires.

Advice. To determine the presence of phase and voltage in the electrical network, it is necessary to use an indicator screwdriver and a voltmeter together. You can use it as a voltmeter.

Now let’s move on to practice and consider some situations with zero that you can independently determine and, if possible, eliminate without involving the utility service:

1. Zero break in the entrance panel of a house or apartment;
2. Zero break at the input or inside the junction box;
3. Short circuit of the neutral conductor to the phase conductor in case of mechanical damage to the insulation.

1. Zero break in the entrance panel of a house or apartment.

In the input panel of a house or apartment, the neutral wire may break at the input circuit breaker or at the neutral bus. As a rule, the screw connection becomes loose, causing contact between the wire and the clamp to be lost, or, in rare cases, the neutral wire breaks off at the clamp and hangs in the air.

Also, due to poor contact between the clamp and the wire, the wire heats up and burns and, as a result, a large transition resistance forms between them in the form soot, which gradually turns into a cliff.

If there is no zero, all electrical appliances in the house will not work. But if at least one household appliance remains plugged into the socket or the light switch remains on, the phase through radio components of the power supply household appliances or filament the lamp will pass unhindered to the zero bus, and from the bus to all neutral wires of the electrical wiring. And as a result, there will be a phase on both sockets of sockets and contacts of switches. This is because all the neutral wires of the electrical wiring are connected together at the neutral bus.

To determine such a malfunction, it is enough to unplug all household appliances from the sockets and turn off all light switches or unscrew the light bulbs. After these actions, the second phase from the sockets and switch contacts will disappear. The malfunction is treated by restoring the contacts on the terminals of the input circuit breaker or on the zero bus.

2. Zero break at the input or inside the distribution box.

If the neutral wire breaks in front of the distribution box or in the box itself, the problem with the neutral and the operation of electrical equipment will be precisely in the room of the house or apartment into which this box distributes voltage. At the same time, everything in the neighboring rooms will work as normal.

In the figure above you can see that in front of the left distribution box the neutral wire has broken, and the phase through the lamp filament (load) reaches the socket neutral.

When searching for such a fault, the problem box is opened and the common zero twist is found (it is the thickest in the box). The strands are cut off, re-cut and twisted together again.

Advice. If the wire is copper, then it is advisable to solder the twist.

When the zero breaks in front of the distribution box, as shown in the top figure, to find the break, you often have to open the groove with this wire in the wall to find the location of the damage.

When searching for such a fault, first they find a twist in the box with a common zero and unwind it into separate wires. Then each neutral conductor is called up to the sockets and to the ceiling. The core that will not ring will be the incoming wire into the box.

Next, this wire is pulled through and the plaster in the wall is opened to look for where the wire is damaged. However, such a malfunction is classified as difficult to solve, because few people undertake to pick at the wall - it’s easier to lay a new route.

3. Short circuit of the neutral conductor to the phase conductor in case of mechanical damage to the insulation.

A situation may arise when, when drilling a hole, screwing in a self-tapping screw, or hammering a nail into a wall, the electrical wiring is disrupted. In addition to this, damage to the wiring is accompanied by a short circuit, due to which the wire is damaged completely or partially. Such a malfunction is treated by opening the damage site and restoring the damaged section of the wire.

Sometimes with such a malfunction you can also observe two phases in the outlet.
At the moment of closure, the phase and neutral conductors are welded together, and therefore the phase freely flows onto the neutral conductor. Moreover, even when the electrical equipment is turned off from the sockets and the lighting switches are turned off, the phase will be present on those sockets and switches that are supplied with voltage from this wire.

The malfunction is treated by restoring the damaged section of the wiring.

If you still have questions, then in addition to the article, watch the video, which also covers the topic of zero loss.

In this article, we examined only the most common faults that occur in a single-phase electrical network when the neutral wire is damaged. Now if you have two phases will appear in the socket, You can easily identify and fix such a malfunction.
Good luck!

Today, every private house or apartment has alternating current. But the principles of operation of this man-made phenomenon are not obvious to every person. To answer the question of why there are two phases in a socket, there is no need to delve into the course of theoretical physics. There are enough clear examples of the operation of electrical appliances.

Names of wires in the circuit

Wires in electrical devices have the following special names:

Phase- carries electrical potential. It is this that poses a danger to human life in case of improper repair or handling of the outlet. The color of the conductor can be anything except blue (usually yellow);
Zero(worker) - painted blue or light blue. Used to equalize phase voltage;
Protective zero() - usually has a yellow-green color. Is inactive when the equipment is working properly. In the event of a short circuit, current begins to flow through those areas where there should not be voltage. The protection takes on this voltage and redirects it to the current source or to the ground. If repair work is being carried out at this moment, the electrician will remain alive and will only feel a small electric shock.

About 15 years ago, protective zero was practically not used. An outdated circuit in the form of only two wires can be found in Soviet electrical products that have survived to this day.

In this video, electrician Vasily Stulnev will show 2 ways to accurately determine the phase in an outlet:

Phase in the socket: left or right?

The idea that the electrical potential carrier in household connectors is located on the left is a fairly common misconception. Among the most frequent arguments given by adherents of this point of view:

This is evidenced by their personal life experience;
Such results are obtained by “ringing” power cords and switches built into electrical appliances;
The specifications of a number of gas boiler manufacturers allegedly indicate this;
Lovers of high-quality sound insist on connecting the plug to the connector with the “right” side, which ensures the purest sound.

But all these arguments have no relation to reality. For European sockets of the “Shuko” type, there is no difference in what position the wire is connected to them. Electrical connectors in our country and all European countries are not polarized. Only the connection standard CEE 7/5, which has a fairly narrow application, contains strict requirements for the order of connecting devices.

In rare cases, installers take for granted that the phase is on the right. But this is done solely for the convenience of measurements and to prevent confusion.

As a result, the phase in the socket may be both left and right, with equal probability.

How to determine the phase in a socket?

The position of the phase and neutral wires can be calculated both with and without the use of devices designed for this purpose. Not every person has the necessary equipment in their home, so the following tips will help:

The wire carrying current is black or gray in color. "Zero" and "ground" have blue and green colors respectively. Rely entirely for this color differentiation it is forbidden, since installers can neglect these rules without any special administrative consequences for themselves;
Craftsmen manage to use a simple light bulb as an indicator. For this purpose, three wires are screwed to the cartridge: a couple of them are connected to the connector, and one is grounded, tied to a cast iron heating radiator. The presence of a glow indicates the functionality of the wiring;
There are also extremely unusual methods when the wires are placed under running water or connected to a battery. Such experiments can end very badly, so highly not recommended for use.

Using special devices

Improvised methods do not always give reliable results, not to mention the danger of some of them to life. A much more reliable method is the use of measuring devices:

Indicator screwdriver. Inside its body there is a resistor connected to the light bulb. The presence of voltage is indicated by a light indication. This is the cheapest and most accessible method for a non-specialist: the device is commercially available and costs a little more than 30 rubles;
A regular one might work too. pocket tester. Before testing begins, the switch is set to AC mode. Only one probe is used (the second one can be left in your hand). If there is current, its value will be shown on the device screen;
Electrical installation safety data meter is a professional device that is designed to determine phase and phase-to-phase voltage, current strength and frequency, resistance, etc. Handling such a device requires special skills, so it is not recommended for non-specialists to purchase it.

Fault: double phase

If the connector is working normally, then when the indicator touches the current carrier in the socket, the light bulb lights up, but when you touch the “zero”, it does not. If there is a light indication in both cases, this indicates presence of phase voltage in both slots.

The reasons for such a malfunction can be varied:

During repairs or re-equipment of a residential premises, the “zero” wire was accidentally broken. In this case, you need to turn off the power to the entire house and remove the plaster in the suspected area of damage. Having discovered the location of the damage, you need to connect the parts of the “zero” and ground them. It is necessary to apply a new layer of plaster only after a detailed check of the system operation;
Problems with the distribution box. When you remove the cover, burnt wiring will be visible. To eliminate the fault, a new connection is created and insulation is made;
In rare cases, the root of the problem is in the power shield. Only qualified specialists have access to it. The electrician detects contacts and connections for faults and repairs them.

In AC networks, the direction of electron movement continuously changes. The specificity of the operation of networks with variable polarization explains the fact why there are two phases in the socket. One of them carries a stream of charged particles, the other is “empty”, but necessary for work. Modern networks require a third wire to ensure voltage safety.

How can there be two phases in an outlet? (video)

In this video, electrician Arkady Borisov will tell you whether there can be two phases in an outlet at the same time, what this could mean:

A three-phase connection makes it possible to switch on high-power generators and electric motors, as well as the ability to work with different voltage parameters, this depends on the type of load connected to the electrical circuit. To work in three-phase network one must understand the relationship of its elements.

Three-phase network elements

The main elements of a three-phase network are a generator, an electrical energy transmission line, and a load (consumer). To consider the question of what linear and phase voltage is in a circuit, we will give a definition of what a phase is.

A phase is an electrical circuit in a system of multiphase electrical circuits. The beginning of the phase is the terminal or end of the electrical conductor through which the electric current enters it. Experts always differed in the number of phases electrical circuits: single-phase, two-phase, three-phase and multi-phase.

The most commonly used is three-phase connection of objects, which has a significant advantage over both multiphase circuits and single-phase circuits. The differences are as follows:

lower costs for transporting electrical energy;
the ability to create an EMF for the operation of asynchronous motors - this is the operation of elevators in multi-storey buildings, equipment in the office and in production;
This type of connection makes it possible to simultaneously use both linear and phase voltage.

What is phase and line voltage?

Phase and line voltages in three-phase circuits are important for manipulations in electrical power panels, as well as for the operation of equipment powered by 380 volts, namely:

What is phase voltage? This is the voltage that is determined between the beginning of a phase and its end; in practice, it is determined between the neutral wire and the phase.
Line voltage is when the value is measured between two phases, between the terminals of different phases.

In practice, the phase voltage differs from the linear voltage by 60%, in other words, the parameters of the linear voltage are 1.73 times greater than the phase voltage. Three-phase circuits can have a line voltage of 380 volts, which makes it possible to obtain a phase voltage of 220 V.

What is the difference?

For society, the concept of “phase-to-phase voltage” is found in apartment buildings, high-rise buildings, when the first floors are provided for office space, as well as in shopping centers, when building objects are connected by several power cables three-phase network, which provide a voltage of 380 Volts. This type of connection at home ensures the operation of asynchronous lift motors, the operation of escalators, and industrial refrigeration equipment.

In practice, wiring a three-phase circuit is quite simple, given that a phase and a neutral wire go to the apartment, and all three phases + a neutral wire go to the office space.

The difficulties of a linear connection diagram lie in the difficulty of identifying the conductor during installation, which can lead to equipment failure. The circuit differs mainly between phase and linear connections, connections of load windings and power supply.

Connection diagrams

There are two schemes for connecting voltage sources (generators) to the network:

"triangle";
"star".

When a star connection is made, the beginning of the generator windings are connected at one point. It does not provide the ability to increase power. A delta connection is when the windings are connected in series, namely, the beginning of the winding of one phase is connected to the end of the winding of the other. This gives the ability to triple the voltage.

For a better understanding of connection diagrams, experts define what phase and line currents are:

line current is the current that flows in the connection between the source of electrical energy and the receiver (load);

phase current is the current flowing in each winding of an electrical energy source or in the load windings.

Linear and phase currents are important when there is an asymmetrical load on the source (generator), this often occurs in the process of connecting objects to the power supply. All parameters related to the line are linear voltages and currents, and those related to the phase are parameters of phase quantities.

From the star connection it is clear that linear currents have the same parameters as phase currents. When the system is symmetrical, there is no need for a neutral wire; in practice, it maintains source symmetry when the load is unsymmetrical.

Due to the asymmetry of the connected load (and in practice this happens with the inclusion of lighting devices in the circuit), it is necessary to ensure independent operation of the three phases of the circuit; this can also be done in a three-wire line, when the phases of the receiver are connected in a triangle.

Experts pay attention to the fact that when the line voltage decreases, the phase voltage parameters change. Knowing the value of the phase-to-phase voltage, you can easily determine the value of the phase voltage.

How to calculate line voltage?

and Ohm's law:

When an extensive system of supplying an object with electricity is being implemented, sometimes there is a need to calculate the voltage between two wires “zero” and “phase”: IF = IL, which indicates that the phase and linear parameters are equal. The relationship between phase wires and linear ones can be found using the formula:

Finding the element of voltage relationships and assessing the power supply system by specialists is performed using linear parameters when their value is known. Four-wire power supply systems are marked 380/220 volts.

Conclusion

Using the capabilities of a three-phase circuit (four-wire circuit), connections can be made in different ways, which makes it possible for its wide application. Experts consider three-phase voltage for connection to be a universal option, since it makes it possible to connect high-power loads, residential premises, and office buildings.

In apartment buildings, the main consumers are household appliances designed for a 220 V network; for this reason, it is important to distribute the load evenly between the phases of the circuit; this is achieved by connecting apartments to the network according to the checkerboard principle. The distribution of the load of private houses differs; in them it is carried out according to the load values on each phase of all household equipment, and the currents in the conductors passing during the period of maximum switching on of the devices.

The menstrual cycle consists of three parts, each of which performs a specific function. In the first phase, the egg matures and the body prepares for possible conception. The second phase is responsible for ovulation and the process of fertilization of the egg released from the follicle. The final stage is the luteal phase. It is characterized by an increase in progesterone levels. Phase 2 of the menstrual cycle is the most important during pregnancy planning.

Main phases of the cycle

The female reproductive system carries out its work according to a certain algorithm. It is customary to distinguish 2 phases of the cycle, but there is also a third – ovulatory. It is fundamental and is characterized by cyclicity between two periods of the menstrual cycle. Every woman of reproductive age should know what the second phase is and what nuances it contains.

The follicular phase of the cycle is the preparatory period of the body for ovulation. Under the influence of estrogen, the follicles and endometrium increase during this period. Closer to ovulation, the dominant follicle begins to be visualized. Symptoms during this period are not particularly pronounced. Vaginal discharge is clear and liquid. There may be some tenderness in the abdomen.
Ovulation is the peak of a woman's fertility. With an average 28-day cycle, it occurs on days 14-15. During this period, the egg leaves the follicle and waits to meet the sperm. How long the second phase lasts after ovulation depends on the individual characteristics of the body. The success of conception is influenced not only by the quality of the egg, but also by the patency of the fallopian tubes, as well as the thickness of the endometrium.
The luteal phase begins after ovulation. At the site of the burst follicle, a corpus luteum is formed, producing progesterone. Under its influence, the endometrium prepares for embryo implantation. If it does not occur, progesterone levels drop sharply, causing the onset of menstruation. Progesterone peaks on day 22. Then it gradually decreases.

Second phase of the menstrual cycle

The second phase of the cycle is responsible for a woman’s reproductive health. It is during this period that a woman can become pregnant. Ovulation is absent in pregnant and lactating women, as well as in adolescence and during menopause. Normally, ovulation occurs up to 10 times a year. Two menstrual cycles during this period may be anovulatory. In order for ovulation to occur, a balance of the hormones LH and FSH is necessary. They are produced by the pituitary gland.

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It is generally accepted that the presence of menstruation is a guarantee of proper ovulation. Actually this is not true. Your period can come regardless of whether ovulation has occurred or not. Special tests that respond to an increase in LH levels in the urine help confirm its presence. But ultrasound monitoring is considered a more reliable way to determine ovulation. With its help, you can monitor the growth of the egg and catch the exact day of its release on abdominal cavity. This method is carried out for diagnostic purposes and to increase the chances of conception when planning a pregnancy.

How long do the cycle phases last?

Every woman has a different length of her menstrual cycle. It depends on hormone levels, heredity and lifestyle. The duration of the first stage of the cycle varies from 7 to 14 days. With hormonal disorders, there may be significant deviations from the norm.

It is impossible to determine how many days the second phase of the cycle lasts. Accurate data can only be obtained in laboratory conditions. On average, this figure ranges from several hours to 3 days. The degree of fertility of a woman depends on how long the second phase of the cycle lasts.

The luteal period, regardless of the length of the menstrual cycle, always lasts two weeks. This information allows you to make a forecast of a woman’s fertility based on the analysis of several cycles. To find out the day of ovulation, subtract 14 days from the duration of menstruation. The resulting number shows the day of the cycle on which the egg was released from the follicle capsule.

What happens during the second phase

The second phase of the menstrual cycle is the most favorable time for sexual intercourse when planning pregnancy. During this period, the woman begins to notice changes occurring in her body. They are expressed as follows:

throbbing pain in one or both ovaries;
liquid discharge resembling the consistency of egg white;
increased sexual desire;
sudden mood swings;
slight breast enlargement.

The described symptoms occur as a result of a sharp increase in hormones. Some women do not notice any significant changes during this period. It all depends on the individual characteristics of the body.

The number of days of the second phase of the menstrual cycle is no more than three. If during this period the sperm does not have time to penetrate the egg, then it dies. At the end of the final stage, the egg leaves the uterine cavity along with menstrual blood and the basal layer of the endometrium.

Disorders of the second phase of the cycle

The second phase determines the further functioning of the reproductive system. If ovulation does not take place for some reason, disturbances in the third phase occur. This affects the regularity of the menstrual cycle and the woman’s well-being. The reasons for violations may be the following:

stressful situations;
hormonal abnormalities;
small ovarian reserve;
mechanical damage to the pituitary gland;
poor nutrition;
endocrine diseases;
thickened lining of the ovaries.

The main stage of phase 2 of the cycle is the rupture of the follicle walls. If this does not happen, then the egg does not leave its boundaries. It regresses or turns into a cyst. In the first case, the woman may not be aware of the pathology, since the regularity of menstruation remains the same. With cystic formations, menstruation is delayed because progesterone does not decrease at the right time.

Short luteal phase

The normal duration of the luteal phase is two weeks. If it is shorter than 10 days, then we are talking about pathology. A short luteal phase leads to infertility. In this case, the functioning of the corpus luteum stops prematurely. This makes the implantation process impossible.

Possible causes of pathology include infectious diseases, serious injuries, chronic inflammatory processes and disruption of the thyroid gland. To lengthen the duration of the luteal period, women are prescribed hormonal medications.

It is not difficult to determine the deviation. To do this, you should pay attention to how many days the cycle lasts. If its duration is less than 28 days, then you need to consult a gynecologist for advice. To confirm the diagnosis, ultrasound monitoring is performed on different days of the cycle. Blood is also donated for hormones.

Long luteal phase

The second phase of the menstrual cycle can also provoke an increase in the duration of the luteal phase. This promotes hormonal changes, which affects a woman’s weight, her well-being and the functioning of her internal organs. Pathology often occurs against the background of increased insulin. It causes increased cravings for sweet foods.

Prolongation of the secretory stage indicates the development of a benign tumor or cyst. It provokes a delay in menstruation, preventing progesterone from decreasing to required sizes. If the cause of the pathology lies in a follicular cyst, then the woman is prescribed special medications. The cyst resolves and menstruation begins.

If the problem lies in tumors that not only do not disappear, but also increase over time, then surgical help may be required. For small formations, laparoscopy is performed. It is characterized by a quick recovery period and ease of implementation. During the operation, punctures are made in the peritoneum through which medical instruments are inserted. Abdominal surgery is performed when the tumor reaches too large a size.

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