How to reduce constant voltage to a certain level. How to reduce DC and AC voltage - an overview of methods

Content:

High and increased voltage. Causes

How our electrical networks may experience high or increased voltage? As a rule, low-quality electrical networks or network failures can lead to increased voltage. Disadvantages of networks include: outdated networks, low-quality network maintenance, high percentage of depreciation of electrical equipment, ineffective planning of transmission lines and distribution stations, uncontrolled growth in the number of consumers. This results in hundreds of thousands of consumers receiving high or increased voltage. The voltage value in such networks can reach 260, 280, 300 and even 380 Volts.

One of the reasons for the increased voltage, oddly enough, may be the reduced voltage of consumers located far from the transformer substation. In this case, electricians often deliberately increase the output voltage of the electrical substation in order to achieve satisfactory current levels for the last consumers in the transmission line. As a result, the first ones in the line will have increased voltage. For the same reason, one can observe increased tension in holiday villages. Here, changes in current parameters are associated with seasonality and frequency of current consumption. In the summer we see an increase in electricity consumption. During this season, there are many people at their dachas, they use a large amount of energy, and in winter, current consumption drops sharply. On weekends, consumption in summer cottages increases, and on weekdays it decreases. As a result, we have a picture of uneven energy consumption. In this case, if you set the output voltage at the substation (and they are usually of insufficient power) to normal (220 Volts), then in the summer and on weekends the voltage will drop sharply and will be reduced. Therefore, electricians initially set the transformer to higher voltage. As a result, in winter and on weekdays the voltage in the villages is high or increased.

The second large group of reasons for the appearance of high voltage is phase imbalances when connecting consumers. It often happens that connecting consumers occurs chaotically without a preliminary plan and project. Or during the implementation of a project or development of settlements, the consumption value changes at different phases of the transmission line. This can lead to the voltage being low on one phase and high on the other phase.

The third group of reasons for increased voltage in the network are accidents on power lines and internal lines. Here we should highlight two main reasons - a break in the zero and the entry of high voltage current into ordinary networks. The second case is rare; it happens in cities during strong winds or hurricanes. It happens that the power line of an electric transport (tram or trolleybus) ends up on a city network line when it breaks. In this case, both 300 and 400 Volts can enter the network.

Now let’s look at what happens when a “zero” disappears into internal home networks. This case happens quite often. If two phases are used in one entrance of a house, then when zero is lost (for example, there is no contact at zero), the voltage value changes on different phases. In the phase where the load in the apartments is now less, the voltage will be overestimated, in the second phase - underestimated. Moreover, the voltage is distributed inversely proportional to the load. So, if on one phase the load at this moment is 10 times greater than on the other, then we can get 30 Volts (low voltage) in the first phase, and 300 Volts (high voltage) in the second phase. Which will lead to burning of electrical appliances and possibly a fire.

Why is high and increased voltage dangerous?

High voltage is dangerous for electrical appliances. A significant increase in voltage can lead to burnout of devices, overheating, and additional wear. Electronic equipment and electromechanical devices are especially critical to high voltage.

Hello friends and blog guests. The color of a cat crossing the road can tell about upcoming events, so experts recommend not ignoring such signs of fate.

Thanks to the observation skills of our ancestors, in the modern world we can easily look into the future in order to prepare for various events and not miss out on our benefits.

Ginger cat

According to legend, a cat of a bright red color running in front of a walking person promises him pleasant events in the near future. Driving away a cat means troubles and turmoil in your personal life.

Another sign says that a red cat is a harbinger of a festive event. For young girls, such a sign may indicate a wedding celebration or meeting a future husband. The sign also promises the end of difficulties and material benefits.

A ginger cat that tries to slip in front of a vehicle, on the contrary, promises big trouble.

Ginger cats attract love. Red cats are recommended for women who want to find a soul mate or get married.

But in order for the energy of a red cat to really work, it is not recommended to keep other animals of the same color in the house, as well as black pets.

It is not recommended to have red cats if you have red hair. In general, people who want to find love will turn their luck away if they get a pet of the opposite sex and with a color similar to the color of their hair.

Gray cat

A gray cat darting in front of your feet promises the end of difficulties associated with your financial situation.

A gray cat crossed the road - wait for lucrative offers.

If a car hits or hits a gray cat, there will be trouble. This sign indicates robbery, problems with finances and health. You can cancel the effect of such a sign by adopting a kitten or donating a certain amount to animal shelters.

Gray cats will be useful to those people in whose lives there are many difficulties, dangers and ill-wishers. A gray pet will divert negativity from the owner and make him inaccessible to dark forces and envy.

Gray cats are also an excellent amulet against damage, the evil eye, love spells and other magical influences. They protect the owner from anything that could harm him.

White cat

According to popular belief, a white cat promises good luck, which means that if it crosses the road, difficulties will soon end.

A white cat indicates a quick pleasant acquaintance, which can be associated with both personal life and a business partnership.

The sign says that if a white cat runs across the road, you can make a wish, and it will definitely come true.

Another sign indicates that a person is being looked after by his guardian angel.

At night, a white cat darting across your path promises trouble. In this case, you should turn off the route and go around the dangerous place.

White cats have always been considered healers. In addition to their medicinal properties, they can attract helpful and kind people to their owner.

White cats subtly sense everyone who enters the house, and in case of energetic danger, they neutralize the negative energy of the unkind guest.

White cats with eyes of different colors are considered special mascots. Their energy is very strong, they attract luck and happy circumstances to their owners. But not everyone is recommended to have them.

Such cats will bring good only to organized and practical people. They will enhance all the positive qualities of the owner’s character, which will help him achieve great success in his career, love and finances.

Black cat

According to legend, a cat running from right to left promises the end of the black streak. Also, such a sign indicates the impossibility of tricks on the part of ill-wishers.

A black cat crossing the path from left to right promises trials and minor troubles.

A black cat throwing itself at your feet warns of danger and that trouble awaits along the way. In this case, a person should choose a different path.

A cat crossing the road at an intersection indicates that you will soon have to sacrifice something for the sake of a prosperous life.

For some reason, in many countries black cats are considered a symbol of failure and misfortune, but in fact this is not the case. Cats and cats of black color attract money to the house. They have a positive effect on business affairs.

There is such a sign that if you let a black cat walk its paws over important documents and contracts, the business meeting will be successful and the business will go uphill. Black cats also bring good luck to those who trade. For such people, black cats are a real magnet for money.

Even though black cats bring good luck, some people should still be wary of them. Those who are unlucky in life should not get a black cat, as it will attract even more problems and misfortunes.

And in general, those who believe in the superstition about black cats should not have such a pet. But lucky people just need to get a cat of this color, then their luck will increase several times.

Multicolored cat

A motley animal running across the street indicates a happy occasion. Usually, after such a sign, luck follows a person for a whole week.

A tricolor cat promises childless couples a quick replenishment, and families with children - good news about their offspring. For unmarried people, such a sign indicates an early meeting with your soulmate.

A tricolor cat, according to superstition, is capable of removing evil eyes and damage, so if it has crossed the road, you should check yourself for the presence of negativity.

The tricolor cat is considered a universal mascot. It can be started by everyone without exception. She will attract prosperity, money, love, luck and health to the house.

Cold smoking of fish and meat products is a troublesome task. In the room where these products are smoked, the temperature should be maintained at no higher than 25°C and constant smoking for about seven days.

A technological process using an electric field is now known, which reduces this work to several hours.

The installation consists of a casing 1 made of galvanized iron. One side of the box is door 2, mounted on hinges. Behind it (in the vertical part of the box) there are 3 hangers. They are scraps of steel (preferably stainless) wire Ø3-4 mm. The hangers are installed in insulating sleeves 4.

A high-voltage (be careful, high voltage) wire from the scanner unit (BR) of the old TV is connected to each hanger. In addition to the BR, you must have a power supply from the same TV.

The negative wire (housing) is connected to the box. A motor 5 with a power of 300-500 W is installed at the lower bell. A cast iron disk 6 Ø80-100 mm and 20-30 mm thick is fixed to the motor axis. An alder block 7 is pressed against the cast iron disk by a powerful spring.

Having hung salted dry fish (meat products) on hangers, turn on the motor and reamer unit. After a few hours (from 1.5 to 6 hours depending on the size of the smoked product), smoking ends.

Read like in a city apartment.

Hello everyone. Today we’ll talk about the well-known sweet, indispensable in cooking and medicinal product, Honey.

There are countless varieties of honey in the world: apple, eucalyptus, pumpkin, tulip, rowan, dandelion, carrot, mint, burdock, chestnut, cornflower. Information about the most useful varieties of honey is in this article.

Lime: antibacterial, anti-inflammatory and expectorant effect. Useful in the treatment of sore throat, runny nose, laryngitis, bronchitis, asthma, inflammation of the gastrointestinal tract, kidney disease, and biliary diseases. Strengthens the heart.

Buckwheat: antibacterial effect. Take for diseases of the respiratory tract and lungs, nervous disorders, atherosclerosis. Strong antioxidant. Prevents anemia, improves vision and memory.

Acacia: antimicrobial action. General strengthening agent. Helps with insomnia, gastrointestinal and kidney diseases. In diluted form, aqueous solutions and ointments for the treatment of eyes and eczema.

Donnikovy: antispasmodic and anti-inflammatory effect. For respiratory diseases, varicose veins, insomnia, high blood pressure, neuroses, headaches. For lactation in nursing mothers.

Chestnut: antimicrobial, bactericidal, antiseptic effect. Use in the treatment of respiratory diseases, sore throat, asthma, prostatitis, nephritis, cystitis, neuroses, insomnia. Increases appetite, stimulates liver function.

Lugovoy: antibacterial, anti-inflammatory, analgesic effect. For kidney diseases. Natural immunostimulant and energy booster. Normalizes metabolism, accelerates metabolism.

Fruit: antimicrobial, dietary effect. To improve blood composition, enhance immunity.

Mountain: tonic, antimicrobial and antibacterial effect. In the treatment of diseases of the gastrointestinal tract and liver. dizziness, shortness of breath, atherosclerosis, insomnia. An excellent sedative.

Storage conditions:

1 . If the conditions are met, honey can be stored for 2-3 years. In a small glass jar with a capacity of 0.5 liters.

2 . In a dark place. Ideally in a dark glass jar.

3 . At temperatures from +5 to +10 degrees.

4 . In places without strong odors (fish, spices).

Natural honey:

Consistency -liquid honey stretches as a thin, uniform “thread” and is laid in layers. Candied honey is soft, plastic, oily, and does not stick to the spoon.

Smell and taste -fragrant, fragrant honey completely dissolves in the mouth, causing a slight burning sensation in the throat.

Impurities -may contain impurities such as pollen, wax particles, propolis.

Weight -one liter weighs more than 1.4 kg.

Fake:

Consistency -the stream is intermittent, honey drips from the spoon. Crystallization of candied honey is rough, uneven, forms lumps, and sticks to the spoon.

Smell and taste -smells of burnt sugar, has a candy, confectionery taste.

Impurities -does not contain impurities.

Weight -one liter weighs less than 1.4 kg.

How to check honey:

1 . Bring a lit match to the honey. High-quality honey will not melt and sizzle immediately.

2 . When diluted with water, natural honey does not form sediment. If you add 2 drops of iodine to the solution, it does not turn blue.

3 . Apply honey to paper. If wet spots form around, the honey is diluted.

4 . Dip a piece of stale bread into honey. After 8-10 minutes the bread should remain just as firm and not soften.

I really hope that the information will be useful when purchasing and consuming an irreplaceable and healthy product - Honey!!!. All the best to everyone.

You need to know how to reduce the voltage in a circuit so as not to damage electrical appliances. Everyone knows that two wires come to houses - zero and phase. This is called single-phase and is extremely rarely used in the private sector and apartment buildings. There is simply no need for it, since all household appliances are powered from a single-phase alternating current network. But in the technology itself it is necessary to make transformations - lower the alternating voltage, convert it to constant, change the amplitude and other characteristics. These are the points that need to be considered.

Voltage reduction using transformers

The easiest way is to use a reduced voltage transformer that does the conversion. The primary winding contains more turns than the secondary winding. If there is a need to reduce the voltage by half or three times, the secondary winding may not be used. The primary winding of the transformer is used as an inductive divider (if there are taps from it). In household appliances, transformers are used, from the secondary windings of which voltage of 5, 12 or 24 Volts is removed.

These are the most commonly used values ​​in modern home appliances. 20-30 years ago, most equipment was powered by a voltage of 9 Volts. And tube TVs and amplifiers required a constant voltage of 150-250 V and an alternating voltage of 6.3 for filaments (some lamps were powered by 12.6 V). Therefore, the secondary winding of the transformers contained the same number of turns as the primary. In modern technology, inverter power supplies are increasingly used (as in computer power supplies); their design includes a step-up transformer, which has very small dimensions.

Voltage divider across inductors

An inductor is a coil wound with (usually) copper wire on a metal or ferromagnetic core. A transformer is a type of inductance. If you make a tap from the middle of the primary winding, then there will be equal voltage between it and the outer terminals. And it will be equal to half the supply voltage. But this is the case if the transformer itself is designed to work with exactly this supply voltage.

But you can use several coils (for example, you can take two), connect them in series and connect them to the AC network. Knowing the values ​​of inductances, it is easy to calculate the drop on each of them:

1. U(L1) = U1 * (L1 / (L1 + L2)).
2. U(L2) = U1 * (L2 / (L1 + L2)).

In these formulas, L1 and L2 are the inductances of the first and second coils, U1 is the supply voltage in Volts, U(L1) and U(L2) are the voltage drop across the first and second inductances, respectively. The circuit of such a divider is widely used in circuits of measuring devices.

Divider on capacitors

A very popular circuit used to reduce the value of the AC supply network. It cannot be used in DC circuits, since, according to Kirchhoff’s theorem, a capacitor in a DC circuit is a break. In other words, no current will flow through it. But when operating in an alternating current circuit, the capacitor has reactance, which is capable of extinguishing the voltage. The divider circuit is similar to the one described above, but capacitors are used instead of inductors. The calculation is made using the following formulas:

1. Capacitor reactance: X(C) = 1 / (2 * 3.14 *f * C).
2. Voltage drop across C1: U(C1) = (C2 * U) / (C1 + C2).
3. Voltage drop across C2: U(C1) = (C1 * U) / (C1 + C2).

Here C1 and C2 are the capacitances of the capacitors, U is the voltage in the supply network, f is the current frequency.

Resistor divider

The circuit is in many ways similar to the previous ones, but fixed resistors are used. The method for calculating such a divisor is slightly different from those given above. The circuit can be used in both AC and DC circuits. We can say that it is universal. With its help you can assemble a step-down voltage converter. The drop across each resistor is calculated using the following formulas:

1. U(R1) = (R1 * U) / (R1 + R2).
2. U(R2) = (R2 * U) / (R1 + R2).

One nuance should be noted: the value of the load resistance should be 1-2 orders of magnitude less than that of sharing resistors. Otherwise, the accuracy of the calculation will be very rough.

Practical power supply circuit: transformer

To select a supply transformer, you will need to know several basic data:

1. Power of consumers that need to be connected.
2. Supply voltage value.
3. The value of the required voltage in the secondary winding.

S = 1.2 *√P1.

And power P1 = P2 / efficiency. The transformer efficiency will never be more than 0.8 (or 80%). Therefore, when calculating, the maximum value is taken - 0.8.

Power in the secondary winding:

P2 = U2 * I2.

This data is known by default, so the calculation is not difficult. Here's how to step down the voltage to 12 volts using a transformer. But that’s not all: household appliances are powered by direct current, and the output of the secondary winding is alternating current. A few more changes will need to be made.

Power supply diagram: rectifier and filter

Next comes the conversion of alternating current to direct current. For this, semiconductor diodes or assemblies are used. The simplest type of rectifier consists of a single diode. It's called half-wave. But the most widespread is the bridge circuit, which allows not only to rectify alternating current, but also to get rid of ripple as much as possible. But such a converter circuit is still incomplete, since semiconductor diodes alone cannot get rid of the variable component. And step-down transformers are capable of converting alternating voltage into the same frequency, but with a lower value.

Electrolytic capacitors are used in power supplies as filters. According to Kirchhoff's theorem, such a capacitor in an alternating current circuit is a conductor, and when working with direct current, it is a discontinuity. Therefore, the constant component will flow unhindered, but the variable will close on itself, and therefore will not pass beyond this filter. Simplicity and reliability are exactly what characterize such filters. Resistances and inductances can also be used to smooth out ripples. Similar designs are used even in car generators.

Voltage stabilization

You have learned how to reduce the voltage to the desired level. Now it needs to be stabilized. For this purpose, special devices are used - zener diodes, which are made of semiconductor components. They are installed at the output of the DC power supply. The principle of operation is that a semiconductor is able to pass a certain voltage, the excess is converted into heat and released through a radiator into the atmosphere. In other words, if the output of the power supply is 15 volts, and a 12 V stabilizer is installed, then it will pass exactly as much as needed. And the difference of 3 V will be used to heat the element (the law of conservation of energy applies).

Conclusion

A completely different design is a step-down voltage stabilizer; it makes several transformations. First, the mains voltage is converted to DC at a high frequency (up to 50,000 Hz). It is stabilized and fed to a pulse transformer. Next, a reverse conversion occurs to the operating voltage (mains voltage or a lower value). Thanks to the use of electronic switches (thyristors), direct voltage is converted into alternating voltage with the required frequency (in the networks of our country - 50 Hz).

Voltage and current are two basic quantities in electricity. In addition to them, a number of other quantities are also distinguished: charge, magnetic field strength, electric field strength, magnetic induction and others. In everyday work, a practicing electrician or electronics engineer most often has to operate with voltage and current - Volts and Amperes. In this article we will talk specifically about tension, what it is and how to work with it.

Determination of a physical quantity

Voltage is the potential difference between two points and characterizes the work done by the electric field to transfer charge from the first point to the second. Voltage is measured in Volts. This means that tension can only be present between two points in space. Therefore, it is impossible to measure voltage at one point.

Potential is denoted by the letter "F", and voltage by the letter "U". If expressed in terms of potential difference, the voltage is equal to:

If expressed in terms of work, then:

where A is work, q is charge.

Voltage measurement

Voltage is measured using a voltmeter. The voltmeter probes are connected to two voltage points between which we are interested, or to the terminals of a part whose voltage drop we want to measure. Moreover, any connection to the circuit can affect its operation. This means that when you add a load in parallel to an element, the current in the circuit changes and the voltage on the element changes according to Ohm’s law.

Conclusion:

The voltmeter must have the highest possible input resistance so that when it is connected, the final resistance in the measured area remains practically unchanged. The resistance of the voltmeter should tend to infinity, and the higher it is, the greater the reliability of the readings.

The measurement accuracy (accuracy class) is influenced by a number of parameters. For pointer instruments, this includes the accuracy of calibration of the measuring scale, the design features of the pointer suspension, the quality and integrity of the electromagnetic coil, the condition of the return springs, the accuracy of shunt selection, etc.

For digital devices - mainly the accuracy of the selection of resistors in the measuring voltage divider, the ADC capacity (the larger, the more accurate), the quality of the measuring probes.

To measure DC voltage using a digital device (for example,), as a rule, it does not matter whether the probes are connected correctly to the circuit being measured. If you connect a positive probe to a point with a more negative potential than the point to which the negative probe is connected, a “-” sign will appear on the display in front of the measurement result.

But if you measure with a pointer instrument, you need to be careful. If the probes are connected incorrectly, the arrow will begin to deviate towards zero and will hit the limiter. When measuring voltages close to the measurement limit or more, it may jam or bend, after which there is no need to talk about the accuracy and further operation of this device.

For most measurements in everyday life and in electronics at the amateur level, a voltmeter built into multimeters such as DT-830 and the like is sufficient.

The larger the measured values, the lower the accuracy requirements, because if you measure fractions of a volt and have an error of 0.1V, this will significantly distort the picture, and if you measure hundreds or thousands of volts, then an error of 5 volts will not play a significant role.

What to do if the voltage is not suitable for powering the load

To power each specific device or apparatus, you need to supply a voltage of a certain value, but it happens that the power source you have is not suitable and produces a low or too high voltage. This problem is solved in different ways, depending on the required power, voltage and current.

How to reduce voltage with resistance?

The resistance limits the current and as it flows, the voltage across the resistance (current-limiting resistor) drops. This method allows you to lower the voltage to power low-power devices with consumption currents of tens, maximum hundreds of milliamps.

An example of such power supply is the inclusion of an LED in a DC network 12 (for example, the on-board network of a car up to 14.7 Volts). Then, if the LED is designed to be powered from 3.3 V, with a current of 20 mA, you need a resistor R:

R=(14.7-3.3)/0.02)= 570 Ohm

But resistors differ in maximum power dissipation:

P=(14.7-3.3)*0.02=0.228 W

The closest higher value is a 0.25 W resistor.

It is the dissipated power that imposes a limitation on this method of power supply; it usually does not exceed 5-10 W. It turns out that if you need to extinguish a large voltage or power a more powerful load in this way, you will have to install several resistors because The power of one is not enough and it can be distributed among several.

The method of reducing voltage with a resistor works in both DC and AC circuits.

The disadvantage is that the output voltage is not stabilized in any way and as the current increases and decreases, it changes in proportion to the resistor value.

How to reduce AC voltage with a choke or capacitor?

If we are talking only about alternating current, then reactance can be used. Reactance exists only in alternating current circuits; this is due to the peculiarities of energy storage in capacitors and inductors and the laws of switching.

The inductor and capacitor in alternating current can be used as a ballast resistor.

The reactance of the inductor (and any inductive element) depends on the frequency of the alternating current (for a household electrical network 50 Hz) and inductance, it is calculated by the formula:

where ω is the angular frequency in rad/s, L is the inductance, 2pi is necessary to convert the angular frequency to normal, f is the voltage frequency in Hz.

The reactance of a capacitor depends on its capacitance (the lower C, the greater the resistance) and the frequency of the current in the circuit (the higher the frequency, the lower the resistance). It can be calculated like this:

An example of the use of inductive reactance is the power supply of fluorescent lighting lamps, DRL lamps and HPS. The choke limits the current through the lamp; in LL and HPS lamps it is used in conjunction with a starter or a pulse ignition device (starting relay) to form a high voltage surge that turns on the lamp. This is due to the nature and operating principle of such lamps.

A capacitor is used to power low-power devices; it is installed in series with the powered circuit. Such a power supply is called a “transformerless power supply with a ballast (quenching) capacitor.”

It is very often found as a current limiter for charging batteries (for example, lead batteries) in portable flashlights and low-power radios. The disadvantages of such a scheme are obvious - there is no control of the battery charge level, they boil over, undercharge, and voltage instability.

How to lower and stabilize DC voltage

To achieve a stable output voltage, you can use parametric and linear stabilizers. They are often made on domestic microcircuits such as KREN or foreign ones such as L78xx, L79xx.

The LM317 linear converter allows you to stabilize any voltage value, it is adjustable up to 37V, you can make a simple adjustable power supply based on it.

If you need to slightly reduce the voltage and stabilize it, the described ICs will not be suitable. For them to work there must be a difference of about 2V or more. LDO (low dropout) stabilizers were created for this purpose. Their difference lies in the fact that in order to stabilize the output voltage, it is necessary that the input voltage exceed it by an amount of 1V. An example of such a stabilizer is the AMS1117, available in versions from 1.2 to 5V, the 5 and 3.3V versions are most often used, for example, and much more.

The design of all the above-described series-type linear step-down stabilizers has a significant drawback - low efficiency. The greater the difference between the input and output voltage, the lower it is. It simply “burns” excess voltage, converting it into heat, and the energy loss is equal to:

Ploss = (Uin-Uout)*I

The AMTECH company produces PWM analogues of L78xx type converters; they operate on the principle of pulse width modulation and their efficiency is always more than 90%.

They simply turn the voltage on and off with a frequency of up to 300 kHz (ripple is minimal). And the current voltage is stabilized at the required level. And the connection circuit is similar to linear analogues.

How to increase constant voltage?

To increase the voltage, pulse voltage converters are produced. They can be switched on in either a boost or buck scheme or a buck-boost scheme. Let's look at a few representatives:

2. Board based on LM2577, works to increase and decrease the output voltage.

3. Converter board based on FP6291, suitable for assembling a 5 V power source, such as a powerbank. By adjusting the resistor values, it can be adjusted to other voltages, like any other similar converter - you need to adjust the feedback circuits.

Here everything is labeled on the board - pads for soldering the input - IN and output - OUT voltages. The boards can have output voltage regulation, and in some cases, current limiting, which allows you to make a simple and effective laboratory power supply. Most converters, both linear and pulsed, have short-circuit protection.

How to increase AC voltage?

To adjust AC voltage, two main methods are used:

1. Autotransformer;

2. Transformer.

Autotransformer- This is a choke with one winding. The winding has a tap from a certain number of turns, so by connecting between one of the ends of the winding and the tap, at the ends of the winding you get an increased voltage as many times as the total number of turns and the number of turns before the tap.

The industry produces LATRs - laboratory autotransformers, special electromechanical devices for voltage regulation. They are widely used in the development of electronic devices and repair of power supplies. The adjustment is achieved through a sliding brush contact to which the powered device is connected.

The disadvantage of such devices is the lack of galvanic isolation. This means that high voltage can easily be present at the output terminals, hence the risk of electric shock.

Transformer- This is a classic way to change the voltage value. There is galvanic isolation from the network, which increases the safety of such installations. The voltage on the secondary winding depends on the voltage on the primary winding and the transformation ratio.

Uvt=Ufirst*Ktr

A separate species is . They operate at high frequencies of tens and hundreds of kHz. Used in the vast majority of switching power supplies, for example:

Charger for your smartphone;

Laptop power supply;

Computer power supply.

Due to operation at high frequencies, the weight and size indicators are reduced, they are several times less than that of network (50/60 Hz) transformers, the number of turns on the windings and, as a result, the price. The transition to switching power supplies has made it possible to reduce the size and weight of all modern electronics and reduce their consumption by increasing efficiency (70-98% in switching circuits).

Electronic transformers are often found in stores; a 220V mains voltage is supplied to their input, and at the output, for example, 12 V high-frequency alternating voltage; for use in a load that is powered by direct current, it is necessary to additionally install high-speed diodes at the output.

Inside there is a pulse transformer, transistor switches, a driver, or a self-oscillator circuit, as shown below.

Advantages: simplicity of the circuit, galvanic isolation and small size.

Disadvantages - most models that are on sale have current feedback, which means that without a load with a minimum power (indicated in the specifications of a particular device), it simply will not turn on. Some copies are already equipped with OS voltage and operate at idle without problems.

They are most often used to power 12V halogen lamps, for example suspended ceiling spotlights.

Conclusion

We covered the basics of voltage, its measurement, and adjustments. A modern element base and a range of ready-made units and converters allows us to implement any power sources with the required output characteristics. You can write a separate article about each of the methods in more detail; within this article, I tried to fit the basic information necessary to quickly select a solution that is convenient for you.

How to reduce the voltage on a transformer.

Hello colleagues!

In this article I will tell you how to transformer with 32 V output, make transformer with a 12 V output. In other words - reduce transformer voltage.

For example, I’ll take the trance from the Chinese b/w TV “Jinlipu”.

I think a lot of people have met him or similar.

So, first we need to define the primary and secondary windings. To do this, you need a regular ohmmeter. We measure the resistance at the terminals of the transformer. On primary winding resistance is greater than secondary and is usually at least 85 Ohms.
Once we have identified these windings, we can begin to disassemble the transformer. It is necessary to separate the W-shaped plates from each other. To do this, we will need some tools, namely: round nose pliers, pliers, a small screwdriver for “picking up” the plates, wire cutters, and a knife.

To pull out the very first record, you will have to work hard, but then the rest will go like clockwork. You need to work very carefully, as you can easily cut yourself on the plates. Specifically on this transformer, we know that its output is 32 V. In the case when we do not know this, we must measure the voltage before analysis, so that in the future we can calculate how many turns go to 1 V.

So, let's start the analysis. Use a knife to peel off the plates from each other and, using wire cutters and pliers, pull them out of the transformer. This is what it looks like:

After the plates have been removed, you need to remove the plastic case from the windings. We do this boldly, since this will not affect the operation of the transformer in any way.

Then we find a contact on the secondary winding that is accessible for unwinding and use wire cutters to “bite it off” from the soldering point. Next, we begin to unwind the winding, and be sure to count the number of turns. To keep the wire out of the way, you can wrap it around a ruler or something similar. Since this transformer has 3 terminals on the secondary winding (two extreme and one middle), it is logical to assume that the voltage at the middle terminal is 16V, exactly half of 32V. We unwind the winding to the middle contact, i.e. to half, and count the number of turns that we unwound. (If the transformer has two terminals on the secondary winding, then unwind it “by eye” to half, count the turns while doing so, then cut off the unwound wire, strip its end, solder it back to the contact and assemble the transformer, doing everything the same as when disassembling, only in the reverse order. After this, you need to again measure the voltage that we got after reducing the turns and calculate how many turns are per 1V. We calculate it like this: let’s say you had a transformer with a voltage of 35V. After you unwinded about half of it and assembled the transformer. back, you have a voltage of 18V. The number of turns that you unwinded is 105. This means that 105 turns are per 17V (35V-18V = 17V). It follows that there are approximately 6.1 turns per 1V (105/17 = 6.176). Now, in order for us to reduce the voltage by another 6V (18V-12V=6V), you need to unwind approximately 36.6 turns (6.1*6=36.6 You can round this figure to 37. For this you need). disassemble the transformer again and do this “procedure.”). In our case, having reached half of the winding, we got 106 turns. This means that these 106 turns are at 16V. We calculate how many turns there are per 1V (106/16=6.625) and unwind about 26.5 more turns (16V-12V=4V; 4V*6.625 turns=26.5 turns). Then we “bite off” the unwound wire, strip the varnish from its end, tin it and solder it to the contact on the transformer from which it was “bitten off”.

Now we assemble the transformer in the same way as we disassembled it, only in the reverse order. Don’t worry if you have one or two plates left, the main thing is that they fit very tightly. Here’s what you should get:

It remains to measure the voltage that we got:

Congratulations, colleagues, everything turned out great!

If something doesn't work out the first time, don't get discouraged or give up. Only by showing persistence and patience can you learn something. If you have any questions, leave them in the comments and I will definitely answer.

In the next article I will tell you how to make a 12V DC power supply from this transformer.