Voltage transformer. How to increase DC and AC voltage

A transformer, a device that transfers electrical energy from one part of a circuit to another through magnetic induction and, as a rule, with a change in voltage. Transformers only work with alternating electric current (AC).

Transformers are essential in power distribution. They increase the voltage generated in power plants to high values ​​in order to efficiently transfer electricity. Other transformers reduce this voltage at the point of consumption.

Many household appliances are equipped with transformers in order to increase or decrease the voltage supplied from the household power grid as needed. For example, the TV and the audio amplifier need a voltage boost, and the doorbell or thermostat needs a low voltage to operate.

How does a transformer work

Typically, a simple transformer consists of two coils wound with insulated wire. In most transformers, wires are wound around a rod of iron called a core.

One of the windings, also called the primary winding, is connected to an alternating current source, which in turn results in a permanently alternating magnetic field around the winding. This alternating magnetic field, in turn, creates an alternating current in the other winding (secondary winding).

The value, defined as the ratio of the number of turns in the primary winding to the number of turns in the secondary winding, determines the scale of the decrease or increase in voltage in the secondary winding. This value is also called the transformation ratio.

For example, if the transformer has 3 turns in the primary winding and 6 turns in the secondary winding, then the voltage in the secondary winding will be 2 times higher than in the primary. Such a transformer is called a step-up transformer.

And on the contrary, if there are 6 turns in the primary winding and 3 turns in the secondary, then the voltage removed from the secondary winding will be 2 times lower than in the primary winding. This type of transformer is called a step-down transformer.

It should also be borne in mind that the ratio of the current in both coils is inversely related to the ratio of their voltages. Thus, the electrical power (voltage times amperage) is the same in both coils.

The impedance (resistance to AC current) of the primary coil depends on the secondary impedance and the transformation ratio. With the correct ratio of the turns of the transformer, almost the same resistance of both circuits can be achieved.

Matching impedances are essential in stereo systems and other electronic systems to allow maximum energy transfer from one circuit block to another.

The voltage drop in the 220 volt primary network is sometimes a very serious problem in rural areas, and not only. The refrigerator does not start, the tile does not heat, you cannot stroke it with an iron, you cannot solder with a soldering iron, but you never know…. If the voltage drop for heating devices that have an active resistance for the network is not a lethal phenomenon, then for the equipment in which the motors are installed, in particular refrigerators, it can become the last in their life.

Let's start with a simple one, with heating equipment. Since the voltage waveform for heaters does not matter at all, it is not a problem to raise the effective (rms or effective) value of the supply voltage for them. We look at the schematic.

This prefix mains voltage (Fig. 1) first rectifies (Fig. 2), and then, due to the energy stored in the capacitors, increases the effective voltage, see Fig. 3.

The rectifier bridge can be used either ready-made or soldered from individual diodes. In rural areas, overhead power lines and high voltage impulse voltage surges not uncommon, so when choosing rectifier elements, pay attention to the maximum operating voltage of the diodes. The higher the better, within reasonable limits of course. The operating current of the diodes must exceed the load current by 2 times 3. You will have to choose the capacitance of the capacitors yourself. It depends both on the magnitude of the mains voltage dip and on the power of your heater. Be careful with this attachment, if the mains voltage returns to normal, then its output voltage will be higher than the operating voltage of the load. The amount of overvoltage depends on the value of the capacitance of the currently connected capacitors. Hence the required current margin for the diodes. I have such an attachment for a large 100W soldering iron in the form of an ax, for its quick warming up.

Now about, for example, a refrigerator. This companion needs a variable sine. Of course, you can buy both an autotransformer and a stabilizer. But you can get by with a simple transformer, the so-called voltage transformer... We look at the schematic.

It can be seen from the diagram that an additional transformer winding is connected in series with the upper wire of the 220 volt network. If it is turned on in phase with the mains, then the voltages will add up (when it is necessary to raise the voltage), If it is turned on in antiphase, then the mains voltage and the voltage on the secondary winding of the transformer will be subtracted, this is the case when the voltage must be reduced.

How to increase the network voltage, calculations.

Now let's count a little, at least approximately. Let's say you have a voltage drop of thirty volts. The required load current is five amperes. It follows that we need a power of 150W. With such power, a transformer from an old tube TV is guaranteed to cope. For instance, TS-180.
Transformer TS-180, TS-180-2, TS180-2V parameters download

So, we downloaded the data, found the TS-180, Add all the turns of the primary windings, 375 + 58 + 375 + 58 = 866 turns. Find the number of turns per volt 866/220 = approximately 4 turns per volt. To get the 30V we need, we multiply 30 by 4 = 120 turns. 60 turns per coil (TC-180 has two of them). The wire diameter for five amperes is 0.7 √I = 0.7√5 = 0.7 ∙ 2.236 ≈ 1.56 mm. Small explanations. After disassembling factory transformers, I always increase the number of turns of the primary winding, first of all, this is due to the fact that it will not be possible to reassemble the core, as is done in production conditions. Therefore, an increase in the no-load current (possibly several times due to the absence of a ferron filler in the gap, since the core is split) is guaranteed. Yes, and the armor core cannot be completely assembled, plate 1,2,3 will still remain.

You have probably already noticed that through such a transformer it is possible to power a motor with a capacity of one kilowatt. The circuit does not have a toggle switch for connecting our transformer. It can switch like the primary winding of a transformer, but there will be losses due to the secondary winding constantly connected to the network, so switch the secondary winding itself, but here there will be losses due to the permanently connected primary winding. While I am writing this text, an idea came to my mind. Now I will add and draw a diagram. So, to switch a transformer, you need two switches or one with several directions. Now everything is about the idea, I drew a diagram. We look at the diagram.

And so, the switch is in the down position, the transformer adds voltage. The switch is in the upper position, the primary winding is short-circuited, which means there is a short circuit in the secondary winding, and this is nothing else that the transformer has disappeared, only the active resistance of the secondary winding remains.

Taaa ... k, another scheme was born. I’ll draw it now. That I hadn’t thought of this before, although on the Web, perhaps, someone drew it a long time ago. We look.

If the switches are both at the bottom or both at the top, then there is no transformer in the circuit, there is a short circuit in the primary winding, the remaining active resistance is less than Ohm. Now left up, right down - a transformer, for example, adds voltage, and right up and left down - reduces. Well, that's all, maybe someone will need it. Good luck. K.V.Yu. Yes, just a little more. And if instead of switches we use H-bridge from field effect transistors, and even a microcontroller that monitors the level of the mains voltage, then you can probably make a relay-type AC voltage stabilizer with a small (relatively) transformer for high (relatively) power. Who would have done all this. At least there is something to think about.
Download the article

What and why boosts the transformer? And at whose expense?

We have already looked at what a transformer is, now let's take a closer look at what a step-up transformer is and what it is used for. Let's start with a simple example to help you understand why step-up transformers are needed.

Take a flashlight and make sure the batteries are not low and the light is on brightly. Now unscrew the head of the flashlight, and power the light bulb through a cable 50 meters long. Do it yourself if you don’t believe us that the light bulb will not light up. This is due to too large line losses for this voltage. Let's note the word "tension".

Roughly the same thing will happen in a normal line between two cities, if the line is 220V. If there is no transformer in such an electrical wiring that increases the voltage, electricity will not reach the second city, it will all go to losses. Due to these losses, the power industry uses a scheme in which, after generating electricity, the voltage at the point of generation rises significantly, electricity is transferred to the consumer through high voltage lines, where it is then reduced to the desired value and distributed to consumers.

So, with very rough strokes, the scheme in this case looks like this:

• Generator that generates electricity;
• Step-up transformer;
• Power transmission line;
• A step-down transformer;
• Local power grids;
• Consumer of electricity.

For clarity, you can give the following picture:

Why exactly energy? The fact is that this is the main area of ​​application of step-up transformers, if we talk about the specific contribution of transformers to the transformation of electricity. That is, it is in this area that they are most in demand, and without them it is impossible to imagine modern energy systems.

In order to understand how the voltage from 110V rises to 220V, or the currents change, you need to remember that the law of conservation of energy has not been canceled and the transformer does not generate any "free" electricity. By the way, it is on the manipulation of the laws of physics that it is built, it is worth plugging them into an outlet.

Quite the opposite, the step-up transformer perfectly illustrates the law of conservation of energy. Why? Yes, because if we consider the transformer as a closed system, then we get:

• The incoming energy (U1) on the primary winding (electricity), the number of turns of which is denoted by N1;
• Alternating magnetic field induced in the magnetic circuit (core);
• Outgoing energy (U2) on the secondary winding, number of turns N2.

(The ratio of U2 to U1 gives a parameter k called the transformation ratio.)

So, if in this system the number of turns is the same, then we will get the same voltage at the output, minus the losses in the transformer itself. This is the first illustration. The second is that if the number of turns differs, then we will get a voltage higher or lower at the output, but at the same time in a closed system "transformer" the power will remain the same at the input and output(minus losses in the transformer itself).

On a note... This is worth considering again. Some effects in electrical engineering seem miraculous to non-specialists, but all these effects always exactly correspond to the law of conservation of energy. Therefore, before thinking about how to choose and where to install a device “which will definitely save a lot of money,” remember this example.

Thus, the step-up transformer works in strict accordance with the laws of conservation of energy and electromagnetic induction in AC networks, changing the voltage and currents, but not changing the power.

Is it possible to replace the transformer?

The types, types and areas of application of the step-up voltage transformer are not easy to find in the network, but very simple. Let's go over so as not to search:

• Phase (one or three);
• By windings (two or three (split-winding varieties)). There are also single-winding ones, these are autotransformers;
• Insulation (oil, dry and non-combustible filling);
• By the type of cooling (oil - natural, with air blowing and with forced circulation, air and with the help of a nitrogen blanket).

The marking of step-up transformers (more precisely all transformers) looks like this:

All these devices are well described, widespread and have a wide variety of applications: from large-scale power engineering to very small household appliances.

In fact, most of the transformers that increase the voltage, it is simply impossible to replace with other devices, but, nevertheless, as the classic said - “There are no irreplaceable people” (c).

It is possible to change the voltage or currents in the power grid in other ways, and the losses will be comparable, and in some cases even lower. One example is the so-called T-shaped transformation scheme:

It may seem that this, in fact, is the circuit of a transformer, step-up or step-down. But in reality, the difference is this:

This is just a transformer circuit, from which it is perfectly clear that the windings are not connected to each other in any way, and the current in the secondary winding is induced without the participation of wires, so to speak. But in the T-shaped equivalent circuit of the transformer, it is clearly visible that there is no wire break.

At the same time, we, just like in a step-up transformer, will receive different voltages U1 and U2. Such methods are used where it is not possible to use a conventional transformer that increases the voltage. So, the transformer can be assembled by hand and connected where necessary, if there is such a need.

As a conclusion, a few words about the fate of transformers

Do not think that we decided to hit the fantasy, we are practical and realistic people. But, nevertheless, today in terms of generation, the situation is such that it is quite possible that transformers in a dozen years will not have such widespread use. The example is just above, this is only one of the options, but this is not the main thing.

Of course, they will serve for tens of years, but in the main field of use - energy, a step-up transformer is needed only as a secondary, auxiliary device. And it is needed only for the transmission of electricity over long distances. However, it is already clear today that over the past 30 years, the focus of this application is increasingly shifting towards large enterprises. If 30 years ago a private house that was not connected to the power grid was exotic, today there are already whole villages that do not use general-purpose networks in any way. Moreover, these settlements themselves are generation, feeding the energy systems with surplus energy.

This is progress and the process that he once launched will surely come to a logical conclusion. An incandescent lamp is perhaps one of the first devices to become widespread, and 50 years ago it seemed to many to be an eternal attribute of the lighting system. But the process is underway and in a dozen years it will be an anachronism. Do not consider this a lyrical digression, this applies to all electrical appliances. It is for this reason that we are so wary of new products, some of which are outright cheating, and some are dead-end branches of evolution, such as, for example.

One of the tasks that our team of authors is trying to solve is to try to predict, assess at the instinct level, if you like, which of the new products will take their rightful place in our home power grids, and which will remain expensive toys and a waste of money. We, of course, may be wrong, but we will try to argue our understanding of these issues, especially in the short term.

Often in villages and dachas they talk about poor voltage in the power grid. This is due not only to their poor technical condition, but also to the purchase of a variety of household appliances that require electricity, which is often in short supply.

At the same time, local power grids are in no hurry to change the equipment to modern, which means, to a more advanced one that can withstand increased loads with dignity.

The participant of the dacha forum "House and Dacha" Terristor somehow ran into a problem - the washing machine stopped working. That is, the drum turned with difficulty, and the pump could not lift water from the well.

The 1st Figure shows the typical operation of a step-down transformer.
On the 2nd, the transformer has already been converted, ready for operation to increase the voltage.

He measured the voltage, and the device showed only 180 volts, and this voltage is not enough for the operation of many household electrical appliances.

But no, a silver lining. Once he was reading the magazine "Radio" and he came across an article on how to make a step-up transformer using a conventional step-down transformer.

And the trick was that if you take which of 220 volts makes 40, dig deeper into it, then after small changes you can get at the output not a decrease, but an increase in voltage by 40 volts from the voltage in the network.

Incidentally, Terristor had such a transformer. And having a little knowledge in radio engineering, he remade it in 15 minutes and made a test run.

Before the test, the voltage was 192 volts, and after that, as planned, the voltage increased by 40 volts. This turned out to be an excellent solution in this situation, and despite the lack of voltage, electrical appliances worked flawlessly.

conclusions

The advantages of this system:

Easy to assemble. For example, if the power of the secondary winding of the transformer is 100 volts, you can connect a 500 W pump without fear.
The real cheapness of the device.

Cons of this system:

The voltage produced by the device is not automatically regulated, and if suddenly the voltage in the network stabilized and became 220 volts, then at the output you will have 260 volts, a bit too much, but not dangerous if you notice it in time.

Terristor himself has been using this transformer all winter. During this time, he never checked the voltage and not a single electrical device deteriorated.

In case the voltage in your area changes frequently, you can use a special outlet that turns off the electrical appliances that are connected to it if the voltage rises above the norm.

Calculation formulas

We need a transformer with a primary winding of 220 volts. Secondary winding - for the required "missing voltage". On the secondary winding, the maximum current is sufficient even for low-power step-down transformers.

The calculation can be done using several formulas.

By rice. one you can calculate the current of the secondary winding where Iн - rated load current A; Pн - rated load power (according to the transformer passport) W; Uн is the rated voltage of the load supply.

Knowing what voltage needs to be added, the required power of the transformer is determined by rice. 2 where P is the power of the transformer in W., I2 is the rated current of the secondary winding A, U2 is the voltage of the secondary winding, V. Then you need to take a transformer with suitable data - in terms of power and output voltage.

In the last formula, you can see that the voltage across the load can be either increased or decreased. To correctly phase the transformer, it is enough to swap the terminals of one of the windings.

It is better to install the transformer in the corridor or in the basement, because the installation is noisy, and from there make the wiring to the necessary electrical appliances.

Posted by a member of the forum "House and Dacha" Terristor
Editor: Adamov Roman

Step-up voltage transformers are devices that used in electrical circuits to change the voltage indicators of electricity upward.

Any voltage transformer is based on the principle of operation based on electromagnetic induction. The iron core is found in insulating oils that do not allow electricity to pass through. The design contains two coils with a different number of windings. There will be more turns in the first coil than in the second.

Step-up voltage transformer includes several components that ensure the operation of the device. At the heart of the structure is an iron core on which two coils are wound. An alternating current voltage is applied through the first coil, as a result of which a magnetic field is formed, which implements the principle of electromagnetic induction. According to the formula dФ / dt, the magnetic field strength can be increased by increasing the current indicators to the required values.

Here, one should not forget about the direct dependence of the magnetic field voltage indicators on a certain number of windings, which are located in the iron core. Accordingly, the fewer turns, the less tension.

Therefore, when the magnetic flux passes through the winding line of the second coil, then there will be a voltage. These indicators will be calculated using the formula: NF / dt, where N is the number of turns of the coil itself. This is the so-called Faraday's law, Whereby the voltage will be the same frequency as on the first coil.

More about the device on video

Types of transformers