Every car enthusiast dreams of having a rectifier at his disposal for charging the battery. Without a doubt, this is a very useful and convenient thing. Let's try to calculate and make a rectifier for charging a 12 volt battery.
A conventional passenger car battery has the following parameters:

• normal voltage 12 volts;
• battery capacity 35 - 60 amp hours.

Accordingly, the charge current is 0.1 of the battery capacity, or 3.5 - 6 amperes.
The rectifier circuit for charging the battery is shown in the figure.

First of all, you need to determine the parameters of the rectifier device.
The secondary winding of the rectifier for charging the battery must be rated for voltage:
U2 \u003d Uak + Uo + Ud where:
- U2 - voltage on the secondary winding in volts;
- Uak - battery voltage is 12 volts;
- Uo - voltage drop across the windings under load is about 1.5 volts;
- Uд - voltage drop across diodes under load is equal to about 2 volts.

Total voltage: U2 \u003d 12.0 + 1.5 + 2.0 \u003d 15.5 volts.

Let's take with a margin for voltage fluctuations in the network: U2 \u003d 17 volts.

The battery charge current is I2 \u003d 5 amperes.

The maximum power in the secondary circuit will be:
P2 \u003d I2 x U2 \u003d 5 amps x 17 volts \u003d 85 watts.
The power of the transformer in the primary circuit (the power that will be consumed from the network), taking into account the efficiency of the transformer, will be:
P1 \u003d P2 / η \u003d 85 / 0.9 \u003d 94 watts. Where:
- Р1 - power in the primary circuit;
- P2 - power in the secondary circuit;
-η \u003d 0.9 - efficiency of the transformer, efficiency.

Let's take P1 \u003d 100 watts.

Let's calculate the steel core of the W-shaped magnetic circuit, the transmitted power depends on the cross-sectional area of \u200b\u200bit.
S \u003d 1,2√ P where:
- S cross-sectional area of \u200b\u200bthe core in cm;
- P \u003d 100 watts power of the primary circuit of the transformer.
S \u003d 1.2√ P \u003d 1.2 x √100 \u003d 1.2 x 10 \u003d 12 cm2
Section of the central rod, on which the frame with the winding S \u003d 12 cm will be located.

Determine the number of turns per 1 volt, in the primary and secondary windings, according to the formula:
n \u003d 50 / S \u003d 50/12 \u003d 4.17 turns.

Take n \u003d 4.2 turns per volt.

Then the number of turns in the primary winding will be:
n1 \u003d U1 n \u003d 220 volts 4.2 \u003d 924 turns.

Number of turns in the secondary winding:
n2 \u003d U2 n \u003d 17 volts 4.2 \u003d 71.4 turns.

Let's take 72 turns.

Determine the current in the primary winding:
I1 \u003d P1 / U1 \u003d 100 watts / 220 volts \u003d 0.45 amps.

Secondary current:
I2 \u003d P2 / U2 \u003d 85/17 \u003d 5 amps.

The diameter of the wire is determined by the formula:
d \u003d 0.8 √I.

Primary wire diameter:
d1 \u003d 0.8 √I1 \u003d 0.8 √ 0.45 \u003d 0.8 0.67 \u003d 0.54 mm.

Secondary wire diameter:
d2 \u003d 0.8√ I2 \u003d 0.8 5 \u003d 0.8 2.25 \u003d 1.8 mm.

The secondary winding is wound with taps.
The first tap is made from 52 turns, then from 56 turns, from 61, from 66 and the last 72 turns.

The conclusion is made with a loop without cutting the wires. then the insulation is peeled off from the loop and the lead wire is soldered to it.

The rectifier charging current is adjusted stepwise by switching the taps from the secondary winding. A switch with powerful contacts is selected.

If there is no such switch, then you can use two toggle switches for three positions designed for currents up to 10 amperes (sold in an auto store).
By switching them, you can sequentially give out to the output of the rectifier, voltage 12 - 17 volts.

Position of toggle switches for output voltages 12 - 13 - 14.5 - 16 - 17 volts.

Diodes should be sized, with a margin, for a current of 10 amperes and each stand on a separate radiator, and all radiators are isolated from each other.

There can be one radiator, and the diodes are installed on it through insulated gaskets.

The area of \u200b\u200bthe radiator per diode is about 20 cm2, if there is one radiator, then its area is 80 - 100 cm2.
The charging current of the rectifier can be monitored with a built-in ammeter for currents up to 5-8 amperes.

You can use this transformer as a step-down transformer to power a 12 volt emergency lamp from the 52 turn tap. (see diagram).
If you need to power a 24 or 36 volt light bulb, then an additional winding is made, based on for every 1 volt 4.2 turns.

This additional winding is connected in series with the main one (see the upper diagram). It is only necessary to phase the main and additional windings (beginning - end) so that the total voltage builds up. Between points: (0 - 1) - 12 volts; (0 -2) - 24 volts; between (0 - 3) - 36 volts.
For instance. For a total voltage of 24 volts, add 28 turns to the main winding, and for a total voltage of 36 volts, another 48 turns of wire with a diameter of 1.0 millimeter.

Possible variant appearance rectifier housing for battery charging, shown in the figure.

How to make a frame for transformer on Ш-shaped core.

We will make a transformer frame for the article"How to calculate a power transformer"

To reduce eddy current losses, transformer cores are assembled from stamped plates from electrical steel. In low-power transformers, "armored" or W-shaped cores are most often used.

The transformer windings are on the frame. The frame for the W-shaped core is located on the central rod, which simplifies the design, allows better use of the window area and partially protects the windings from mechanical stress. Hence the name of the transformer -, armored ,. .

To assemble the armor cores, W-shaped plates and jumpers to them are used. To eliminate the gap between the plates and the bridges, the core is assembled over the cover.

The cross-sectional area of \u200b\u200bthe W-shaped core, S, is the product of the width of the central rod by the thickness of the set of plates (in centimeters). The correct core plates must be selected.

For example, from the article "How to calculate a 220/36 volt transformer":

- transformer power P \u003d 75 watts;
- cross-sectional area of \u200b\u200bthe magnetic circuit S \u003d 10 cm2 \u003d 1000 mm2

We select plates for such a section of the magnetic circuit:

— width b \u003d 26 mm. ,
- the height of the plate window c \u003d 47 mm,
- window width - 17 mm.,

If other plate sizes are available, you can use those as well.

The thickness of the plate pack set will be:

S: 26 \u003d 1000: 26 \u003d 38.46. Let's take: a \u003d 38.5 mm.

There are many ways of making frames for a W-shaped heart from different materials: electric cardboard, press-board, textolite, etc. Frameless winding is sometimes used. For low-power transformers up to 100 W. frames glued from cardboard and paper turn out well.

Frame fabrication.

How to calculate a 220/36 volt transformer.

In a household, it may be necessary to equip lighting in damp rooms: basement or cellar, etc. These rooms have an increased risk of electric shock.
In these cases, use electrical equipment designed for reduced supply voltage, no more than 42 volts.
You can use a battery-powered flashlight or use a step-down transformer from 220 volts to 36 volts.
We will calculate and manufacture a 220/36 volt single-phase power transformer, with an output voltage of 36 volts, powered by a 220 volt alternating current network.

To illuminate such rooms an electric light bulb is suitable at 36 volts and a power of 25 - 60 watts. Such bulbs with a base for an ordinary electric cartridge are sold in electrical stores.
If you find a light bulb for a different power, for example, 40 watts, it's okay - it will do too. The transformer will simply be made with a power reserve.

Let's make a simplified calculation of a 220/36 volt transformer.

Secondary power: P_2 \u003d U_2 I_2 \u003d 60 watts

Where:
Р_2 - power at the output of the transformer, we set 60 watts;
U _2 - voltage at the output of the transformer, we set 36 volts;
I _2 - current in the secondary circuit, in the load.

The efficiency of a transformer with power up to 100 watts is usually no more than η \u003d 0.8.
The efficiency determines how much of the power consumed from the network goes to the load. The rest goes to heating the wires and core. This power is irretrievably lost.
Let's determine the power consumed by the transformer from the network, taking into account losses:

P_1 \u003d P_2 / η \u003d 60 / 0.8 \u003d 75 watts.

Power is transferred from the primary to the secondary through the magnetic flux in the magnetic circuit. Therefore, from the meaning P_1, power consumed from the 220 volt network, the cross-sectional area of \u200b\u200bthe magnetic circuit S depends.

The magnetic circuit is a W-shaped or O-shaped core made from transformer steel sheets. The core will contain the primary and secondary windings of the wire.

The cross-sectional area of \u200b\u200bthe magnetic circuit is calculated by the formula:

S \u003d 1.2 √P_1.

Where:
S - area in square centimeters,
P _1 is the power of the primary network in watts.

S \u003d 1.2 · √75 \u003d 1.2 · 8.66 \u003d 10.4 cm².

The value of S determines the number of turns w per volt by the formula:

w \u003d 50 / S

In our case, the cross-sectional area of \u200b\u200bthe core is S \u003d 10.4 cm2.

w \u003d 50 / 10.4 \u003d 4.8 turns per volt.

Let's calculate the number of turns in the primary and secondary windings.

The number of turns in the primary winding for 220 volts:

W1 \u003d U_1 w \u003d 220 4.8 \u003d 1056 turns.

The number of turns in the secondary winding at 36 volts:

W2 \u003d U_2 w \u003d 36 4.8 \u003d 172.8 turns,

round up to 173 turns.

In load mode, there may be a noticeable loss of part of the voltage on the active resistance of the secondary winding wire. Therefore, it is recommended for them to take the number of turns by 5-10% more than the calculated one. Take W2 \u003d 180 turns.

The value of the current in the primary winding of the transformer:

I_1 \u003d P_1 / U_1 \u003d 75/220 \u003d 0.34 amperes.

Current in the secondary winding of the transformer:

I_2 \u003d P_2 / U_2 \u003d 60/36 \u003d 1.67 amperes.

The diameters of the wires of the primary and secondary windings are determined by the values \u200b\u200bof the currents in them based on the permissible current density, the number of amperes per 1 square millimeter of the conductor area. For transformers, the current density, for copper wire, taken 2 A / mm².

With such a current density, the diameter of the wire without insulation in millimeters is determined by the formula: d \u003d 0.8√I.

For the primary winding, the wire diameter will be:

d_1 \u003d 0.8 √1_1 \u003d 0.8 √0.34 \u003d 0.8 0.58 \u003d 0.46 mm. Take 0.5mm.

Secondary wire diameter:

d_2 \u003d 0.8 √1_2 \u003d 0.8 √1.67 \u003d 0.8 1.3 \u003d 1.04 mm. Let's take 1.1 mm.

IF THERE IS NO WIRE OF THE RIGHT DIAMETER, then you can take several, connected in parallel, thinner wires. Their total cross-sectional area must be at least that corresponding to the calculated one wire.

The cross-sectional area of \u200b\u200bthe wire is determined by the formula:

s \u003d 0.8 · d².

where: d is the wire diameter.

For example: we could not find a wire for the secondary winding with a diameter of 1.1 mm.

The cross-sectional area of \u200b\u200ba wire with a diameter of 1.1 mm. is equal to:

s \u003d 0.8 · d² \u003d 0.8 · 1.1² \u003d 0.8 · 1.21 \u003d 0.97 mm².

Let's round up to 1.0 mm².

Ofchoose the diameters of the two wires, the sum of the cross-sectional areas of which is 1.0 mm².

For example, these are two wires with a diameter of 0.8 mm. and an area of \u200b\u200b0.5 mm².

Or two wires:
- the first with a diameter of 1.0 mm. and a cross-sectional area of \u200b\u200b0.79 mm²,
- the second with a diameter of 0.5 mm. and a cross-sectional area of \u200b\u200b0.196 mm².
which adds up to: 0.79 + 0.196 \u003d 0.986 mm².

Winding a transformer with your own hands is not so much a difficult process as a long one, requiring constant concentration of attention.

Those who start such work for the first time find it difficult to figure out which material to use and how to check the finished device. The step-by-step instructions below will give newbies answers to all questions.

Before proceeding directly to winding, you need to stock up on all the devices and tools necessary to do the job:

The types and methods, directions of winding of the transformer windings are shown in the photo:

Insulation of winding layers

In some cases, insulation spacers are required between the wires. Most often, capacitor or cable paper is used for this.

The middle of adjacent transformer windings should be insulated more strongly. For insulating and leveling the surface for the next layer of winding you will need a special varnished clothto be wrapped with paper on both sides. If there is no varnish, then the problem can be solved with the help of the same paper folded in several layers.

The paper strips for insulation should be 2-4 mm wider than the winding.

To check, first of all, it is necessary to determine the conclusions of all its windings. Useful tips on how to test a transformer with a multimeter for operation, read the next article.

Algorithm of actions

1. Fasten the wire with the coil in the winding device, and the frame of the transformer is in the winding device. Rotations should be soft, moderate, without disruptions.
2. Lower the wire from the coil onto the frame.
3. Leave between the table and the wire at least 20 cmso that you can place your hand on the table and fix the wire. Also, all related materials should be on the table: sandpaper, scissors, insulation paper, an included soldering tool, a pencil or pen.
4. With one hand, smoothly rotate the winding device, and with the other hand, fix the wire. It is necessary that the wire lies flat, turn to turn.
5. Transformer insulate the frame, and pass the withdrawn end of the wire through the frame hole and briefly fix it on the axis of the winding device.
6. Winding should be started without haste: you need to "fill your hand" so that it turns out to stack turns next to each other.
7. Make sure that the angle of the wire and the tension are constant. You should not wind each subsequent layer "all the way", since the wires can slip and fall into the frame "cheeks".
8. Set the counting device (if any) to zero or count the turns carefullyorally.
9. Glue the insulating material or press it with a soft rubber ring.
10. Each subsequent turn is 1-2 turns thinner than the previous one.

See the video clip for winding the transformer coils with your own hands:

Wire connection

If a break occurs during winding, then:

• thin wires (thinner than 0.1 mm) twist and brew;
• medium wire ends (less than 0.3mm) should be freed from the insulating material by 1-1.5 cm, twisted and soldered;
• ends of thick wires (thicker than 0.3 mm) you need to strip a little and solder without twisting;
• insulate the place of soldering (welding).

Important points

If a thin wire is used for winding, then the number of turns must exceed several thousand... From above, the winding must be protected with insulation paper or leatherette.

If the transformer is wrapped with thick wire, no external protection is required.

Test

After the winding is finished, it is necessary to test the transformer in action, for this, its primary winding should be connected to the network.

To check the device for the occurrence of short circuits, the primary winding and the lamp should be connected in series to the power source.

Insulation reliability checked by alternate touch the lead-out end of the wire of each lead-out end of the network winding.

The test of the transformer should be very careful and careful so as not to get under the voltage of the step-up winding.

If religiously follow the instructions and do not neglect any of the points, then winding the transformer manually will not present any difficulties, and even a beginner can cope with it.

In this article I want to talk about winding a transformer for a powerful 12-220 car inverter.
This transformer was coiled to work with a Chinese automotive voltage converter board.

Such inverters have recently found wide popularity due to their light weight, compact size and low price, an indispensable thing if you need to connect mains loads in a car that need a 220 Volt power source, and even an alternating current with a frequency of 50 Hz, the inverter is completely can provide such conditions. A few words about the converter itself, its approximate diagram is shown below.

The diagram is provided only to show the principle of operation, but this business works in a rather simple way.

Two generators, both TL494, the first of them operates at a frequency of about 60 kHz and is designed to drive the power transistors of the primary circuit, which in turn drive the power pulse transformer. The second generator is tuned to a frequency of about 100 Hz and controls high-voltage power transistors.

The rectified voltage after the secondary winding of the transformer goes to high-voltage field workers, which, when triggered at a given frequency, convert direct current into alternating current - with a frequency of 50 Hz. The output waveform is rectangular or, more correctly, a modified sinusoid.

Our transformer is the main power component of the inverter and its winding is the most crucial moment.

The primary winding is in the form of a bus (unfortunately I cannot specify the exact length), the width of this bus is about 24mm, thickness is 0.5mm.

Operating frequency and type of master oscillator.
Inverter input voltage
Overall dimensions and type (brand) of the transformer core

First, the primary winding was wound. Two shoulders were wound with one solid tape, the number of turns is 2x2 turns. After winding the first two turns, a branch was made, then the remaining two turns were wound.

On top of the primary winding, it is imperative to put insulation, in my case, ordinary electrical tape. The number of insulation layers is 5.

The secondary winding winds in the same direction as the primary, for example, clockwise.

To obtain 220 Volts of output voltage, in my case, the winding contains 42 turns, moreover, the winding was made in layers - the first layer is 14 turns, on top of two more layers that contain exactly the same number of turns.
The winding was wound with two parallel strands of 0.8mm wire, a calculation example is shown below.

After all this, we assemble the transformer - we fasten the halves of the core using any electrical tape or tape, I do not advise glue, since it can penetrate between the halves of the ferrite and form an artificial gap, which will lead to an increase in the quiescent current of the circuit and to the combustion of the input transistors of the inverter, so that you need this factor draw great attention.

In operation, the transformer behaves very calmly, the no-load current consumption is in the region of 300 mA, but this is taking into account the consumption of the high-voltage part.

The maximum overall power of the core that I used is around 1000 watts, of course the winding data will be different depending on the type of core used. By the way, winding can be done both on W-shaped cores and on ferrite rings.

On such a basis, only all transformers are wound, both in industrial and in homemade pulse converters voltage, by the way - the designs of home-made inverters are very often repeated by radio amateurs in projects of subwoofer amplifiers and not only, so that I think the article was interesting for many.

A transformer is a device that is a core with two windings. They must have the same number of turns, and the core itself is made of electrical steel.

At the input of the device, a voltage is applied, an electromotive force appears in the winding, which creates a magnetic field. The turns of one of the coils pass through this field, due to which a self-induction force arises. In the other, a voltage arises that differs from the primary by as many times as the number of turns of both windings differs.

The transformer works like this:

• The current flows through the primary coil, which creates a magnetic field.
• All power lines are closed near the coil conductors. Some of these lines of force are closed near the conductors of another coil. It turns out that both connected by magnetic lines.
• The farther the windings are located from each other, the less force a magnetic connection arises between them, since a smaller number of lines of force of the first clings to the lines of force of the second.
• Through the first alternating current flows (which changes in time and according to a certain law), which means that the magnetic field that is created will also be variable, that is, it will change in time and according to the law.
• Due to the change in current in the first one, in both coils magnetic flux arrives, which changes the magnitude and direction.
  Induction of variable electromotive force occurs. This is stated in the law of electromagnetic induction.
• If the ends of the second are connected to receivers of electricity, then a current will appear in the chain of receivers. The first from the generator will receive energy that is equal to the energy given to the second chain. Energy is transmitted through variable magnetic flux.

A step-down transformer is needed to convert electricity, namely to lower its performance, so that the combustion of electrical equipment can be prevented.

Assembly order and connection

Despite the fact that this device seems at first glance a complex device, you can assemble it yourself. To do this, follow these steps:

An example of a connection diagram for a 220 step-down transformer for 12 V:

To make it easier to wind the coils (in factories, special equipment is used for this), you can use two wooden posts fixed to the board, and a metal axle threaded between the holes in the posts. At one end, a metal rod should be bent in the form of a handle.

Simple Tips about working capacity, read the next review.

In 1891, Nikola Tesla developed a transformer (coil), with which he experimented with high voltage electrical discharges. Find out how to make a Tesla transformer with your own hands.

Useful and interesting information about connecting halogen lamps through a transformer -.

Outcome

• The transformer is called device with a core and two winding coils... At the input of the device, electricity is supplied, which is reduced to the required values.
• The principle of operation of a step-down transformer is to create electromotive force that creates a magnetic field... The turns of one of the coils pass through this field, and self-induction force appears. The current changes, its magnitude and direction change. Energy is supplied using an alternating magnetic field.
• Such a device is needed to convert energy, thereby preventing the combustion of electrical equipment and its failure.
• The assembly procedure for such a device is very simple.... First, you need to do some calculations and you can get to work. In order to be able to quickly and easily wind the coils, it is necessary to make a simple device from a board, stands and a handle.

In conclusion, we bring to your attention another way of assembling and connecting a step-down transformer from 220 to 12 volts:

Step-up or step-down transformers are used to convert the voltage from low to high, and vice versa. They are high efficiency electrical machines and are used in many areas of technology.

Can I make a transformer with my own hands at home? What materials and devices should be used in the production of such work? In order to properly assemble a step-up transformer, it is necessary to accurately follow the entire technological process and recommendations for assembling this type of electrical machines, which will be given below.

What do you need to know and have for self-winding a transformer?

If there is a need for this device, then you need to have answers to the following questions:

1. What is a transformer for: increase or decrease the voltage?
2. What voltages should be at the input and output of the device?
3. Does the device operate from an alternating current of 50 Hz, or should it be counted on a different frequency?
4. What will be the power of a homemade transformer?

After receiving answers, you can start buying the materials you need. To do this, buy tape insulation (varnished cloth) for the future transformer, a core for it (if there is a suitable power from an old, burned-out TV, then you can use it), the required amount of wire in enamel insulation.

For winding windings, you can make a simple winding machine. To do this, take a board 40 cm long and 100 mm wide. Two bars of 50 x 50 millimeters are attached to it with screws so that the distance between them is 30 cm.They must be drilled at the same height with a drill with a diameter of 8 mm. A rod is inserted into these holes, on which the coil of the future transformer is preliminarily put on.

On one side, a thread should be cut on the pin to a length of 3 cm and a handle should be fixed on it with the help of two nuts, which rotate the bar with the coil when winding the transformer.

The dimensions of the winding machine described above are not critical - it all depends on the dimensions of the core. If it is made of ferroalloys and has a ring shape, then it will have to be done manually.

A preliminary calculation of the number of turns can be done based on the required power of the apparatus. For example, if you need a step-up transformer from 12 to 220 V, then the required power of such an apparatus will be in the range of 90-150 W. We choose an O-shaped type of magnetic circuit from an old TV or buy a similar one in a store. Its cross-section should be chosen according to the formula from the electrical reference book. In this example, it is approximately 10-11 cm².

The next step is to determine the number of turns per volt, which in this case is 50 Hz divided by 10-11, something about 4.7-5 units per volt. Now you can count the number of turns of the primary and secondary winding: W1 \u003d 12 X 5 \u003d 60 and W2 \u003d 220 X 5 \u003d 1100.

Then you need to determine the currents in them: I1 \u003d 150: 12 \u003d 12.5 A and I2 \u003d 150: 220 \u003d 0.7 A.

Let's find the cross-sections and diameters of the winding wires according to the formulas from the reference book.

The step-up transformer is pre-calculated, you can start winding it.

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Workflow for making bobbins

They are made from cardboard. The interior should be slightly larger than the core shaft, and the cheeks should fit freely into the transformer window. When using an O-shaped core, two coils must be made, and when using W-shaped plates, one.

When using a round core from LATRA, it is pre-wrapped with tape insulation and then a wire is directly wound on it, distributing the required number of turns over the entire ring. After the winding of the primary winding is completed, it is closed with 3-4 layers of varnished cloth and then the turns of its secondary part are started from above. After that, the wire is closed with tape insulation, having previously brought out the ends of the windings. When using conventional magnetic cores, the coil frame is done as follows:

• a pattern is made for a sleeve with cuffs on the sides of the ends;
• cheeks are cut out of cardboard;
• roll the coil body along the marked lines into a small box and glue it;
• put the upper parts (cheeks) on the sleeve and, turning the lapels, glue.

Back to the table of contents

Manufacturing step-up transformer windings

The coil is put on a wooden block with the dimensions of a magnetic core. A hole for the winding bar is pre-drilled in it. This part is inserted into the machine and the winding manufacturing process begins:

• 2 layers of varnished cloth are wound on a reel;
• one end of the wire is fixed on the cheek and begins to slowly rotate the handle of the machine;
• the turns must be laid tightly, isolating each wound layer from the neighboring one with varnished cloth;
• after the coil of the primary winding is wound, the wire is cut and its second end is fixed on the cheek next to the first;
• Insulating tubes are put on both terminals, and from the outside the winding is closed with insulation;
• In the same sequence, the coil of the secondary winding is wound.