Let's see how to calculate the transformer. Let's start with the simplest example, there will be time - let's do some complicated things. Consider common issues that stumble beginners. A transformer is a simple thing, not everyone knows the principle of operation. Just say, for the calculations easier to use online calculators, special computer programs. Although, of course, you will find an old Soviet textbook on calculating transformers.
The transformer mainly converts the network parameters to the desired shape. Lowers voltage from 220 to 12 volts. There are many thin turns of the primary winding, the secondary winding is inferior to the number, it lived thicker. Transformer power( considering efficiency) is transmitted completely. Lowering the voltage, we increase the output current. Noticed, if the transformer primary winding is powered, the secondary is deprived of the load, there is no short circuit. Copper wire, high conductivity. .. Occurs due to the presence of inductive reactance of a transformer.
The twisted wire starts, roughly speaking, when an alternating current flows, it interacts with itself. The voltage of the transformer is shifted phase relative to the initial, the resistance increases sharply. The higher the network frequency, the effects are more noticeable. More precisely, a strict relationship is derived:
R = ω L,
ω = 2 P f - circular frequency;L is inductance. P = 3.14 - Pi number;f - network frequency, expressed in hertz. The inductance resistance of the transformer is an imaginary value, neglecting the contribution of the copper conductor to the active component. The vector lies perpendicular to the axis of the real numbers. Due to the presence of pure imaginary resistance, a phase shift occurs between the current and voltage. Equal to 90 degrees( determines the ratio of the ohmic resistance of the wire, the value of inductance).
Having received power to the outlet, the transformer does not demonstrate a short circuit. An inductance of 100 mH gives the resistance R = 2 x 3.14 x 50 x 100/1000 = 31.4 ohms. Approximately corresponds to a current of 7 A network of 220 volts. The power is 1.5 kW.The value of inductance is higher. In order for the idling of the transformer( devoid of the load on the secondary winding) to work, the input resistance is increased. Carried out the calculation, discarding the contribution of the ohmic component. It develops with the imaginary rule of a right triangle. The hypotenuse will become the desired quantity. The value is complex, the term resistance is replaced by the relevant word impedance.
Let's discuss what happens when the transformer receives the load. The primary winding generates a magnetic field. Directed perpendicular to the area of the coils. The energy is conveyed to the secondary winding of the magnetic core. Any steel( ferromagnetic material) is suitable. Electrical technology is endowed with two features:
- Plain steel shows a tendency to peremagnetized. In parallel, the metal is heated, taking the energy of the magnetic field. It is considered the parasitic effect of the transformer, the steel is applied special electrical. Easier to get, dismantling the old transformer. During the perestroika, the collapse of the USSR, people had nothing to eat, they donated copper in large quantities. The magnetic cores of transformers were scattered everywhere.
- Consist of plates. The magnetic field goes along the axis of the wire. The trajectory of the square( see figure).Attempts to induce circular currents in the perpendicular plane( gimlet rule).The effect is blocked by splitting a single magnetic circuit with mutually isolated plates lying side by side like a deck of cards. Special lacquer is used for separation.
In one place of the transformer magnetic core, the primary winding is wound, in the other - the secondary. The field goes, following a given trajectory, leads on the output turns of the EMF( useful eddy currents).The contact of the secondary winding of the transformer form a voltage. A bonus in the use of a transformer is galvanic isolation. The transformer removes the DC link.
Following the number of turns of the primary, secondary windings, the ratio of the number, the desired transmission coefficient arises. Selected wire section.
Assemble a transformer with your own hands
We are looking for a transformer calculation tool
The question is able to cause the smile of the master of the old school, for the modern Internet the problem is relevant. Most webmasters are unable to describe how the current transformer is calculated. We find ridiculous suggestions. We decided to explore the network, looking for practical options. Suppose, before you make the simplest transformer, we perform a material search. Flying on the mortgage, most readers are deprived of a chance to get electrical steel. To cut, following the results of calculating the calculator, only the technologist of the specialized enterprise is capable. It will have to be calculated, starting with the end:
- Try to find more molded electrical steel of the old transformer.
- Carefully measure the plate thickness, other dimensions.
- Estimate, size, configuration of the core of the magnetic circuit.
We search for the number of turns, the sectional area of the cores. Note, butt-seated core is rarely collected. Air gaps are created, causing magnetic field losses. More often plates are put with an overlap. The efficiency of the transformer directly determines the quality of the core. Let's try to isolate the calculation tool. Go here http: //www.skrutka.ru/sk/ tekst.php? Id = 19.We see the opportunity to calculate the parameters of the transformer, excluding the core.
We will estimate the typical numbers:
- The power is set indirectly through the secondary current. Calculate watts by multiplying by voltage( see below).
- The inductance of the core is given. .. We assume that the webmaster oversaw, an error.
Online calculators do not always believe. Taking the resource http://energo-novgorod.ru /calcs/ calc-trans / for the basis of calculation, we see a similar result. Observes also difference. What to believe? The first nuance of the information community: the authors are too lazy to explain the prerequisites( excluding the VashTehnik portal), the process does not guarantee a truthful result. The result of the desire of resource owners to present the audience with a cheap dish. The second resource, apparently, forgets to take into account the efficiency, giving the opportunity to choose the parameters of the core. Set goals fits more. It remains to verify the arguments of the authors. We'll have to look for a third program( calculator).
The above resource is noticeably a truncated version of http: //astar3.ucoz.ru/index/ 0-6.It is explained that ideal parameters are selected for the given size of the magnetic circuit and the stresses. There is no possibility to choose power. Losing convenience, we get the opportunity to understand the suitability of the found core to the intended goals.
A working version of the Trans50Hz program was found. The network is teeming with trimmed versions. Below is the screen of the application, the address that allows you to download for personal use: http://audio-cxem.ru /programmyi/ raschet-transformatorov / programma-dlya-rascheta-silovyih-transformatorov-s-chastotoy-50-gts-trans50hz-3700.html. Important information, weed out a billion non-working options, stupid applications. Unaware that the search for benefits, showing how to calculate the transformer power and parameters, is so complicated. Repeatedly came across thematic notes that were not meticulously checked.
Having provided the reader with detailed information, they are completely calm. Add, the application interface offers to choose one of the five available core options. Readers get a choice.
We will pick up a varnish. Pre-clean the plate from rust. Different techniques are suitable, you will have to try several. Pay attention to the means of combating scum. There may be citric, acetic acid, a special descaler for teapots. Coin cleaning products are quite suitable, some use comets( citric acid is included).Sometimes it is useful to use the sandpaper, grinder, grinding wheel. The main thing that the armor plates were cleaned:
- Lime juice mixed with salt, soak steel.
- Soda, brush sometimes help cope.
- Soak steel, put fresh sliced potatoes on top, hold for an hour or two.
- A kilo of oxalic acid costs 890 rubles. The reagent is suitable for cleaning steel.
- For the persistent, we recommend orthophosphoric acid, an auto gas tank cleaner. The risk is less, the chance to get a result more than in the fight against the vagaries of foreign cars. Means are often called rust converters. Find in the store for car enthusiasts.
The main thing is to rinse the parts thoroughly after finishing operations. Then you need to work with varnish, you need perfect cleanliness. Lovers recommend PF-238.Take varnish without acetone. Can damage wire insulation. Lacquer, soluble in acetone. According to choose materials, constructing the core. Varnish KO 916 is priced at about 330 rubles kg. It is rumored that the assembly of steel plates of the transformer magnetic circuit is ideal.
The winding method determines the shape of the core. Take a typical rectangle with a single jumper in the center( plate W), it is permissible to arrange the primary winding over the secondary. It is desirable that the height after the operation is uniform. Approximately estimate the parameter, focusing on the number of turns, section. The wire is usually taken with lacquer insulation. The Trans50Hz program suggests using the PET-155 brand by default. Look through the listBox( drop-down list), looking for the right options.
Choose a transformer by preference. Familiarize yourself with existing wire sizes. Find the GOST, visit the manufacturer's website, run the price. Allows you to more accurately select the desired parameters. We are finishing the review, we strongly recommend to see how the current transformers are installed.