Calculation of the transformer went calculator online. Calculation of the transformer on the calculator at home. Connection of windings of CCI transformers
In the household, it may be necessary to equip lighting in damp areas: basement or cellar, etc. These rooms have an increased degree of danger of electric shock.
In these cases, you should use electrical equipment designed for reduced supply voltage, no more than 42 volts.
You can use a battery-powered electric flashlight or use a step-down transformer from 220 volts to 36 volts.
We will calculate and manufacture a single-phase power transformer 220/36 volts, with an output voltage of 36 volts, powered by an AC electrical network with a voltage of 220 volts.
To illuminate such areas suitable light bulb at 36 volts and a power of 25 - 60 watts. Such light 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. It's just that the transformer will be made with a power margin.
Let's make a simplified calculation of the 220/36 volt transformer.
Power in the secondary circuit: P_2 \u003d U_2 I_2 \u003d 60 watts
Where:
P_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 a power of up to 100 watts is usually equal to no more than η = 0.8.
Efficiency determines how much of the power consumed from the network goes to the load. The rest is used to heat the wires and the core. This power is irretrievably lost.
Let's determine the power consumed by the transformer from the network, taking into account losses:
P_1 = P_2 / η = 60 / 0.8 = 75 watts.
Power is transferred from the primary winding to the secondary winding through the magnetic flux in the magnetic circuit. Therefore, from the value R_1, power consumed from a network of 220 volts, depends on the cross-sectional area of the magnetic core S.
The magnetic circuit is a W - shaped or O - shaped core, assembled from sheets of transformer steel. The primary and secondary windings of the wire will be located on the core.
The cross-sectional area of the magnetic circuit is calculated by the formula:
S = 1.2 √P_1.
Where:
S is the 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 = 50/S
In our case, the cross-sectional area of the core is S = 10.4 cm2.
w \u003d 50 / 10.4 \u003d 4.8 turns per 1 volt.
Calculate the number of turns in the primary and secondary windings.
The number of turns in the primary winding for 220 volts:
W1 = U_1 w = 220 4.8 = 1056 turns.
The number of turns in the secondary winding at 36 volts:
W2 = U_2 w = 36 4.8 = 172.8 turns,
round up to 173 turns.
In load mode, there may be a noticeable loss of part of the voltage across the active resistance of the secondary winding wire. Therefore, for them it is recommended to take the number of turns by 5-10% more than the calculated one. Take W2 = 180 turns.
The magnitude of the current in the primary winding of the transformer:
I_1 = P_1/U_1 = 75/220 = 0.34 amps.
Current in the secondary winding of the transformer:
I_2 = P_2/U_2 = 60/36 = 1.67 amps.
The diameters of the wires of the primary and secondary windings are determined by the values of the currents in them based on the permissible current density, the number of amperes per 1 square millimeter of conductor area. For transformers current density, for copper wire 2 A/mm² is accepted.
With such a current density, the diameter of the wire without insulation in millimeters is determined by the formula: d = 0.8√I.
For the primary winding, the wire diameter will be:
d_1 = 0.8 √1_1 = 0.8 √0.34 = 0.8 0.58 = 0.46 mm. Take 0.5 mm.
Secondary wire diameter:
d_2 = 0.8 √1_2 = 0.8 √1.67 = 0.8 1.3 = 1.04 mm. Let's take 1.1 mm.
IF THERE IS NO WIRE OF THE REQUIRED DIAMETER, then you can take several, connected in parallel, thinner wires. Their total cross-sectional area must be at least that which corresponds to the calculated one wire.
The cross-sectional area of the wire is determined by the formula:
s = 0.8 d².
where: d is the diameter of the wire.
For example: we could not find a wire for the secondary winding with a diameter of 1.1 mm.
The cross-sectional area of the wire with a diameter of 1.1 mm. is equal to:
s = 0.8 d² = 0.8 1.1² = 0.8 1.21 = 0.97 mm².
Rounded up to 1.0 mm².
Fromselect 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 0.5 mm².
Or two wires:
- the first with a diameter of 1.0 mm. and a cross-sectional area of 0.79 mm²,
- the second diameter is 0.5 mm. and a cross-sectional area of 0.196 mm².
which in total gives: 0.79 + 0.196 = 0.986 mm².
The coil is wound with two wires at the same time, an equal number of turns of both wires is strictly maintained. The beginnings of these wires are interconnected. The ends of these wires are also connected.
It turns out, as it were, one wire with a total cross section of two wires.
See articles:Transformers are electromagnetic devices that have two or more inductively coupled windings and are used to determine the value of alternating current (voltage). The structure of the device includes a magnetic core with windings placed on it. Single-phase low voltage units are used to power control circuits.
The winding connected to the voltage source is called primary, and those to which current consumers are connected are secondary. Units are divided depending on the result of the work.
Radio amateurs are aware of such a situation when it is necessary to make a transformer that has current and voltage indicators that differ from standard indicators. Sometimes it is possible to find a ready-made device with the required winding parameters, but more often the transformer has to make one's own.
There is a need to calculate the transformer, which in an industrial situation is a complex process, but radio amateurs can calculate their units according to a relatively simplified scheme:
First, they are determined with the values of the parameters at the output of the future device. The optimal rated power is selected, which is calculated by summing the powers of all secondary windings. This indicator on each winding is determined by multiplying the voltage in volts and output current in amperes.
The rated power will allow you to calculate the cross section of the core, obtained in square centimeters. The choice of the core is influenced by the width of its central plate and the thickness of the typesetting layer. To determine the cross section of the core, multiply these two parameters. Power changes as current flows from the primary winding to the secondary. This is due to the magnetic flux in the core, so the size of the core area directly depends on the power indicator.
The optimal type is armor core. If we take for comparison the toroidal or rod type, then one and a half times less wire for the winding device will be required to manufacture the armored one. The toroidal design consists of a ring on which the windings are located, this type has the smallest magnetic radiation of all.
The rod design assumes the presence of two coils with wire winding on each. The windings are divided into two and connected in series. Difficulties arise with determining the direction of the winding; rod types of cores are usually used for powerful transformers. The armored core design is used for small and medium-sized transformers and consists of a single coil with a convenient winding arrangement.
To check if all the windings will fit on the selected unit, use window fill factor. To check it, calculate the area of the window in the core. After that, a coefficient is found showing the number of turns that need to be wound to raise the voltage to a size on the winding of 1 volt.
The number of turns is calculated according to the need for one winding turn per 50 cm2. If you measure the area of \u200b\u200bthe core, then the number of turns is considered to be dividing the resulting area by 50. For example, if the cross-sectional area is 100 cm, then you need to make two turns of the winding per 1 volt.
The calculation of the total number of turns of wire is done by multiplying the amount obtained by 1 volt by the total voltage. For example, 2 turns multiplied by 220, we get 440 turns in one winding. In the loaded mode of operation of the transformer, part of the voltage may be lost to overcome the resistance of the secondary windings. Recommended number of turns determine 5-9% more received in the calculation.
The winding voltage indicator is multiplied by the obtained coefficient, such a calculation is identical for all transformer windings. The operating current indicator is calculated from the parameters of the voltage in the network and the power of the transformer. The resulting operating current value is converted to milliamps and the wire diameter is calculated.
Using a table
To select the optimal indicator for the number of wires, special tables are used that show how the resulting wire diameter is replaced instead of one by two or more identical in terms of joint work.
For example, the value obtained in the calculation is 0.52 mm, therefore, according to the table, it is determined that such an indicator can be changed to two wires of 0.32 mm each or take three wires of 0.28 mm. This means that the wire diameter can consist of several diameters, the total value of which should not be lower than that obtained in the calculation.
Checking the correctness of the choice
Finally, the window fill factor is checked. It should not be higher than 0.5, taking into account the insulation of the wire. If its value is greater, then you need to take a larger section of the core and the whole calculation is done again.
The principle of calculating the transformer online
This calculation allows quickly change settings, while reducing the time to develop the capacity of the transformer. Initial indicators and data from automatic tables are entered into the fields of different colors. You can correct the data by entering your own indicators. The calculator will allow you to calculate the required wire area and the number of turns in each of the windings.
Data to be entered in the automatic calculator field
Before you can automatically calculate the transformer online, you should define indicators for input:
- voltage in the primary winding, usually substitute the value of 220 V;
- output voltage of the secondary winding in volts (substitutes data from your requirement);
- output current of the secondary winding in amperes (enter your own value);
- parameters of the outer and inner diameter of the core (set your value);
- specify the height of the core according to its own parameters.
The calculation of the transformer according to the formulas selected from the sources is carried out rather slowly, there is a danger of making mistakes. Online calculation will allow you to design quickly and efficiently. Such a convenient calculation is suitable for beginner radio amateurs, and professionals can use it with no less success. The fastest way to calculate is enter all the data and click the button.
Positive aspects of working with automatic calculation online
The calculations of the old transformer that fell into the hands will not seem difficult and long now. The data obtained for rewinding the transformer will be ideal for those initial data that are entered into the fields of the table, in addition, an automatic calculator has a lot of advantages:
Transformer constructors got a reliable assistant in the form of an online calculator, now any novice radio amateur will fulfill his dreams of making a transformer with his own hands.
Such transformer calculation method Of course, it is very approximate, but it is quite suitable for amateur radio practice.
In addition, all the following calculations are relevant only for transformers with an E-shaped core and for operation with an industrial frequency current of 50 Hz.
So, let's begin....
Task: you need a transformer with an output voltage of 12V and a current on the secondary winding of at least 1A. (if there are several windings, then the currents add up).
The power of the secondary winding is 12V * 1A = 12W.
Since the efficiency of transformers is approximately 85%, the power taken by the primary during operation will be approximately 1.2 times higher and it will turn out 12W * 1.2 = 14.4W.
Where S- area of the core, P1- power of the primary winding.
get 4.93 sq. cm. (let's round it up to 5...)
This is the required minimum core area. If you can use more, that's even better.
Here:
W- number of turns,
Ktr - transformation ratio,
Sc - cross-sectional area of the core.
Since we decided to take Ktr = 50, we consider:
W1= 50/5 * 220 = 2200
W2= 50/5 * 12 = 120
where I is the current flowing through the winding.
Oh, yes .... we still do not know the current that the primary will consume ....
Well, well, this is also not a problem: we know the voltage, the power too, it turns out:
I1= P1/U1=14.4/220=0.065A.
So:
the diameter of the wire for the primary will be:
D1 \u003d 0.7 * per root of 0.065 \u003d 0.18 mm.
For the secondary winding:
D2 = 0.7 * per root of 1 = 0.7 mm.
That's the whole calculation!
How to calculate a power transformer and wind it yourself.
You can choose a ready-made transformer from among the unified types of TN, TA, TNA, Chamber of Commerce and others. And if you need to wind or rewind a transformer for the required voltage, what should you do then?
Then it is necessary to choose a power transformer suitable for power from an old TV, for example, a TS-180 transformer and the like.
It must be clearly understood that the more turns in the primary winding the greater its resistance and therefore less heating, and secondly, the thicker the wire, the more current can be obtained, but it depends on the size of the core - whether you can place the winding.
What do we do next if the number of turns per volt is unknown? This requires LATR, a multimeter (tester) and a device that measures alternating current - an ammeter. We wind, at your discretion, the winding over the existing one, any wire diameter, for convenience, we can wind it simply with a mounting wire in insulation.
Formula for calculating the turns of a transformer
50/S
Related formulas: P=U2*I2 Sheart(cm2)= √ P(va) N=50/S I1(a)=P/220 W1=220*N W2=U*N D1=0.02*√i1(ma) D2 =0.02*√i2(ma) K=Swindows/(W1*s1+W2*s2)
50/S is an empirical formula, where S is the area of the transformer core in cm2 (width x thickness), it is believed that it is valid up to a power of the order of 1kW.
Having measured the area of \u200b\u200bthe core, we estimate how many turns to wind at 10 volts, if it is not very difficult, without disassembling the transformer, we wind the control winding through the free space (slot). We connect the laboratory autotransformer to the primary winding and apply voltage to it, turn on the control ammeter in series, gradually increase the voltage with the LATR-th, until the no-load current begins to appear.
If you plan to wind a transformer with a fairly "hard" characteristic, for example, it can be a transmitter power amplifier in SSB, telegraph mode, where rather sharp load current surges occur at high voltage (2500 -3000 V), for example, then the no-load current transformer, we set about 10% of the maximum current, at the maximum load of the transformer. By measuring the resulting voltage, wound secondary control winding, we calculate the number of turns per volt.
Example: input voltage 220 volts, measured secondary voltage 7.8 volts, number of turns 14.
Calculate the number of turns per volt
14/7.8=1.8 turns per volt.
If there is no ammeter at hand, then you can use a voltmeter instead, measuring the voltage drop across the resistor included in the break in the voltage supply to the primary winding, then calculate the current from the measurements obtained.
Option 2 for calculating the transformer.
Knowing the required voltage on the secondary winding (U2) and the maximum load current (In), the transformer is calculated in the following sequence:
1. Determine the value of the current flowing through the secondary winding of the transformer: I2 \u003d 1.5 In, where: I2 - current through the winding II of the transformer, A; In - maximum load current, A. 2. Determine the power consumed by the rectifier from the secondary winding of the transformer: P2 = U2 * I2, where: P2 - maximum power consumed from the secondary winding, W; I2 - maximum current through the secondary winding of the transformer, A. 3. We calculate the power of the transformer: Ptr \u003d 1.25 P2, where: Ptr - transformer power, W; P2 - maximum power consumed from the secondary winding of the transformer, W. If the transformer must have several secondary windings, then first calculate their total power, and then the power of the transformer itself. 4. Determine the value of the current flowing in the primary winding: I1 = Ptr / U1 , where: I1 - current through the winding I, A; Ptr - calculated power of the transformer, W; U1 - voltage on the primary winding of the transformer (mains voltage). |
5. We calculate the required cross-sectional area of the core of the magnetic circuit: S = 1.3 Ptr , where: S - cross section of the core of the magnetic circuit, cm2; Ptr - transformer power, W. 6. Determine the number of turns of the primary (network) winding: w1 = 50 U1 / S , where: w1 - number of winding turns; U1 - voltage on the primary winding, V; S - cross section of the core of the magnetic circuit, cm2. 7. Count the number of turns of the secondary winding: w2 = 55 U2 / S , where: w2 - number of turns of the secondary winding; U2 - voltage on the secondary winding, V; S-section of the core of the magnetic circuit, cm2. 8. Calculate the diameter of the wires of the transformer windings: d = 0.02I, where: d-wire diameter, mm; I-current through the winding, mA. |
The approximate diameter of the wire for winding the windings of the transformer in table 1.
Table 1 | ||||||||
Ichange, ma | <25 | 25 - 60 | 60 - 100 | 100 - 160 | 160 - 250 | 250 - 400 | 400 - 700 | 700 - 1000 |
d, mm | 0,1 | 0,15 | 0,2 | 0,25 | 0,3 | 0,4 | 0,5 | 0,6 |
After performing the calculations, we proceed to the choice of the transformer iron itself, the wires for winding and the manufacture of the frame on which we will wind the windings. To lay the insulation between the layers of the windings, we will prepare varnished cloth, harsh threads, varnish, and fluoroplastic tape. We take into account the fact that the Ш - shaped core has a different window area, so it will not be superfluous to calculate the check: will they fit on the selected core. Before winding, we calculate whether the windings will fit on the selected core.
To calculate the determination of the possibility of placing the required number of windings:
1. We divide the width of the winding window by the diameter of the wound wire, we get the number of turns wound
on one layer - N¹.
2. We calculate how many layers are needed to wind the primary winding, for this we divide W1 (the number of turns of the primary winding) by N¹.
3. Calculate the thickness of the winding layers of the primary winding. Knowing the number of layers for winding the primary winding, we multiply by the diameter of the wire being wound, taking into account the thickness of the insulation between the layers.
4. Similarly, we consider for all secondary windings.
5. After adding up the thicknesses of the windings, we conclude: can we place the required number of turns of all windings on the transformer frame.
Another a method for calculating the power of a transformer by dimensions.
You can roughly calculate the power of the transformer using the formula:
P=0.022*S*С*H*Bm*F*J*Кcu*efficiency;
P - transformer power, V * A;
S - core section, cm²
L, W - dimensions of the core window, cm;
Bm - maximum magnetic induction in the core, T;
F - frequency, Hz;
Кcu - filling factor of the core window with copper;
Efficiency - efficiency of the transformer;
Keeping in mind that for iron, the maximum induction is 1 T.
Value options for calculating the power of the transformer Efficiency = 0.9, f = 50, B = 1 - magnetic induction [T], j = 2.5 - current density in the winding wire for continuous operation, Efficiency = 0.45 - 0.33.
If you have a fairly common iron - OSM transformer-0.63 U3 and the like, can you rewind it?
Explanation of OSM designations: O - single-phase, C - dry, M - multi-purpose.
According to its technical characteristics, it is not suitable for switching on a single-phase 220 volt network. Designed for a primary winding voltage of 380 volts.
What to do in this case?
There are two solutions.
1. Rewind all windings and rewind.
2. Wind only the secondary windings and leave the primary winding, but since it is designed for 380V, it is necessary to wind only part of the winding from it, leaving it at 220V.
When winding the primary winding, approximately 440 turns (380V) are obtained when the core is W-shaped, and when the core of the OSM transformer is wound on the SL, these are different - the number of turns is less.
Data of primary windings for 220V of OSM transformers of the Minsk Electrotechnical Plant, 1980.
- 0.063 - 998 turns, wire diameter 0.33 mm
- 0.1 - 616 turns, wire diameter 0.41 mm
- 0.16 - 490 turns, wire diameter 0.59 mm
- 0.25 - 393 turns, wire diameter 0.77 mm
- 0.4 - 316 turns, wire diameter 1.04 mm
- 0.63 - 255 turns, wire diameter 1.56 mm
- 1.0 - 160 turns, wire diameter 1.88 mm
OSM 1.0 (power 1 kW), weight 14.4 kg. Core 50x80mm. Iхх-300mA
Connection of windings of CCI transformers
Let's look at an example CCI-312-127/220-50 armor structure.
Depending on the voltage in the network, voltage can be applied to the primary winding at terminals 2-7 by connecting terminals 3-9 to each other, if it is increased, then at 1-7 (connect 3-9), etc. The connection diagram shows the case of low voltage in the network.
Often there is a need to use unified transformers such as TAN, TN, TA, CCI for the desired voltage and to obtain the necessary load capacity, and in simple terms we need to select, for example, a transformer with a secondary winding of 36 volts and so that it gives 4 amperes under load, the primary of course 220 volts.
How to choose a transformer?
From the beginning, we determine the required power of the transformer, we need a 150 W transformer.
The input voltage is single-phase 220 volts, the output voltage is 36 volts.
After selection according to the technical data, we determine that in this case the transformer of the TPP-312-127 / 220-50 brand with an overall power of 160 W (the closest value to the big side) is most suitable for us, transformers of the TN and TAN brands are not suitable in this case.
The secondary windings of TPP-312 have three separate windings with a voltage of 10.1v 20.2v and 5.05v, if you connect them in series 10.1 + 20.2 + 5.05 = 35.35 volts, then we get an output voltage of almost 36 volt. The current of the secondary windings according to the passport is 2.29A, if we connect two identical windings in parallel, we get a load capacity of 4.58A (2.29 + 2.29).
After choosing, we only have to correctly connect the output windings in parallel and in series.
We connect the windings in series for inclusion in the 220 volt network. We turn on the secondary windings in series, gaining the required voltage of 36V each on both halves of the transformer and connect them in parallel to obtain a double value of the load capacity.
The most important thing is to correctly connect the windings in parallel and series connection, both primary and secondary windings.
If the transformer windings are not turned on correctly, it will hum and overheat, which will then lead to premature failure.
By the same principle, you can choose a ready-made transformer for almost any voltage and current, for power up to 200 W, of course, if the voltage and current have more or less standard values.
Miscellaneous questions and advice.
1. We check the finished transformer, and its primary winding current turns out to be too high, what should I do? In order not to rewind and not waste extra time, wind another winding on top, turning it on in series with the primary.
2. When winding the primary winding, when we make a large margin in order to reduce the no-load current, then keep in mind that the efficiency of the trance also decreases accordingly.
3. For high-quality winding, if a wire with a diameter of 0.6 or more is used, then it must be straightened out so that it does not have the slightest bend and fits tightly when winding, clamp one end of the wire in a vise and pull it with force through a dry rag, then wind with the necessary effort, gradually winding layer by layer. If you have to take a break, then provide for fixing the coil and wire, otherwise you will have to do it all over again. Sometimes preparatory work takes a lot of time, but it's worth it to get a quality result.
4. For a practical determination of the number of turns per volt, for iron in the shed, you can wind a winding around the core with a wire. For convenience, it is better to wind a multiple of 10, i.e. 10 turns, 20 turns or 30 turns, winding more does not make much sense. Further from LATR, we gradually apply voltage increasing it from 0 and until the tested core starts to buzz, this is the limit. Next, we divide the resulting voltage supplied from LATR by the number of wound turns and get the number of turns per volt, but we slightly increase this value. In practice, it is better to wind an additional winding with taps to select the voltage and no-load current.
5. When disassembling - assembling armor cores, be sure to mark the halves as they fit to each other and assemble them in the reverse order, otherwise you are guaranteed buzz and rattle. Sometimes buzz cannot be avoided even with proper assembly, so it is recommended to assemble the core and fasten it with something (or assemble it on a table, and put a heavy load on top through a piece of board), apply voltage and try to find a good position of the halves and only then finally fix it. This advice also helps, put the finished assembled transformer in varnish and then dry it well at a temperature until completely dry (sometimes they use epoxy, gluing the ends and drying until completely polymerized under weight).
Connection of windings of individual transformers
Sometimes it is necessary to obtain a voltage of the desired value or a larger current, and there are ready-made separate unified transformers available, but for a lower voltage than necessary, the question arises: can individual transformers be connected together to obtain the desired current or voltage value?
In order to get a constant voltage from two transformers, for example 600 volts direct current, it is necessary to have two transformers that would give out 300 volts after the rectifier and after connecting them in series two sources of constant voltage we get 600 volts at the output.
Very often, a step-down transformer is required to power amateur radio designs or to power finished devices. The exact calculation of a power transformer is very complicated, but for an approximate calculation, you can use simplified formulas. In this article, we will consider how to calculate a transformer assembled on the most common magnetic circuit from W-shaped plates.
To calculate the transformer, we need to know: the desired voltage on the secondary winding and the load current. If the load current is not known, but its power is known, then it will not be difficult to calculate the current - you need to divide the power by the voltage on the secondary winding.
1. Calculation of the current of the secondary winding
I2 = 1.5*In, Where
- I2 - current in the secondary winding, A,
- In - load current, A.
2. Determination of the power consumed from the secondary winding
P2 = U2*I2, Where
- P2 is the power of the secondary winding, W,
- U2 - voltage of the secondary winding, V,
- I2 - current of the secondary winding, A.
If several secondary windings are needed, then we consider the power of each winding, and then add the power of all secondary windings and substitute in the following formula.
3. Determining the power of the transformer
Pt = 1.25*P2, Where
- RT is the total power of the transformer, W,
- P2 is the power of the secondary winding, W.
4. Calculation of the current of the primary winding
I1 = Pt/U1, Where
- I1 - current in the primary winding of the transformer, A,
- Pt - transformer power, W,
- U1 is the voltage of the primary winding, V.
5. Determining the required cross section of the core of the magnetic circuit
S = 1.3* √ Pt, Where
- ² ,
It should be noted that the magnetic circuit must be selected so that the ratio of the width of the core (central plate) of the magnetic circuit to the thickness of the set is within 1 ÷ 2.
6. Calculation of the number of turns in the primary winding
W1=50*U1/S, Where
- W1 is the number of turns of the primary winding, pcs,
- U1 is the voltage of the primary winding, V,
- S is the cross-sectional area of the core of the magnetic circuit, cm ² .
7. Calculation of the number of turns in the secondary winding
W2 = 55*U2/S, Where
- W2 - number of turns of the secondary winding, pcs,
- U1 - voltage of the secondary winding, V,
- S is the cross-sectional area of the core of the magnetic circuit, cm ² .
8. Determination of the diameters of the wires of the transformer windings
d = 0.632*√ I, Where
- d - wire diameter, mm,
- I is the winding current, A (respectively, we substitute I1 and I2 for the primary and secondary windings).
The calculation is given for copper wire.
9. Checking the occupancy of the windows of the magnetic circuit
After selecting the plates of the magnetic core, you should check whether the wire will fit on the transformer frame.
So \u003d 50 * Pt, Where
- So - the area occupied by the wound wires, in one window of the magnetic circuit, mm 2,
- Pt is the power of the transformer, W.
If the window area of the selected magnetic circuit is greater than or equal to the calculated one, then the wire will fit.
The plates of the magnetic circuit must be assembled in overlap, as shown in the figure above.
The magnetic circuit should be tightened with a cage or studs with nuts, the studs must be wrapped with paper or other insulating material so that the studs do not close the plates. If the magnetic circuit is poorly tightened, then it will buzz.
The wires should be wound evenly and tightly (otherwise they may not fit). Between each row it is necessary to lay thin paper or lavsan film in 1-2 layers and 3-4 layers between the windings.
For the convenience of winding, you can make a simple device shown in the figure:
The device consists of two plywood racks fixed on a common base and a metal bar inserted into them, curved in the form of a handle at one end. With one hand we turn the handle, with the second we direct the wire, the coil with the wire can be placed on one more bar, but without a handle.