Calculate a toroidal transformer: principle of operation, core section, advantages of operation

High quality transformers are widely used in various industries. Many craftsmen appreciate such units because they are quite compact and lightweight, but the efficiency is at a high level. These characteristics are especially important in welding machines and voltage stabilizers. But in order for such a unit to work properly, it is necessary to correctly calculate the toroidal transformer.

Short description

Modern manufacturers are engaged in the industrial production of several types of magnetic circuits for transformers - armored, rod, toroidal. If we compare their performance characteristics and areas of use, then the latter option can be considered more effective. It's all about what it is the device has extremely positive parameters, thanks to which it is actively used in modern industry.

High performance and long service life have influenced the fact that now the toroidal transformer is the basic element in lighting equipment, voltage stabilizers, uninterruptible power supplies, radio engineering, as well as medical and diagnostic equipment.

The manufacturers themselves claim that such a unit is presented in the form of a single-phase installation, which can both reduce and increase power. For high-quality operation, the transformer is equipped with a powerful core with two or more windings. But the principle of its operation is no different from those models that are equipped with armored or rod winding.

Regardless of its performance, a transformer is a device whose main task is to convert electricity from one quantity to another. However, even the smallest design changes can significantly alter the overall dimensions and weight of an electrical installation. Due to this, the technical and economic parameters will only increase.

Main advantages

In such a transformer, the magnetic circuit has the shape of a toroid, in other words - all rings have a rectangular cross section. The unique performance characteristics are highly regarded in both domestic and industrial applications. Besides, The toroidal unit has a number of additional advantages in contrast to standard rod and armored models:

1. The craftsmen had an excellent opportunity to use steel with increased magnetic permeability for the core (E-370, 340).
2. It is known that the final scattering flux in an ideal toroidal coil should be zero. In such a transformer, this indicator has a certain finite value. But such leakage fluxes are not as large as in conventional models, therefore external magnetic fields do not affect the coordinated operation of the transformer.
3. There are no gaps and joints in the core.
4. The master can safely use the structural properties of the core, since in the toroidal unit the direction of the magnetic field completely coincides with the rolling of the tape.

All of the above advantages allow achieving high economic and electrical performance. Due to this, the performance of the equipment significantly increases:

• The total number of turns that are used to obtain the magnitude of the inductive primary winding is significantly reduced. This effect is achieved through the use of steels with high magnetic permeability. In some designs, the craftsmen managed to reduce the final copper consumption by 25%.
• The complete absence of gaps and the presence of high-alloy steel is the reason that higher induction is achieved in the transformer core. This functional advantage has absolutely no effect on THD. As a result, the master manages to double Bmax, which is considered impossible in armored transformers. As a result, the total weight and volume of the working core are reduced.
• A uniform frequency response of the stage is achieved due to the small value of the leakage inductance. The presence of minimal distortion due to transient processes allows the use of a rather deep negative feedback type.

Due to the fact that the toroidal transformer has a small magnetic field, even the closest installation does not affect the interaction with other structural elements.

Independent manufacture of the unit

Before proceeding with the creation of such a unit, it is necessary to prepare all the necessary tools and materials. You may even need a sewing machine, a sturdy needle and ordinary matches to make a better model, but such parts can be found in almost every home.

The main consumable material is iron, from which the base parts of the transformer are made. For work, you need high-quality steel, which should be in the shape of a torus. Do not forget about a good wire in varnish insulation. Reliable fixation cannot do without PVA glue and masking tape.

Separately, it is worth considering that the high-quality work of the windings depends on tissue-based electrical tape. It is also worth purchasing a high-quality wire in rubber or silicone insulation. This element is needed to securely connect all ends of the winding.

Preparation of transformer steel

It may seem to novice craftsmen that it is extremely difficult to get the basic structural element, but in practice everything is completely different. The fact is that even ordinary metal collection points often have inoperative voltage stabilizers. In the Soviet period, they were very common, as they were used in black and white televisions, which prolonged the performance of picture tubes.

The serviceability of such a device does not matter at all, since only toroidal transformers, which are located in the internal compartment of the stabilizer, are of particular value. It is this part that is used by the craftsmen as the basis of the entire structure.

On the way to the removal of transformers, there is always a winding made of aluminum wire. Do not forget that the core also needs preparatory work. The master must round off the sharp edges of this part as much as possible, since the varnish insulation may be damaged during the winding process. On top of the transformer steel, an electrical tape on a fabric basis must be laid. In this case, only one insulating layer is needed.

Winding rules

Before proceeding with this type of work, you need to make a calculation of the toroidal transformer over the cross section of the core. Of course, the master can use special online calculators, of which there are a lot on the Internet. But you can choose a simpler option, where for all calculations you need to prepare only a ruler and a calculator.

Of course, it may have some errors, since the calculation does not imply compliance with all those factors that occur in nature. The main thing is to adhere to the rule that the final power in the secondary coil should not exceed those in the first winding.

When the master has reached this stage and needs to wind the toroidal unit, he should be extremely careful, since this process is quite time consuming. An excellent option is considered when it is possible to independently disassemble the magnetic circuit, and after winding, assemble it.

Otherwise, you can resort to using an ordinary spindle, on which you need to carefully wind a certain amount of pre-prepared wire. Only after this can the spindle be passed the required number of times through the torus, evenly laying the turns of the windings. Of course, it will take a lot of time to implement such an idea, but the result is worth it.

It should be noted that in standard situations the craftsmen carry out additional insulation of the toroidal core from the windings (even if varnished wire is used). High quality electrical board is especially popular., which meets all GOST 2824 standards. The thickness of this material is within 0.8 mm.

During the work, the wizards adhere to the following scheme:

• The cardboard is neatly wound onto the core with a slight grip of the previous round. The end of the material must be fixed with keeper tape or PVA glue.
• All ends of the core should be protected with cardboard washers with small notches from 10 to 20 mm, pitch length - 35 mm. Both the outer and inner edges must be closed with small stripes. It should be noted that the technological washers are fixed at the finishing stage, and all rubberized teeth are bent. A keeper tape is wound over the entire structure.
• If the cuts were made on the strips themselves, then a small margin must be present in order to achieve a greater end height. All rings must be attached strictly in width, they are superimposed over the folds.
• In rare cases, the rings can be made of special electrical plywood, thick PCB. The vulnerable inner and outer edges are protected with cardboard strips with slight folds along the edges. There should be a small air gap between the first turns of the winding and the core. This approach is especially important when the edges under the wire will fray. Thus, the vulnerable current-carrying part will never touch the toroidal core. A keeper tape must be wound on the top layer. In some cases, craftsmen prefer to smooth the outer edge of the rings, due to which the winding of the corners goes smoothly.

If the transformer has increased power, then the copper wire should be rectangular. This approach saves space. The vein must be thick so that it does not melt while a lot of stress passes through it.

Subtleties of calculation manipulations

Most often, the primary winding is powered by a conventional 220 V alternating voltage network. If the master needs two secondary windings so that each produces at least 12 V, then the cross-sectional area should be at least 0.23 sq. mm. But these data are not enough to correctly calculate the toroidal transformer.

The master needs to divide 220 V by a certain amount of secondary voltages. So you can get a coefficient of 3.9, which will mean that the cross-section of the wire for the secondary winding should be similar to this indicator. But in order to determine the number of turns, you need to resort to a fairly simple formula: voltage 220 V multiplied by a factor of 40, and the resulting figure should be divided by the cross-sectional area magnetic circuit.

Separately, it should be taken into account that the level of efficiency of a toroidal transformer and its operational life depend on the correctness of the calculations performed. That is why it is better to double-check everything several times in order to avoid the most common mistakes.

Specialist recommendations

When the master has carefully studied the method of making a transformer with his own hands, he can safely proceed to the practical part. Since winding turns is considered a very difficult process, you will need to be patient in order for the final result to meet all expectations. After all, the operational characteristics of the device depend on how well this stage is performed.

To simplify this task, you can use a special machine designed for winding toroidal transformers. The price of such a unit is considered affordable, and if desired, it can be made with your own hands.