Designs and characteristics of magnetic cores of transformers

   The magnetic cores of low frequency 50Hz transformers are usually made of sheet electrical steel (and in the case of circular magnetic cores for toroidal transformers- from coiled steel) containing from 0.5 to 5% silicon (Si), up to 1% carbon (C), the rest is iron (F). Due to the fact that their losses increase significantly with increasing frequency, they are usually applied within the limits of no higher than audio frequencies. The grades of electrical steel, according to GOST 802-58, are designated by the letter E, which means electric steel. The first number indicates the average percentage of silicon content, the second characterizes

electromagnetic properties: number 1 - normal losses, 2 - reduced, 3 - very small, 4 - normal at 400 Hz. The second numbers 5 and 6 indicate increased magnetic permeability in weak fields (less than 0.01 AW / cm), 7 and 8 in medium fields (0.1-10 AW / cm). The third digit 0 indicates that the steel is cold rolled textured. The third and fourth - 00 - denote cold-rolled low-textured steel. The letter A after the numbers denotes particularly low specific losses. For steels with increased accuracy of rolled and surface finishing, the letter P is introduced at the end. Cold-rolled steels E310-E380, in addition to silicon (3-3.25%) and carbon (0.0003%), contain sulfur (0.003%), manganese and phosphorus (less than 0 , 1%). These steels differ from others in that they have high permeability along the rolled stock and low permeability across the rolled stock. One of the main parameters of steel is loss in steel, which includes:
  • losses due to hysteresis;
  • eddy currents;
  • on aftereffect;
Hysteresis loss is the work expended to reverse the magnetization of steel. It is usually assumed that the hysteresis losses do not depend on the sheet thickness, but when the sheet is rolled 0.2 mm and thinner, the steel is compacted (since adjustment to the required values is performed on cold sheets) and the hysteresis losses increase. Hysteresis losses per one cycle of magnetization reversal (at constant induction) in the limit of 10–20 times the frequency change (50–1000 Hz) can be practically considered constant. Consequently, when referred to a unit of time (1 sec), they increase in proportion to an increase in frequency.
Eddy currents are currents that appear in steel under the influence of e. etc., induced by a magnetic flux (in planes perpendicular to the direction of the flux). These currents lead to losses. With a decrease in the thickness of the plate, the emf decreases. etc. with. plates and the ohmic resistance of steel increases. The total losses in the steel of the magnetic circuit for eddy currents decrease approximately in proportion to the decrease in the thickness of the plate. But currents can also be closed in the thickness of the magnetic circuit through the contacting surfaces of the plates, therefore, there must be insulation between the plates, especially with an increase in the width of the plates and an increase in induction. The value of eddy currents and losses is also influenced by the ohmic resistance of the steel (not to be confused with the magnetic resistance). The ohmic resistance of steel (like wires) in ohms corresponds to the resistance of 1 m of length with a cross section of 1 mm2. With an increase in the percentage of silicon, the ohmic resistance of steel increases. The loss increases in proportion to the square of the increase in frequency.
Aftereffect losses are caused by the magnetic viscosity of the material and depend on the processing of ferromagnetic materials. They are determined by the difference between the total losses and losses due to hysteresis and eddy currents. With increasing frequency, these losses increase proportionally.
  The total active losses of electrical steels with changes in induction (within the operating values) change in proportion to the square of the induction, at inductions below 0.5-0.7 T they are somewhat overestimated against this ratio. The total active losses in steel and the reactive component determine the magnitude of the magnetizing current.

Table 1 shows the active losses at a frequency of 50 Hz for basic electrical steels.

steel grade Sheet thickness, mm Specific losses W / kg at V = 1.0 T Specific losses W / kg at V = 1.5 T Specific losses W / kg at V = 1.7 T Induction В, T 300АВ / cm  
E11-E12 1,0 5,8-5,5 13,4-12,5 2,00-1,98
E11-E13 0,5 3.3-2,8 7,7-6,5 2,00-1,98
E21-E22 0,5 2,5-2,2 6,1-5,3 1,95
E31-E32 0,5 2,0-1,8 4,4-3,9 1,94-1,92
E31-E32 0,35 1,6-1,4 3,6-3,2 1,92
E41-E42 0,5 1.55-1.4 3,5-3,1 1,9-1,89
E43-E43A 0,5 1,25-1.15 2,9-2,7 1,89
E41-E42 0,35 1,35-1,2 3,0-2,8 1,9-1,89
E43-E43A 0,35 1,05-0.9 2,5-2,2 1,89
E310-E320 0,5 1,1-0.95 2,45-2,1 3,2-2,8 1,98-2,00
E330 0,5 0,8 1,75 2,5 2,00
E310-E320 0,35 0,8-0,7 1,75-1,5 2,5-2,2 1,98-2,00
E330-E330A 0,35 0,6-0,5 1.3-1,1 1,9-1,6 2,00
In various transformers, steel sheets with a thickness of 1.0 are used; 0.5; 0.35mm various brands. In household appliances for power transformers, chokes, etc. mainly used steel grades E41, E42 (less often E43), E310, E320 with a thickness of 0.35 mm (rarely 0.5 mm). In transformers used in technology for various devices and operating mainly at a constant supply voltage, it is advisable to use the above brands and additionally E43, E43A, EZZO, EZZOA. Steel 0.35 mm thick should be used. It is steels with such a thickness that provide the minimum values of the above losses. In automation devices, telemetry using frequencies of 200, 400, 1000 Hz, steel grades E44, E340 should be used, with a sheet thickness of 0.2 mm. These steels are also used in transformers for audio amplifiers. When manufacturing transformers for the indicated frequencies, all calculations, starting with the formula wSc = 45E / B, where Sc is the section of the magnetic circuit, E-emf, w is the number of winding turns, B is the magnetic induction, T are performed taking into account the corresponding frequency ... Table 2 shows the losses for these brands at a frequency of 400 Hz.
In addition to these brands, there are E1100-E3200 brands, which are close in their parameters to the E11-E32 brands. They are not used for low power transformers.
steel grade Sheet thickness, mm Specific losses W / kg at B = 0.75T Specific losses W / kg at B = 1.0 T Specific electrical resistance Ohm * mm2 / m
E44 0,35 10,7 19 0,57
E44 0.20 7,2 12,5 0,57
E44 0.10 6 10,5 0,57
E340 0,20 7 12 0,47
 Loss at the joints of the magnetic circuit. As mentioned above, it is customary to build the magnetization characteristics according to the magnetic field strength (AB / cm). But at the same time, the magnetic resistance of the steel of the magnetic circuit (and the cross section) must be the same along the entire length of the middle magnetic line of the magnetic circuit. A magnetic circuit that meets these requirements is a ring magnetic circuit, the so-called torroid. Small torroids are widely used in automation schemes, where they are made either stacked from stamped rings of sheet steel, or twisted from a tape of the corresponding steel grade and are called twisted or tape (see Fig.) тороидальный магнитопроводMagnetic tape circuits with a magnetic line length from 0.4 to 1.5 m have found wide application in the manufacture of current transformers installed in high voltage installations. For voltages of 6 and 10 kV, these transformers are made both tape and stacked from stamped L-shaped plates. Magnetic cores made of stamped plates are assembled so that the gaps alternate with solid plates (overlap). Since each plate has two gaps, there will be four joints in the path of the magnetic flux. Part of the magnetic flux passes through the gap, but most of the flux passes from the contact plane to the adjacent plates, which significantly increases the induction in these plates, increasing the magnetizing current. Thus, there are four areas of increased resistance in the path of the magnetic flux. For an approximate assessment of the increase in tension in these joints, one can compare the characteristics of magnetization, taken up to significant multiplicities of strengths (up to 100 AV / cm) on tape magnetic circuits and type-set from L-shaped plates. The figure shows the factory averaged characteristics for some steel grades. Characteristics 1 and 2 are given by double lines, the upper ones correspond to the best steels, the lower ones correspond to the worst ones.характеристика трансформаторной стали  1 - tape magnetic circuit, steel E41, E42; 2-stacked, from stamped L-shaped plates, steel E11. E-12, E15, E45, E46, E47, E48; 3 - tape, steel E310.
The characteristics of curve 2 are plotted for magnetic conductors with an average magnetic path length of 45 cm. overcoming increased resistance at the joints of the plates. Comparing curves 1 and 2, you can approximately determine the loss at the joints. Thus, at an induction of 1.0 T, the magnetization current of curve 2 (according to the averaged curve shown by the dotted line) is more than 2 times higher than the magnetization current of curve 1 (1.8-0.7 Av / cm). Of course, the gap itself is fractions of a millimeter, but one should also take into account the adjacent sections of the plates, where the flow transitions to the through plates. In this case, the flow in the through plates should reach 2 T, but since even at a strength of 300 Av / cm the induction of these steels does not exceed 1.9 T and the permeability of the steel approaches the permeability of air, large scattering fluxes are inevitable. As is clear from a comparison of the curves, the operating induction with a magnetic tape can be taken higher, since at 2.5 Av / cm the induction of curve 1 will be 1.4 T, curve 2 - 1.1 T. The difference between the strengths of characteristics 2 and 1 (with the same induction) is determined by the increased resistance of the joints. Let us designate Нс the tension in the joints, Н1 - by the intensities of characteristics 2 and 1 (with the same Н2 - the tension, which determines the characteristic 2. Comparative data are summarized in Table 3.
Induction B, T 0,5 0,8 1,0 1,2 1,4 1,5 1,6 1,7
H1 0,3 0,5 0,7 1,2 1,4 3,5 6,5 10,0
H2 0,6 1,2 1.8 4,0 11.5 17,0 27,5 40,0
NS 0,3 0,7 1,1 2,8 10,1 13,5 21,0 30,0
Ks = Hs / H1 1,0 1,4 1,57 2.33 7,23 3,9 3.25 3,0
The coefficient Kc determines the ratio of Hc to H1. The largest value of the coefficient corresponds to an induction slightly higher than 1.4 T. With a further increase in induction, the value of Kc decreases and tends to zero in the limit, which corresponds to the value of induction, which is far beyond the working part of the characteristic.
Since the resistance of the joints is determined by the increased value of the induction in the joints and at these inductions the characteristics of all steels approach each other (see graph), the losses in the joints depend little on the quality of the steels and, if there are joints in the magnetic circuit, they enter as a constant and very significant component, equalizing the steels of increased and reduced quality (as can be seen from curves 2). Since in transformers with smaller dimensions, the magnitude of the magnetizing current is determined mainly by the joints of the plates, the working inductions in small transformers are taken much less than in high-power transformers.
    Stamped plates for magnetic circuits. Most of the low-power transformers are made on two types of magnetic circuits, armored — assembled from W-shaped plates, rod assembled from U-shaped, L-shaped and straight-sided plates. The plates are stamped from sheet steel with a thickness of 0.35 and 0.5 mm of the corresponding configuration.
In armored transformers (see Fig. 1), the middle rod is the main one; the winding is placed on it (usually on the frame). The plates are assembled over the cover, so that the gaps in the plates are located alternately on different sides of the winding. For the plates shown in the figure, the bridge (short side) is a separate part. For the plates shown in Fig. B and c, the bridge is integral with the main plate. The assembly of all plates of the core magnetic circuit is performed over the cover. Consider the ratio of the dimensions of the magnetic circuit. The main dimensions are: width of the main

rod A and the thickness of the package of the magnetic circuit B.

a — c - armored W-shaped: g — e - rod: U-shaped, L-shaped, type-setting of rectangular plates; st - joints in the magnetorhetoid.                                                                                                                                             

схема магнитопровода броневого трансформатора

Their product AB = Sс is the section of the steel of the magnetic circuit. The width of the magnetic circuit window B, its length D-section of the magnetic circuit window: BD = S0.
     Here are the approximate ratios of the remaining dimensions of the magnetic circuit. The thickness of the package is usually taken as B = (1-2) * A. For W-shaped plates, the width of the outer rods (and jumpers) is taken C = (0.5-0.6) * A. For rod magnetic circuits, the width of the window for single-coil transformers is taken B = (1-1.5) * A, for double-coil B = (1.5-2.5) * A. The length of the window is D = (2-3) * A. It must be borne in mind that these relations in a number of cases can significantly
The influence of the joints of the magnetic circuit on the resistance of the magnetic path was shown above. Consider W-shaped plates. The most commonly used plates are shown in Fig. a, less often, in Fig. b The plates shown in Fig. c used to be common, but recently they are rarely used. Magnetic circuit,
assembled on the plates shown in Fig. b and c, has two joints in the path of the magnetic flux; the magnetic circuit, assembled on the plates shown in Fig., and has four joints. With the width of the outer rods, 0.6 of the average induction in the outer rods (and in the bridge sides) is reduced by 20% induction in the main rod. Therefore, if in the latter the induction is 1.2 T, then in the extreme rods 1T. In this case, the resistance at joints with an induction of 1 T will be approximately 2 times less than the resistance at joints with an induction of 1.2 T (curve 2 in the graph). In the magnetically driven wheel on the plates shown in Fig. b, both joints fall on sections with an induction of 1.2 T. The resistance of the joints does not depend on the width of the outer rods. In the plates in Fig. in the joints fall on areas with reduced induction. The resistance of the joints is almost halved. On the plates (see Figure a), of the four joints, two joints fall on sections with reduced induction. The resistance is less than with the width of the outer rods equal to 0.5 of the width of the middle rod, but more than on the plates (Fig. B), and much more than on the plates (Fig. E.) But even with the width of the outer rods 0, 5 of the middle plate (Fig. C) have an advantage over the plates (Fig. B) in a simpler assembly and the possibility of using a frame of normal length.
    Rod magnetic conductors (Fig., D, e) have four joints. Both rods are usually made of the same width, regardless of whether one or both are working (having a winding). In relation to them, what has been said about the W-shaped plates remains valid. A magnetic circuit made of rectangular plates (Fig. E) has such a high magnetizing current that it cannot be recommended even for transformers with a capacity of 1-2 kVA.
It should be noted that there is a large dependence of the magnetizing current on the quality of stamping and assembly of plates. As said
above, a portion of the flow at the junction passes directly through the gap. With a low quality of stamping and the presence of burrs, as well as with poor-quality assembly, the gap may increase, which will lead to an increase in the magnetizing current. Especially poor-quality stamping affects the assembly of plates according to Fig. b. Since the joints fall at the ends of the frame sleeve, a swelling occurs in these places, which reduces the density of the package assembly. Consider a magnetic circuit assembled on W-shaped plates. These plates differ from those previously shown by the absence of an upper closing plate. The lower web is made of the same width as the middle bar. The plates are assembled over the lid. Above and below from the end, a lattice with longitudinal gaps is obtained. The cross-section of steel along the entire magnetic circuit turns out to be the same, except for the corners, where the cross-section is twice as large. The transition of the flux to the transverse plates occurs along the plane of contact of the plates, which is A2 * (n-1) for the magnetic flux, where n is the number of plates in the stack. If in the plates (in the figure) the flow transition to neighboring plates created areas of increased resistance, then in a magnetic core with a broadened base on the plates, the induction in the flow transition areas is almost 2 times lower than the induction in the rods, therefore, the flow transition to adjacent plates does not lead to an increase in current magnetization. Rod transformers are made in a similar way. In this case, the connecting sides must have a width equal to the double width of the rod, i.e. 2A. The contact area increases in comparison with W-shaped magnetic circuits up to 2A2 (n-1).
It should be said that plates of this configuration have been used in some rare cases for a long time. But their use was determined by the stability of the magnetic circuit and the constancy of the magnetizing current, which practically does not depend on the quality of stamping and assembly, than these plates compare favorably with the plates in the figure. In addition, the assembly of the magnetic circuit is greatly simplified.
   But the advantages of the magnetic characteristics of this configuration have been neglected for a long time. Of course, when with the plates in the figure it is necessary to reduce the induction by 20-25%, and for small transformers by 40-50% so that the induction at the joints in the through plates does not exceed the permissible value, the nature of the change in the magnetizing current also remains unchanged. The transformer works satisfactorily, but the steel is not used to the full.
    Permalloy alloys. Only after the appearance of sheet magnetic materials with very low losses (with a narrow hysteresis loop), with a sharp transition of the characteristic to the saturation region, various automation devices, magnetic converters, magnetic amplifiers, pulse circuits and other devices began to be introduced; at the same time, the complete unsuitability of the magpipelines with joints in the path of the magnetic flux was revealed. To clarify the possibility of using new magnetic materials not only in the form of torroids, but also with the use of steel plates, which are more convenient in terms of production technology, tests were carried out everywhere. The conclusions on tests carried out independently by different authors coincided. In many cases, torroids for new magnetic materials can be replaced with magnetic cores made of plates. Permalloy alloys are sheet materials with very high initial permeability and very low losses. These alloys contain from 40 to 80% nickel, up to 10% alloying metals (in some alloys they are absent), the rest is iron. The name of the brand of some alloys includes its composition, for example: H50 (nickel 50%, the rest is iron), H79M5 (nickel 79%, molybdenum 5%, the rest is iron). The main quality of alloys (in addition to high initial permeability and low losses) is a high linearity of the initial part of the characteristic, a sharp transition
in the saturated part and the small dependence of this part of the characteristic on the tension. If for ordinary electrical steel the use of a magnetic circuit with joints only reduces the quality of the magnetic circuit, then when using such magnetic materials as permalloy, the latter loses its basic qualities necessary for highly efficient magnetic converters.
    For permalloy alloys, the unsuitability of the outdated configuration of the magnetic core plates was obvious, which contributed to the widespread introduction of a new plate configuration for these materials.
Twisted magnetic circuits of armored and rod type. In the conditions of small-scale production, twisted magnetic circuits (tape, spiral) can be performed. They are manufactured as armored and rod types (Fig. 2).конструкция ленточного магнитопровода For such magnetopods, it is best to use strip steel, for example, brands E310, E320 and others with a thickness of 0.35 mm (or 0.2 mm to ensure a tighter winding). From flax-
You steel cut strips of the required width. Other steel grades can be used and strips can be cut from the steel sheet. In the absence of sheets of the required length, the strips can be joined. Docking is performed with an overlap (Fig. 3)стыковка листов в магнитопроводе , while the subsequent sheet will overlap and tighten the docking place. In places of bends, it is recommended to lay liners, which can be made of dense wood or getinax, according to one of the samples shown (depending on the thickness of the steel sheet and the width of the gap). The liners will provide a tighter winding of the core. Winding is carried out until the frame window is completely filled, then it is wedged by a strip of getinax with a thickness of 0.5-1.0 mm. When winding the core of a two-frame magnetic circuit, a strip of steel passes through both frames (when assembling, take into account the correct polarity of the windings). Previously, before winding the core, it is recommended to fasten both frames. For an armored transformer, the core is wound simultaneously with two tapes, so that they enter the frame window on one side. Both half-cores are wedged with one strip of getinax. The advantages of such magnetic circuits are: the size of the frame is not limited to the predetermined dimensions of the magnetic circuit; there are no areas of increased resistance in the magnetic circuit. The disadvantages include the complexity of manufacturing and repair. Currently, tape cores are widely used in various automation and electronics devices. However, the above implementation cannot be conveyed, which is a major hurdle. At the factory, the tape core is glued, cut into two horseshoes and the ends are ground. Transformers are usually made with rod type with two frames. The joints of the magnetic wire are inside the frames. According to engineers
Ulrich Crable and Gerhard Gezinhagei, on the basis of their tests, when grinding joints with an accuracy of 5 microns, the resistance of the magnetic circuit rises to 20%. This is much less than on a magnetic circuit with joints. In semi-handicraft workshops, it is impossible to ensure an accurate fit. When such a transformer is repaired and the ends of the magnetic core are corroded or if the core is not glued properly, the quality of the magnetic core will significantly decrease. The influence of the holes for the magnetic core tie. Previously, as a rule, the plates were equipped with holes for tying the magnetic circuit with pins. In addition, the studs were insulated from steel and metal brackets to avoid short-circuiting. For this, the holes were punched taking into account the insulation. Most of the specialized enterprises have completely abandoned the punching of a hole for the tie of small magnetic circuits, and a number of factories perform the tie of magnetic circuits of 100-200 W or more without punching holes. However, in non-specialized enterprises, stamping of plates with holes is still widely used. The latter, by decreasing the cross section, increase the magnetic resistance and, consequently, the magnetizing current. To a very large extent, this affects the W-shaped plates with a separate lining, since the holes fall on areas that already have increased resistance, further increasing it. This is especially true when the width of the extreme rods is 0.5 of the width of the middle one. The resistance of the joints is also high in rod-shaped magnet conductors, but due to the double width of the rods, the influence of the holes is much less. When using plates with a broadened base, the effect of the holes is small, but with the width of the outer rods of 0.5 of the average, it affects. Additionally, it is necessary to consider how justified the use of insulation of the studs from the steel of the magnetic circuit and from the clamping brackets is. Figure 4, a shows the direction of the magnetic lines in the bar magnetic circuit. направление магнитных линий в стержневом магнитопроводеIf all the pins are connected on each side of the magnetic circuit with tie pads, then from the inner corner of the magnetic circuit, where the magnetic lines are sealed, they partially leave under the coil formed by the pins and pads, but return to the next corner. An emf is induced in each half of the loop. but in both halves these e. etc. with. directed oppositely, while there will be no current in the loop. Therefore, the holes should be made along the studs without unnecessary reserves, so as not to weaken the steel sections. With an W-shaped magnetic circuit, the flux coming out of the middle rod diverges in both directions. (Fig. 4.b) Those parts of the flux that pass along the outer sides of the holes first pass through the coil formed by tie rods and linings, as well as steel plates contacting the studs. The amount of flow through the outer sides of the holes is up to 20% total flow (depending on induction). A short-circuited turn formed by pins and pads can reduce this part of the flow by several times, especially with an increase in the steel section, when e. etc. with. the turn rises significantly. At the same time, losses increase. In the absence of overlays, short-circuited turns remain due to the steel plates in contact with the studs. Insulating studs from steel and linings requires enlarging the holes, which also increases losses. It should be pointed out that these losses are accidental and cannot be accounted for.
       Brace and fasteners of the transformer. It was said above that the steel plates must be insulated. At inductions below 0.9-1.0 T, scale is usually sufficient insulation. However, to prevent corrosion, the plates must be varnished on both sides. The sometimes practice of pasting the plates with paper is not recommended: the filling of the steel decreases and the corrosion increases. It is used in large transformers, mainly in oil. Tightening of small transformers is usually done with clips or staples. стяжка магнитопроводов и крепление трансформаторовFigure 5 a-b shows the tie and fastening of the W- and U-shaped magnetic circuits with clips. The clips on the chassis are fastened with paws (two or four), passing through the slots in the chassis, or with screws. Often the magnetic core in the cage is fixed with free paws — fig. 5 c, d (shown below, without the chassis), or the legs are cut off. With a horizontal arrangement of magnetic circuits (both W- and U-shaped) on the chassis, they can be fastened with brackets, and larger ones - pulled together with strips and pins (Fig. 5, e). In the latter version, the lower bar is located under the chassis, which creates a more rigid connection with the chassis. With vertical fastening of the magnetic core, the width of the lamella (small dimensions are made without grooves). Sometimes similar grooves are made on W-shaped plates of the usual design. With grooves, significantly less losses are created than with holes, especially with plates with an increased width of the outermost rods on the closing side. In addition, short-circuited turns are not formed in this case. When tying the magnetic core with two pins, the use of tightening frames is inevitable in order to avoid vibration of the steel plates. For screeds, use frames with flanges for rigidity, which are quite simple to perform on double mandrels made of 8-10 mm steel. A workpiece is clamped between the mandrels in a vice (from a sheet of steel from 1.2 to 1.8 mm, depending on the size of the magnetic circuit). The workpiece is bent with light hammer blows, and a window is cut through it. Rod magnetic circuits with a power of 100 W and above are easiest to pull together with overlays (or corners) and pins, as shown in Fig. 5, f. But often, especially with large sizes of magnetic cores, they are fastened with pins (or bolts) through the holes. Such a tie is simpler in technology and reliable. Although this fastener does not create closed turns, when installed on a chassis (or large transformers on a frame), closed turns can appear for part of the steel section from the outside of the magnetic circuit to the hole due to studs, fastening brackets and the chassis (or frame), as shown in fig. 6. With twisted magnetic circuits, a thin press panel or getinax should be laid between the magnetic conductor and the clamping brackets, avoiding the formation of closed loops. (The arrow shows the path of the short-circuited loop)


Total comments: 6

  • Дима
    By Dima Added on September 18, 2018 at 15:27

    I need steel E43A with a thickness of 0.35 10 sq.

    To answer
    • leader
      By leader Added on September 18, 2018 at 4:33 pm

      Good afternoon, we do not sell steel, we buy it

      To answer
  • Камал
    By Kamal Added on November 8, 2018 at 15:13

    Hi, what is the best sheet thickness for trannies on 50 percent permalloy? 0.05 or 0.1 mm

    To answer
  • Vovan007
    By Vovan007 Added on March 16, 2019 at 12:38 pm

    Best on amorphous iron. The core shape of any coil is cylindrical.

    To answer
  • Юрий
    By Yuri Added on December 22, 2019 at 12:05

    I got a very good idea from you for the output transformer, thanks! I wind two frames, insert a steel tape with a large coil, and tighten the tape, starting from the inside.

    To answer
  • Василий
    By Vasily Posted on March 31, 2021 at 15:19

    A one-sided cut of a toroidal transformer iron with an inserted gasket of insulating material in the cut gap. What is the purpose of this?
    For an illustrative example, see this link.

    To answer

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