RU2069402C1 - High-frequency transformer - Google Patents

Abstract

FIELD: electrothermy; induction heating; high-frequency welding of metals, melting, soldering, hardening. SUBSTANCE: high-frequency transformer has primary winding 1,2 and secondary winding 3,4 of single-turn disk type made in the form of flat spiral and arranged coaxially with radial clearance in secondary winding disks and terminal buses connected to secondary winding disks. Terminal buses 7 of secondary disk-type winding are placed in radial clearance of this winding perpendicular to disk plane. EFFECT: improved design. 5 dwg

Description

 The invention relates to electrothermal, in particular to induction heating, and can be used in electrothermal installations for high-frequency welding of metals, smelting, brazing, hardening, etc.

A high-frequency transformer is known, consisting of a spiral multi-turn cylindrical primary winding located concentrically inside a single-turn secondary winding, between which an air gap is made, which serves as electrical insulation between the windings. The high-frequency transformer matches the output voltage of the tube generator with the voltage of the process circuit (inductor, conductor, etc.) [1]
Transformers of this design have a large scattering field, high efficiency. The screening of such transformers is performed with large gaps, which leads to an increase in the volume occupied by the entire structure.

 Closest to the proposed technical solution is a transformer [2] containing a primary disk winding (p. 172, Fig. 6-12), a secondary single-turn disk winding with a radial clearance in the disks and output buses connected to them (p. 170, Fig. 6 -10).

 Lead plates 4 in fig. 6-14, connected by a terminal block, are located in a plane perpendicular to the lines of force of the magnetic flux and are concentrators of the "floor" of the current and the greater the higher the frequency of the current, which leads to their overheating and lower efficiency. Known transformers will have increased losses in the transitional parts of the secondary winding (p. 96, 97, Fig. 3-19) when used at high frequencies (440 kHz and above) and at powers of hundreds of thousands of kW.

 The compensation of the output busbars in the known solution does not save the situation, because the overlapped part of the secondary winding, located closer to the primary winding, shields the further one (since the penetration of the field and current into copper at a frequency of 440 kHz 0.1 mm) As a result, the shielded part does not interact with the magnetic field of both the primary coil and the overlapped part of the secondary coil due to the high frequency and the absence of a magnetic circuit.

 Thus, transformers of known designs do not solve the problems associated with the transfer of energy from the secondary windings of the transformer to the load devices with the least losses at current frequencies of more than hundreds of thousands of hertz and loads of more than hundreds of thousands of kilowatts.

 In the book of Tira L.L. [2] consider transformers of increased frequency up to 10000 Hz (10 kHz) (p.3) with cores made of electrical steel, which increase the coupling coefficient and reduce the number of turns in the windings.

 At high frequencies (above 66 kHz, GOST 12.2.007.10-87), cores made of electrical steel do not apply in view of unacceptable eddy current losses.

 At high frequencies, "air" transformers have been widely used, i.e. not having a core.

 The technical problem solved by the invention is to increase the efficiency of the transformer.

 The problem is solved due to the fact that in the high-frequency transformer, consisting of primary and secondary single-turn disk windings made in the form of a flat spiral and arranged coaxially with the radial clearance in the secondary winding disks and connected to the secondary winding disks of the output buses, according to the invention, output buses the secondary disk windings are placed in the radial gap of this winding perpendicular to the plane of the disks.

 Due to this design, the direction of the streamlines of the primary and secondary windings coincide along the entire length of the secondary winding, and the electrodynamic forces from the proximity in the gap of the output buses are always directed perpendicular to the plane of the output buses, therefore, they cannot affect the current density distribution along the radius of the secondary winding. This eliminates energy losses in the transitional parts of the secondary winding and increases the efficiency of the transformer.

 The invention is illustrated by drawings, which shows the design of a high-frequency transformer.

 In FIG. 1 is a side view; FIG. 2 is a plan view of FIG. 3 is a section bb in FIG. 1, in FIG. 4 is an electric circuit of an autotransformer, in FIG. 5 electrical diagram of the transformer.

 The transformer consists of two parts, each of which contains the primary half-windings 1 and 2 in the form of flat spirals and secondary half-windings, consisting of two pairs of disks 3 and 4 with a radial clearance (Fig. 1).

 The output buses 6, 7 (Fig. 2, 3) are located in the radial clearance of the secondary winding disks 3, 4 and are connected to the latter by welding, soldering, etc. The radial clearance of the secondary winding disks 3, 4 is made so that, taking into account the thickness of the plates of the output busbars, the gap between them was not more than 8 mm to reduce the inductance of the output busbars.

 To fulfill the assembly conditions of the high-frequency transformer, the outer disks of the secondary winding are removable, therefore, the output buses 6, 7 are made detachable.

 Primary 1 and secondary 3 half-windings are electrically connected to each other at point 5 near the output bus 7 (Fig. 2). The primary 2 and secondary 4 half-windings are connected in a similar way (the connection point is not shown). The gaps 8, 9 between the primary 1, 2 and secondary 3, 4 semi-windings are filled with a dielectric.

 In transformers (Fig. 5) (autotransformers, Fig. 4), the midpoints of the secondary and primary windings are earthed for electrical safety. The proposed design proposes the implementation of an autotransformer circuit and grounding is performed through a plate 13, which is only a structural element.

 The ends 10, 11 (Fig. 1) of the primary half-windings 1, 2 are mounted on the insulator 12, they are high-voltage and through their transformer is connected to a capacitor bank (not shown).

 The proposed design has sufficient rigidity (fasteners for installation in the housing is not shown).

The current from the power source passes through the primary half-winding 1 from the high-voltage end 10 to the connection point 5 with the secondary half-winding 3, flows through the secondary half-windings 3 and 4, connected by the output busbars 6, 7 and the connecting plate 13. Then through the second connection point of the primary and secondary half-windings (not shown) passes to the primary half-winding 2, flows around it and closes to the power source through the high-voltage end 11. The technological circuit, for example, an inductor, is connected to the output buses 6 and 7, in which the current of the secondary half-windings induced by the electromagnetic field of the primary half-windings is summed. In addition to the induced current, the primary semi-winding current flows in the inductor, as primary and secondary semi-windings are connected in series, and in the inductor, these currents are summed. A feature of the transformer is the size of the gaps 8, 9, which should be within 5 ^o C8 mm With large gaps, as practice shows, the current density of the secondary winding rises sharply to the center of the transformer, which leads to an increase in copper heating losses. Disks made of a solid high-frequency dielectric (fluoroplastic, plexiglass, etc.) can be introduced into the gaps 8, 9.

 A high-frequency transformer was tested in the production of a batch of pipes measuring 57x3.2 mm at TESA 20-114.

 The use of a high-frequency transformer of the claimed design makes it easier to integrate it into the line of a pipe-welding mill by reducing its dimensions, reducing the loss of electricity for heating the windings and increasing the efficiency by 5-10%. The introduction of the transformer is planned at TESA 20-114 at the experimental plant of electric-welded pipes in Topki Kemerovskaya area.

Claims (1)

 High-frequency transformer containing primary and single-turn secondary windings, made in the form of disks in the form of a flat spiral and arranged coaxially, in the disks of the secondary winding there are made radial gaps with the output buses located in them, connecting the disks of the secondary winding, characterized in that the output buses are perpendicular to the plane drives.

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