RU2525298C2 - Transformer with three-phase and circular windings - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to electric engineering and may be used in multi-phase semiconductor converters, in particular, in rectifiers, inverters and frequency converters. A transformer with rotary magnetic field, three-phase and circular windings comprises an inner laminated magnetic conductor made of plates with semi-closed slots for full height of coil groups, where a three-phase winding and a circular winding are laid with taps. An external laminated magnetic conductor in the form of a hollow cylinder, which is moved onto the inner laminated magnetic conductor with an air gap, providing for necessary linearity of the main magnetisation curve by rotary magnetic field, providing for improved spectral composition of the magnetic field curve, and closing main magnetic flux, developed by windings arranged in slots of the inner magnetic conductor.

EFFECT: technical result consists in increased quality of supply and output voltage of a controlled converter, increased capacity, efficiency and coefficient of transformer and converter capacity as a whole.

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Description

The technical field to which the invention relates. The invention relates to transformer construction and can be used in multiphase semiconductor converters, in particular in rectifiers, inverters and frequency converters.

The level of technology. A multiphase transformer with a rotating magnetic field is known from the prior art, comprising a middle magnetic circuit, bursted from packets of different profiles with grooves on the end, inner and side surfaces in which three-phase and multiphase windings are laid. Two extreme packages of the middle lined magnetic core have grooves to the full height of the coil group. The central part of the middle charged magnetic circuit has grooves at the outer and inner surfaces for laying winding coils therein. Additional magnetic cores are made twisted without grooves. (Patent for the invention RU 2305339 C1; IPC H01F 30/14, H02M 5/14, published August 27, 2007, Bulletin No. 24). The disadvantages of this analogue are the following factors:

- the presence of a direct open groove, due to which hard-toothed tooth harmonic components with relative frequencies ν _Z = kZ / p ± 1 appear in the magnetic field curve where:

k - numbers of the natural number (1, 2, 3, ...);

Z is the number of grooves;

p is the number of pairs of winding poles;

- low utilization of electrical steel due to early saturation of the magnetic system at low values of magnetomotive force (MDS);

- significant air gap between the central and side twisted magnetic cores.

The closest to the claimed invention in technical essence and the achieved result is a multiphase transformer with a rotating magnetic field, containing a middle twisted magnetic circuit with grooves on the end surfaces, in which the primary three-phase winding and two side twisted magnetic circuit with grooves on the end surfaces adjacent to the ends of the middle a twisted magnetic circuit with multiphase windings, each of which covers the side magnetic circuit in the grooves of which it is laid (Patent for the invention RU 2115186 C1; IPC H01F 30/14, H02M 5/14, published July 10, 1998 in Bulletin No. 19). This analogue is taken as a prototype.

The disadvantages of the prototype include the following:

- use as an output multiphase multipath winding, which significantly complicates the manufacturing technology of a transformer with a rotating magnetic field;

- the use of open grooves in the outer and inner parts of the middle lined magnetic core;

- the presence of significant magnetic fluxes of scattering in connection with the winding of the windings on the cylindrical surface of the middle twisted magnetic circuit that does not have grooves on the side surface, since the grooves in the middle magnetic circuit are cut only on its end surfaces;

- the use of the diametrical pitch of the windings, which leads to the appearance of the frontal parts of the transformer, eliminating the tight fit of the side twisted magnetic circuits to the middle twisted magnetic circuit through a thin non-magnetic gasket;

- the use of three-phase and circular windings with a diametrical pitch, which negatively affects the quality of the supply and output voltage;

- the use of additional side twisted magnetic cores, which significantly increases the mass, dimensions and cost of the transformer;

- relatively low values of efficiency (efficiency) and power factor;

Disclosure of the invention. The essence of the claimed technical solution lies in the fact that the yoke of the inner lined cylindrical magnetic circuit is made of packets of the same profile with half-closed grooves to the full height of the coil groups, in which three-phase and circular anchor windings with taps are laid with a shortened pitch, the number of grooves of both windings per pole and the phase is selected fractional, and the outer lined ring magnetic circuit, made in the form of a cylinder, is pushed onto the inner lined magnetic circuit with the required clearance for echeniya required linearity primary magnetization curve of the magnetic core and the magnetic flux circuit to reduce leakage flux to the side of the transformer.

The proposed technical solution is new, having six fundamental differences from the prototype:

- the active part of the inner yoke of the magnetic circuit is made of bursts from packets of the same profile with half-closed grooves to the full height of the coil group;

- the outer lined ring magnetic circuit, made in the form of a cylinder, is pushed onto the inner lined magnetic circuit with the required clearance to provide the necessary linearity of the main magnetization curve of the magnetic circuit and to close the main magnetic flux in order to reduce the scattering flux from the side surface of the transformer;

- having a shortened pitch, three-phase and circular anchor windings with taps are laid in half-closed grooves;

- the number of grooves per pole and phase for three-phase and circular windings is selected fractional;

- three-phase and circular anchor windings with taps are laid in half-closed grooves using the general technology of the windings;

- excludes two additional side twisted magnetic circuit.

The proposed solution has an inventive step, since the set of essential features of the invention leads to a new technical result - an increase in the electromagnetic compatibility of semiconductor converters equipped with the proposed transformer, with a supply network and a load due to the use of an external charged ring magnetic circuit made in the form of a cylinder thrust on an internal charged magnetic circuit with the required clearance to ensure the necessary linearity of the main curve to us rotting of the magnetic circuit and for closing the main magnetic flux in order to reduce the scattering fluxes from the transformer side surface, manufacturing an internal lined magnetic circuit with a half-closed groove and applying a shortened pitch for laying three-phase and circular windings, choosing a fractional number of grooves per pole and phase for three-phase and circular windings, which leads to the suppression of the higher spatial harmonic components of the magnetic field and the tooth harmonics, the decrease in weight and size characteristics due to there are exceptions to two additional twisted side magnetic circuits, reducing or maintaining the cost of manufacturing a new transformer at the prototype level, using a single technology of winding three-phase and circular windings, increasing the installed power of the transformer, reducing heat loss, increasing efficiency and power factor of the transformer and the semiconductor converter as a whole.

The task to which the claimed technical solution is directed is to develop a transformer design with a rotating magnetic field that surpasses the prototype in terms of supply and output voltage quality, lower mass and dimensions of the magnetic circuit while reducing or maintaining its manufacturing cost at the prototype level by eliminating two additional side twisted magnetic cores, manufacturing a lined cylindrical magnetic circuit with a half-closed groove, replacing three-phase and circular windings with a diameter a short step to the windings with a shortened step to suppress the higher spatial harmonic components of the magnetic field, as well as the suppression of the tooth harmonic components through the use of a fractional number of grooves per pole and phase, which reduces the magnetic flux scattering of the frontal parts of the windings of the cylindrical transformer and helps to increase its installed power by value up to 25%, increase in efficiency by 5% and power factor from 0.85 to 0.95.

A brief description of the drawings. The invention is illustrated by drawings. Figure 1 shows a transverse section of a transformer with an indication of the location of the three-phase 3 and circular 4 windings in the grooves of the internal magnetic circuit 2, on which the external magnetic circuit 1 is dressed. Figure 2 shows a cross-sectional view of the groove of the transformer with three-phase 3 and circular 4 windings with an interlayer 6 and groove 7 insulation, fixed in the groove by the wedge 8, air gap 5 between the external 1 and internal 2 magnetic circuits. Figure 3 shows the internal magnetic circuit 2 of the transformer in a perspective view. Figure 4 shows a linear scan of a three-phase two-layer six-zone winding for the case when the magnetic circuit contains 27 grooves. Figure 5 shows a linear scan of a circular two-layer nine-section winding for the case when the magnetic circuit contains 27 grooves. Figure 6 shows the magnetic field curve and its spectrum, which are obtained by modeling the operation of the transformer for the case when the internal magnetic circuit is made with open slots. Figure 7 shows the magnetic field curve and its spectrum, which are obtained by modeling the operation of the transformer and experiment for the case when the internal magnetic circuit is made with half-closed grooves.

возбуждает в круговой обмотке ЭДС индукции, сдвинутые относительно друг друга на угол 2π/n, где n - число секций круговой обмотки трансформатора. В результате происходит преобразование симметричной трехфазной системы напряжений в симметричную n-фазную систему напряжений, которая преобразуется в выпрямленное напряжение с помощью полупроводникового коммутатора, подключающего максимально близкие к диаметру отводы круговой обмотки на сборные шины выпрямителя.The implementation of the invention. The transformer with three-phase and circular windings contains an inner and outer lined magnetic cores. An outer lined circular magnetic core made in the form of a hollow cylinder is pushed onto the inner lined magnetic core with the required clearance to provide the necessary linearity of the main magnetization curve of the magnetic circuit and to close the main magnetic flux in order to reduce the scattering flux from the side surface of the transformer. The inner lined cylindrical magnetic core is made of packets of the same profile with half-closed grooves to the full height of the coil groups, in which a three-phase and circular anchor winding with taps are laid with a shortened pitch, and the number of grooves in both windings per pole and phase is selected fractional. When a three-phase symmetrical voltage system is applied to a three-phase winding, it creates a rotating magnetic field in the transformer magnetic circuit, which, in accordance with the law of electromagnetic induction $$e(t)=-\frac{\partial }{\partial t}\Psi (t)$$

excites in the circular winding EMF induction shifted relative to each other by an angle of 2π / n, where n is the number of sections of the circular winding of the transformer. As a result, the symmetric three-phase voltage system is transformed into a symmetric n-phase voltage system, which is converted into rectified voltage using a semiconductor switch that connects the circular winding taps as close as possible to the rectifier busbars.

When performing the internal magnetic circuit with an open groove, the magnetic field curve has a clearly expressed non-sinusoidal character (Fig. 6), which, in the absence of structural measures in the transformer (shortening the winding pitch, choosing a fractional number of grooves per pole and phase, using a half-closed groove), leads to non-sinusoidality primary and secondary stresses, which was noted during calculations and modeling, as well as confirmed by experiments.

When performing the internal magnetic circuit with a half-closed groove and windings with a shortened pitch and a fractional number of grooves per pole and phase, the magnetic field curve significantly approaches the sinusoidal shape (Fig.7). At the same time, the tooth harmonic components, which have the largest value compared to the fundamental harmonic, are shifted to the high-frequency part of the spectrum and decrease in amplitude by 2–3 times.

Thus, the present invention allows, in comparison with the prototype, to obtain the design of a transformer having improved electromagnetic compatibility with the mains and the load. At the same time, the magnetic fluxes of scattering of the frontal parts of the primary and secondary windings are reduced, which allows to increase the installed power of the transformer, to increase the efficiency and power factor.

Claims (1)

A transformer with a rotating magnetic field, intended for use in multiphase semiconductor converters, comprising an outer ring and an inner lined magnetic core with three-phase and circular windings with taps located in the grooves of the inner lined magnetic core, characterized in that the ring lined magnetic core made in the form of a hollow cylinder pushed onto the internal lined magnetic core with a gap providing the necessary linearity of the main curve magnetizing a magnetic circuit that closes the main magnetic flux and excludes magnetic fluxes of scattering from the side surface of the transformer, and the internal lined magnetic circuit is made with half-closed grooves to the full height of the coil groups, into which three-phase and circular windings with a shortened pitch and a fractional number of grooves per pole and phase are laid, which allows to reduce the overall dimensions of the transformer, suppress the tooth harmonic components of the magnetic field, reduce the magnetic fluxes of scattering, increase the installation ennuyu power efficiency and power factor.

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