RU167099U1 - TRANSFORMER CONVERTER THREE-PHASE MULTI-WIND - Google Patents

Abstract

1. A three-phase multi-winding converter transformer containing a three-core magnetic circuit, a three-phase primary winding and a multiphase secondary winding, characterized in that the magnetic circuit is assembled with anisotropic electrical steel plates with a Step-lap type charge; the primary winding is made internal and covers the rods of the magnetic circuit; the secondary winding 3 is made external, covers the outside of the primary winding 2 and is located from it at a distance that provides electric strength of the air gap; a precharge winding is introduced, located at the bottom of the core of the magnetic circuit under the primary and secondary windings; the magnetic circuit, the primary and secondary windings are equipped with channels for air cooling; the transformer is placed in a casing equipped with axial, tangential fans and a barrier; temperature sensors are installed in the magnetic circuit, primary, secondary and pre-charge windings with the ability to display information on the display of the temperature control unit; while the height of the core of the magnetic circuit, the secondary winding is divided into separate sections, combined into groups, and different sections of the secondary winding within the same group have a different number of turns providing specified lag angles; wherein the sections of the secondary winding with predetermined lag angles are located in the same sequence within each of the groups, and the windings of one section located on different rods of the magnetic circuit have the same number of turns; while the secondary winding is located from the primary winding at a distance that provides

Description

The utility model relates to electrical engineering, transformer construction and can be used to ensure the operability of multi-level frequency converters of frequency-controlled drives of main pumping units of oil pipelines.

The electromagnetic transformer is known from the prior art (US patent for invention No. 5317299, patent holder - Sundstrand (US), publ. 05/31/1994, IPC H01F 30/12; H01F 33/00; H02 J3 / 00).

The transformer has primary and secondary windings located respectively on the outer and inner cores to create a rotating electromagnetic field. When a three-phase voltage is applied to the primary winding, a rotating magnetic field is generated, which creates several three-phase voltages in the secondary windings. The primary and secondary windings are connected in a star or in a triangle. A rotating magnetic field is symmetrical with respect to any of the secondary windings. This is the main advantage of transformers based on magnetic cores, similar to the design of the stator of three-phase electric motors. A similar input transformer is patented by Siemens (US patent for invention No. 7948340 "Three-phase multi-winding transformer", publ. 03.03.2009, IPC H01F 27/24; H01F 30/14; H01F 2041/0662).

The disadvantage of transformers with toroidal magnetic cores is the complexity of their manufacture at high power (17 MB A and above) with the set reliability indicators when working as part of frequency converters of frequency-controlled drives of main pumping units of oil pipelines.

A multiphase transformer is also known ”(RF patent No. 113416, published 02.10.2012, IPC H01F 30/12, H01F 27/245 (2006.01), H01F 27/28), in which the use of a multiphase transformer is proposed as an integral part in a multilevel frequency converter . This transformer consists of a core, primary and secondary windings, the magnetic circuit is composed of laminated plates of electrical steel isolated from each other, interconnected by a yoke, sections of a three-phase primary winding are made in the form of identical coils impregnated with insulation varnish in vacuum, the turns of which are formed by a split copper conductor, consisting of several plates separated by a dielectric, the width of the plates corresponds to the width of the window of the magnetic circuit, the ends and the beginning of the insulation wafers are connected to each other in the leads, while the ends of the wafers are connected to a star, and the beginnings form the leads of the primary winding, each of the primary windings is a high-voltage filter at the input of a multiphase transformer, the secondary windings of each phase have the same number of turns made of split copper a conductor of circular or rectangular cross section, with each of the windings covering the core of a 3-core magnetic circuit and located on intermediate dielectric holders one above different along the length of the rod for a single phase, the beginnings of the secondary windings are leads, the ends of the windings are combined into a star with a zero lead.

The described design can be considered typical, but it has several limitations when performing transformers for high power and transformers for frequency converters with a high degree of pulsation of the rectification circuit.

The main limitations include: high losses in the windings and the magnetic circuit of the transformer; high values of additional losses; significant values of short circuit currents in the secondary windings of the transformer; significant inrush currents of magnetization (comparable in magnitude to short-circuit currents) at the moment the transformer is energized; difficulties in organizing effective heat removal from heated elements. long transformer; difficulties in placing numerous secondary windings in the main insulation channel, taking into account the requirements for the electrical strength of the transformer windings and the requirements for the reliability indicators of the transformer.

The objective of the proposed utility model is to develop a three-phase converter multi-winding transformer with a capacity of 17 MB A for a voltage class of 10 kV with an open air cooling system that ensures the operation of a frequency converter with a high pulse frequency rectification circuit

The technical result consists in increasing the reliability of a three-phase converter multi-winding transformer, which ensures the operability of a multi-level frequency converter of the type Perfect Harmony WCIII of the Siemens company for variable-frequency electric drives of the main pumping units of oil pipelines.

The problem is solved, and the technical result is achieved due to the fact that the three-phase multi-winding converter transformer contains a three-core magnetic circuit, a three-phase primary winding and a multiphase secondary winding, the magnetic circuit being assembled with anisotropic electrical steel plates with a Step-lap type charge; the primary winding is made internal and covers the rods of the magnetic circuit; the secondary winding 3 is made external, covers the outside of the primary winding 2 and is located from it at a distance that provides electric strength of the air gap; a precharge winding is introduced, located at the bottom of the core of the magnetic circuit under the primary and secondary windings; the magnetic circuit, the primary and secondary windings are equipped with channels for air cooling; the transformer is placed in a casing equipped with axial, tangential fans and a barrier; temperature sensors are installed in the magnetic circuit, primary, secondary and pre-charge windings with the ability to display information on the display of the temperature control unit; while the height of the core of the magnetic circuit, the secondary winding is divided into separate sections, combined into groups, and different sections of the secondary winding within the same group have a different number of turns providing specified lag angles; wherein the sections of the secondary winding with predetermined lag angles are located in the same sequence within each of the groups, and the windings of one section located on different rods of the magnetic circuit have the same number of turns; while the secondary winding is located from the primary winding at a distance that provides electric strength of the air gap.

In addition, the specified technical result is achieved in special cases of the implementation of the utility model due to the fact that:

- the primary and secondary windings are made of copper foil, the precharge winding is made of copper wire, and aramid paper is used as insulation for the windings, while the windings are impregnated with high-temperature varnish using vacuum pressure technology followed by high-temperature polymerization .;

- the power of the pre-charge winding is 1% of the total power of the transformer, and the supply voltage is 380 V;

- lag angles for sections of the secondary windings are + 25 °, + 15 °, + 5 °, -5 ° -15 °, -25 °;

- the inlet air flow is formed in the lower part of the casing, concentrated and guided by a barrier into the channels for air cooling, followed by forced removal of hot air by axial fans located in the upper part of the casing with the connection, upon overheating, of tangential fans located in the lower part of the casing;

- the secondary winding is located from the primary winding at a distance providing electrical strength of the air gap of 28 kV;

- axial and tangential fans has a total ventilation capacity of 33,000 m / h;

- pt100 type temperature sensors are used as temperature sensors;

The claimed design of the device is illustrated by drawings:

- in FIG. 1 shows a transformer (left view, section);

- in FIG. 2 shows a schematic diagram of the main components of a transformer.

In FIG. 1 and FIG. 2 is indicated:

1 - magnetic circuit;

2 - primary winding;

3 - secondary winding;

4 - precharge winding;

5 - section of the secondary winding;

6 - a group of sections of the secondary winding; 7- tap of the secondary section;

8 - directional air flow;

9 - a casing;

10- barrier;

11-axis fan;

12 - tangential fan;

13 - inlet air flow;

14 - output air flow;

15 - linear taps of the primary winding.

The magnetic core 1 of the transformer is made of three rods and is made of anisotropic electrical steel with a batch of plates of the “Step-Lap” type, which ensures a reduction in current values and no-load losses. The magnetic circuit 1 has channels for air cooling (not shown in FIGS. 1, 2) and is coated with heat-resistant varnish, which protects it from corrosion.

Primary 2 and secondary 3 windings are made of copper foil with aramid insulation and have cooling channels (not shown in Fig. 1, 2), the pre-charge winding 4 is made of copper wire. Aramid paper was used as insulation for all windings.

Aramid paper has high electrical and mechanical strength, good resistance to chemical products and high heat resistance, does not ignite and does not support combustion. The material, after impregnation, has low hygroscopicity with increasing environmental humidity, which is important to maintain high dielectric strength.

The primary winding 2 and the pre-charge winding 4 have a “star” connection diagram, and the secondary winding 3 is realized according to a “triangle with extended sides” connection diagram. The secondary winding consists of eighteen sections of the secondary winding 5, each of which is located on the three rods of the magnetic circuit 1.

The windings are impregnated with high-temperature varnish using vacuum-pressure technology, followed by high-temperature polymerization.

This winding design provides the best resistance to short circuit currents.

A distinctive feature of this transformer is the following:

- the primary winding 2 is made internal, located directly near the core of the magnetic circuit 1, covering it.

- the secondary winding 3 is made external, covers the outside of the primary winding 2 and is located at a distance from it, providing electric strength of the air gap. With a large number of sections, secondary winding 5, this arrangement allows you to perform complex winding connection schemes (the developed transformer has a “triangle with extended sides” connection scheme), as well as connecting the frequency converter cables (not shown in Fig. 1, 2) to branch bends of the secondary winding 5, taking into account the requirements of safety, reliability and ease of maintenance.

According to the height of the rod, the secondary winding 3 is divided into independent windings - sections of the secondary winding 5, which are allocated along the core of the magnetic circuit into groups of sections of the secondary winding 6. Different sections of the secondary winding within the same group have a different number of turns to achieve different connection groups with predetermined lag angles. In the developed transformer, the following lag angles for the secondary winding sections are set: + 25 °, b + 15 °, + 5 °, -5 °, -15 °, -25 °. Sections of the secondary winding 5 with predetermined lag angles are located in the same sequence within each of the groups. The windings of one section of the secondary winding 5, located on different rods of the magnetic circuit 1, have the same number of turns;

- a pre-charge winding 4 is introduced into the transformer design. It is an additional low-power winding for pre-charging the power cells of the frequency converter and eliminating the inrush of the magnetizing current when the transformer is energized. These windings are designed for short-term operation. The pre-charge winding 4 is similar in design to the primary 2 and secondary 3 windings. The precharge winding is located at the bottom of the cores of the magnetic circuit 1 under all other windings.

To effectively remove a large amount of heat from heated long elements of the transformer, a directed air stream 8 is required in the channels for air cooling. For this, the transformer is placed in a casing 9, equipped with a barrier 10, axial 11 and tangential 12 fans.

The barrier is a sheet of electrical insulating material (for example, fiberglass) with holes in which the gap between the walls of the barrier and the outer surface of the secondary section of the winding provides the desired direction and concentration of the inlet air stream 13.

The inlet air stream 13 is formed in the lower part of the casing 9, is concentrated by the barrier 10 and is directed in the form of a directed air stream 8 into the channels for cooling the magnetic circuit and windings, followed by forced removal of the output air stream 14 in the form of hot air by axial 11 fans from the upper part of the casing 9.

This technical solution allows the manufacture of high power transformers. Under normal temperature conditions, air flow is pumped only by axial fans 11 located in the upper part of the casing 9.

Also on the transformer are tangential fans 12 located in the lower part of the casing 9, which are designed for additional cooling of the transformer in case of overheating of the windings.

In order to control the temperature state of the transformer in the magnetic circuit 1 and windings 2, 3, 4, temperature sensors are installed in the places of greatest heating (not shown in Fig. 1, 2), information from temperature sensors is output to the temperature control unit (in Fig. 1, 2 not shown) with the ability to display incoming information on the display.

The intake air stream 13 is taken from the installation site of the frequency converter through the lower panels (not shown in Fig. 1, 2) of the casing 9. The degree of protection of the transformer casing corresponds to IP21.

The output air stream 14 in the form of hot air is discharged from the casing 9 of the transformer into the installation room of the frequency converter or through ducts outside the installation room.

The casing 9 is structurally composed of sections with removable panels (not shown in FIGS. 1, 2), which facilitates the installation and maintenance of the transformer at its place of operation.

Features of the proposed utility model is:

- inclusion in the design of the transformer of the pre-charge winding 4, which allows for the manufacture of high-power transformers without the use of additional transformers in the frequency converter, designed to prevent magnetizing current surges at the time of start-up, which improves the transformer resistance to electrodynamic influences and, therefore, improves reliability transformer;

- the implementation of the external location of the secondary winding 3 with respect to the primary winding 2, which improves the reliability of the transformer by improving the cooling conditions of the windings and increasing the electric strength of the air gap between the primary 2 and secondary 3 windings due to transfer from the space between the primary 2 and secondary 3 windings cables (not shown in FIGS. 1, 2) for connecting the frequency converter and taps of the secondary winding sections 3 and their circuit jumpers (not shown in FIGS. 1, 2). An additional positive effect is the ease of maintenance of contact joints of the taps of the secondary windings section 3;

- the use of windings made of copper foil with aramid insulation, impregnated with high-temperature varnish according to vacuum pressure technology with subsequent high-temperature polymerization, which allows to increase the transformer resistance to short circuit currents;

- - the use of a barrier 10 for efficient heat removal from the surfaces of the heated elements of the active part of the transformer, having a large length, which improves the reliability of the transformer transformers of high power with an air cooling system.

The transformer operates as follows.

When the transformer is energized, the three-phase voltage of industrial frequency is supplied to the linear taps of the primary winding 15. The magnetizing current flowing through the primary winding 2 creates an alternating magnetic field in the magnetic circuit 1, which, in turn, induces an electromotive force in the secondary winding 3. In this case, the primary winding 2, connected according to the "star" scheme, is a filter of higher harmonics. When connecting the secondary winding 3, connected according to the "triangle with extended sides" to the frequency converter in the sections of the secondary winding 5, a current proportional to the load occurs.

Since the load for the secondary winding 3 is the capacitors of the rectification circuit of the frequency converter, at the time the voltage is applied to the transformer, the magnetization current reaches values comparable to short circuit currents (discharged capacitors of the rectification circuit are actually in short circuit mode). When the transformer is run at high powers, the magnetization current becomes significant, which leads to an increase in the amplitude of the inrush currents of the magnetization (and, as a result, an increase in the amplitude of the electrodynamic forces acting on the transformer windings), which significantly reduces the reliability of the transformer.

In order to increase reliability, a low-power pre-charge winding is added to the transformer design 4. Before applying three-phase voltage of the industrial frequency to the primary winding 2, the three-phase voltage of the industrial frequency is supplied to the pre-charge winding 4. (The rated voltage can correspond to the voltage supplied to the primary winding, or can be reduced to less than 1 kV, which will simplify the design and improve the reliability of the transformer). In the developed transformer, the pre-charge winding 4 is designed for a nominal voltage of 380 V. The power of this winding is selected based on the condition for ensuring the charge of the capacitors of the power cells of the frequency converter. In the developed transformer, the power of the pre-charge coil 4 is 1% of the total power of the transformer. Upon completion of the charge of the capacitors of the rectification circuit of the frequency converter, the voltage from the pre-charge winding 4 is removed, at the same time, voltage is supplied to the linear taps of the primary winding 2 and the subsequent conversion of this voltage in the secondary winding 3.

Upon reaching a certain set value of the temperature of the primary 2, secondary winding 3 and / or the magnetic circuit 1, the axial fans 11 are started, creating a directed air flow 8. The directed movement and concentration of cooling air at heated surfaces is achieved by using a barrier 10. In case of insufficient axial efficiency fans 11 and exceeding the set temperature values, the tangential fans 12 are launched, increasing the volume of incoming air stream 13.

The application of the proposed technical solutions makes it possible to produce three-phase converter multi-winding transformers of high power for operation as part of a frequency converter with a high pulse frequency rectification circuit and ensures high reliability of the product.

The tests of the developed transformer of the three-phase converter multi-winding power of 17 MBA for a voltage class of 10 kV in the conditions of a testing laboratory, subsequent tests at the facility as part of the frequency converter and the pilot-industrial operation confirmed the high level of reliability and efficiency of the transformer and the adopted technical solutions. During the tests, it was found that the nomenclature of reliability indicators in accordance with GOST 27.003-90 corresponds to the following indicators: the established MTBF of at least 40,000 hours, the assigned service life of 340,000 hours, the probability of uptime of 8800 hours is at least 0,995, and the service life is not less than 40 years.

The utility model provides reliable uninterrupted operation of frequency converters of the Perfect Harmony WCIII type operated at the facilities of the VSTO-1 pipeline system of Transneft, JSC.

Claims (8)

1. A three-phase multi-winding converter transformer containing a three-core magnetic circuit, a three-phase primary winding and a multiphase secondary winding, characterized in that the magnetic circuit is assembled with anisotropic electrical steel plates with a Step-lap type charge; the primary winding is made internal and covers the rods of the magnetic circuit; the secondary winding 3 is made external, covers the outside of the primary winding 2 and is located from it at a distance that provides electric strength of the air gap; a precharge winding is introduced, located at the bottom of the core of the magnetic circuit under the primary and secondary windings; the magnetic circuit, the primary and secondary windings are equipped with channels for air cooling; the transformer is placed in a casing equipped with axial, tangential fans and a barrier; temperature sensors are installed in the magnetic circuit, primary, secondary and pre-charge windings with the ability to display information on the display of the temperature control unit; while the height of the core of the magnetic circuit, the secondary winding is divided into separate sections, combined into groups, and different sections of the secondary winding within the same group have a different number of turns providing specified lag angles; wherein the sections of the secondary winding with predetermined lag angles are located in the same sequence within each of the groups, and the windings of one section located on different rods of the magnetic circuit have the same number of turns; while the secondary winding is located from the primary winding at a distance that provides electric strength of the air gap. 2. The transformer according to claim 1, characterized in that the primary and secondary windings are made of copper foil, the precharge winding is made of copper wire, and aramid paper is used as insulation of the windings, while the windings are impregnated with high-temperature varnish using vacuum pressure technology with subsequent high temperature polymerization. 3. The transformer according to claim 1, characterized in that the pre-charge winding power is 1% of the total transformer power, and the supply voltage is 380 V. 4. The transformer according to claim 1, characterized in that the lag angles for the sections of the secondary windings are + 25 °, + 15 °, + 5 °, -5 °, -15 °, -25 °. 5. The transformer according to claim 1, characterized in that the inlet air flow is formed in the lower part of the casing, is concentrated and guided by a barrier into the air cooling channels, followed by forced removal of hot air by axial fans located in the upper part of the casing with the connection of overheating tangential fans located at the bottom of the casing. 6. The transformer according to claim 1, characterized in that the secondary winding is located from the primary winding at a distance providing electric strength of the air gap of 28 kV. 7. The transformer according to claim 1, characterized in that the axial and tangential fans have a total ventilation capacity of 33,000 m ³ / h. 8. The transformer according to claim 1, characterized in that pt100 type temperature sensors are used as temperature sensors.

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