Amorphous alloy distribution transformer application sa METRO power supply system

Sa mga nakaraang tuig, human sa pagpabilis sa pag-unlad sa sakop sa urban rail transit sa China, ang karga sa kuryente ug ilaw sa subways mao usab nang madaghan, ug ang problema sa electric energy nga gikunsumo pinaagi sa self - losses sa distribution transformers naging mas prominent. Labi na kon ang nasod nagpadayon sa pag-advocate sa energy conservation ug environmental protection, ang amorphous alloy core transformers, nga gigamit ang amorphous alloy strips nga may excellent magnetic conductivity isip magnetic - conducting material, nakamit ang kaayo ka gamay nga no - load losses ug no - load currents, ug gitukod usab isip usa sa mga direksyon sa pag-unlad sa energy - saving transformers. Sa background sa Line 14 sa Beijing Subway, ang paper niini magsugyot sa principles, structures, ug technical characteristics sa dry - type amorphous alloy core distribution transformers (sa sunod mahimong irefer kay "amorphous dry - type transformers"), maghatag og maong pagbalhin sa epekto sa on - site implementation, ug mogahin og relevant suggestions alang sa long - term operation, nga may hangin sa paghatag og references ug experiences alang sa selection ug application sa distribution transformers sa subways.
Structure and Working Principle of Amorphous Dry - Type Transformers
Structure of Amorphous Dry - Type Transformers
Ang amorphous alloy distribution transformers mogili og amorphous alloy nga may soft magnetic properties isip core material. Kini may high saturation magnetic induction intensity, ultra - low losses, low exciting current, ug low coercivity, ug usa ka energy - saving ug environmentally friendly transformer nga may good stability. Ang amorphous dry - type transformers nagkombinahan sa mga characteristics sa epoxy - cast dry - type transformers sama sa low halogen content, flame retardancy, low smoke generation, ug self - extinguishing properties, uban sa low - loss advantages sa amorphous alloy strips, nga makapuyo kini mas maayo sa panginahanglan sa public environments sama sa subways.

Ang amorphous alloy strips usa ka thin (uban sa thickness nga humoltor 0.03 mm) ug brittle magnetic - conducting materials. Dili kini mapugos sa pag-design sa wound core structure. Kasagaran, ang structures sa epoxy - cast amorphous dry - type transformers may duha ka kategoriya, ang three - phase three - limb structure ug ang three - phase five - limb structure, same sa Figure 1. Ang core sa three - phase five - limb structure gibuo pinaagi sa pag-combine sa upat ka frames, same sa Figure 2 a; ang core sa three - phase three - limb structure gibuo pinaagi sa pag-combine sa tulo ka frames, same sa Figure 2 b. Tungod kay ang cross - section sa core sa amorphous alloy transformers rectangular, ang high - ug low - voltage coils karaniwan gi-design ngadto sa rectangular structure uban rounded corners. Tungod kay ang magnetic flux density ug lamination factor sa amorphous alloy core mas gamay kaysa silicon steel sheets, ang volume sa amorphous alloy core dako kaayo kaysa silicon steel sheet core sa sama nga capacity. Ang amorphous dry - type transformers sa usa ka subway line naggamit sa three - phase five - limb core design, nga may advantages sa good heat dissipation, compact overall structure, ug relatively small volume.

Working Principle of Amorphous Dry - type Transformers

Ang crystals sa amorphous alloy core material, silicon steel, mas conducive sa magnetization ug demagnetization tungod sa ilang structure ug characteristics. Ang typical amorphous alloy may humoltor 80% iron, uban sa uban nga main components mao ang materials sama sa silicon ug boron. Ang daghang tests naghimo sa clear nga ang crystallization temperature sa amorphous alloy 550°C, ug ang Curie temperature humoltor 415°C. Kini nga temperatures makapuyo sa requirements sa processing sa amorphous alloy, sa annealing after core forming, normal operating temperature, ug thermal - stable temperature during short - circuits, wala kini issues sa application sa amorphous dry - type transformers.

Pinaagi sa pagtumong sa three - phase, four - frame, five - limb amorphous alloy distribution transformer isip example, tungod kay ang matag winding sleeve sa duha ka frames uban independent magnetic circuits, ang magnetic flux sa matag frame gicompose sa fundamental - wave magnetic flux ug some third - harmonic magnetic flux. Ang ratio sa third - harmonic sa fundamental - wave depende sa rated magnetic flux density. Pero, ang third - harmonic magnetic fluxes sa duha ka core frames sa usa ka winding opposite sa phase ug equal sa value. Tungod niini, ang third - harmonic magnetic flux vector sa matag winding zero. Kon ang high - voltage coil connected in a delta (D) configuration, adunay path sa third - harmonic current sa coil. Tungod niini, walay third - harmonic voltage component sa induced secondary - side voltage waveform. Pero, ang no - load loss sa matag frame paingon affected sa third - harmonic current sa interior sa frame. Ang duha ka side yokes sa structure kini makapuyo sa path sa zero - sequence component o higher - order harmonics sa magnetic flux.

Main Technical Characteristics of Amorphous Dry - type Transformers
Characteristics of Amorphous Dry - type Transformers

Ang amorphous alloy strips extremely sensitive sa pressure. Kon damaged, wala kini mauli. Tungod niini, sa manufacturing process, kinahanglan sigurado ang duha ka points: Unang, ang core only bears its own weight, ug ang weight sa high - ug low - voltage coils supported sa steel - structure components sama sa base, upper ug lower clamping pieces. Pangalawa, ang short - circuit withstand capability improved pinaagi sa optimized design structure.

Ang rectangular - structured windings sa amorphous dry - type transformers dili tanan uniformly stressed sama sa circular windings. Kon ang transformer withstands short - circuit current, ang long - axis direction mas prone sa deformation. Sa actual production, ang high - voltage windings rigid - structured wires cast sa epoxy resin ug fixed sa resin layer. Dynamic ug thermal stability calculations ug practical simulations naghimo sa clear nga ang high - voltage coils can withstand the electrodynamic force during short - circuits.

Ang low - voltage windings mostly wound sa copper foils ug may thermally cured epoxy - resin end - sealing structure, uban slightly lower rigidity. Mas prone sila sa deformation during short - circuits, subjecting the amorphous alloy strips sa stress. Tungod niini, sa design process, kinahanglan iwasan ang large ratio between the long ug short axes sa low - voltage coil windings. Moreover, during the assembly process, supporting spacers must be placed between the core ug low - voltage coils to enhance the short - circuit withstand capability.

Ang noise sa transformer mainly comes from the magnetostriction sa core. The magnetostriction sa amorphous alloy approximately 10% higher sa silicon steel sheets. By comparing the national standards "JB/T 10088 - 2004 Sound Levels for 6 kV - 500 kV Power Transformers" ug "GB/T 22072 - 2008 Technical Parameters and Requirements for Dry - type Amorphous Alloy Core Distribution Transformers", it can be seen that the noise requirements for dry - type amorphous alloy core distribution transformers in the national standards are the same as those for silicon steel sheet core distribution transformers.

This increases the difficulty of manufacturing amorphous dry - type transformers. However, through the rational design of the structure of amorphous dry - type transformers, the noise can still be controlled within the national standard range. The magnetic flux density is an important factor affecting the noise of amorphous dry - type transformers.

For every 0.05 T increase in magnetic flux density, the no - load noise increases by approximately 2 dB(A), and the transformer noise increases by 5 dB(A)[1]. Therefore, the magnetic flux density of amorphous dry - type transformers should be reasonably selected to achieve noise reduction. Under normal circumstances, a magnetic flux density of less than 1.25 T is sufficient for amorphous dry - type transformers.

However, considering the special situation of high passenger flow density in subways, the noise level should be controlled even lower, and the magnetic flux density is generally selected to be less than 1.2 T. In addition, the noise of amorphous dry - type transformers needs to be suppressed by optimizing the structure. For example, appropriate space should be left in the frame composed of the core and clamping pieces to avoid excessive stress on the core and control the increase in core vibration. Sound - absorbing materials should also be padded between the core and the frame to effectively reduce noise.

During transportation and installation, amorphous dry - type transformers should be strictly operated in accordance with the operation specifications and procedures to avoid situations such as the core being stressed or knocked.

Economic Performance Analysis of Amorphous Dry - type Transformers

Amorphous dry - type transformers have obvious energy - saving effects. The following conducts an economic analysis of SCBH15 - type amorphous dry - type transformers and SCB10 - type silicon steel sheet distribution transformers with different capacities. The comparison is made in terms of the value of amorphous materials and silicon steel sheet materials, annual electricity cost savings, the number of years to recover the additional cost, and cost savings, as shown in Table 1.

It can be seen from Table 1 that amorphous dry - type transformers have more advantages in energy - saving compared to traditional silicon steel sheet transformers. Translated into operating costs, it is quite remarkable. The maximum number of years to recover the additional cost is only 5 years, showing great application prospects.

Application and Effect of Amorphous Dry - type Transformers in Subways
Application of Amorphous Dry - type Transformers in Subways

Through the elaboration of the structure and principle of amorphous dry - type transformers and the economic performance analysis, combined with the engineering situation of Line 14 of the Beijing Subway, for the application scheme of amorphous dry - type transformers, key research should be carried out on technical aspects such as the short - circuit withstand capability, noise control, loss index, and installation scheme of amorphous dry - type transformers, so as to give full play to the good energy - saving performance of amorphous dry - type transformers and improve the energy - saving level of subways.

On - site Implementation Effect

Taking the SCBH15 - 800/10/0.4 amorphous dry - type transformer that has been put into operation on Line 14 of the subway as an example, compared with the SCB10 - 800/10.0.4 dry - type transformer, ΔP0 = 1.05 kW; ΔPk = 0. The annual reduction in power consumption of one unit can be calculated as follows:

ΔWk = 8 760×(1.05 + 0.62×0) = 9 198 kW·h

Through calculation, it can be seen that the energy - saving effect of amorphous dry - type transformers is relatively obvious.

Relevant Suggestions for Long - term Online Operation

For the long - term operation of amorphous dry - type transformers on subway lines, their design, production, maintenance, and overhaul should be meticulously carried out in accordance with their unique characteristics. The author puts forward the following suggestions:

• Given that the magnetic saturation density of amorphous alloy materials is relatively low and their magnetostriction is relatively large, during product design, the rated magnetic flux density should not be set excessively high. Generally speaking, it is preferable to select a value below 1.2 T.

• Throughout the design and production processes, due attention must be paid to the short - circuit withstand capability of amorphous dry - type transformers. This capability should be enhanced through means such as process refinement and structural optimization.

• Amorphous alloys exhibit extreme sensitivity to mechanical stress. Therefore, in structural design, it is necessary to avoid the traditional design approach that uses the core as the main load - bearing component.

• To achieve excellent low - loss characteristics, annealing of the amorphous alloy core is an indispensable process.

• Regular maintenance and repair of amorphous dry - type transformers are essential. This helps to eliminate potential safety hazards and prolong the service life of the transformers.

Conclusion

Against the backdrop of the country's vigorous promotion of energy conservation and emission reduction, all industries are making strenuous efforts to cut down energy consumption. As a significant electricity consumer within urban power grids, the widespread adoption of amorphous dry - type transformers in subways is in line with national industrial policies and holds broad prospects for application.

It should be noted that the cost of amorphous alloy distribution transformers is higher than that of traditional silicon steel sheet transformers, and their installation also has certain unique features. Therefore, a rational transformer selection scheme should be formulated based on a comprehensive analysis of regional and line - specific conditions.

Since amorphous alloy distribution transformers demand a high standard of design and production processes, when choosing suppliers, it is advisable to opt for enterprises that have a track record of successful applications and possess advanced technical capabilities.