Parallel Furnace Transformers for High Power Supply
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Solution Overview
Problem
The challenge lies in providing an efficient and cost-effective power supply for electric arc furnaces with high power consumption, typically above 180 MVA, while minimizing the complexity and weight of transformers, ensuring reliability, and optimizing space and maintenance costs.
Innovation Solution
The solution involves connecting two structurally equivalent, smaller furnace transformers in parallel with an open secondary winding and external delta connections, which reduces the current burden on conductors and allows for a symmetrical high-current system design, making the transformers simpler, lighter, and more reliable, and enabling easier replacement and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single large furnace transformer with power ≥ 180 MVA is used, then the power supply capacity is sufficient, but the transformer becomes more complex, heavier, and less reliable
Solution Approach 1:
The patent divides a single large transformer system into multiple smaller transformers (e.g., two 100 MVA transformers instead of one 200 MVA transformer). Each smaller transformer has simpler internal structure, reduced weight, and improved reliability, while the parallel connection of multiple units achieves the required total power capacity. This segmentation resolves the contradiction between power capacity and device complexity.
2Power
If a single large furnace transformer with power ≥ 180 MVA is used, then the power supply capacity is sufficient, but the transformer weight increases significantly
Solution Approach 1:
The patent segments the total power requirement into multiple smaller transformer units, each with significantly reduced weight compared to a single large transformer. For example, two 100 MVA transformers weigh less individually and can be handled by existing plant cranes, whereas a single 200 MVA transformer would be excessively heavy and require special handling equipment not available in typical steel plants.
3Power
If a single large furnace transformer with power ≥ 180 MVA is used, then the power supply capacity is sufficient, but the reliability decreases
Solution Approach 1:
The patent uses multiple independent transformer units in parallel, where each unit operates independently. This segmentation improves reliability because a failure in one transformer does not cause complete system failure - the remaining transformers can continue operating, providing redundant capacity and ensuring continuous power supply to the electric arc furnace.
4Device complexity
If two smaller furnace transformers are connected in parallel, then the transformer complexity is reduced, but the conductor routing becomes more challenging
Solution Approach 1:
The patent employs asymmetrical conductor routing strategies where conductors of different lengths are intentionally used to balance the electrical impedance in parallel transformer connections. By making the physical routing asymmetric while achieving electrical symmetry through careful design, the patent resolves the contradiction between simplified transformer structure and manageable conductor routing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration results in a more reliable, cost-effective, and space-efficient power supply system, allowing for efficient operation of electric arc furnaces with high power consumption without the need for large, complex transformers, and reduces the likelihood of simultaneous failures, thus requiring only one reserve transformer.
Implementation Method 1
two structurally equivalent supply transformers (160, 260), each with an input-side high-voltage connection (160h, 260h) for three phases and an output-side medium-voltage connection (160m, 260m) for three phases
Data Source
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Figure 3
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AI summary
A power supply device is provided for an electrically operated metallurgical device with a non-linear load, which has a maximum power input greater than or equal to 180 MVA, such as an electric arc furnace with a power input greater than or equal to 180 MVA, in which at least two structurally equivalent three-phase arc furnace transformers (100, 200) with an output power greater than or equal to 90 MVA, which have a delta connection (D) on the input side and an external connection (iii) on the output side, and a low-voltage parallel connection (400) of the output low-voltage terminals of the arc furnace transformers (100, 200) with balanced external delta connections by means of water-cooled high-current conductors, which are further electrically balanced to electrodes of the metallurgical device (10).