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Vacuum Interrupter Design for On-Load Tap-Changer of Large-capacity Converter Transformer

Vacuum interrupter is the key component of on-load tap-changer of large-capacity converter transformer. Existing products are not reliable enough after long mechanical life and electrical life. To solve this problem, this paper proposes a new design scheme based on a systematic analysis of technical requirements and difficulties. In this new design, contact material selection, arc shielding system arrangement, design margin of corrugated tube, weld structure, static end design, and guide rod diameter are all discussed. In addition, electric field calculation is adopted in structure design, and contact design as well as shielding system are compared between the proposed schemes and existing products. Experimental tests include material selection and seven important projects: closing force, reaction force, vacuum degree, short time power frequency withstanding voltage, lightning impulse withstanding voltage, environmental test and X-ray test. The results show that the proposed schemes are much better than existing products and qualified in all tests.