Due to the high switching frequency, the on load tap changer of converter transformer has been exposed for many times, and the internal metal or insulating structural parts have cracks or even fractures, which seriously endangers the safety of high-capacity HVDC transmission system. In this paper, the transient dynamic model of the converter on load tap changer is established, the stress analysis of the action process of the new vacuum on load tap changer is carried out, the stress distribution of each part of the tap changer under different boss angles is analyzed, and the optimal angle of the tap on / off boss is given based on the yield strength of the material, It provides a useful numerical simulation method for the research and development of new tap changer.

mechanical performance, crack, simulation calculation, converter transformer, HVDC