Enhanced breakdown strength and corona aging life in PI dielectric based on heterogeneous all-organic design

The high-speed train is developing towards higher speed and greater load capacity. As an important part of this, inverter-fed traction motors need higher power. As the turn-to-turn insulating material for inverter-fed traction motors, polyimide (PI) does not satisfy the requirements for breakdown strength and corona aging life with higher power. In this paper, the heterogeneous all-organic composite is designed with polyimide as matrix and acrylic elastomer (DE) as reinforcing material. When the load of DE is 0.5 wt%, the breakdown strength of the thermosetting DE/PI composites is up to 740 kV/mm, which is 60 % higher than PI (462 kV/mm) and the corona aging life is up to 70.4 h which is increased by about 340 % compared with PI (16 h). The synergy of free volume and trap makes comprehensive properties enhanced in the thermosetting DE/PI composite. This work provides a new design for turn-to-turn insulation with a high voltage level and a high operating frequency.