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The polyimide (PI) film is widely used in power apparatus due to its excellent electrical properties, but space charge will accumulate in PI film to result in the degradation of its insulating properties. In order to obtain the PI film with excellent insulating properties, it is necessary to further study the dynamic accumulation and migration process of space charge inside PI film and optimize its internal structure. On the basis of bipolar charge transport model, the space charge distribution of PI film under DC voltage was analyzed, and the effects of electric field intensity and temperature on the space charge distribution characteristics of PI film were discussed. The results show that the space charge accumulated in PI film increases with the extension of applied voltage time. After applying the voltage for 180 min, the anode and cathode accumulate 0.635 C/m3 and -0.712 C/m3 of charge, respectively. The existence of space charge causes serious distortion of potential inside the PI film. The increase of electric field strength and temperature make the charge obtain more energy to overcome the interface barrier and inject into the film, so that the film accumulates more space charge, and the electric field distortion is more serious. The distortion rate of electric field inside the film reaches 0.968% at 308 K. Because the migration rate of charges becomes faster with the increase of temperature and electric field strength, the distribution of space charge in the PI film is more complicated under strong electric field and high temperature field.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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