In order to obtain superhydrophobic film by simple and mold free method, on the basis of the transformation of 3D printer transmission system, we filled hydrophobic silica nanoparticles in thermoplastic elastomer solution material to prepare printing ink. Then ordered porous superhydrophobic film was prepared using the ink by 3D printing technology. The printability of ink and the wettability, wear resistance, insulating property, and oil-water separation of the film were investigated. The results show that the porous structure film prepared by this method shows well super-hydrophobicity, high oil-water separation efficiency, good insulating property and mechanical properties such as wear resistance and durability.

The surface flashover of insulating material is affected by many factors, such as surface roughness, nano fillers, and chemical functional groups. In this study, polyamide mesh was used as support and hydrophobic nano silica particles were used as modified materials. Nano fillers were embedded into polyamide mesh by the treatment method of dissolution and resolidification. The microstructure was determined by changing the mesh size, and the chemical groups on the composite surface were changed by fluorinated nanoparticles. The coupling effect of microstructure/nano filler on surface flashover was studied, and the material was endowed with superhydrophobic properties. The results show that with the polyamide mesh of 300 mesh, the composite has the best anti flashover performance, and the flashover voltage was increased by 20%.

Accelerated thermal ageing test was conducted on mineral oil-paper, natural ester-paper, mineral oil, and natural ester at 140℃ for 1 640 h. The change law of acid value and dielectric dissipation factor of the four oil samples in different ageing stage were emphatically analyzed, and the appearance changes of aged oil and paper were compared. According to that, the influence of the participation of insulating paper on the properties of different insulating oils during the ageing process was comprehensively compared. The results show that the acid value, dielectric dissipation factor, and ageing degree of the aged oil samples without insulating paper are higher than those with insulating paper. The ageing difference of natural esters with and without insulating paper is smaller than that of mineral oil, and the holding capacity for acidic substances is better than that of mineral oil, which can delay the ageing of insulating paper to a certain extent.

In order to supply more accurate input voltage to the design of insulation structure for variable frequency wind generator, we took the stator winding of permanent magnet synchronous wind generator as the research object, the equivalent circuit model of cable and motor stator winding coil was built by MATLAB software, and the effects of cable length and the pulse width modulation (PWM) pulse rising edge time output by frequency converter on the transient voltage distribution characteristics of motor winding were analyzed. The results show that with the increase of cable length and the decrease of pulse rising edge time, the maximum voltage to ground and inter turn of motor end and winding increases, and the maximum voltage to ground transfers from the middle coil to the first coil. When the pulse rising edge time is 2.0 µs, the voltage distribution in the winding tends to be uniform.

In this paper, the compatibility of four kinds of insulation materials, including enamelled round wire, enamelled rectangular wire, impregnated resin, and rubber gasket materials, with automatic transmission fluid (ATF) for oil-cooled electric vehicle motor was studied. Deionized water was added to ATF and the volume fraction was 0.5%, the compatibility experiments of four insulation materials with ATF were conducted at 155℃ according to the thermal class. The results show that the enamelled round wire, enamelled rectangular wire, and the impregnated resin has good compatibility with ATF. The performance of acrylic rubber was degraded obviously during the experiment, which does not meet the performance requirements of sealing materials.

In this paper, five kinds of epoxy resin samples with different ratios of acid anhydride curing agent were prepared by hot pressing method. The thermal and dielectric properties of the samples were tested, and then the best anhydride curing agent ratios were selected, and the steric effects caused by methyl substitution were analyzed. The results show that the mixed anhydride curing sample with the molar ratio of methylhexahydrophthalic anhydride and hexahydrophthalic anhydride of 8∶2 shows the highest glass transition temperature, and the electrical strength is improved, while the dielectric loss remains unchanged, which is closely related to the increased rigidity of the system.

The high frequency repetitive impulse generated by the inverter can lead to uneven overvoltage with high amplitude along the stator windings, which will accelerate the ageing of insulation system and even cause faults. On the basis of the transient analysis software PSCAD/EMTDC, the equivalent circuit model for three-phase stator windings of 2.5 MW permanent magnet direct-drive generator was established, and the parameters of corresponding equivalent circuit were calculated by finite element method. Moreover, the experimental platform was built for verifying the validity of the calculation results. The results show that under the effect of three-phase pulse width modulation (PWM) pulse voltage, the amplitudes of the overvoltage to ground, coil to coil overvoltage, and turn to turn overvoltage of the stator winding for permanent magnet direct-drive wind generator show a decreasing trend from the connecting terminal of motor to the neutral point of winding. The experimental results further verify the accuracy of the equivalent circuit model of three-phase stator winding.

Vegetable insulating oil is a kind of environment-friendly insulating oil with high ignition point, its electrical performance is similar with that of mineral insulating oil, but the kinematic viscosity is higher than that of mineral insulating oil. In this paper, the process conditions for preparing insulating oil with low viscosity by transesterification reaction using vegetable insulating oil as raw material and NaOH and ethanol as catalyst were discussed. And the effect of transesterification reaction conditions on the kinematic viscosity of vegetable insulating oil was investigated. The results show that when the molar ratio of alcohol to oil is 6∶1, the reaction time is 1h, the reaction temperature is 70℃, and the mass fraction of NaOH is 0.5%, the kinematic viscosity of the product can reach to 5.81 mm²/s, which is close to that of mineral oil. When the mass fraction of catalyst is no more than 0.5%, the kinematic viscosity of the product is inversely proportional to the amount of catalyst, and vegetable insulating oils with different kinematic viscosity can be prepared by controlling the amount of catalyst.

This article introduced the relevant characteristics of fungi. Fungi were cultivated under laboratory conditions and transplanted to the surface of silicone rubber insulators. Then, the static contact angle, ESDD, NSDD, and pollution flashover voltage of contaminated silicone rubber insulators were measured. The inhibition of fungi on the hydrophobicity of silicone rubber insulators and its influence on the pollution flashover voltage were analyzed. The results show that the adhesion of fungi on the surface of the silicone rubber insulator decreases the hydrophobicity of the insulator. The higher the concentration of fungus, the worse the hydrophobicity; the pollution flashover voltage on the surface of the silicone rubber insulator decreases slightly due to the adhesion of fungi; at the same time, the higher the concentration of fungi, the higher the ESDD and NSDD.

Combined with the special application environment and special structural characteristics of traction motor, the polyester imide insulation system of traction motor based on polyesterimide resin and three-in-one mica tape was studied in this paper. The heat resistance and processability of polyesterimide resin were studied by thermogravimetric analysis (TGA) and viscosity-temperature curve, on the basis of it, simulated insulation structure was prepared using the three-in-one mica tape with good compatibility with polyesterimide resin to verify the electrical ageing performance and reliability of the insulation system. The results show that the insulation system based on the selected polyesterimide resin and three-in-one mica tape has outstanding processability, mechanical properties, electrical properties, heat resistance, reliability, and low cost. The heat resistance index reaches to 215, which meets the requirements of high bonding strength, high heat resistance, and high reliability of traction motor.