Development And Research Of New Insulation Materials For Motor

The larger the capacity of large turbine generators, the higher the voltage, and the higher the requirements for the main insulation of stator bars. Generators manufactured by major companies in the world have their own insulation systems. The main insulation of stator bars is very thin, but the voltage withstand level is very high. At the beginning of the 21st century, the stator bars of large turbogenerators will be made by vacuum solvent-free impregnation (VPI) after being wrapped with low rubber mica tape with good bonding strength. There is a great difference between the peak and valley of power consumption in the power grid, which requires that the insulation of the stator and rotor windings of the generator be verified by 10000 cold and thermal cycle tests. The thermal conductivity of the insulation of air and hydrogen cooled surface cooled turbogenerators is required to be greatly improved, which requires improving the thermal conductivity of mica tape, paint and other materials. Since the 1980s, the discipline of insulation materials and insulation technology has made new development in the world. In particular, the development of basic technologies such as nanotechnology, interpenetrating network technology and fiber reinforced technology will be applied to the transformation or development of new insulation technologies. More than 10 years ago, nano technology titanium dioxide, silicon dioxide, aluminum oxide, calcium carbonate, etc. were added to insulating materials abroad to improve the toughness, elongation and other properties of materials, while traditional technology usually reduces the toughness and elongation while improving the strength of materials.

In recent years, China has also vigorously developed nanotechnology. For example, adding 5% ~ 20% nano titanium dioxide or silicon dioxide to polyimide film can greatly improve the corona resistance of polyimide film, and adding 10% calcium carbonate to unsaturated polyester plastic can improve its heat resistance by about 10%. The price of nanomaterials has also gradually decreased from tens of thousands yuan to thousands yuan per ton. In recent years, the application research on the modification of insulating materials by interpenetrating network technology is also developing. Interpenetrating network technology is to fully mix two or more kinds of polymers and then solidify them. The interpenetrating polymers do not undergo chemical reaction, but cross penetrate and mechanically wind each other. This network forces mutual solubility and synergy at the molecular level, effectively improving the dispersion and interface affinity of the system, so as to improve the phase stability and achieve complementary performance, It is an effective method to improve the properties of polymer materials. At present, binary and j-ary networks among polyacrylate, epoxy resin polyurethane, polystyrene and vinyl resins and interpenetrating networks among their different varieties have been applied.

In recent years, insulating material workers have developed bone shaped (dumbbell shaped) short fibers based on the reinforcement principle of animal long bones, which are very effective in strengthening composite materials. The concept of fiber shape design is introduced to solve the contradiction between strength and toughness of composite materials through profiled fibers, and overcome the problem that short fibers are easy to be removed from the matrix due to short interfacial bonding time, leading to composite failure. It has application prospects in laminates.

In recent years, a lot of research work has been carried out on the co curing reaction process of epoxy resin and hydrogen ester abroad. The hygrothermal properties and dielectric properties of composites made of epoxy resin modified or cured with hydrogen ester have been greatly improved compared with the original epoxy resin, which has been widely used in the fields of electronics, electricity, aerospace, and may also be used in large generators in the future.

Experiment and practical research on stator winding using high heat conduction materials. For air, hydrogen or evaporative surface cooling generators, the heat consumption of stator winding copper needs to be dissipated to the core or air duct cooling medium through the insulator. The thermal conductivity of stator winding insulator has a direct impact on the maximum temperature rise of stator winding, and the thermal conductivity of stator winding insulation layer.