Research On The Vacuum Pressure Impregnation Resins And Perfermances Of Insulation System For High Efficient Motors

Energy conservation for sustainable development is one of the hottest issues of the world today. It is known that more than 60 % electricity of the world is consumed by motors, so the wide application of high efficient motors that are famous for energy saving and high energy efficiency is very important for energy saving. The key for fabricating high efficient motors is to develop high performance resins that not only have high heat stability, high breakdown strength, high bond strength and excellent corona resistance, but also are suitable for vacuum pressure impregnation?VPI? technique; however, few resins simultaneously possess these features. Herein, existing problems of VPI resins for high efficiency motors were investigated systematically.First, unsaturated polyester?UP? is the main type resin for producing high efficiency motors through VPI technique, which has low cost, fast curing speed and insulation performance. However, the heat-resistance class of available UP resins is only F class?155 °C?, does not meet the increasing development on high efficiency motors. A unique kind of high performance resin is developed by co-polymerizing UP resin with a novel benzyl alcohol terminated hyperbranched polysiloxane?Vi-HPSi?. Results show that Vi-HPSi/UP resins have better curing feature and thus endowing cured resins with higher crosslinking density and reduced free volume than UP resin. In addition, compared with UP resin, Vi-HPSi/UP resins have high thermal stability. Typically, for the Vi-HPSi/UP resin with 20 wt% Vi-HPSi?20Vi-HPSi/UP?, its initial degradation temperature is as high as 331 °C, about 80°C higher than that of UP resin. In addition, the modified resins have much better toughness and bond strength, reduced dielectric loss, demonstrating that Vi-HPSi/UP resins have great potential in fabricating high efficiency motors.Second, existing impregnated resins for high efficient motors is basically contain toxic solvents such as styrene, which can cause serious environmental pollution and resource waste during service. Therefore it is urgent to develop environmental VPI resins without toxic solvents and have low curing volatilization, this is significantly important for upgrading impregnated resin products and improving impregnating environment for high efficient motors. However, few environmental resins have been reported and available resins have very low hanging-paint quantity and poor heat resistance. A new tri-functional acrylic ester containing epoxy and Si-O groups was synthesized and used as active crosslinking monomer to develop a new polyester imide resin?SiPEI? for VPI technique. Based on this, a unique environmental friendly resin based on SiPEI, gas phase nano SiO₂ and rheological additive?SiPEI/TH-SiO₂? was developed. SiPEI has very low curing volatile content?<1 wt%? and toxicity, high flash point and fast curing speed, showing environmental friendly features. SiPEI/TH-SiO₂ not only meets the strict processing requirements of VPI technique, but also has high hanging paint quantity. Typically, for the SiPEI/TH-SiO₂ resin with 2 wt% TH-SiO₂, its hanging paint quantity is 0.46 g, increasing 84 % compared to that of SiPEI?0.25 g?, the maximum bond strengths at 25 °C and 155 °C are 203 N and 91 N, about 1.4 and 1.8 times of that of SiPEI resin, respectively, demonstrating that SiPEI/TH-SiO₂ has great potential to be used in the environmental insulation impregnation process for high efficiency motors.Third, as the main high efficient motor, invertor motors suffer the damage of high frequency pulse voltage and corona corrosion, which will accelerate the breakdown and premature failure of the insulation system. To improve the ability for resisting high frequency pulse voltage and increasing the life of invertor motors, VPI resins should have excellent corona resistance and high breakdown strength. For low voltage invertor motors, a series of unique hybridized resins based on polyester imide resin?EPEI? and hyperbranched polysiloxane coated nano-TiO₂?HSi-TiO₂? were prepared. EPEI/HSi-TiO₂ resins have excellent storage stability and are suitable for VPI, completely overcome the disadvantages of traditional nano-filler modified resins. In addition, HSi-TiO₂ can change the microstructure of crosslinked network, endowing EPEI/HSi-TiO₂ resins with outstanding corona resistance, high breakdown strength and remarkably decreased partial discharge. The maximum corona resistant life is 1586 min, about 57 times of that of EPEI resin. These attractive performances demonstrate that EPEI/HSi-TiO₂ resins have great potential in fabricating inverter motors.Fourth, epoxy resin/anhydride?EA? system is the most important VPI resin in the world at present, which has environmental friendly feature, high breakdown strength and desirable electric aging life, so the system has been widely used in the field of high voltage motors?more than 3 k V?, but the commercial or reported EA system for VPI has poor toughness, corona resistance and thermal stability. A novel resin system was developed by hybridizing EA with specially modified silica?mSiO₂? and grinding technology. EA/mSiO₂ resins have good processing features for VPI technique, reflected by suitably low viscosity and very long work life??24 months?, they also show much higher impact and flexural strengths, corona resistance and thermal stability than EA resin. For the EA/mSiO₂ resin with 9 wt% mSiO₂, its impact strength and corona resistant life are 25.2 kJ/m2 and 806 min, more than 3.4 and 16.1 times of those of EA resin, respectively. Simulation stator coils impregnated with EA/mSiO₂ resins exhibit much better electrical insulation than those with EA resin, demonstrating that EA/mSiO₂ resins are right candidate for fabricating high voltage motors, generators and transformers.Fifth, 80% failure of invertor motors has been caused by the damage of the insulation system. High and low voltage corona resistant insulation systems were prepared by using EPEI/HSi-TiO₂ and EA/mSiO₂ resins respectively, their comprehensive performances were intensively researched. Compared conventional insulation system, EPEI/HSi-TiO₂ insulation system has significantly improved corona resistance, which increases gradually as the content of HSi-TiO₂ increase. The corona resistance of insulation system impregnated with 15EPEI/HSi-TiO₂ is more than 13.8 time of that of conventional insulation system. In addition, EPEI/HSi-TiO₂ insulation system has excellent moisture resistance and oil resistant performance, meeting the rigorous requirements of low voltage inverter motors. For EA/mSiO₂ insulation system, the breakdown voltage of wind generator insulation system increases gradually as the mSiO₂ content increases. Compared to traditional polyester system for wind generators, corona resistance has obvious improvement, and breakdown voltage conservation rate is above 90 % after corona aging for 700 h. EA/mSiO₂ has good permeability with mica tapes in high voltage motors?such as 6 kV and 10 kV?, and thus forming no air gap insulation system with low dielectric loss and low dielectric loss increment. In addition, EA/mSiO₂ insulation system has excellent hot dielectric loss and breakdown voltage strength. The electrical aging life at 20 kV of EA/mSiO₂ insulation system is 2609 h, significantly higher than the technical requirement recorded in the international standard IEC 60034-18-32-60034 of 1200 h.