Micro-arc oxidation （MAO） process was carried out on AZ91D alloy in alkaline borate solution using an alternative square-wave power source with different parameters. The effects of voltage, frequency and duty cycle ...Micro-arc oxidation （MAO） process was carried out on AZ91D alloy in alkaline borate solution using an alternative square-wave power source with different parameters. The effects of voltage, frequency and duty cycle on the coatings were investigated by orthogonal experiment. It is found that the thickness of coatings increases with the increase of voltage and duty cycle, but decreases with the increase of frequency. The structure and morphology of the coatings also depend on voltage, frequency and duty cycle. The coatings become more porous and crack with increasing voltage and duty cycle. The coating is thin and transparent when the voltage is lower than 120 V. The corrosion resistances of different coatings were evaluated by polarization curves and electrochemical impedance spectroscopy （EIS） in 3.5% NaCl （mass fraction） solution. When the optimized values of voltage, frequency and duty cycle are 140 V, 2 000 Hz and 0.4, respectively, the anodic coating shows the best corrosion resistance.展开更多
Synchronous reluctance machine(SynRM)can be perceived as a special type of permanent magnet synchronous machine(PMSM),and shares similar control method,i.e.the sine-wave current drive with sinusoidal phase currents.In...Synchronous reluctance machine(SynRM)can be perceived as a special type of permanent magnet synchronous machine(PMSM),and shares similar control method,i.e.the sine-wave current drive with sinusoidal phase currents.In this paper,square-wave drive,which is employed for permanent magnet brushless(BLDC)motors,is employed for the SynRM,in order to economically reduce the cost of rotor position sensor.It is revealed that the torque density and efficiency are slightly sacrificed,whereas torque ripple is deteriorated,proving the SynRM with square-wave drive still promising for the cost-sensitive application if torque ripple is not considered as a critical issue.To further investigate the additional pulsating torque under square-wave drive,mathematical model based on a-b-c phase inductance and d-q axis inductance are established,together with the time-stepping FE calculated currents.It is concluded that the harmonics in the currents tend to cause non-sinusoidal variation of the magnetic reluctance,which can be represented as additional inductance harmonics.The harmonics of the current and inductance interact with each other,thus undesirable torque ripple components are produced.展开更多
基金Project (50801056) supported by the National Natural Science Foundation of ChinaProject (2005DKA10400-Z20) supported by the National R&D Infrastructure and Facility Development Program of ChinaProject supported by the Zijin Project of Zhejiang University, China
文摘Micro-arc oxidation （MAO） process was carried out on AZ91D alloy in alkaline borate solution using an alternative square-wave power source with different parameters. The effects of voltage, frequency and duty cycle on the coatings were investigated by orthogonal experiment. It is found that the thickness of coatings increases with the increase of voltage and duty cycle, but decreases with the increase of frequency. The structure and morphology of the coatings also depend on voltage, frequency and duty cycle. The coatings become more porous and crack with increasing voltage and duty cycle. The coating is thin and transparent when the voltage is lower than 120 V. The corrosion resistances of different coatings were evaluated by polarization curves and electrochemical impedance spectroscopy （EIS） in 3.5% NaCl （mass fraction） solution. When the optimized values of voltage, frequency and duty cycle are 140 V, 2 000 Hz and 0.4, respectively, the anodic coating shows the best corrosion resistance.
基金supported in part by the National Natural Science Foundation of China under Grant 52007161.
文摘Synchronous reluctance machine(SynRM)can be perceived as a special type of permanent magnet synchronous machine(PMSM),and shares similar control method,i.e.the sine-wave current drive with sinusoidal phase currents.In this paper,square-wave drive,which is employed for permanent magnet brushless(BLDC)motors,is employed for the SynRM,in order to economically reduce the cost of rotor position sensor.It is revealed that the torque density and efficiency are slightly sacrificed,whereas torque ripple is deteriorated,proving the SynRM with square-wave drive still promising for the cost-sensitive application if torque ripple is not considered as a critical issue.To further investigate the additional pulsating torque under square-wave drive,mathematical model based on a-b-c phase inductance and d-q axis inductance are established,together with the time-stepping FE calculated currents.It is concluded that the harmonics in the currents tend to cause non-sinusoidal variation of the magnetic reluctance,which can be represented as additional inductance harmonics.The harmonics of the current and inductance interact with each other,thus undesirable torque ripple components are produced.
