Individual grains with diverse dimensional parameters were introduced to investigate the magnetization reversals in anisotropic Nd2 Fe_(14)B magnets. The micromagnetic simulations were carried out via Object Oriented ...Individual grains with diverse dimensional parameters were introduced to investigate the magnetization reversals in anisotropic Nd2 Fe_(14)B magnets. The micromagnetic simulations were carried out via Object Oriented MicroMagnetic Framework(OOMMF). With the same bottom area and height, analysis results show that the coercive fields for different bottom shapes are of similar values. Designed as a cubic grain,the coercive field presents descending tendency as grain volume ascends. Under constant grain volume,with aspect ratio increasing, the coercive field decreases in the beginning and increases soon. Based on the demagnetization field vector, the effects of bottom shape, grain volume and aspect ratio on the coercive field can be explained. The nucleation point is chosen to discuss. Its synthetic field and reversal field are calculated by parallelogram law and inverse external field equation, respectively. The synthetic field equal to the reversal field is defined as critical field, which always shows the same tendency as the coercive field for all cases of this study. It can be concluded that critical field is qualified to be a reference index to measure the magnitude of coercive field.展开更多
In this study, we investigate the demagnetization resistance of a concentrated winding IPMSM （interior permanent magnet synchronous motor） accounting for field weakening control by changing the magnetization directi...In this study, we investigate the demagnetization resistance of a concentrated winding IPMSM （interior permanent magnet synchronous motor） accounting for field weakening control by changing the magnetization direction of the permanent magnet under a high-temperature environment. IPMSMs are investigated by FEA （finite element analysis） using the same volume of the permanent magnet while changing the magnet’s width, thickness and magnetic field orientation angle. FEA found that a V-shaped angle Va = 100° and a changed magnet length of 97% using an oblique magnetic-field-oriented magnet strike a good balance between demagnetization resistance and torque at 180 ℃. Comparison between demagnetization of negative d-axis current （current phase β = 90°） and demagnetization of field weakening control （β = 80°） using concentrated winding IPMSM with V-shaped angle Va = 100° is conducted. With the demagnetization factor at β = 80° for β = 90°, the demagnetization factor 0.39 （2.6 times） at α = 0° decreases to 0.23 （4.3 times） at α = 20°. The demagnetization resistance in the field weakening control is further improved.展开更多
基金Project supported by the National Natural Science Foundation of China(51590882,51871063)
文摘Individual grains with diverse dimensional parameters were introduced to investigate the magnetization reversals in anisotropic Nd2 Fe_(14)B magnets. The micromagnetic simulations were carried out via Object Oriented MicroMagnetic Framework(OOMMF). With the same bottom area and height, analysis results show that the coercive fields for different bottom shapes are of similar values. Designed as a cubic grain,the coercive field presents descending tendency as grain volume ascends. Under constant grain volume,with aspect ratio increasing, the coercive field decreases in the beginning and increases soon. Based on the demagnetization field vector, the effects of bottom shape, grain volume and aspect ratio on the coercive field can be explained. The nucleation point is chosen to discuss. Its synthetic field and reversal field are calculated by parallelogram law and inverse external field equation, respectively. The synthetic field equal to the reversal field is defined as critical field, which always shows the same tendency as the coercive field for all cases of this study. It can be concluded that critical field is qualified to be a reference index to measure the magnitude of coercive field.
基金Natural Science Foundation of China(No.50371029)New Century Excellent Talents in University(No.NCET-04-0702)Elitist in Natural Science Foundation of Hubei Province(No.2005ABB002)
文摘In this study, we investigate the demagnetization resistance of a concentrated winding IPMSM （interior permanent magnet synchronous motor） accounting for field weakening control by changing the magnetization direction of the permanent magnet under a high-temperature environment. IPMSMs are investigated by FEA （finite element analysis） using the same volume of the permanent magnet while changing the magnet’s width, thickness and magnetic field orientation angle. FEA found that a V-shaped angle Va = 100° and a changed magnet length of 97% using an oblique magnetic-field-oriented magnet strike a good balance between demagnetization resistance and torque at 180 ℃. Comparison between demagnetization of negative d-axis current （current phase β = 90°） and demagnetization of field weakening control （β = 80°） using concentrated winding IPMSM with V-shaped angle Va = 100° is conducted. With the demagnetization factor at β = 80° for β = 90°, the demagnetization factor 0.39 （2.6 times） at α = 0° decreases to 0.23 （4.3 times） at α = 20°. The demagnetization resistance in the field weakening control is further improved.
