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永磁同步电机转子磁极的极性判别方法 总被引:1,自引:0,他引:1
针对永磁同步电机转子磁极的极性判别问题,依据电枢绕组的磁饱和特性,从电机的高频数学模型入手,提出一种以PWM逆变器载波频率成份作为高频信号源的极性判别方法。为了能够产生旋转的载波频率成份信号,逆变器采用三相三角波载波SPWM调制方式,并给出了该调制模式下的载波频率成份电压表达式。推导了α-β坐标系下的载波频率成份电流矢量方程,方程中的饱和分量幅值包含转子磁极的极性信息。利用外差处理电路提取饱和分量,进而实现了对永磁同步电机转子磁极的极性辨别。仿真和实验结果证明了理论分析的正确性。该方法不需要知道电机的精确参数,也不需要向电机注入额外的特定高频信号,能够判别PMSM转子磁极的极性。 相似文献
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磁悬浮轴承常应用于高速工况,传统滚珠轴承的极限转速较低,成为制约其作为辅助轴承可靠性的关键因素,而采用双层轴承将有效提高轴承的极限转速.以单层混合陶瓷球轴承为对象,分析磁悬浮轴承失电后高速转子跌落至辅助轴承后的动力学过程,得到轴承转速变化规律;进而研究双层轴承相较于单层轴承的转速分配情况,分析其转速提升情况.通过对双层... 相似文献
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针对传统的直接转矩控制转矩脉动大、开关频率不恒定等问题,在分析永磁同步电机数学模型的基础上,综合矢量控制的特点,提出一种基于空间矢量脉宽调制的新型直接转矩控制系统,用PI调节器取代滞环控制器,用空间矢量脉宽调制取代开关表.同时为了提高系统性能,模糊控制被应用于该系统.在Matlab环境下建立永磁同步电机新型直接转矩控制系统仿真模型并进行仿真研究,仿真结果证明了新型直接转矩控制系统设计可行有效,在提高系统响应速度的同时,能有效减小转矩和磁链的脉动,改善控制系统的性能. 相似文献
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Chengtao Wen Shuning Wang Hao Zhang Muhammad Junaid Khan 《International Journal of Circuit Theory and Applications》2005,33(1):87-97
A new compact MAX representation for 2‐D continuous piecewise‐linear (PWL) functions is developed in this paper. The representation is promising since it can be easily generalized into higher dimensions. We also establish the explicit functional form of basis function and demonstrate that the proposed basis function is the elementary ‘building block’ from which a fully general 2‐D PWL function can be constructed. In addition, we reveal the relationship of basis function with minimal degenerate intersection and Hinging Hyperplane, which shows that the MAX model can unify Chua's canonical expression, Li's representation, lattice PWL function and Bremann's Hinging Finding Algorithm into one common theoretical framework. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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OBJECT: A selective-excitation radiofrequency (RF) pulse that uses hard pulses composed of a sequence of composite pulses with positive and negative phases (P/N pulse) is proposed herein. Because the amplitude of the RF signal is unchanged during the excitation, RF amplification can be accomplished using a nonlinear RF power amplifier (i.e., class C or D type). MATERIALS AND METHODS: In this article, Fourier series have been first used to analyze the equivalence between the proposed P/N pulse and the conventional soft pulse on selective excitation. Subsequently, computer simulations based on density-matrix theory are used to compare the excitation profiles of both the soft and the P/N pulses. RESULTS: The excitation profiles of the P/N pulses have been measured experimentally through a home-built 0.3-T magnetic resonance imaging (MRI) system. In addition, several slices of images have been obtained as proofs by using the multislice two-dimensional spin echo sequence through replacement of the conventional soft pulse by the proposed P/N pulse. CONCLUSION: Because the perfect selectivity of the proposed P/N pulse, it can be used for imaging studies to improve the efficiency of amplification at the lowest cost. 相似文献
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永磁同步电机神经网络逆解耦控制研究 总被引:1,自引:0,他引:1
针对永磁同步电机的非线性、多变量、强耦合的特点,将神经网络与逆系统解耦方法相结合,并用于永磁同步电机的解耦控制.分析永磁同步电机的数学模型与解析逆模型,完成系统可逆性证明,将永磁同步电机与解析逆系统等效成两个伪线性子系统,构造神经网络逆系统,将永磁同步电机动态解耦为一阶线性磁链子系统与二阶线性转速子系统,利用两个PID控制器对伪线性子系统进行闭环控制器设计,实现系统转速与定子磁链动态解耦控制.利用dSPACE半物理仿真系统完成神经网络训练数据的采集与系统解耦控制实验.结果表明神经网络逆系统方法可以实现永磁同步电机的高新能控制,对负载扰动具有较强的鲁棒性. 相似文献
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An unbalance on a rotor causes whirling motions of the rotor and alternating forces of the bearings in rotating machines. The authors have shown a magnetic bearing control system in which an unbalanced rotor can be suspended without whirling. The concept of designing the control system involved an observer estimating the effects of unbalance and then cancelling using the electromagnetic forces of the bearing. With the control method applied, the position of the rotor can be maintained at the desired position with high precision. However, it is suitable for some machines to minimize the variation of exciting currents or vibratory force transmitted to the base through the bearing. This paper presents control methods that can eliminate stationary alternating components from exciting currents or electromagnetic forces by using the output of the observer. Another control method is presented in which feedback of the estimated signals of the displacements of the principal axis occurs; such signals are obtained by compensating synchronous observatory disturbances by use of the output of the observer. It is shown that the proposed three control methods are equivalent when unbalance stiffness due to the bias magnetic flux is null. 相似文献
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AbstractIn order to improve power density of high-power electric motorcycle driving motor, the air-gap length is usually minimized, which aggravates the influence of armature reaction on air-gap magnetic field. Considering the fact of unidirectional driving of electric motorcycle, the eccentric air-gap is used in each pole air-gap magnetic field strengthened area to suppress armature reaction, thus an asymmetric eccentric air-gap structure is designed. The torque and efficiency of motor are improved by asymmetric structure optimizing to improve the comfort, load capacity and battery life of vehicle, the ratio of maximum air-gap to minimum air-gap is eventually determined to be 3.2. The results of simulation and experiment show that, for the specified rotation direction, the distortion of air-gap magnetic density and back electromotive force (back-EMF) caused by armature reaction can be significantly suppressed by the determined asymmetric structure, hence the torque ripple and iron loss are reduced by 70.66% and 20.9% under rated load, respectively. Meanwhile, the proposed motor can provide a wide speed range and superior speed control performance, thus, verifying the validity and feasibility of the proposed asymmetric eccentric air-gap structure. 相似文献
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Hartwig V Vanello N Giovannetti G Lombardi M Landini L Santarelli MF 《Magma (New York, N.Y.)》2011,24(6):323-330
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Staff operating in the environment of magnetic resonance imaging (MRI) scanners are exposed daily to static magnetic fields (MFs). To protect workers several guidelines are present in literature reporting exposure limits values expressed in terms of magnetic flux density or induced current density. We present here a novel tool for estimating the induced current density due to worker movement in the MR environment. 相似文献13.
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实心磁铁推力磁轴承最佳工作点求解方法 总被引:1,自引:0,他引:1
力和温升是影响实心磁铁推力磁轴承工作性能的主要因素。本文建立了实心磁铁推力磁轴承承载力-温升分析模型。通过一个应用实例的计算,对系统承载力、温升及力-温升特性进行了分析。结果表明:实心磁铁推力磁轴承存在最佳工作点,影响轴承承载力-温升特性的主要因素是静态气隙和绕组安匝数,且对静态气隙更敏感。选定了适当的静态气隙后,可以通过调整安匝数使轴承运行在最佳工作点附近,从而实现了轴承性能优化。 相似文献
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