Design, analysis, and control of DC-excited memory motors

In this paper, a new type of memory motors, namely the dc-excited memory motor, is proposed and implemented. The concept of dc-excited memory is due to the nature that the magnetization level of permanent magnets (PMs) in the motor can be regulated by a temporary dc current pulse and be automatically memorized. Based on an outer-rotor doubly salient motor structure, the proposed dc-excited memory motor can offer effective and efficient online air-gap flux control. Hence, it possesses the advantages of mechanical robustness, high efficiency, and wide constant power operation region. Both simulation and experimentation are carried out to verify the validity of the proposed motor. © 2010 IEEE.published_or_final_versio

Dual-mode operation of DC-excited memory motors under flux regulation

The concept of memory is due to the fact that the magnetization level of permanent magnets (PMs) in the motor can be easily regulated by a temporary dc current pulse and then be memorized automatically. By incorporating this concept into the hybrid-field doubly salient PM (DSPM) motor, the resulting dc-excited memory motor can offer effective and efficient air-gap flux control. The purpose of this paper is to newly propose and implement dual-mode operation for the dc-excited memory motor. Namely, by regulating the magnetization level of the PMs, the motor can operate either under the DSPM mode or under the switched reluctance mode while maintaining similar operating performances. Both simulation and experimentation are used to verify the validity of the proposed dual-mode operation. © 2011 IEEE.published_or_final_versio

A flux-mnemonic permanent magnet brushless motor for electric vehicles

In this paper, a new permanent magnet (PM) brushless motor is proposed for electric vehicles. The key is to incorporate the concept of memory motors, namely, the online tunable flux-mnemonic PMs, into the stator doubly fed doubly salient PM motor, hence achieving effective air-gap flux control. By further employing the outer-rotor and double-layer-stator topology, the proposed motor takes the definite advantages of compact structure, low armature reaction, and direct-drive capability. Increasingly, this motor can offer the unique features of pole dropping and pole reversing. Finite element analysis and, hence, computer simulation are given to verify the validity of the proposed motor. © 2008 American Institute of Physics.link_to_subscribed_fulltextThe 52nd Annual Conference on Magnetism and Magnetic Materials, Tampa Bay, Florida, 5–9 November 2007. In Journal Of Applied Physics, 2008, v. 103 n. 7, article no. 07F10

Efficiency optimization of a permanent-magnet hybrid brushless machine using dc field current control

This paper proposes a new efficiency optimization approach for a new kind of permanent-magnet hybrid brushless (PMHB) machine. The key is to propose the self-searching control (SSC) for the PMHB machine in such a way that the input power at the given load and speed can be progressively minimized by tuning the dc field current. A loss analysis of the machine is given to justify the use of dc field current as the control parameter. Detailed experimental results confirm that the proposed approach can effectively accomplish the desired efficiency optimization. © 2009 IEEE.published_or_final_versio

Analysis of doubly salient memory motors using preisach theory

With the introduction of doubly salient memory (DSM) motors, the flux controllability and hence the speed range of permanent magnet (PM) motors have reached a new height. This paper presents a new method to accurately analyze the DSM motor. The key is to incorporate the general expressions of the Preisach hysteresis model (PHM) of the AlNiCo-PM into the time-stepping finite element method (TS-FEM). Based on the proposed PHM-TS-FEM, both static and transient performances of the DSM motor are successfully simulated. Finally, the validity and accuracy of the proposed method are verified by experimental results. © 2009 IEEE.published_or_final_versio

Analytical calculation of magnetic field in surface-inset permanent magnet motors

This paper presents an analytical approach to calculate the magnetic field distribution in surface-inset permanent magnet motors. A series-slot analytical model is newly proposed to describe the magnetic field behavior by a set of partial differential equations in terms of scalar magnetic potentials. The field solutions are determined by considering the boundary constraints. Then, the cogging torque characteristic is deduced by calculating the Maxwell tensors. The accuracy of the proposed analytical calculation is verified by comparing the field distribution and cogging torque results with those obtained from the finite element method. © 2009 IEEE.published_or_final_versio

Design of doubly salient permanent magnet motors with minimum torque ripple

This paper presents a design approach for doubly salient permanent magnet (DSPM) motors, aiming to minimize the torque ripple. The key is to propose the design criteria that the reluctance of all magnetic paths is the same, and the armature windings can be artfully connected to compensate the variation of self-inductance. Based on these criteria, the magnetic characteristics become symmetric, and the variation of self inductance is suppressed. Thus, the resulting torque ripple can be minimized. By using the time-stepping finite element method, the proposed DSPM motor and the existing DSPM motor are quantitatively compared in terms of their back-EMFs, self-inductances, and torque ripples, hence confirming the validity of the proposed design approach. © 2009 IEEE.published_or_final_versio

Reconstructing phylogenetic level-1 networks from nondense binet and trinet sets

Binets and trinets are phylogenetic networks with two and three leaves, respectively. Here we consider the problem of deciding if there exists a binary level-1 phylogenetic network displaying a given set T of binary binets or trinets over a taxon set X, and constructing such a network whenever it exists. We show that this is NP-hard for trinets but polynomial-time solvable for binets. Moreover, we show that the problem is still polynomial-time solvable for inputs consisting of binets and trinets as long as the cycles in the trinets have size three. Finally, we present an O(3^{|X|} poly(|X|)) time algorithm for general sets of binets and trinets. The latter two algorithms generalise to instances containing level-1 networks with arbitrarily many leaves, and thus provide some of the first supernetwork algorithms for computing networks from a set of rooted 1 phylogenetic networks

Dynamic breakage and fragmentation of brittle single particle of various sizes and strength

2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Comparison of coaxial magnetic gears with different topologies

This paper quantitatively compares two coaxial magnetic gears (CMGs) with different topologies, namely, the CMG installed with radially magnetized permanent magnets (CMGRM) and the CMG installed with Halbach magnetized permanent magnets (CMGHM). By using the 3D finite element method, the end-effect and the performances of both CMGs are investigated. Analysis results show that the CMGHM can offer higher pull-out torque, lower torque ripple and lower iron losses than the CMGRM. Experimental results are also given for verification. © 2009 IEEE.published_or_final_versio