Papers by Patrick Chi Kwong LUK
2015 6th International Conference on Power Electronics Systems and Applications (PESA), 2015
Due to the low residual flux density of ferrite magnets, flux-focusing and multi-layer configurat... more Due to the low residual flux density of ferrite magnets, flux-focusing and multi-layer configurations have been deployed to harness both the permanent magnet torque and reluctance torque. Here, a new configuration featuring a V-spoke rotor structure embracing a combined configuration of the conventional V- and spoke-shaped interior permanent magnet (IPM) machines is proposed for its superior torque density over equivalent counterparts. The magnetic open-circuit characteristic of the V-spoke machine is first analysed and compared with that of the equivalent V- and spoke-shaped machines. Then finite element analysis (FEA) simulations are performed for on-load conditions to confirm the superior performance of the proposed design. The frozen permeability method is carried out to provide further insights into the torque production mechanism. Operating efficiency, torque profiles and power-speed performance are also be investigated and evaluated to confirm the utility of the proposed ferrite machine design.
IEEE Transactions on Industrial Informatics, 2016
Simultaneous wireless charging of multiple devices is a unique advantage of wireless power transf... more Simultaneous wireless charging of multiple devices is a unique advantage of wireless power transfer (WPT). Meanwhile, the multiple-receiver configuration makes it more challenging to analyze and optimize the operation of the system. This paper aims at providing a general analysis on the multiplereceiver WPT systems and compensation for the influence of the cross coupling. A two-receiver WPT system is first investigated as an example. It shows that theoretically by having derived optimal load reactances the important system characteristics can be preserved such as the original system efficiency, input impedance, and power distribution when there is no cross coupling between receivers. The discussion is then extended to general multiplereceiver WPT systems with more than two receivers. Similar results are obtained that show the possibility of compensating the cross coupling by having the derived optimal load reactances. Finally, the theoretical analysis is validated by model-based calculation and final experiments using real two-and threereceiver systems.
IEEE Transactions on Power Electronics, 2015
Power Systems, 2008
Page 1. 6 High Frequency AC Power Distribution Platforms Patrick Chi-Kwong Luk and Andy Seng Yim ... more Page 1. 6 High Frequency AC Power Distribution Platforms Patrick Chi-Kwong Luk and Andy Seng Yim Ng Defence ... 1] Sood and Lipo [3] proposed another 20 kHz HFAC system for space application, as shown in Figure 6.2. ...
IEEE Transactions on Magnetics, 2009
IEEE Transactions on Industry Applications, 2012
IEEE Transactions on Industrial Electronics, 2012
This paper investigates a material-efficient axial pole pairing method for torque ripple reductio... more This paper investigates a material-efficient axial pole pairing method for torque ripple reduction in a direct-drive outer-rotor surface-mounted permanent-magnet synchronous machine. The effects of the magnet pole arc width on the torque ripple characteristics of the machine are first established by both analytical and two-dimensional finite element approaches. Furthermore the effectiveness of the axial pole pairing technique in mitigating the machine cogging torque, back electromotive force harmonics and overall torque quality is comprehensively examined. Finally three-dimensional finite element analysis and experiments are carried out to validate the proposed approach, and the results show that axial pole pairing can be cost-efficiently implemented in terms of magnet material usage and assembly. Index Terms-Axial pole pairing, back electromotive force, cogging torque, direct drive, finite element analysis, fractional slot, magnet pole arc width, permanent magnet synchronous machine, torque ripple reduction. NOMENCLATURE A 2 nN Phase angle of the nN th harmonic of B 2 mag. p Magnet pole arc width ratio. pj Magnet pole arc width ratio of the j th magnet set. B ag Open-circuit air gap radial magnetic flux density. B mag Open-circuit air gap radial magnetic flux density without slot effect consideration. B n Peak value of the n th harmonic of B mag. B 2 nN Peak value of the nN th harmonic of B 2 mag. e Phase back electromotive force (EMF). e a , e b , e c Back EMFs of phase a, b, c. E 1 Peak value of the fundamental component of phase back EMF. E 6n±1 Peak value of the (6n±1) th harmonic of phase back EMF. i Magnet set number. i a , i b , i c Currents of phase a, b, c. I 1 Peak value of the fundamental component of phase current. Electrical angle by which current leads the back EMF. k wn Winding factor of the n th harmonic. l e Active axial length of the machine. l ej Active axial length of the j th magnet set. ag Relative permeance function in air gap with slot effect consideration. m Peak value of the m th harmonic of ag. 2 nN Peak value of the nN th harmonic of 2 ag. 0 Air permeability. N Least common multiple of 2p and p s. N s Number of turns in series of each phase winding. p Magnet pole pair number. p s Stator slot number.
COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, 2011
PurposeThe purpose of this paper is to propose a new outer‐rotor permanent‐magnet flux‐switching ... more PurposeThe purpose of this paper is to propose a new outer‐rotor permanent‐magnet flux‐switching machine (ORPMFSM) for electric vehicle (EV) in‐wheel propulsion. The paper documents both the design procedure and performance investigation of this novel machine.Design/methodology/approachThe topology and preliminary sizing equations of the ORPMFSM are introduced. The rotor poles are optimized, whilst the machine losses are particularly investigated, using 2‐D finite element analysis (FEA).FindingsAn ORPMFSM, with 12 stator poles and 22 rotor poles, is most suitable for the proposed EV application. The analytical sizing equations are quite efficient with a sufficient accuracy for the preliminary design. The optimal rotor pole width from the FEA results is nearly 1.3 times the original value which was proposed in early literatures. The efficiency of the proposed machine under rated load is slightly low, as a result of significant eddy current losses in the permanent magnets. The losses ...
World Electric Vehicle Journal
This paper proposes a novel hybridized vehicle interdependent control transmission architecture (... more This paper proposes a novel hybridized vehicle interdependent control transmission architecture (VICTA) that offers key advantages over existing systems. It embodies a compact torque generation system formed by two or more electric machines axially linked through a conventional mechanical differential gear assembly by means of a simple yet innovative pair of co-axial shafts. The resultant electric-mechanical hybridized drivetrain system allows a unique and automatic way of transmitting, differentially and interdependently , the electromagnetic torques generated by the motors at either side of differential gear. A realistic virtual prototype of the VICTA based on MATLAB/Simulink modules is developed to validate the concept. Comprehensive performance prediction tests, including steering maneuvering and variations of the road surface, are undertaken. Excellent simulation results from the VICTA virtual prototype demonstrate its stability and motility performance. The results also confirm the VICTA concept has key advantages such as reliability, modularity, high efficiency and simplicity, and yet does not inherit the undesirable features of high unsprung mass or complex software control that continue to challenge and even flaw the existing systems.
The misalignment of inductively coupled coils in a wireless power transfer system reduces the pow... more The misalignment of inductively coupled coils in a wireless power transfer system reduces the power efficiency and limits the amount of power that can be transferred. Coil misalignment leads the primary coil driver to operate in an untuned state causing non optimised switching conditions and leads to an increase in switching losses. This paper presents a novel method to electronically tune a Class E inverter used as a primary coil driver in an inductive wireless power transfer link to reduce the effect of displacements between the coupled coils which may occur during operation. The tuning method uses current controlled inductors (saturable reactor) based on a Mollypermalloy magnetic core and switching frequency variation to achieve optimum switching conditions regardless of the displacement. Mathematical analysis is performed based on an improved model of a resonant inductive link. Experimental results are presented confirming the analysis approach and the suitability of the propose...
PEMD 2014
In-wheel direct-drive electric vehicles have been attracting more and more interests due to their... more In-wheel direct-drive electric vehicles have been attracting more and more interests due to their simple yet flexible drivetrain configuration. Robust electric machines with high torque density and great efficiency are highly demanded. As the machine rotor is rolling together with the wheel, outerrotor surface permanent magnet synchronous machine with fractional-slot concentrated-winding configuration becomes the ideal candidate for the application. The electromagnetic performance of the machines with various stator slot and rotor pole combinations is optimized by particle swarm algorithm based on finite element analysis. The final optimal designs are comprehensively discussed and compared to obtain the best one. The study manifests that the particle swarm optimization method is an efficient compromise between computational time and effectiveness for the proposed machine optimization.
Power Electronics and …, 2011
A novel High Frequency Alternating Current (HFAC) based fluorescent lighting system that distribu... more A novel High Frequency Alternating Current (HFAC) based fluorescent lighting system that distributes sinusoidal voltage and current to individual lamp drivers in a self-regulatory and modular fashion is proposed. The new system offers opportunities for ...
Journal of the American …, 1993
Page 1. 1664 J. Am. Chem. SOC. 1993, 115, 1664-1669 Table 1. Selected Bond Distances and Andes in... more Page 1. 1664 J. Am. Chem. SOC. 1993, 115, 1664-1669 Table 1. Selected Bond Distances and Andes in 5(1) Bond Distances (A) PN 1 2.771(4) P-N3 1.620(3) P-N2 1.636(3) P-N4 1.618(3) Bond Angles (deg) N2-P-N3 110.8 ...
Journal of neuroendocrinology, Nov 1, 2001
The effects of K+ channel blockers on basal gonadotropin II (GTH-II) release were examined in cul... more The effects of K+ channel blockers on basal gonadotropin II (GTH-II) release were examined in cultured goldfish gonadotropes. Tetraethylammonium (TEA) inhibited basal GTH-II release, whereas 4-aminopyridine (4-AP) increased basal release, although both K+ channel blockers generated increases in [Ca 2+] i. Other K+ channel blockers had no significant effect on GTH-II release. We examined whether Ca 2+ entry that arises from blockade of K+ channels by 4-AP mediates the secretory response. Secretion evoked by 4 ...
A novel control scheme for sensorless switched reluctance motor drives is proposed. The scheme em... more A novel control scheme for sensorless switched reluctance motor drives is proposed. The scheme embodies a modified motor winding and a simple drive circuit so that `voltage vector' is utilised in a fashion similar to that of an AC drive. A key part of the control embraces a direct flux compensation which enables robust estimation of rotor position without the use of magnetisation curves or sensors
Electric Power Applications, IET, 2010
A high-speed coreless surface mounted axial flux permanent magnet generator with circular magnets... more A high-speed coreless surface mounted axial flux permanent magnet generator with circular magnets and coils is proposed and studied. The performances of the machine are estimated and optimised by approximate theoretical analysis and comprehensive ...
Power Electronics in Smart Electrical Energy …, 2008
Page 1. 6 High Frequency AC Power Distribution Platforms Patrick Chi-Kwong Luk and Andy Seng Yim ... more Page 1. 6 High Frequency AC Power Distribution Platforms Patrick Chi-Kwong Luk and Andy Seng Yim Ng Defence ... 1] Sood and Lipo [3] proposed another 20 kHz HFAC system for space application, as shown in Figure 6.2. ...
IEEE Transactions on Power Electronics, 2014
Abstract—This paper presents a state-space based analysis of a Class E 2 converter for wireless p... more Abstract—This paper presents a state-space based analysis of a Class E 2 converter for wireless power systems based on a two-coil inductive link. The Class E2 converter consists of a 200 kHz Class E inverter as the primary coil driver and a voltage driven Class E synchronous rectifier at the secondary coil of the inductive link. A piecewise linear 7th order state-space model is used to calculate several parameters and values to achieve optimum switching operation of the Class E inverter and the Class E rectifier. Simulation results are presented to compare the accuracy of the state-space modelling approach with the established analytical approach. For validation of the state-space analysis, an investigation of the influence of variation of coil alignment and load for a 20 W Class E2 converter prototype system is performed by means of a novel compensation method that maintains optimum switching conditions irrespective of variations. Experimental results are presented to confirm the a...
Due to the low residual flux density of ferrite magnets, flux-focusing and multi-layer configurat... more Due to the low residual flux density of ferrite magnets, flux-focusing and multi-layer configurations have been deployed to harness both the permanent magnet torque and reluctance torque. Here, a new configuration featuring a V-spoke rotor structure embracing a combined configuration of the conventional V-and spoke-shaped interior permanent magnet (IPM) machines is proposed for its superior torque density over equivalent counterparts. The magnetic open circuit characteristic of the V-spoke machine is first analysed and compared with that of the equivalent V-and spoke shaped machines. Then finite element analysis (FEA) simulations are performed for on-load conditions to confirm the superior performance of the proposed design. The frozen permeability method is carried out to provide further insights into the torque production mechanism. Operating efficiency, torque profiles and power-speed performance are also be investigated and evaluated to confirm the utility of the proposed ferrite machine design.
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Papers by Patrick Chi Kwong LUK