Imra Europe Sas Uk Research Center

Brighton, United Kingdom

Imra Europe Sas Uk Research Center

Brighton, United Kingdom
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Hua H.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Pride A.,Imra Europe Sas Uk Research Center | Deodhar R.,Imra Europe Sas Uk Research Center | Sasaki T.,Imra Europe Sas Uk Research Center
ECCE 2016 - IEEE Energy Conversion Congress and Exposition, Proceedings | Year: 2016

This paper proposes a novel variable flux memory (VFM) machine, in which the 'constant' permanent magnet (PM) (CPM) with high coercive force and the 'variable' PM (VPM) with low coercive force are alternatively located in the interior-PM (IPM) rotor. Thus, the VPMs and CPMs are magnetically connected in series, with which the CPMs can assist the VPMs to withstand the unintentional demagnetization caused by armature reaction. Therefore, a high armature current can be applied to the machine. Meanwhile, the reluctance torque is retrieved. Thus, a high torque density can be obtained. Based on two-dimensional (2-D) finite element (FE) analysis, the electromagnetic performance of the proposed VFM machine in two extreme magnetization states is firstly evaluated in detail. Then, the demagnetization and re-magnetization characteristics are investigated, in which the working points of VPMs are illustrated. Furthermore, the advantages of improved efficiency of the proposed VFM machine are demonstrated. A prototype machine is manufactured and tested to validate the predictions. © 2016 IEEE.


Wu D.,University of Sheffield | Liu X.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Pride A.,Imra Europe Sas Uk Research Center | And 2 more authors.
IET Electric Power Applications | Year: 2014

A novel switched flux permanent magnet machine (SFPMM) with both normal NdFeB and low coercive force (LCF) magnets has been developed in this paper. Outside a conventional SFPMM, the LCF magnets are mounted on the back of every U-shaped stator lamination segment with parallel magnetisation direction and alternative polarities. A lamination ring yoke is placed around all the LCF magnets, while extra magnetisation coils are wound on each of them. By injecting different directions of current pulses into the magnetisation coils, the polarities of the LCF magnets can be rewritten in order to enhance or weaken the field generated by normal NdFeB magnets. Therefore the back EMF and torque capability could be adjusted in a wide range. In this paper, the operation principle and machine topology are introduced firstly. Then the stator/rotor pole combinations and design considerations of the machine have been discussed. With the help of two-dimensional finite element software, a 6/5 stator/rotor pole machine has been globally optimised as an example to show the machine performances such as open-circuit field and back EMF, dq-axis inductances, torque capabilities and magnetisation. Finally, a prototype with the same dimensions has been manufactured and tested to validate the analysis results. © The Institution of Engineering and Technology 2015.


Liu X.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Hasegawa M.,Imra Europe Sas Uk Research Center | Pride A.,Imra Europe Sas Uk Research Center | And 3 more authors.
IEEE Energy Conversion Congress and Exposition: Energy Conversion Innovation for a Clean Energy Future, ECCE 2011, Proceedings | Year: 2011

Although different drive topologies have been developed for switched reluctance machine (SRM), the inherent disadvantages, including high dc-link voltage and current pulsations and low drive efficiency, in addition to relatively high torque ripples and acoustic noise and vibration, have limited their application to many applications. To solve this problem, the SRM may be operated as a synchronous reluctance machine but with concentrate winding, and the vector control strategy can then be employed. Compared with conventional unipolar excitation in SRM, it has the advantages of significant reduction of dc-link capacitance, moreover, lower noise and vibration and higher efficiency are also achieved. In this way, it is possible to replace the electrolytic aluminum capacitors with the film ones, which results in much lower cost and higher reliability of the whole drive system, which is very attractive for many applications. Experimental results on a prototype 6/4 SRM validate the effectiveness of sinusoidal bipolar excitation. © 2011 IEEE.


Liu X.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Hasegawa M.,Imra Europe Sas Uk Research Center | Pride A.,Imra Europe Sas Uk Research Center | And 3 more authors.
IEEE Energy Conversion Congress and Exposition: Energy Conversion Innovation for a Clean Energy Future, ECCE 2011, Proceedings | Year: 2011

In this paper, the electromagnetic performance of switched reluctance machines (SRMs) with unipolar and bipolar excitations, either sinusoidal or rectangular current waveforms, is investigated in terms of torque capability and torque ripple, iron loss etc. By employing a cost effective standard 3-phase full bridge inverter, both rectangular and sinusoidal bipolar excitations are implemented. Compared with unipolar and rectangular bipolar excitations, the torque ripple and iron loss are significantly reduced with sinusoidal bipolar excitation, albeit with reduced torque capability. Experiments on a prototype 6/4 SRM are carried out to demonstrate the advantages of sinusoidal bipolar excitation. © 2011 IEEE.


Liu X.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Hasegawa M.,Imra Europe Sas Uk Research Center | Pride A.,Imra Europe Sas Uk Research Center | Deodhar R.,Imra Europe Sas Uk Research Center
IEEE International Symposium on Industrial Electronics | Year: 2012

Vibration and acoustic noise are two critical issues for switched reluctance machine (SRM). The abrupt change of phase current mainly contributes to high vibration and noise under conventional unipolar excitation, sinusoidal bipolar excitation considered in this paper can suppress the vibration in SRM. However, to realize the smooth sinusoidal bipolar excitation, different pulse-width modulation (PWM) strategies can be employed. In this paper vibration and acoustic noise of a prototype 6/4 SRM under different load and speed, which employs hysteresis current control (HCC) and space vector pulse-width modulation (SVPWM), is investigated, together with the conventional unipolar excitation, which is modulated by voltage PWM. It shows that the lowest vibration and acoustic noise are obtained if the SRM excited by the sinusoidal bipolar excitation modulated by the SVPWM, regardless the speed and load. However, the HCC technique exhibits the worst vibration and acoustic noise due to random switching frequencies and mechanical resonances, although less sensitive to the load and speed. In contrast, the acoustic noise with the conventional unipolar excitation is sensitive to both load and rotor speed, when the sinusoidal bipolar excitation modulated by SVPWM is employed it is sensitive to the speed but not to the load. © 2012 IEEE.


Liu X.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Hasegawa M.,Imra Europe Sas Uk Research Center | Pride A.,Imra Europe Sas Uk Research Center | Deodhar R.,Imra Europe Sas Uk Research Center
Conference Proceedings - 2012 IEEE 7th International Power Electronics and Motion Control Conference - ECCE Asia, IPEMC 2012 | Year: 2012

The vibration and acoustic noise are investigated in a novel variable flux reluctance machine, which utilizes a DC-field coil in the stator to achieve on-line adjustment of air-gap flux density. The capability of adjusting air-gap flux density is expected to improve the efficiency and extend the speed range. The doubly salient structure in switched reluctance machines (SRM) is employed in the variable flux reluctance machine, together with the non-overlapping concentrated windings to reduce the copper loss. The 2D and 3D-finite element analyses are employed to predict the radial force and vibration modes in the variable flux reluctance machine, respectively. With the aid of vector control, which employs space vector pulse-width modulation, the vibration and acoustic noise in this novel machine are experimentally investigated, together with the comparison with SRM, which has the same stator/rotor pole combination. Compared with SRM, under the same load condition, the variable flux reluctance machine significantly reduces the vibration of mode 2, which is dominant in the SRM. © 2012 IEEE.


Shen Y.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Chen J.T.,University of Sheffield | Deodhar R.P.,Imra Europe Sas Uk Research Center
PEDES 2012 - IEEE International Conference on Power Electronics, Drives and Energy Systems | Year: 2012

Nowadays, the replacement of rare-earth permanent magnet is one of the primary targets to enhance the cost-effective design for electrical machines. A claw-pole rotor brushless machine with DC excitation is desirable as a magnetless machine because it is reliable, low-cost, and does not need slip ring etc. However, the inherent 3D structure makes numerical analysis very time-consuming. In this paper, a lumped-parameter magnetic circuit model is developed to model and design an 18-slot/6-pole claw-pole rotor brushless machine with DC excitation, while its validity is examined by using 3D finite-element analysis. The optimization is also carried out, together with optimal skew and unequal rotor pole thickness. © 2012 IEEE.


Shen Y.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Chen J.T.,University of Sheffield | Deodhar R.P.,Imra Europe Sas Uk Research Center | Pride A.,Imra Europe Sas Uk Research Center
IEEE Transactions on Magnetics | Year: 2013

Since the claw-pole machines can exhibit a number of attractive features, they have been widely applied to automotive and domestic markets. Nowadays, with the development of rare-earth permanent magnet (PM) and powder metallurgy techniques, high performance and cost-effective design of a multiphase claw-pole stator SPM brushless machine becomes achievable. However, the inherent 3-D structure makes finite-element analysis very time-consuming. Thus, a lumped-parameter magnetic circuit model is developed and validated by 3-D finite element analysis in this paper to design three-phase 10-pole claw-pole stator surface-mounted PM brushless machine having soft magnetic composite made stator core. A prototype machine is built and tested in accordance with analytically optimized overall design parameters. © 2013 IEEE.


Wu D.,University of Sheffield | Liu X.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Pride A.,Imra Europe Sas Uk Research Center | And 2 more authors.
IET Conference Publications | Year: 2014

Based on the traditional switched flux PM machine, a novel switched flux hybrid magnet memory motor is developed in this paper, which has extra low coercive force (LCF) magnets and magnetization coils. By changing the magnetization state of LCF magnets during operation, flux enhancing and weakening can be achieved without extra copper loss. The design considerations such as stator/rotor pole combinations, cross coupling effect and online magnetization strategy are discussed. Meanwhile, the performances of a 6/5 stator/rotor pole model are investigated, such as open circuit flux density, back EMF, torque capability, magnetization capability as well as efficiency map. The results show that by changing the magnetization state, the back EMF and average torque can be adjusted over a wide range, while the overall maximum efficiency region increases significantly.


Wu D.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Liu X.,University of Sheffield | Pride A.,Imra Europe Sas Uk Research Center | And 2 more authors.
7th IET International Conference on Power Electronics, Machines and Drives, PEMD 2014 | Year: 2014

Memory motor has been researched extensively in the last decade due to its online magnetization capability. Among many types of designs, hybrid magnet memory motor (HMMM) has highest torque density. This paper investigates the cross coupling effect of HMMM in the motor topology proposed by Sakai. The analysis model is introduced firstly. Based on the magnetic circuit model, the mechanism of opencircuit cross coupling effect is investigated while the ideal condition for eliminating this effect is proposed. Later, the on-load cross coupling effect is also analysed by both magnetic circuit model and 2D FEA focusing on coercive force (Hc) of magnet and interaction between two types of magnets as well as magnetic saturation. Meanwhile, the magnetization characteristics are calculated as well. The results show that increasing Hc of low coercive force (LCF) magnet can reduce the cross coupling effect but increase the difficulty of online magnetization. Therefore, a trade-off exists for choosing proper LCF magnet in HMMM.

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