EPE Journal Volume 143  
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EPE Journal Volume 143  Editorial EPE Journal Volume 143  Papers


EPE Journal Volume 143  Editorial  
Editorial
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By E. Levi The Editorial of the EPE Journal Volume 14 N°3, written by Prof. E. Levi.  
EPE Journal Volume 143  Papers  
Polyphase PM brushless DC motor for high reliability application
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By J. Figueroa; J. Cros; P. Viarouge This paper presents a comparative analysis of the fault tolerance of polyphase motors. Since each phase generates a smaller part of the total torque than in the case of a threephase machine, it is easier to improve the fault tolerance with a polyphase motor. An open phase, a shortcircuited phase and an inverter transistor fault are the typical faults which are considered. The current compensation of the torque ripple under fault condition for a five and seven phase machine are determined. The design of the machine must be also adapted to improve the fault tolerance. Different suitable 7phase and 5phase machine designs with concentrated windings are presented. A simplified control system using only one Hall effect sensor per phase is described. An 7phase experimental setup validates the results obtained in the case of open and shortcircuited phase faults.  
A FivePhase Brushless DCMachine Direct Drive System
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By M. Godoy Simoes; P. Vieira Jr. The paper describes the design, analysis, simulation, modeling and control implementation of a hightorque, lowspeed, multiphase, permanent magnet, brushless dc machine. The main focus is on issues regarding the highlevel modeling, comprised of a transient model, in conjunction with corresponding experimental evaluation. The general assumption of ideal rectangular current waveforms for brushlessdc machines is not encountered in practice; the existing distortions can be modeled by incorporating mutual inductance and armature reaction in order to avoid erroneous control strategy development. Analyses are made to put together modeling efforts with the expected behavior so as to build a model of the expected behavior so realistic simulation results can be verified. Coherent and consistent results were observed by comparing simulation and experimentation. A digital signal processing (DSP) system control was developed to implement the strategies that corroborate the work.  
Multiphase System Supplied by SVM VSI: A New Fast Algorithm to Compute Duty Cycles
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By X. Kestelyn; E. Semail; J.P. Hautier Multiphase drives are more and more often used in industry, especially for highpower applications [17, 18, 20]. Space Vector Modulation (SVM) is now widely implemented and possesses many advantages over carrierbased pulse width modulation (PWM): – natural overmodulation implementation; – easy solution for saturation treatment; – fast and convenient to compute; – easy implementation of switching constraints for example to reduce harmonic currents [19]. Many authors proposed SVM VSI applied to multiphase drives. For example, [2] and [15] have chosen instantaneous vectors to control dual 3phase induction machines with low generated harmonic currents, [4] and [6] to control 5phase machines. The initial space is split onto orthogonal subspaces (dq and zerosequence) and the initial reference vector can be expressed at any sampling time in terms of several reference vectors, each one belonging to one subspace (plane and/or line). Each reference vector is located onto a sector, bounded by two active vectors, and decomposed onto these vectors. Once the two vector components are known, duty ratios are determined. Then, zero vectors are chosen and switching sequencing is imposed. Due to the high number of phases, a high number of sectors exist and the location of the different reference vectors leads to a great computational requirement (Fig. 1a). Using the equivalence between a multiphase machine and a set of fictitious onephase or two phase machines which are magnetically independent but mechanically and electrically coupled [1, 13], we propose a new fast algorithm to compute the duty cycles of each VSI leg. This algorithm, based on a vectorial approach of inverters developed in [3, 5, 7, 22], thereby reduces computation time and allows to use low computational requirements. This paper shows that, compared to classical techniques [9, 10, 11, 12], it is no more necessary to find the location of the reference vectors to get explicitly the duty cycle of each leg. Fig. 1 shows the difference between classical algorithm (Fig. 1a) and proposed one (Fig. 1b). This proposed technique is at first illustrated on a 3phase drive. Geometrical representations allow then to establish links with usual 3phase SVM. The implementation of the proposed SVM is achieved in the vector control of a 5phase drive. Experimental results are presented and confirm the theoretical approach.  
Feasibility of a Group Drive with Two Permanent Magnet Synchronous Traction Motors for Commuter Trains
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By O. Koerner; A. Binder Gearless permanent magnet synchronous traction motors (PMSM) offer lower life cycle costs compared to induction motors with gear units; however, PMSM usually require one inverter per motor. In commuter trains, one inverter feeds up to four induction motors – a cost advantage for induction motor drives. The feasibility of a group drive with two PMSM fed by one inverter is investigated to limit the number of inverters.  
A FivePhase TwoMachine Vector Controlled Induction Motor Drive Supplied from a Single Inverter
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By E. Levi; M. Jones; S. N. Vukosavic; H. A. Toliyat Twomotor drive systems, which require independent control of the two machines, are nowadays traditionally realised by using two threephase voltage source inverters supplying independently two machines, paralleled to the common DClink (Fig. 1). However, application of power electronics in electric drives enables utilisation of ACmachines with a phase number higher than three. If the number of phases is increased to five, an entirely different solution for the realisation of a twomotor drive system becomes feasible. It is shown in the paper that an increase of the stator phase number to five enables completely independent vector control of two fivephase machines that are supplied from a single currentcontrolled voltage source inverter. In order to achieve such an independent control it is necessary to connect fivephase stator windings of the two machines in series and perform an appropriate phase sequence transposition (Fig. 2). The concept is equally applicable to any fivephase AC machine type and its major advantage, compared with an equivalent twomotor threephase drive, is the saving of one inverter leg. Instead of six inverter legs, only five are required. Detailed verification of the novel fivephase twomotor drive configuration is provided by simulating the operation in the torque and speed mode, using indirect rotor flux oriented control principles. The concept can be extended to higher number of phases in a simple manner. Its main advantages and drawbacks are addressed as well.  
Independant Speed Control of Two SixPhase Induction Motors Using a Single SixPhase Inverter
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By K. K. Mohapatra; M. R. Baiju; K. Gopakumar Split phase (Double star, sixphase) induction motors are obtained by splitting the stator windings of threephase induction motor into two equal halves which are spatially phase separated by 30 electrical degrees. The resulting six phases can be decomposed into three orthogonal sets of phase sequences, i.e. positive sequence components and two zero sequence components. The positive sequence component consists of all the 12n ± 1 (n = 0, 1, 2, 3….etc.) order harmonics. One of the two zero sequence components consists of all the 6n ± 1 (n = 1, 3, 5….etc.) order harmonics. The triplen harmonic components 3n (n = 1, 3, 5….etc.) constitute the other zero sequence component. The zero sequence components do not contribute towards air gap flux production with the existing winding disposition. Only the positive sequence components contribute for the air gap flux and electromagnetic torque production in the motor. In this paper, a scheme is proposed where one of the zero sequence components is impressed across a second six phase motor in proper sequence so that it will become a positive sequence component for the second motor and, hence, will develop air gap flux and electromagnetic torque in the second motor. By following this method of orthogonal decomposition of the harmonic voltages of the split phase sequence, two split phase (double star, sixphase) motors can be independently controlled by a single sixphase inverter. 