Bassel Aslan

General Analytical Model of Magnet Average Eddy-Current Volume Losses for Comparison of Multiphase PM Machines With Concentrated Winding

This paper studies magnet eddy-current losses in permanent-magnet (PM) machines with concentrated winding. First, space harmonics of magnetomotive force (MMF) and their influence on magnet losses in electrical machines are investigated. Second, an analytical model of magnet volume losses is developed by studying the interaction between MMF harmonics wavelengths and magnet pole dimensions. Different cases of this interaction are exhibited according to the ratio between each harmonic wavelength and magnet pole width. Then, various losses submodels are deduced. Using this analytical model, magnet volume losses for many slots/poles combinations of three-, five-, and seven-phase machines with concentrated winding are compared. This comparison leads to classify combinations into different families, depending on their magnet losses level. Finally, in order to verify the theoretical study, finite-element models are built and simulation results are compared with analytical calculations.

Slot/pole combinations choice for concentrated multiphase machines dedicated to mild-hybrid applications

This paper presents multiphase permanent magnet machines with concentrated non-overlapped winding as a good candidate for automotive low voltage mild-hybrid applications. These machines often require a trade-off between low speed performances such as high torque density and high speed performances like flux weakening capabilities. This paper describes how to choose a key design parameter to ease this compromise, the slots/poles combination, according to three parameters: winding factor including harmonics factor, rotor losses amount thanks to a comparison factor, and radial forces balancing. The comparison criterions are based on both analytical formula and Finite Element Analysis.

Analytical model of magnet eddy-current volume losses in multi-phase PM machines with concentrated winding

This paper studies magnet eddy-current losses in permanent magnet (PM) machines with concentrated winding. First of all, space harmonics of magnetomotive force (MMF) and their influence on magnet losses in electrical machines are investigated. Secondly, analytical model of magnet volume losses is developed by studying the interaction between MMF harmonics wavelengths and magnet pole dimensions. Different cases of this interaction are studied according to the ratio between each harmonic wavelength and magnet pole width (following flux density variation). Then various losses sub-models are deduced. Finally, using this analytical model, magnet volume losses for many slots/poles combinations of 3, 5, and 7 phase machines with concentrated winding are compared. This comparison leads to classify combinations into different families depending on their magnet losses level. Besides, in order to validate the theoretical study, Finite Element models are built and simulation results are compared with analytical calculations.

Computation of optimal current references for flux-weakening of multi-phase synchronous machines

Multi-phase synchronous machines are more and more used in specific applications where high power density, low bus voltage, wide speed range and fault-tolerant capabilities are required. Due to the high number of degrees of freedom, multi-phase machines are difficult to optimally operate in flux-weakening zones. This paper proposes a technique to numerically compute optimal current references that can be used for feed-forward flux-weakening techniques in order to exploit the maximum machine performances for given DC bus voltage and current limits. The proposed technique is applied to a five-phase permanent magnet synchronous machine specifically developed for an automotive application.

High-speed functionality optimization of five-phase PM machine using third harmonic current

Purpose – The purpose of this paper is to apply some surrogate-assisted optimization techniques in order to improve the performances of a five-phase permanent magnet machine in the context of a complex model requiring computation time. Design/methodology/approach – An optimal control of four independent currents is proposed in order to minimize the total losses with the respect of functioning constraints. Moreover, some geometrical parameters are added to the optimization process allowing a co-design between control and dimensioning. Findings – The optimization results prove the remarkable effect of using the freedom degree offered by a five-phase structure on iron and magnets losses. The performances of the five-phase machine with concentrated windings are notably improved at high speed (16,000 rpm). Originality/value – The effectiveness of the method allows solving the challenge which consists in taking into account inside the control strategy the eddy-current losses in magnets and iron. In fact, magnet...

Different virtual stator winding configurations of open-end winding five-phase PM machines for wide speed range without flux weakening operation

This paper presents a specific control strategy of double-ended inverter system for wide-speed range of open-end winding five phase PM machines. Different virtual winding configurations (star, pentagon, pentacle and bipolar) can be obtained by choosing the appropriated switching sequences of two inverters. The motors speed range is thus increased.

Maximum Torque Per Ampere strategy for a biharmonic five-phase synchronous machine

The paper studies the impact of first and third current-harmonic repartition in a five-phase Permanent Magnet machine whose Electromotive Forces (emfs) have first and third harmonics of the same amplitude. With a five-phase machine, it is possible for the torque production to achieve independent controls of the first and third harmonics of currents by using a vector control in each one of the two characteristic orthogonal sub-spaces of the machine. The same torque quality as obtained with a three-phase machine with sinusoidal emf can be thus obtained with a non-sinusoidal emf and with one more supplementary degree of freedom for the control. Based on the Maximum Torque Per Ampere (MTPA) strategy used for three-phase machines, a comparison of the obtained torque/speed characteristics of the machine is achieved using either one or two harmonics. The voltage limits imposed by the Voltage Source Inverter and two different values of the maximum allowed current densities are taken into account for obtaining the optimum repartition between first and third harmonics of currents: it appears that at first, from the point of view of efficiency, the MTPA is not optimal except for low speeds and secondly that the repartition of currents is not trivial and depends for example on the considered maximum current densities.

A signal-based technique for fault detection and isolation of inverter faults in multi-phase drives

A method for fault detection and isolation is proposed and applied to inverter faults in multi-phase drives. An analysis of simulations in faulty conditions leads to the derivation of suitable fault indices. These are based on the unbalance of the phase currents and their instantaneous frequency. The method is applied to a five-phase permanent-magnet synchronous machine drive. Simulations and experiments validate the proposed method.

Design Considerations of Five-Phase Machine with Double p/3p Polarity

In the context of traction drives with required torque transient capabilities and a classically wide flux weakening speed range, this paper gives design considerations of a particular double-polarity (DP) five-phase machine. Beyond its intrinsic fault tolerance due to its five phases, its specificity is the ability to develop torques of comparable values under three kinds of supply: with only first, third or both first, and third sinusoidal currents. This property, due to first

Influence of Rotor Structure and Number of Phases on Torque and Flux Weakening Characteristics of V-Shape Interior PM Electrical Machine

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