Interest in permanent magnet synchronous machines for safety-critical applications has been increasing over the years. One of the most common methods for providing fault tolerance to a permanent magnet machine is the active control from the drive side. This method requires designing machines with the lowest possible mutual coupling between phases and a selfinductance that is high enough to limit the fault currents. Fractional-slot concentrated windings have been proposed as the most advantageous solution to meet these requirements. When comparing the numerous combinations of phases, poles and slots that give rise to a fractional-slot concentrated winding, the usual criteria only focus on obtaining a single-layer winding and do not actually consider the relationship between the self-inductance and the mutual inductance between phases. Moreover, they give no recommendations regarding the optimal number of phases from a magnetic point of view. The present work aims to cover this gap by obtaining analytical expressions for the calculation of the inductances in a permanent magnet machine. The derived expressions are investigated regardless of the geometry of the machine, and the criteria for selecting the most promising combinations in terms of the machine's fault tolerance are extracted. Nomenclature List of acronymsFEA finite-element analysis FEM finite-element method FSCW fractional-slot concentrated winding GCD greatest common divisor (mathematical function) ISA integrated starter alternator MMF magneto motive force PMSM permanent magnet synchronous machine List of symbols A magnetic vector potential [T·m] B magnetic flux density [T] H magnetic field intensity [A/m] L b base inductance [H] L ii phase self-inductance [H] L ij mutual inductance between phases [H] N s number of turns wound in series per phase Q number of stator slots R r rotor outer radius [m] R s stator inner radius [m] W magnetic energy [J] B slot width [m] b 0 slot opening width [m] g air-gap length [m] h slot height [m] h 0 slot opening height [m] i slot slot current [A] j slot slot current density [A/m 2 ] k w, s1 fundamental winding factor l ef effective length of the machine [m] m number of phases p number of pole pairs q number of slots per pole and phase t electric periodicity of the machine, GCD( p, Q) w magnetic energy density [J/m 3 ] α 0 slot opening angle [rad] α slot slot angle [rad] β slot leakage-related dimensionless parameter γ slot leakage-related dimensionless parameter δ air-gap inductance-related dimensionless parameter l permeance coefficient μ 0 permeability of free space [H/m] j relationship between air-gap inductance coefficients ς relationship between slot inductance coefficients f figure of merit

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This paper studies the feasibility of using synchronous reluctance machines (SynRM) for low speed-high torque applications. The challenge lies in obtaining low torque ripple values, high power factor, and, especially, high torque density values, comparable to those of permanent magnet synchronous machines (PMSMs), but without resorting to use permanent magnets. A design and calculation procedure based on multistatic finite element analysis is developed and experimentally validated via a 200 Nm, 160 rpm prototype SynRM. After that, machine designs with different rotor pole and stator slot number combinations are studied, together with different winding types: integral-slot distributed-windings (ISDW), fractional-slot distributed-windings (FSDW) and fractional-slot concentrated-windings (FSCW). Some design criteria for low-speed SynRM are drawn from the results of the study. Finally, a performance comparison between a PMSM and a SynRM is performed for the same application and the conclusions of the study are summarized.

This paper presents a MATLAB/Simulink simulation model for a Direct Space Vector modulated Matrix Converter (MC). The power circuit model, consisting of an input filter, a matrix of bidirectional switches and an RL load, is completely implemented using the power library in Simulink, contributing to the simplicity and clearness of the whole model. Two switching strategies are modeled, simulated and analyzed together with the Direct Space Vector Modulation (DSVM): Symmetrical SVM and Asymmetrical SVM. Two sets of rules are proposed for these techniques in order to simplify the model implementation. Principal input and output converter variables are presented in simulations so that MCs' characteristics and advantages can be observed. Moreover, this model is also very flexible about changing the modulation technique, the load, or removing the input filter, making it suitable for an introduction of this kind of converters in an educational environment.