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In this study, the electromagnetic performances of dual 3‐phase permanent magnet (PM) machines with coil span of two slot‐pitches are comparatively investigated. It mainly focuses on two PM machines with different slot/pole number combinations (Ns/2p), that is, the 24‐slot/10‐pole and 24‐slot/14‐pole machines (2p = Ns/2 ± 2). First, winding configurations are illustrated for these two dual 3‐phase machines with 30° angle displacement. Then, the winding factor, back electromotive force, average torque, torque ripple, iron and PM losses, short‐circuit (SC) current, and PM irreversible demagnetisation are analysed and compared for both machines on the conditions of healthy operation and one set of three‐phase fault, that is, SC or open circuit (OC), respectively. The comparative results show that on healthy condition the 14‐pole PM machine has a slightly larger torque output. Besides, on 3‐phase OC condition, the 14‐pole machine also performs better over‐rating torque capability. In terms of iron and PM losses, the 10‐pole machine has smaller iron losses but larger PM losses than the 14‐pole machine. Moreover, on 3‐phase SC condition, the 14‐pole machine has a significantly lower risk of PM irreversible demagnetisation than the 10‐pole machine, although both machines have very similar SC currents. Finally, the 24‐slot/10‐ and 14‐pole dual 3‐phase PM machines are both prototyped and some tests are carried out for validation. [ABSTRACT FROM AUTHOR]

This study investigates the underlying mechanism of low‐power factor issue of variable flux reluctance machines (VFRMs) from the perspective of magneto‐motive force (MMF)‐permeance model. On the basis of a simplified analytical model, the relationship between the design parameters and the power factor is identified and systematically summarised into three predictable ratios: the rotor permeance ratio, stator/rotor‐pole ratio and DC/AC winding ampere turns ratio. Specifically, the smaller the rotor‐pole arc, the air‐gap length, the rotor‐pole number and the AC/DC winding ampere turns ratio are, the higher the power factor will be. In addition, the weak coupling between the field and armature windings caused by the modulation effect of the salient rotor is responsible for the low‐power factor issue of VFRMs, regardless of the control scheme, winding configuration or saturation effect. A 6‐stator‐pole/4‐rotor‐pole VFRM is prototyped and tested for verification. [ABSTRACT FROM AUTHOR]

The split ratio of rotor outer diameter to stator outer diameter is one of the most important design parameters due to its significant impact on machine torque density and efficiency. It has been optimised analytically in existing papers with due account given only for the thermal limitations. Here, the optimised split ratio for high‐speed permanent magnet machines (HSPMM) with consideration of the mechanical constraints is investigated analytically. In addition, the influences of flux density ratio, maximum operating speed and sleeve material on the optimised split ratio are discussed in detail. The analytical results are verified by finite‐element analyses. It is demonstrated that the optimised split ratio as well as the achievable torque of HSPMM is significantly reduced when the mechanical constraints are taken into consideration. The experimental results on a 6/slot‐4pole HSPMM confirm the validity of previous analyses. [ABSTRACT FROM AUTHOR]

This study proposes a novel method for the parameter determination of permanent magnet (PM) synchronous machines under different load conditions. It can identify the total dq‐axis flux linkages and also the PM flux linkage separately by the addition of a pair of negative and positive position offsets. It is also noteworthy that the influence of uncertain inverter non‐linearity and winding resistance is cancelled during the modelling process, and the experimental results on two different PM synchronous machines show a good agreement with the finite‐element prediction results. More importantly, it shows good performance in online tracking the variation of PM flux linkage, which is an important feature for aiding the condition monitoring of PMs, for example, monitoring the temperature of PMs. [ABSTRACT FROM AUTHOR]