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Fractional‐slot concentrated‐windings are appreciated for their simple construction, short end‐winding length, high copper fill factor, low cogging torque, good field‐weakening capability and fault‐tolerant ability. However, in comparison to the conventional distributed windings, the fractional‐slot concentrated‐windings are characterised with high space magnetomotive force (MMF) harmonics, which results in undesirable effects on the machine performance, such as localised core saturation, eddy current loss in the rotor and noise and vibration. In order to improve winding characteristics, several techniques have been developed recently. This manuscript introduces the 5 new winding topologies by using the general concept of stator slot shifting. It means that, in order to cancel undesirable MMF harmonics, by doubling (or tripling or even multiplying) the slot number and dividing the winding and then relatively shifting the winding by one (or more) slots, the undesirable harmonics have been eliminated effectively. The best choice is chosen according to the lowest amount of the MMF harmonic, highest value of winding factor and torque desirable characteristics. At the end, comprehensive comparisons for the designed synchronous reluctance motor (SynRel) equipped with proposed windings and also distributed winding are presented. The analytical study and 2D FEM analysis results show that it is possible to get an ideal low space‐harmonic winding topology, and consequently, a low torque ripple for these motors. [ABSTRACT FROM AUTHOR]

Multi air‐gap tubular linear machines usually take the form of a double‐sided tubular linear machine (DSTLM). Such machines have a higher space utilisation and higher power density than their single air‐gap counterparts, but at the same time the structure is more complex. It is traditionally very difficult to mechanically implement a movement between two slotted stators, whilst maintaining an even air gap distribution. Thermally, the inner stator is another complex aspect of a DSTLM. However, very little understanding of these two aspects and how they influence the performances of tubular machines exists today. Therefore in this paper, the aim is to accurately analyse the influence of temperature rise and eccentricity fault on the performances of DSTLM. A two‐way electromagnetic‐fluid‐thermal multi‐physics coupling model of the DSTLM is established. The variations of electromagnetic, fluid and thermal characteristics with the eccentricity are systematically analysed. A physical prototype is manufactured and the analysed results are verified by the experiments. [ABSTRACT FROM AUTHOR]

Brushless doubly-fed induction machine (BDFIM) has recently gained considerable research interests due to its promising features when incorporated as wind generator or variable speed drive. The BDFIM has two three-phase stator windings with different pole-pair numbers and excitation frequencies. The performance of the machine is based on the magnetic cross-coupling of rotating fields produced by the stator windings through a special squirrel cage rotor. Contrary to the conventional induction machine (IM), the rotor slip and frequency are high throughout the operating speed range. Hence, the rotor core loss cannot be ignored in the steady-state analysis. Although the core loss components have much more study of BDFIM. In this study, analytical expressions are individually derived for a number of core loss components caused by the complicated nature than those of an IM, the precise calculation of these components is important especially on the efficiency each stator winding field. Then, the modified steady-state electric equivalent model is developed by considering the components. The experiments and finite element analysis based on a 3 kW prototype BDFIM verify the accuracy of the proposed model. [ABSTRACT FROM AUTHOR]

Here, static and dynamic (rotating) misalignments between the low-speed rotor (LSR) and the stator of axial flux magnetically geared machines are studied with the aid of 3-D finite element analysis (FEA). The influence of rotor/stator axis misalignments on machine performance in terms of cogging torque, air-gap flux density, and back-EMF is investigated with reference to the fully healthy condition. The results show that the LSR and HSR cogging torques are significantly affected by such misalignments due to distorted air-gap flux density. However, the amplitude and the harmonics of the back-EMF are only slightly changed. Furthermore, the influence of the misalignments on the machine torque performance is investigated. It is shown that the machine torque is significantly reduced when the LSR axis is misaligned with the axis of the stator. Thus, it is concluded that the torque performance of axial flux magnetically geared machines significantly deteriorates under static and dynamic axis misalignments. In addition, the two types of misalignments have similar effects on machine performance. [ABSTRACT FROM AUTHOR]