As a computationally efficient tool for the machine’s steady–state performance prediction, equivalent circuit model (ECM) of induction machines (IMs) has been an established option in literature. The results and performance predictions obtained from ECM are significantly affected by: (i) the leakage reactances as the function of the geometry of the machine’s rotor and stator slots (ii) the skin, proximity, and slotting effects and (iii) the saturation of the core. Simultaneous consideration of these effects has been ignored in conventional ECM of IMs for simplicity. In this paper, a novel permeance-based ECM is proposed and developed based on the dimensions of the stator and rotor slots to simultaneously incorporate leakage zig–zag, tooth top and overhang reactances into modeling steps. Saturation, slotting, proximity and skin effects are also fully taken into account to improve the accuracy of the modeling and performance prediction compared to the conventional ECM. Finite element analysis is used to verify the accuracy of the proposed ECM when compared to the conventional ECM based on the steady state performance characteristics such as torque, electromagnetic loss, and efficiency predictions.

The direct-drive (gearless) permanent magnet generator system has a high potential for wind turbines because of its performance efficiency, robustness, low maintenance, and reliability compared to other generator systems. Transverse flux permanent magnet generators (TFPMGs) have high-power density and modular structures, making them a proper candidate for direct-drive wind turbine applications. The main disadvantage TFPMGs is the high cost of PMs and increment of PM demagnetization risk with rising temperature. This paper is dedicated to a comprehensive comparison of the three-phase constructed rare-earth and Ferrite TFPMGs considered in small-scale direct-drive wind generator applications (320 rpm, 3000 W). The comparison includes operation principles, design procedure, performance (in terms of analyzing methods, electric and magnetic characteristics), cost, materials, and structures. It will be shown that the Ferrite TFPMGs can have acceptable performance for low-cost wind turbines applications.

Asymmetrical star-delta winding interior permanent magnet synchronous motor (IPMSM) is introduced as a capable option in supporting higher torque and lower torque ripple characteristics compared to the symmetrical star-delta winding IPMSM. This is at the expense of having higher radial electromagnetic (EM) force and potential vibration-related concerns including high acceleration. EM force and vibration reduction in the asymmetrical star-delta winding IPMSMs have not been well addressed in the literature so far. In order to improve the EM force and acceleration characteristics of the asymmetrical star-delta winding IPMSM while keeping its developed torque within the desired ranges, various stator and rotor geometrical parameters are defined and are changed individually. A sensitivity analysis is utilized to introduce the most effective geometrical design variables for the highlighted objectives. The reduction in the EM force, through the Maxwell-Stress tensor method, and the acceleration on the outer surface of the motor housing of the improved asymmetrical star-delta winding IPMSM structure over a base asymmetrical star-delta winding IPMSM model are investigated and reported via EM and structural simulations.

Induction machines are a popular choice for tractive applications due to inherent cost savings and performance benefits driving industry to search for an optimal rotor bar design. Induction machines suffer from low torque densities due to larger size and increased losses incurred in the rotor bars making these the performance objectives to be improved through optimization. Communicating through objective functions (OFs), a performance model to rapidly evaluate design parameters coupled with genetic algorithm (GA) can be used to produce an optimal rotor bar; however, conventional OF modeling may introduce function bias or complex coefficient calculations leading to dominated objectives, stalling and premature convergence leading to an unoptimized solution. In this paper, the rotor bar of a squirrel cage induction machine (SCIM) is modeled by a permeance based equivalent circuit model (ECM) creating a link between the rotor slot geometry and equivalent circuit parameters. The model considering skin and slotting effect as well as slot, zigzag, tooth top and overhang leakage reactance effects coupled with a multi- objective GA through novel hyperbolic tangent based OFs to optimize the rotor bar geometry. The optimal rotor bar shape proposed offers increased output torque and reduced total machine losses resulting in a higher operating efficiency.

Weight, torque, and efficiency of induction machines (IMs) are directly affected by their stator winding configuration. To evaluate this, this paper presents the electromagnetic (EM) performance comparison of four squirrel cage IMs using different winding configurations, namely, integral slot distributed winding (ISDW), fractional slot concentrated winding (FSCW), integral slot concentrated winding (ISCW) and integer slot concentric winding (ISCW2). The same active volumes with identical electric and magnetic loading constraints were assigned for all IMs with the same materials. The weight, torque, EM losses, and efficiency values in both maximum torque per ampere (MTPA) and field weakening regions were assessed. The results indicate that the ISCW2 IM possessed the best overall performance and characteristics in terms of torque, torque density and efficiency in a wide speed range among the investigated IMs; except its lower developed torque compared to the ISDW IM in MTPA region. To resolve this issue, a winding layout optimization was carried out via a winding function-based analysis to improve the torque performance of the ISCW2 IM in MTPA region as well.