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In this paper, the open-circuit dc-winding-induced voltage in a wound field switched flux (WFSFs) machines is analyzed. The phenomenon of open-circuit dc-winding-induced voltage is illustrated and the mechanism is explained. Rotor skewing is proposed to reduce the open-circuit dc-winding-induced voltage, and the optimal skewing angle is analytically derived based on the analytically deduced harmonic orders of the open-circuit dc-winding-induced voltage. Finite-element (FE) analyses show that the open-circuit dc-winding-induced voltages in the analyzed 12-stator-pole partitioned stator WFSF machines having 10-, 11-, 13-, and 14-rotor-pole rotors can be effectively reduced by >94%, while the ac-winding phase-fundamental back-EMFs can be maintained by >95%. Twelve/ten-stator/rotor-pole prototypes with skewed and nonskewed rotors are built and tested to verify the analytical and FE results. [ABSTRACT FROM AUTHOR]

DC winding induced voltage pulsation in the wound field synchronous machines (WFSMs) will cause dc winding current ripple, challenge the dc power supply, and deteriorate the control performance, especially at high speed. In this paper, the influence of dc winding configuration including the dc coil number and the parallel branch number on its induced voltage pulsation is investigated for WFSMs. Based on the modeling of both open-circuit and on-load dc winding induced voltages, the preferred dc winding configurations for WFSMs having various stator/rotor pole number combinations with double layer or single layer ac windings are obtained and validated by finite element (FE) analysis on four typical partitioned stator WFSMs (PS-WFSMs). A PS-WFSM prototype is built and tested to validate both analytical and FE analyses. [ABSTRACT FROM AUTHOR]

Novel stator slot permanent magnet (SSPM) machines with doubly salient structure have attractive features, such as a robust rotor and fail-safe capability during faults due to their peculiar PM excitation characteristics. In this paper, average electromagnetic torque production in SSPM machines is investigated using the frozen permeability analysis for the 12/10 stator/rotor pole machine. The single layer (SL) and double layer (DL) winding SSPM machines with 12/10 stator/rotor poles are further investigated, accounting for the influence of stator tooth-tips. The key findings include that the average electromagnetic torque can be enhanced by 9%–10% at the rated current for the DL and SL winding machines with stator tooth-tips. The influence of design parameters, open-circuit characteristics, inductances, electromagnetic torque, torque ripple, and losses is studied. Finally, the 2-D finite-element analysis is experimentally validated. [ABSTRACT FROM AUTHOR]

In mass production, fabrication processes of electrical machines are not perfectly repeatable with time, leading to dispersions on the dimensions which are not equal to their nominal values. The issue is then to link the dispersions on the dimensions, which are uncertain to the performance of electrical machines in order to evaluate their influence. To deal with uncertainty, there is a growing interest in the stochastic approach, which consists of modeling the uncertain parameters with random variables. In fact, this approach enables us to quantify the influence of the variability of the uncertain parameters on the variability of the quantities of interest. In this paper, a stochastic approach coupled with a 3-D finite-element model is used to study the influence of the fabrication process imperfections, such as the rotor eccentricity and the stator deformation, on the performance of a claw pole synchronous machine. [ABSTRACT FROM AUTHOR]

A novel stator hybrid-excited, parallel flux path, synchronous machine of doubly salient topology is proposed. It has the novel features of: 1) hybrid dc field and permanent magnet (PM) excitation in the stator; 2) magnets placed in the slots between adjacent salient stator poles; and 3) the magnetic poles of PMs arranged, such that the flux premagnetizes the stator, but it is in a direction to oppose the dc excitation flux. The electromagnetic characteristics of the machine are analyzed on open-circuit and load. Since the new machine topology is developed from the variable-flux machine (VFM), a comparison of their electromagnetic torque and machine losses is conducted. The average electromagnetic torque of the hybrid-excited machine can be increased by 18% for fixed copper loss in comparison with the VFM due to the reduction of magnetic saturation in the stator. It is also shown that at high temperatures some risk of PM demagnetization exists when excited with dc and armature currents due to fringing flux that exists between the stator and the rotor poles. However, this affects only a very small area of the PMs. The performance of the hybrid-excited machine is predicted by a 2-D finite-element analysis and experimentally validated. [ABSTRACT FROM AUTHOR]