Generators are a key technological element of wind power generation systems. The use of synchronous generators that employ heavy rare-earth permanent magnets is increasing owing to the demand for higher efficiencies. However, these magnets are expensive and undergo an unbalanced supply and demand. Therefore, spoke-type structures have been developed and used in various fields to compensate for the deficient performance when using a ferrite magnet, which is inexpensive and provides a stable supply and demand. However, permanent magnet synchronous generators (PMSGs) with adopted spoke-type structures and an output power of 1 kW or higher have not been studied and practically applied sufficiently. Additionally, new designs must consider differences between the target specifications of a generator and wind turbine. In this study, we designed and analyzed the characteristics of an alternative bridge spoke-type PMSG modeling a generator for a 3-kW class wind turbine. We analyzed the performance of the existing spoke-type generator and proposed an alternative bridge spoke shape with an improved performance by removing the leakage flux of the bridge. The performance of the existing spoke model was compared using the finite element method (FEM), and the performance of the proposed model was verified more accurately by performing a three-dimensional (3D) analysis considering the 3D effect. Additionally, we analyzed the voltage fluctuation rate according to the number of stator slots and overhang structure and designed a final model. Considering the characteristics of the ferrite magnet used in the spoke-type design, the irreversible demagnetization characteristics of the conventional and final models were compared using simulations, followed by a comparison between the stiffness characteristics of the two models. Finally, a prototype was manufactured, and the feasibility of the final design was verified using the performance tests.

In an interior permanent magnet synchronous motor, an adhesive such as bond is generally injected into the magnet tolerance to prevent vibration of the permanent magnet within the insertion space. In this case, a disadvantage is that the magnet tolerance does not contribute to the performance. In this paper, ferrofluid is inserted to improve the torque density, utilizing the magnet tolerance. When inserting ferrofluid into the magnet tolerance, it is important to fix the magnet because conventional adhesives are not used, and it is important that the ferrofluid does not act as a leakage path within the insertion space. In this study, a new rotor configuration using a plastic barrier that satisfies these considerations was introduced. The analysis was conducted through finite element analysis (FEA), and this technique was verified by comparing the simulation results and the experimental results through a dynamo test. It was confirmed that the no-load back electromotive force in the final model increased through ferrofluid injection.

Double-cage rotors are used to produce induction motors with high efficiency and high starting torque. Most often, experience constants are used in the design of the working bars of double-cage rotors. However, an error occurs, resulting in lower efficiency than actual in the characteristic analysis results. In this study, a new working bar design process is proposed using correct factor and regression, instead of using the existing experience constant when designing the working bar of the double-cage rotor. The performance of a 15-kW-class construction motor model using the existing experience constant was compared with that of the proposed design process through magnetic equivalent circuit (MEC). Finally, the finite-element method (FEM) and start-up performance tests proved the validity of the process.

With the recent increase in the demand for convenient handheld home appliances, the quietness, power density, and weight of motors have been extensively studied. To this end, this article proposes a separated teeth motor (STM) with improved weight reduction and higher productivity than those of existing hair dryer motors. To reduce the weight of the stator, which possesses a high weight specificity in the motor, an STM model was designed with divided teeth to facilitate reduced iron consumption. Using this model, improvements in the production and performance of STM motors are proposed. For example, the workability of the motor is increased for the same torque; moreover, manufacture of compact and lightweight STMs is deemed possible. In addition, a reduction in torque ripple, cogging torque, and total harmonic distortion has been demonstrated via a finite-element method.

The claw-pole motor, known for its simple structure, is widely used in various fields due to its cost competitiveness. However, a drawback of the fixed-stator-type claw-pole motor is its vulnerability to eddy current losses. Therefore, this paper presents a single-phase claw-pole motor applied as a motor for cooling fans, with the aim of reducing eddy current losses and improving performance based on shape optimization, ultimately resulting in a single-phase claw-pole motor that meets the desired performance. The validity of this approach is verified through 3D finite element analysis (FEA).