Currently, the automotive market is undergoing a vibrant transition toward component electrification driven by the widespread adoption of electric vehicles. The steering system, electric power steering (EPS), has evolved gradually from traditional hydraulic systems (HPSs) to electric systems. The current state sees the majority of commercial vehicles equipped with electric EPS systems. EPS reduces the steering effort applied to the steering wheel during low-speed driving, enhancing driving convenience. It is widely adopted in most commercial vehicles due to numerous advantages such as system simplification, speed-dependent steering control, and vehicle weight reduction compared to traditional HPSs. EPS can achieve a 3%–5% improvement in fuel efficiency compared to traditional HPSs because it operates only when the driver manipulates the steering wheel. However, what matters most in EPS is vibration and noise. Drivers are directly exposed to the vibration and noise of EPS. Therefore, it is crucial to implement electromagnetic designs that reduce cogging torque and torque ripple, which are the causes of vibrations and noise in electric motors. However, due to the inherent characteristics of electric motors, in structures designed for winding coil windings, such as fixed stator slots and teeth, the variation in reluctance during operation is not consistent. Consequently, this leads to an increase in the occurrence of cogging torque and torque ripple. However, if an EPS motor is designed with a structure lacking stator teeth, the change in reluctance during rotor rotation remains constant. In theory, this would significantly reduce cogging torque and torque ripple when the rotor is in motion. Therefore, in this article, the conventional EPS motor, designed with a structure containing stator teeth resulting in cogging torque and torque ripple, is targeted for reduction. This article designed a slotless motor structure with the goal of significantly minimizing these effects. In this article, pursued a design to achieve the target output of the EPS slotless motor and enhance the overall output density. Ultimately, this motor designed, fabricated, and analyzed a motor for the automotive EPS system with the capability to reduce vibrations and noise while achieving weight reduction.

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.

Permanent magnet synchronous generators (PMSGs) with high output density per unit volume are becoming widespread in wind-power generation systems. Among them, spoke-type PMSGs are more challenging to magnetize than other PMSGs, owing to their structural characteristics. Magnetization performance is critical because it is directly related to the demagnetization and mass productivity of permanent magnets, and load performance is reduced when non-magnetization occurs due to the low magnetization performance. Additionally, the starting performance is crucial in wind turbines and is influenced by the cogging torque of the PMSG. This is because starting a wind turbine with a large cogging torque is more challenging. Therefore, this study proposes a spoke-type PMSG rotor shape design for low capacity wind turbines that considers magnetization and cogging torques. We analyzed the principle of magnetization and the factors influencing magnetization performance, and designed a rotor shape with improved magnetization performance. Additionally, we applied an asymmetric rotor barrier structure to reduce the cogging torque and analyze the performance of the final model using finite element analysis. We analyzed the temperature saturation during the operation of the final model using a thermal network method and validated the irreversible demagnetization accordingly.

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.