Cheon-Ho Song

A dual-stator permanent magnet synchronous motor (DS-PMSM) offers both structural and electrical redundancy, making it suitable for high-reliability applications such as urban air mobility (UAM). To address vibration issues that reduce the reliability of propulsion systems, this study proposed a combined mechanical–electrical shifting method that combines mechanical stator shifting with electrical phase adjustment of armature currents. To determine the optimum stator shift angle for effective vibration reduction, the radial air-gap electromagnetic force density (radial AEFD), which is the primary cause of vibration, was analytically derived from the spatial harmonics of the radial air-gap magnetic flux density (AMFD). The variation in AEFD with respect to the stator shift angle and current amplitude was analyzed, and the resulting stator deformation was evaluated using finite-element analysis (FEA). Experimental validation was conducted to verify the stator shift angle that resulted in the minimum deformation and to confirm the trend of deformation variation. The proposed method enables the identification of an optimum stator shift angle that reduces vibration while maintaining torque and efficiency.

Urban air mobility (UAM) requires highly reliable propulsion systems, for which the dual stator permanent magnet synchronous motor (PMSM) is suitable owing to its structural redundancy. Accurate parameter estimation is essential for modeling such motors. This paper proposes a frozen permeability method (FPM) that maintains the magnetic flux path under load conditions to improve the accuracy of parameter estimation. In this method, the permanent magnet (PM) is retained as a magnetic source during flux linkage calculation, and its internal magnetization direction is considered. To verify the effectiveness of the proposed method, the conventional FPM, which treats the PM as air, was defined as a comparison reference. Simulation results confirmed that the proposed method reduces torque estimation errors by maintaining the correct flux path under load conditions. Experimental validation was also conducted, confirming the applicability of the proposed method under various current amplitudes and phase angle conditions. The proposed method contributes to improving parameter estimation accuracy for dual stator PMSM, which is expected to enhance the modeling accuracy of motor systems in high-precision control and digital twin-based applications.

During the motor design stage, it is crucial to accurately predict the characteristics of the motor at various operating points. Performing finite-element analysis (FEA) for each point is time-consuming and impractical. Therefore, the motor parameters and losses are typically calculated for each load point and used to solve the voltage and torque equations, thereby reducing the time required for motor characteristic analysis. Thus, the accurate prediction of motor parameters is essential for optimizing the motor design. This study proposes a parameter estimation method for the design process of induction motors (IMs). Accordingly, the circuit parameters are estimated using a reduced amount of FEA data. A common approach for evaluating the circuit parameters of IMs is through locked-rotor and no-load tests. However, these methods have limitations, because they use a fixed frequency that may not be suitable for electric vehicle traction motors owing to their various driving points, high torque, and high power density. This article introduces an iterative method for estimating the magnetizing inductance in IMs, owing to its significant impact on torque. This method is based on the changes in saturation according to current and slip frequency.

The dual inverter and dual stator system is suitable for air mobility due to its redundant system. Motor analysis for transportation should encompass not only electromagnetic characteristics but also drive and multiphysics systems to account for real operating conditions. To reduce the considerable time of system integrated analysis, especially those involving drive and multiphysics systems, a parameter-based model can be employed as a substitute for the finite element analysis (FEA) co-simulation. Therefore, an accurate and fast parameter-deriving method is required. The conventional method, the frozen-permeability method, is accurate but time-consuming because the dual stator system has doubled inputs. In this article, a parameter estimation method based on the incremental method is proposed to consider a dual stator motor. Subsequently, the frozen-permeability method and the proposed method are compared to assess their accuracy. The results show that the proposed method can acquire accurate data faster than the frozen-permeability method. In addition, experiments are conducted to validate the parameter-deriving methods.

The motor in high power electric vehicle (EV) easily reached at voltage limit because of its large magnetic flux. Therefore, the motor should be designed so that the voltage is controlled at the limit. To achieve well voltage control condition, the interior permanent-magnet synchronous motor (IPMSM) is controlled by the field-weakening control method after the constant torque region. This is conducted by canceling the magnetic flux from the permanent magnet with the magnetic flux of the stator winding. However, this method generates many harmonics. In this paper, a design that effectively controls the voltage by reducing the harmonics generated in the field-weakening control is proposed. To reduce the harmonics in the field-weakening region, change stator and rotor design parameters, and the reason for using v-type permanent magnet arrangement for high-speed operation will be elucidated.

In this paper, the design process of brushless DC (BLDC) motor adopting the dual rotor structure that can reduce the overall size of the motor while generating the same torque as the conventional permanent magnet BLDC motor is analyzed. A simple size is selected by obtaining the torque per rotor volume (TRV), and a method of matching the counter electromotive force by selecting the pole-arc of the magnet through a magnetic equivalent circuit is analyzed. Since the efficiency is low because the 120-degree commutation method is selected, the middle stator is optimized through detailed design through the experimental design method. Afterwards, it has the advantage of being able to shift without stopping due to the characteristic of a dual rotor. For this, an analysis of the driving characteristics for each mode is performed.

In this paper, the design process of BLDC adopting the dual rotor method that can reduce the overall size of the motor while generating the same torque as the conventional Permanent Magnet BLDC is analyzed. A simple size is selected by obtaining the torque per rotor volume (TRV), and a method of matching the counter electromotive force by selecting the pole arc of the magnet through a magnetic equivalent circuit is analyzed. Since the efficiency is low because the 120-degree commutation method is selected, the middle stator is optimized through detailed design through the experimental design method. Afterwards, it has the advantage of being able to shift without stopping due to the characteristic of a dual rotor. For this, an analysis of the driving characteristics for each mode is performed.

In the paper, the core loss of SPWM inverter drive IPMSM is analyzed considering high frequency harmonics caused by SPWM and field weakening control. The output current of SPWM inverter has many high frequency harmonics at the field weakening region. The high frequency harmonics would affect the core loss on each part such as the yoke, teeth, shoe, and rotor. Therefore, IPMSM core of double layer type is divided into 6 parts to analyze the core loss in each part. In order to calculate the core loss considering the harmonics, the SPWM current is required. This is extracted by linking the SPWM inverter drive IPMSM. FEM analysis is used to compare the core loss when sinusoidal current and SPWM current are applied. The result that which part of the core is most affected is analyzed by FFT analysis applying the P.U. system.

The interior permanent magnet synchronous motor uses a barrier structure to block the magnetic flux circulating inside the rotor and to send the magnetic flux into the air gap. Although the airgap magnetic flux density can be increased through the barrier, there is the disadvantage of increased torque ripple. Thus, this study is conducted to determine if the torque ripple could be reduced by changing the barrier shape. The problem here is that the torque inevitably decreases when the torque ripple is decreased. Therefore, in this study, a novel shape of the bridge is proposed in a model in which the torque ripple is reduced but the torque is not. The notch structure is applied to the bridge and is analyzed through finite element method analysis. To intuitively express the relationship between the torque and the torque ripple, a torque efficiency factor is devised, and as a result, the torque is maintained but the torque ripple is reduced.