Conference Agenda

Recently, achieving high efficiency in propulsion motors is a crucial factor for improving the mileage of electric vehicles. While designing motor geometry for high efficiency is important, incorporating control strategies for high efficiency operation also plays a critical role in the design stage. Subsequently, the importance of maximum efficiency per ampere (MEPA) control, which considers not only copper loss but also iron loss, is increasing. However, implementing MEPA control requires the iron loss data set, which increases computational cost. Therefore, this paper proposes a calculation method using polynomial regression of d-q parameters and interpolation of the frequency-dependent saturation factor to derive the data required for MEPA control. The efficiency map derived from the proposed method was validated by comparing the result with FEA-based, with a maximum error of 0.8%p.

This paper proposes a computationally efficient method for evaluating pulsewdith modulation (PWM)-induced alternating current (AC) copper losses. The conductive coils are simplified into equivalent magnetic domains using complex permeability modeling. Time-stepping finite element analysis (FEA) and time-harmonic FEA are conducted to compute the AC copper losses under the sinusoidal envelope currents and PWM-induced current ripples, respectively. The proposed approach is validated using a case study model of a 12slot 10pole axial flux permanent magnet synchronous machine. Results demonstrate good agreement with those obtained from the pure time-stepping FEA, which requires significantly higher computational resources.

Transient finite element analysis (FEA), a common method to analyze induction motors, suffers from a long analysis time. As the speed of the induction motor increases and the slip frequency decreases, the analysis time grows exponentially. This paper proposes a computationally efficient method for calculating the radial electromagnetic force in an induction motor using time-harmonic FEA. Unlike conventional time-harmonic FEA, stepping time-harmonic FEA is performed by mechanically and electrically rotating over one cycle during the analysis. The radial and tangential airgap flux densities were compared for different slip frequencies, and the radial electromagnetic force was calculated using Maxwell stress tensor. Furthermore, a spectrum analysis of the radial electromagnetic force was performed using 2-dimensional fast Fourier transform, and the validity and efficiency of the proposed method were confirmed by comparing it with the transient FEA in terms of accuracy and analysis time.

A multi-layer interior permanent magnet synchronous motor (IPMSM) offers high power density, with increased saliency ratio and reluctance torque achieved by adjusting the number of permanent magnet (PM) layers. However, this also raises induced voltage harmonics, which can exceed the DC-link voltage, leading to unstable control. To ensure stable operation, the induced voltage must remain within the DC-link voltage. This paper proposes a design method to analyze and mitigate the significant harmonic components by decomposing the induced voltage. Using 2D finite element analysis (FEA) with a fixed permeability method, the induced voltage is separated, and its main harmonic components are identified. A design strategy is then introduced to reduce harmonic magnitude by optimizing the number of slots and applying rotor skew and eccentricity. The proposed method is validated through both simulations and experiments conducted on a prototype.

The dual stator permanent magnet synchronous motor is suitable for air mobility applications, where safety must be ensured, due to its structural and electrical advantages in facilitating redundancy. To achieve such safety, accurate motor performance prediction is essential, requiring precise motor modeling and accurate parameter estimation methods. For motor modeling, frozen permeability method capable of predicting inductance mutual components has been widely used. However, conventional frozen permeability method for dual stator modeling is somewhat inaccurate. The primary issue arises from treating permanent magnets as air for phase linkage flux calculation, failing to replicate the center of the flux path in dual stator permanent magnet synchronous motor, which leads to errors in calculating the phase flux linkage. In this paper, an improved frozen permeability method is proposed to more appropriately describe the flux path under load conditions. The proposed method retains the permanent magnets during phase flux linkage calculation. Additionally, it includes an extra calculation process to separate the field flux linkage, enabling more accurate parameter estimation compared to conventional methods. Finally, to validate the proposed method, the torque estimated using both the conventional and proposed methods is compared against finite element analysis torque.

A motor emulator is an active load that drains the desired current to flow through the inverter terminals.

It uses the inverter phase voltage and the motor mathematical model to calculate the appropriate current reference value.

In this paper, a power-hardware-in the-loop (PHIL) simulation for motor emulation is proposed when the inverter gate drive failure occurs.

In order to reconstruct the pulse width modulation (PWM) voltage into sinusoidal phase voltage, an integrator with a reset switch is used.

When the inverter gate open fault occurs, the reconstructed voltage error causes current command divergence.

The proposed method solves the problem of current command value diverging due to voltage reconstruction error.

A control block diagram is proposed and its validity is demonstrated by the simulation.

This paper presents the design and analysis of an interior permanent magnet synchronous motor (IPMSM) rotor with a carbon fiber-reinforced plastic (CFRP) sleeve, based on electromagnetic-mechanical coupled analysis. To address the stress issues arising from the increase in the rotor’s maximum rotational speed, this study emphasizes the specific considerations necessary for its construction, which is complicated by the incorporation of the CFRP sleeve. This added complexity distinguishes the design of the rotor from that of conventional IPMSMs.

This paper proposes a sizing method of wound field synchronous motor (WFSM) using a 2D equivalent magnetic circuit (EMC) considering nonlinear characteristics. The conventional sizing method is an analytical method predicting motor performance using a proportional formula based on size-related variables of the motor, which are shape ratio (SR), torque per rotor volume (TRV), and torque density (TD). However, accurate results cannot be obtained only from the proportional formula because the performance of the motor varies greatly depending on the magnetic saturation of the core. In particular, since the WFSM does not use a permanent magnet (PM) for the field, it is important to reflect the magnetic saturation of the field core. Therefore, in this paper, a novel sizing method of WFSM based on the 2D EMC, which is a numerical method used to fast and accurately calculate the performance of the motor considering the magnetic saturation of the core, is proposed. Using the proposed design method, it is possible to not only accurately predict the motor characteristics according to the size but also determine the motor size that satisfies the requirement performances. The validity of the proposed sizing process is verified through simulations and experiments.

This paper investigates the application of model order reduction techniques for efficient implementation of a core-loss model in synchronous machine simulations. The machine state-space model is constructed by solving multiple static finite element (FE) simulations, representing the winding flux linkages and flux-density distribution in the FE nodes as functions of the stator currents and rotor angle, and storing these results into lookup-tables. Three different approaches for implementing the core-loss model are explored. The proper orthogonal decomposition and discrete empirical interpolation method are employed to reduce computational complexity of these implementations while maintaining model accuracy. The reduced-order model demonstrates good agreement with the full model, achieving an 18-fold increase in the execution speed and an 8 times reduction in the pre-computation time.

This paper presents a finite element (FE) based state-space model for AC winding losses in synchronous machines. The model is constructed by storing the solutions of multiple static FE simulations into lookup-tables to express the magnetic vector potential on the boundaries of the slot region as a function of stator currents and rotor position. The geometry-dependent FE matrices derived from the mesh are computed only once, while the dynamic simulation evaluates AC winding losses at each time step based on the instantaneous operating conditions. The preliminary results show fast execution in Simulink and good match with the FE solution.

This paper presents the development and analysis of a DC arc fault diagnostic device tailored for 1000V-class electric vehicle (EV) systems. As the voltage levels in EV batteries increase from 400V to 1000V to improve charging efficiency and extend driving range, the risk of DC arc faults also rises. Unlike AC systems, DC systems lack current zero-crossing points, making arc extinguishing challenging and heightening fire risks. Through experimental testing using a 1000V, 400A DC power system, this study investigates arc voltage and power characteristics under various load and electrode configurations. The arc behavior was measured at low current levels and predicted at high current levels using the Paukert V-I equation. Results indicate that arc faults must be diagnosed or interrupted within 0.16 seconds to prevent excessive arc energy exceeding 750J, as prescribed by UL1699B standards. The findings provide a foundation for developing a real-time arc fault detection device for high-voltage EV systems.

The propulsion motor of Autonomous Underwater Vehicle (AUV) requires overload capability to enable the vehicle to have short-term acceleration capability. The overload capability is determined by the thermal boundary conditions. This article uses an LPTN coupled with electromagnetic field and thermal field to model a 40kW shaftless motor for AUV propulsion , and an empirical method based on experimental training data and a particle swarm algorithm are used to identify the LPTN parameters. Then, the LPTN is used to predict the temperature rise under different overload conditions and analyze the runtime within the thermal boundary conditions of the shaft-less propulsion motor. The experimental results show that the error between the simulated runtime and the experimental value is within 15%. Further, this method not only reduces the calculation time but can also be used for overload capability analysis of other propulsion motors.