In recent years, controllable magnetic devices gained a major interest in different application areas as they offer another level of freedom to power electronic systems, improving system efficiency, power density and controllability. However, comprehensive physical behavior of variable inductors (VIs) remains poorly studied with respect to controllability and coupling effects between the auxiliary and primary winding. This paper introduces a novel measurement-based characterization method for identifying and quantifying mutual coupling effects in dc-biased magnetic devices. Therefore, two toroidal core structures, an orthogonal (OM) and a mixed-biased (MB) pre-magnetized core, are investigated, highlighting the differences in coupling behavior. The method applies Fast Fourier Transformation (FFT) to induced voltages on the auxiliary winding, enabling the assignment of specific harmonic components to distinct coupling mechanisms. Harmonic-specific coupling factors are proposed to isolate individual effect. Thus, this paper aims to provide a characterization method applicable to any dc-biased magnetic device, helping to isolate coupling effects and quantify magnetic coupling by means of specific factors. A general analytical model will be proposed to interpret the measured coupling effects.

Accurate consideration of end leakage inductance is essential to avoid overestimation of the high-speed output power in permanent magnet synchronous traction motors. However, the end leakage inductance is often neglected or estimated empirically, since its calculation involves a time-consuming Three Dimensional (3D) Finite Element Method (FEM), together with the normally used Two Dimensional (2D) FEM model. Most of the end-turn leakage inductance calculations in the literature are for Radial Flux Machines (RFMs). This paper investigates the possibilities of using a modified 2D FEM model that can incorporate the estimated end leakage effects of an off-the-shelf 4kW Axial Flux Permanent Magnet (AFPM) machine with Concentrated Windings (CWs). Such calculation methods can be used efficiently for optimization and control purposes. Two methods from literature are examined and adapted whereof, one method is originally proposed for RFMs and the other method was suggested for single-layer AFMs. It is found with FEM that the end-turn leakage inductances in the d- and q-directions are 22% and 21% of the total d- and q-axis inductance, respectively. The impact on the maximum high-speed power shows around 10% decrease. The investigated analytical/empirical methods found from the literature fail to capture the end-turn inductance well, with the best guess of a 30% lower value compared to FEM simulations.

In this work, a follow-up study of estimating optimal operating points by an improved parameter-based model of three-phase induction machines (IMs) is conducted and presented. The main objective is to examine the representation of IMs' parameters within a specified operating boundary. The paper begins by reviewing the theory behind the inverse$\Gamma$-form model (IGFM) and maximum torque control. This review serves as a foundation for developing methods for estimating operating points. Finally, the study compares the results obtained using a 2D electromagnetic finite element method (FEM) model of a 15kW IM with those derived using a parameter-based model obtained through the conventional method, demonstrating the practical utility of the improved parameter-based model.

A preliminary design of a representative light duty battery electric vehicle (BEV) traction electric motor with minimum rare-earth material content is presented. A quasi-3D approach for electromagnetic loss distribution is chosen to handle the higher end-winding temperatures. The losses from the electromagnetic solver are then fed into the full 3D conjugate heat transfer computations (CHT) to investigate electric motor cooling jacket concepts, which were designed using a novel full 3D fluid mechanic topology optimization approach. In the presented topology optimization technique, the design space is not limited to the parametrized geometric entity as done in the conventional parametric optimization technique, but instead the whole packaging space is taken as the parameter set. Dimensioned in a multidisciplinary fashion to meet thermal, fluid mechanic and electromagnetic requirements, the reported electric motor is expected to be cooled at a higher rate. Finally, a system study to quantify the impact of increased cooling on the traction motor is also included.

This paper presents a comparison of power losses for two silicon carbide (SiC) and one silicon insulated gate bipolar transistor (Si IGBT) power modules in a three-phase inverter, when considering the effect of blanking time and the MOSFET's reverse conduction. The total power losses versus different switching frequencies are also compared for the three inverters. The focus of this paper is to determine the influence of junction temperature and thermal feedback on the power loss calculation. The analysis shows that, without accounting for the thermal feedback, the loss levels are substantially underestimated, 11-15% on the conduction losses of the SiC inverters and up to 18% on the switching losses of the IGBT inverter. The data is derived at a chosen high torque, low speed operating point of a permanent magnet synchronous machine (PMSM). The operating point is considered as a worse operating condition from the power loss perspective.

This paper shows two approaches to determine the battery impedance of battery cells or battery modules when used in a reconfigurable battery system (RBS) or in any type of modular multilevel converter (MMC) for electric drive applications. A generic battery model is used and the concepts of the recursive time and frequency-domain parameter extraction, using a current step and an electrochemical impedance spectroscopy, are explained. Thus, it is shown and demonstrated that the balancing current of neighboring cells/modules ,when in parallel operation, can be used, similar to the time-domain parameter extraction utilizing a current step, to determine the battery parameters. Furthermore, it is shown and demonstrated that a part of the inverter can be used as variable AC voltage source to control a sinusoidal current through the motor inductances of the drive train, which can be injected to the inserted battery cells/modules of an adjacent phase to perform an on-board impedance spectroscopy. Using either of the two presented approaches, the individual battery impedances can be easily determined, yielding the state of health (SOH) and the power capability of individual battery cells/modules. Nonetheless, the analyzed approaches were just considered to be applied at machine standstill, which is not suitable for grid-tied applications.

This paper shows a sensorless capacitor voltage balancing control approach for a grid-connected, single-phase hybrid multilevel inverter based on an NPC main stage with a voltage stiff DC-link and an arbitrary number of H-Bridge modules (capacitor modules) with asymmetric capacitor voltages. Using nearest-level control, a model predictive control (MPC) approach with a prediction horizon of one time step is chosen to find an optimal switching-state combination among the redundant switching combinations to balance the capacitor voltages as quick as possible. Using the Lyapunov stability criterion, it is shown that an offline calculated optimal switching-state sequence for each discrete output voltage level can be used to operate the inverter without using any voltage sensors for the capacitor voltages. To validate the stability of the approach, a laboratory inverter with a resistive load is operated with the offline calculated optimal switching-state sequences and it is shown that the capacitor voltages converge to their desired reference voltages.

In this work, 1700 V IGBT and SiC MOSFET based power electronic converters used in a wave energy application are compared, from a performance perspective, as well as economically, in order to obtain a favorable design. The converter losses of the variants are compared and the efficiencies and the annual energy losses achieved by both are presented. The economical impact is studied through life cycle cost analysis, where the investment costs and the net present value of the losses of the IGBT and SiC MOSFET WEC systems are compared, as well as their life cycle costs. The study shows that by utilizing SiC MOSFETs, and in total the converter losses decrease by over 1000 W. This results in a 4.3 MWh annual energy loss reduction, which has a positive economical impact of e23000 during the life time of the wave enery converter. The high cost of the SiC MOSFETs increase the investment cost to twice of the IGBT system, however due to the significant reduction of the net present value of the losses, the life cycle cost of the SiC MOSFET system is e15500 lower than its IGBT counterpart.

This paper address the effect of magnet coverage on the torque, iron and magnet loss components and torque ripple of two surface permanent magnet synchronous generators of 5MW. The values of torque, torque ripple, iron and magnet losses are calculated using a FEM program. It is concluded that the optimal magnet coverage can only be found by extensive investigations for each specific machine. However, an estimate value of magnet coverage can be found from recommendations and formulas, including only the number of phases and the number of slots per pole per phase. It is shown that by investigating each individual machine for a magnet coverage between 0.7-0.9, the torque ripple can be reduced up to 40% and magnet loss can be reduced up to 28%.

This paper analytically evaluates when it is suitable to use a multilevel inverter in an electrified vehicle. The multilevel inverter is compared to a classical two level inverter for different operation points and for different drive cycles.

In this paper, a hard switched and zero-voltage switching full bridge converter for high power applications are compared in terms of their losses. The important issue in designing these kinds of converters is to manage the converter parasitics. Moreover, evaluating the losses at the high frequency transformer with square wave input is another critical point in designing such a high power density converter. The proposed full bridge converters are designed to convert 4 kV input voltage to 6 kV with rated power of 2.4 MW. The comparison is done for three different frequencies: 500 Hz, 1 kHz and 2 kHz. Also, the simulation results and loss calculations are presented.