Conference Agenda

In this paper, rotor teeth skewing technique is proposed to reduce the cogging torque of an axial flux-switching permanent magnet machine (AFSPMM). The analytical expression of the cogging torque of AFSPMM is derived. The influence of design parameters on cogging torque, back electromotive force (EMF) and total harmonic distortion (THD) of the back EMF of the machine are investigated by three-dimensional FEA. The results showed 20% reduction of cogging torque in the machine with dual-skew rotor teeth compared to that with the conventional fan-shaped rotor teeth can be obtained.

In order to reduce the volume of transformers or motors and improve the utilization rate of electrical steel, it is significant to explore the performance of soft magnetic materials within the scope of the mid- or high- frequency. In this paper, an improved dynamic Jiles–Atherton (JA) model coupled with a Multi-Scale (MS) model has been proposed to evaluate magnetic property of electrical steel under the mid-frequency. The Multi-Scale modeling method of magnetization process is employed to calculate the anhysteretic response instead of the Langevin’s polynomial in the JA model. The dependence of frequency on hysteresis loss is reflected in the model parameters which are determined by the Gaussian response surface method. The validity of the MS-JA model is verified with experimental data.

Accurately diagnosing winding faults of transformer is of great importance to the stable operation of the electric grid. In this paper, by combining frequency response analysis (FRA) with relevance vector machine (RVM) optimized by particle swarm optimization (PSO), a new method, namely PSO-RVM, is proposed to classify typical radial faults of transformer winding including forced buckling (FDB) and free buckling (FB). First, a series of FB and FDB faults are artificially set on a transformer winding model and corresponding FRA tests are conducted to collect the FRA dataset at the same time. Second, RVM optimized by particle swarm optimization (PSO) is introduced to set up the PSO-RVM classifier. Then, as inputs of the PSO-RVM, the features of FRA dataset are extracted by using different numerical indices. After training and testing, the classification results of PSO-RVM for FB and FDB faults are obtained by leave-one-out (LOO) cross validation method. Finally, the feasibility and accuracy of the proposed method are validated by comparison with PSO-SVM. The comparison result indicates that PSO-RVM can accurately identify the FB and FDB faults of winding and it can achieve a very high classification accuracy rate as with PSO-SVM.

An interpolation-based augmentation method is presented to generate feature values for the unmeasured loading levels from the existing few measured loading levels for healthy and three broken rotor bar cases of the induction machine. The random variation of feature values is captured by constructing an overlapping window and through a fitted normal probability distribution function (PDF). Furthermore, several degrees of polynomial functions are fitted to estimate the mean and standard deviation of the unmeasured loading levels. Later, the normal distribution is constructed with the fitted mean and standard deviation to generate random feature values for 37.5\% and 75\% loading levels. An excellent agreement is found between the augmented and actual feature values computed from the measured data, which can be used to develop more generalized and robust machine learning models.

The dry-type reactor is an important transmission and substation equipment in the power system. The thermal analysis of a dry-type iron-core reactor is helpful to evaluate the operation status of the reactor and avoid overheating failure. Based on the multi-physics mutual coupling method, the calculation model of temperature rises for dry-type iron-core reactors is presented in this paper. Taking a 10 kV dry-type iron-core series reactor as an example, the transient multi-physical numerical simulation model of the reactor is established. The temperature field distribution and fluid field distribution of the reactor under the rated operation state are calculated, and the temperature rise characteristics of the reactor and the changing trends of hot-spot temperature are analyzed. The transient simulation results show that the temperature distribution of the dry-type iron-core reactor reaches a steady state value after running for 168 hours. The hot-spot temperature of the reactor is 80.6 ℃, which is located at a height of 80%-85% of the reactor coil. At last, the surface temperature of the 10 kV dry-type iron-core reactor running in a 110kV substation is measured by the infrared thermal imaging method. The simulation results are in good agreement with the measurement results, and the deviation rate of hot-spot temperature rise obtained by simulation is 4.16%.

DC transmission systems in monopole-grounded return operation mode may cause DC magnetic bias in some transformers in AC power systems, causing rich harmonics, local overheating and as a result threaten the operation of the transformer. There are, however, persisting difficulties in assessing the core loss when the induction waveform is affected by a DC bias. In this paper a generalized Preisach hysteresis model is considered to evaluate the core loss and its distribution in power transformers under DC bias. The generalized Preisach model has been proposed by incorporating the reversible and irreversible magnetization components, its Preisach distribution function and the reversible magnetization component are determined only based on the M-H limiting loop. To verify the accuracy of the proposed method, a transformer laminated core prototype is developed. Core losses of the prototype under magnetizations with DC bias are predicted by hysteresis model coupling finite element method, and the comparison between the preidiction and experiment confirms good agreement.

Traditional equivalent model for calculating the transient voltage distribution of high-voltage dry-type hollow reactors with complex

topology during lightning impulse testing suffers from excessive inaccuracies. In this study, the reactor’s inductance, capacitance, and

resistance parameters were calculated using the finite element method with the layers of the winding as the subdivision units. The

improved equivalent circuit model adds mutual capacitance between non-adjacent units. After comparing simulation and experimental

results, the improved equivalent circuit model proposed achieves the accurate simulation of the reactor’s voltage distribution.

The Jiles-Atherton (J-A) model has been widely applied to simulate the hysteresis characteristics of soft magnetic material due to its simple formulation. However, the classical and existing modified J-A models suffer from low accuracy in simulating symmetrical and asymmetrical minor loops either or both. In this paper, a new modified J-A model is developed to accurately simulate different kinds of hysteresis loops of soft magnetic material, that are symmetrical and asymmetrical hysteresis loops. Firstly, two scaling factors that control the variation rate of irreversible magnetization component are proposed. In addition, the pinning site density factor and mean-field coefficient and found to change with the maximum magnetic flux density. The limitations of the existing J-A models are thereby overcome. The papameters of proposed modified J-A model can be identified only by the measured symmetrical loops, but this model can accurately simulate the symmetrical and asymmetrical hysteresis loops both, showing appealing features in the fields that need to simulate the hysteresis characteristics of soft magnetic material accurately and efficently under complex working conditons.

The 3D-printed electrical machines gather increasing interest at the last few years since they meet the challenges of high-speed operation. For this reason, two equally-operated high-speed outer-rotor permanent magnet synchronous motors are analyzed and compared to each other herein. The first one includes a 3D-printed stator core (made of magnetic iron polylactic acid filament) and a Halbach array permanent magnets structure. The latter one has surface-mounted magnets and a stator laminated core made of a non-oriented silicon steel. Their electromagnetic behavior is determined through finite element analysis (FEA) and the derived findings reveal that the performance of the 3D-printed core motor is superior when the rotational speed becomes higher than 3,600 rpm.

A dual three-phase motor can be working with two three-phase systems, thus it has more capability to implement the various control strategies, compared with other multi-phase machines. This paper presents the characteristic analysis of 8-pole 36-slot dual three-phase synchronous reluctance motor according to the control strategies. Based on winding function theory, inductance behaviors of each winding configuration are computed under the normal and half control modes. By using the inductance values, the torque components are also calculated at the rated current. Additionally, each torque characteristic of two-type winding arrangements are compared. Finally, the torque characteristics resulted from the winding function theory are verified through experiments.

Accurate modeling of the hysteresis loops of electrical steels under different magnetization levels is required to optimize electrical machines. In particular, an inverted hysteresis model is needed to calculate the field by the magnetic vectorial potential in finite element analysis (FEA). However, the existing inverted Preisach model cannot accurately describe the materials' reversible magnetization process, resulting in large errors in simulating the inner symmetric small loops. This paper presents an improved inverse Preisach model by incorporating the reversible magnetization component with an irreversible hysteresis component using a parametric distribution function by comparing the simulated hysteresis loops with the measured data of B30P105 grain-oriented (GO) silicon steel.

In this paper, the magnetic field of high-power wireless transfer systems in two trucks parked next to each other under misalignment is investigated. This application scenario is intended to represent daily situations in parking lots or depots when several vehicles are charging simultaneously. For these investigations, unipolar coil arrangements are designed and arranged for high-power transfer. The analyses are performed using finite element analysis modeling. The preliminary results show that depending on the relative positioning of the considered vehicles, measures to guarantee electromagnetic field safety-level compliance might become necessary.

This digest proposes torque contribution analysis and optimization of a novel partitioned stator hybrid excited dual-PM vernier machine (PS-HEDVM) based on frozen permeability. Firstly, the basic principle of the proposed PS-HEDVM is introduced, and the torque contribution calculation method based on frozen permeability is presented. influence of the unequal length teeth on the torque density and flux regulating capacity is analyzed. Then the torque contributions of stator-PM, rotor-PM and DC bias are analyzed and optimized with different parameters. Finally, various FEA simulation, optimization studies, and experiments of the proposed machine are performed. The results verified the effectiveness of the proposed method.

Voltage transformers play a vital role in the power system in various aspects. However, due to the existence of magnetic cores, traditional electromagnetic voltage transformers have the problem of saturation. If an electromagnetic voltage transformer becomes saturated while operation, it may not only lead to inaccurate measure result of voltage, overheat, or even damage to transformer itself, but also can cause problems such as ferroresonance, which will endanger the safety of the grid and the power system. This paper presents a new type of electromagnetic voltage transformer based on magnetic valve, which can compensate the distortion of measured voltage after saturation and expand the measuring range. The correctness of the principle is verified by finite element simulation and prototype experiments under different working conditions. Its structure is similar to the traditional electromagnetic voltage transformer, and it improves the anti-saturation ability through the magnetic valve and magnetic field sensor. Meanwhile, it has the characteristics of simple manufacturing and low cost, which will have a high engineering practical application value.

This paper focuses on the electromagnetic vibration of transverse flux permanent magnet linear submersible motor. Firstly, the radial electromagnetic force of the motor is analyzed. Secondly, the influence of secondary eccentricity on the frequency spectrum of electromagnetic force is further concluded. Finally, the natural frequency of the motor is obtained through modal analysis of the motor. The magnetic solid coupling analysis of the primary radial direction of the motor is carried out, and the distribution of the motor vibration response is obtained.

An extended Preisach-based vector hysteresis model with new identification and implementation algorithms is presented in this paper. By adopting a new anisotropic function with several undetermined parameters which describes the relationship between the vector Everett function of all magnetization directions, the proposed model shows stronger adaptability and better matching with experimental data. In addition, an implementation procedure which takes scalar Everett functions of rolling direction (RD) and traverse direction (TD) as input is suggested to simplify the identification process of anisotropic vector Everett function without losing the accuracy of the numerical solution. The validity of the proposed vector hysteresis model is investigated through comparison with the experimental results of non-oriented (NO) electrical steel under both alternating and rotational magnetization.

Performance of the electrical equipment is strongly depending on the magnetic hysteresis characteristics of the ferromagnetic materials, especially considering the magneto-elastic effect. From the perspective of magnetic domain structure, interaction of stress and magnetic field cause the magneto-elastic coupling effect. It is essential to describe a relationship between the magnetic properties and the microscopic magnetic domain, which can be analyzed quantitatively by observing the magnetized domains motion under tensile stress. A new anhysteresis magnetization formula is proposed to consider the effect of tensile stress on the magnetic hysteresis properties based on Jiles-Atherton model. The magnetic properties of grain-oriented silicon steel GT100 at 50 Hz under different tensile stresses are measured. The accuracy of the improved model is verified by comparing the measured results with the predicted results.