Flux Waveforms Research Articles

Deep learning model for enhanced power loss prediction in the frequency domain for magnetic materials

AbstractThis paper outlines the methodology for predicting power loss in magnetic materials. It starts by introducing the concept of core loss and the complexity of modelling it. Steinmetz's equation is presented to calculate power loss based on frequency and magnetic flux density, but its limitations are highlighted. As an alternative, a neural network‐based method is introduced. The proposed methodology adopts a long short‐term memory network, expressing the core loss as a function of magnetic flux density, frequency, temperature, and wave classification. Fast Fourier transform was implemented to reduce the data points of the sampled flux density waveform while preserving its characteristics. Analyzing in the frequency domain enabled streamlining the training of the model. The input features were arranged as required, and the network architecture was designed with appropriate layers and optimal activation functions. Through extensive training using the datasets, the model assimilated intricate relationships between input variables and known power loss. Evaluation and validation metrics were subsequently employed to gauge the performance of the trained network. This innovative methodology aims to significantly augment the precision of power loss predictions, providing valuable insights into the nuanced behaviour of magnetic materials.

Current and flux correlation analysis for detection, location, and phase identification of stator inter-turn short-circuit fault in doubly-fed induction generator

This study proposes an innovative method for identifying and locating inter-turn short-circuit faults in doubly-fed induction generators (DFIGs), commonly used in wind-energy production. Our approach uniquely integrates data from both current and magnetic-flux monitoring, offering a complete framework for fault diagnostics. We effectively distinguish between normal and abnormal conditions in the generators by observing the patterns in current and flux waveforms. Normal conditions are marked by uniform waveforms, whereas faults create noticeable imbalances. A key feature of our research is the development of a technique to accurately determine which phase of the generator is affected by the fault, facilitating quicker and more effective repairs. To pinpoint the exact location of the fault, we use a set of four magnetic-flux sensors strategically placed around the generator. These sensors detect variations in magnetic flux, enabling the precise location of the fault. By focusing on these three essential elements—fault detection, phase identification, and exact fault localisation—our proposed algorithm significantly improves the dependability of DFIGs in wind-power applications.

Hysteresis loss in Brushless Doubly Fed Induction Machines

Brushless doubly fed machine (BDFM) is a potential for future wind energy generation, due to its lower maintenance costs and higher reliability than conventional doubly fed systems. While efficiency and design optimization of the machine has become critical issues recently, no analytical core loss model is investigated in the literature. Furthermore, core loss modeling is different from conventional induction machines, because of double frequency excitation of the machine. In this paper, a dynamical system is used for modeling of hysteretic behavior of iron core, and hysteresis losses of BDFM are analyzed and modeled mathematically. The flux waveforms of BDFM are assumed pure double sine, as in wound rotor BDFM lower harmonic values than nested loop design exist.

A core loss estimation method based on improved waveform coefficient Steinmetz equation for asymmetric triangular flux density waveform

Accurate estimation of high frequency magnetic core losses under non-sinusoidal excitations is critical to the design of solid-state transformers. This paper proposes a waveform transformation principle, termed the equal derivative transformation (EDT), for piecewise linear flux density waveforms. Under the same maximum flux density, an asymmetric triangular flux density wave can be transformed into a symmetric one with a different frequency in terms of the calculation of core losses, hence the introduction of the improved waveform coefficient Steinmetz equation (iWcSE). The magnetic characteristics of three different toroidal samples (nanocrystalline alloy FT-3KL, amorphous alloy 1K101, ferrite N87) under square excitation at different duty ratios and certain frequencies are measured. Core losses predicted by the model are in good agreement with the measurement.

A Review on the Empirical Core Loss Models for Symmetric Flux Waveforms

A Review on the Empirical Core Loss Models for Symmetric Flux Waveforms

Incorporating the coupled effects of slot opening, armature reaction and saturation in the model of the airgap flux density distribution of permanent magnet synchronous machines

AbstractA new analytic model for calculating of the air‐gap flux density (AGFD) of surface‐mounted permanent magnet synchronous machines (SMPMSMs) is presented. This proposed model is capable to taking into account the effects of magnetic saturation, armature reaction and stator slots opening. Furthermore, the real form of air‐gap distribution and spatial distribution of flux density of the PM poles are considered. The armature reaction effect is modeled using phasor diagram analysis of the motor as a function of the load torque, the armature current amplitude, power factor and the inverse air gap length. Also, saturation phenomenon predicted using the new non‐linear proposed function in connection with the armature reaction effects and the properties of the lamination material. It is shown that the proposed model capable to predicting acceptably the air gap flux density waveform of the SMPMSMs at lagging and leading power factors and with the load torque variation. The presented analytical approach is verified by the two‐dimensional finite‐element analysis (FEA) results.

Design of Rotor Magnetic Barrier Structure of Built-in Permanent Magnet Motor Based on Taguchi Method

In this paper, a 20kW vehicle built-in permanent magnet synchronous motor is taken as an example, and a magnetic barrier structure is added to the rotor of the motor to solve the uneven saturation problem of the rotor side magnetic bridge. This structure improves the air-gap flux density waveform of the motor by influencing the internal magnetic flux path of the motor rotor, thus improving the sine of the no-load back EMF waveform of the motor and reducing the torque ripple of the motor. At the same time, Taguchi method is used to optimize the structural parameters of the added magnetic barrier. In order to facilitate the analysis of its uneven saturation phenomenon and improve the optimization effect, a simple equivalent magnetic network (EMN) model considering the uneven saturation of rotor magnetic bridge is established in this paper, and the initial values of optimization factors are selected based on this model. Finally, the no-load back EMF waveform distortion rate, torque ripple and output torque of the optimized motor are compared and analyzed, and the influence of magnetic barrier structure parameters on the electromagnetic performance of the motor is also analyzed. The results show that the optimized motor can not change the output torque of the motor as much as possible on the basis of reducing the waveform distortion rate of no-load back EMF and torque ripple.

Model Order Reduction of Cage Induction Motor With Skewed Rotor Slots Using Multiport Cauer Ladder Network Method

A method for efficiently deriving a reduced-order model of a cage induction motor (IM) with skewed rotor slots is proposed based on the multiport Cauer ladder network (CLN) method. This paper presents several formulations of the multiport CLN method for the skewed rotor, in which the continuity of the bar currents and the space harmonics included in the air-gap flux density waveform are treated differently. The effectiveness of the developed methods was verified from the viewpoints of computational accuracy and cost through application to a practical cage IM with skewed rotor slots.

Time‐harmonic field‐circuit model for brushless doubly fed induction machine

AbstractA computationally efficient time‐harmonic finite element model for the steady‐state analysis of a brushless doubly fed induction machine (BDFIM) is proposed. In the model, the electromagnetic couplings of the BDFIM are described by means of the sum of two complex magnetic vector potentials that represent the two fundamental harmonic time components of the magnetic flux density distribution in the rotor frame of reference. As in an ordinary induction motor, the non‐linearity of the magnetisation characteristic is accounted for using an effective magnetic permeability. For the BDFIM, this is derived by considering the features of modulated magnetic flux density waveform. The accuracy of the approach has been validated by comparing the characteristics of a D270 machine operating in the double‐feed mode with ones obtained from the experimentally verified time‐stepping model at various operating conditions. High accuracy of the results coming from the proposed model is demonstrated even under deep saturation conditions within the magnetic circuit.

Gravity influence in one-dimensional blood flow modeling

One-dimensional blood flow model accuracy has been verified in many studies. The topic of this work is introducing gravity into a one-dimensional model. For this purpose, gravitational force was introduced into an existing model. To account for gravity, the boundary conditions also must be adjusted to reflect the body's adaptation. For this purpose, a method for calculating the arterial resistance of the terminal arteries during gravity changes has been developed and presented in this article. The technique is based on the idea that the human body reacts to changes in gravity in such a way as to preserve the volume of blood delivered to the organs. Experiments have shown that not only the pressure, but also the flux waveform and the pressure waveform change when the flow is preserved. The method of adjusting the boundary conditions is such that the flow almost does not change after applying the gravity, but it is possible to estimate the change in pressure dynamics. This methodology can be used to study the blood flow in different cases related to gravity.

The Loss and Efficiency Analysis and Research of Interior Permanent Magnet Synchronous Motors for Traction Applications

An IPMSM with I2V type rotor topology structure is proposed, its loss, efficiency and torque are analyzed and compared with V and IV type. Firstly, the optimized rotor topology structures are used to analyze the no-load air-gap flux density waveform and harmonic contents of the IPMSM. The results show that the THD of the no-load air-gap flux density with the I2V type is the smallest and the sinusoidal degree of the waveform is the highest. Secondly, the loss of the IPMSM with optimized rotor topology structures are analyzed and compared. Compared with the other two rotors, the results show that the iron loss of the IPMSM with the I2V type is the smallest. The iron loss of the IPMSM with I2V type is significantly less than that of the other two rotors especially under the deep flux weakening conditions. The output torque of the IPMSM under different current angles, current densities and speed are analyzed and compared. The results show that the torque performance of the IPMSM with I2V type is better than the other two rotors. this paper proposes a simple and effective method to optimize the position and diameter of the magnetic isolation holes by establishing a parameterized model. The results show that the torque ripple and cogging torque with the further optimized I2V type rotor topology structure are greatly reduced, the iron loss and magnet loss are also effectively reduced. Finally, the von Mises stress and the total displacement of the rotor deformation of the IPMSM with the further optimized I2V type under different working conditions are verified by finite element analysis. The results show that the rotor will not rupture, the displacement is small enough to avoid the touch between stator and rotor.

Flux density waveform control based on root-finding algorithms

Two magnetic flux controllers based on root-finding algorithms are proposed, using respectively Newton’s and Broyden’s method. The main advantage of these solutions is to be parameters free, thus allowing for quick and easy measurements. Experimental work validates their good operation in a variety of test conditions, despite difficulties which question the adaptation of Newton’s method. The other controller, however, displays a good stability and adequate speed.

Accurate Analytical Model for Synchronous Reluctance Machine With Multiple Flux Barriers Considering the Slotting Effect

This article presents an accurate analytical model (AM) for synchronous reluctance machine (SynRM) that incorporates the effect of stator slots on the air gap flux density and torque waveforms. From the formulation of magnetic potential in the air gap for both the stator and rotor, the flux density is obtained, considering the first harmonic of the flux density and the electric loading, the average torque is calculated using the Lorentz’s force. The ripple torque is obtained from the energy stored in magnetic circuit. The method is developed for a rotor with one flux barrier per pole and then extended to a larger number of barriers. To validate the results obtained by the AM proposed finite element analysis have been carried out. Several comparisons have been derived considering different rotor positions as well as different harmonic orders, and the pros and cons of the method are highlighted. The model performs fast and can predict results with high accuracy, and can be adopted to speed up the preliminary design and optimizations of this type of motors, with respect to finite element. In addition, from the analytical expressions it is possible to obtain all the correlations between electrical, magnetic, and geometrical characteristics of the machine, with the advantage of enabling a faster machine design.

An Efficient Air-Gap Flux Density Analysis Method for the Design of Induction Machines

The magnetic field distribution in the air gap is of great importance in the design of rotary machines. In this article, an efficient analytical method is presented, which is capable of plotting the air-gap flux density waveform of induction machines (IMs) less time-consuming than the finite element method (FEM) does. The proposed method, based on the product of the current linkage waveform and the permeance waveform, utilizes the calculations of the steady-state equivalent circuit to ensure the accuracy and an equivalent air-gap reluctance model to take into account both the slot opening effect and the rotor movement. The method is tested on a general IM with different load cases and different design parameters, and the results are compared to the FEM calculations. It can be concluded that the proposed analytical method is an efficient option in the motor design to investigate the influence of the parameters on the flux density distribution.

Design optimization with genetic algorithm of open slotted axial flux permanent magnet generator for wind turbines

ABSTRACT In this study, the design parameters of Open Slotted Axial Flux Permanent Magnet (OSAFPM) Generator for wind turbines are presented using Genetic Algorithms (GA), an optimization algorithm based on natural selection and genetic mechanisms. Electromagnetic analysis of Open Slotted Axial Flux Permanent Magnet generator has been performed by using parameters optimized with Genetic Algorithms. The ANSYS Maxwell program, which uses the finite element method (FEM), has been used for electromagnetic analysis. Compared to ANSYS Maxwell, it is observed that the genetic algorithm significantly reduces the computational time required for design optimization. However, initial design and optimization with Genetic Algorithms have resulted by 8.94% increase in power densities. In addition, 12.71%, 38.62%, 62.02%, and 56.39% improvements have been obtained for air gap magnetic flux density, flux linkage, induced voltage, and current waveforms, respectively. This suggests that optimization with a Genetic algorithm improves the Open Slotted Axial Flux Permanent Magnet generator parameters.

Analysis of Characteristics of the Magnetic Field in Demagnetization Fault for Permanent Magnet Synchronous Motor

To demagnetization fault for permanent magnet synchronous motor, referring to the 96-slot 32-pole permanent magnet synchronous motor, set up motor model using finite element software, and the demagnetization fault of single magnetic steel and double magnetic steel in the motor were simulated and analyzed. The motor flux-density waveforms on different kinds of demagnetization fault were analyzed for the flux-density wave-form periodic trends and volatility in different numbers of magnets or different demagnetization rates. The motor flux-density component path diagram on different kinds of demagnetization fault were analyzed to get radial-tangential flux-density path diagram to analyze regular of path diagram distribution. The air gap flux-density waveform is analyzed by finite element software on different kinds of demagnetization fault, which fourier analysis is used to analyze each harmonic frequency and its weight, and the rule of change of harmonic between the normal condition and under the condition of demagnetization fault is compared. The simulation of tooth electromagnetic force density waveform curves and harmonics for different demagnetization faults is used to analyze its effect on the vibration. The results concerning permanent magnet motor of demagnetization fault lays the foundation of motor fault tolerance analysis and characteristic analysis.

A Design Method of the Rotor Auxiliary Slot for the Water-filled Submersible Induction Motors

Aiming at the problem of electromagnetic vibration of the water-filled submersible induction motor (WSIM), a method of opening auxiliary slots on the rotor side is proposed to weaken the air-gap field harmonics caused by the rotor slot permeance harmonics. By analyzing the research status of electromagnetic vibration of the WSIM and the composition of the air-gap magnetic field of the motor, the idea that the auxiliary slots mainly affect the air-gap field harmonics by changing the air-gap permeance of the motor is put forward. The mathematical model of air-gap permeance of WSIM is established to simulate the influence of auxiliary slots on the air-gap permeance. Through the parametric analysis of the mathematical model, the change of auxiliary slot size is simulated. The air-gap permeance waveform is decomposed by the two-dimensional Fourier transform, and then the variation of the air-gap permeance harmonics with the size of the auxiliary slot is analyzed. Finally, the finite element simulation model of the WSIM with the auxiliary slots is established, and the waveform of the air-gap flux density of the motor is analyzed to verify the effectiveness of the mathematical model. Meanwhile, the results show that after opening the auxiliary slot, the radial electromagnetic force of the motor was reduced by 28.4%.

Thermal analysis of simultaneously evolving laminar pulsatile flow through two large parallel plates with time-dependent heat flux boundary conditions

Understanding unsteady convective heat transfer (UCHT) behavior of simultaneously evolving laminar pulsatile flow between two large parallel plates exposed to time-dependent thermal boundary conditions is the goal of this research. The time-dependent sinusoidal velocity waveform is applied at the entrance of the two large parallel plates exposed to time-dependent sinusoidal heat flux boundary conditions (TSHBC). The finite volume technique is used in the present work. The current results have been compared to the literature data under the same operating conditions and found to be in good concurrence. The influence of various parameters, for instance, amplitude, frequency, phase difference, heat flux ratio, and the Reynolds number on the transient Nusselt number, is investigated. An improvement in energy transfer is observed when the pulsatile flow between two large parallel plates with TSHBC than the non-pulsatile flow with a fixed heat flux type boundary. Furthermore, the energy transfer improvement is observed once the velocity and heat flux waveform frequency is equal. The applicability of the present work could be found in the solar heating system, cooling of electronic devices, etc., whereby a more robust understanding of the unsteady convective heat transfer could facilitate the design and develop an efficient system.

An adaptive method for calculation of iron losses in switched reluctance motors using a minimum number of magnetostatic finite element simulations

PurposeThis paper aims to present an adaptive method based on finite element analysis to calculate iron losses in switched reluctance motors (SRMs). Calculation of iron losses by analytical formulas has limited accuracy. On the other hand, its estimation in rotating electrical machines through fully dynamic simulations with a fine time-step is time-consuming. However, in the initial design process, a quick and sufficiently accurate method, i.e. a value close to that of iron losses, is always welcome. The method presented in this paper is a semi-analytical approach. The main problem is that iron losses depend on d B/d t. Therefore, the accuracy of the calculation of iron losses depends on the accuracy of the calculation of the first derivative of the flux density waveform. When adopting a magnetostatic model to estimate the iron losses, an important question arises: by how many magnetostatic simulations can the iron losses be estimated within the desired accuracy? In the proposed algorithm, the aim is not to accurately calculate the value of iron losses in SRMs. The objective is to find a numerical error criterion to calculate iron losses in SRMs with a minimum number of magnetostatic simulations.Design/methodology/approachA finite element solver is developed by authors in MATLAB to solve the 2 D nonlinear magnetostatic problem using the Newton–Raphson method. A parametric program is developed to create geometry and mesh. The proposed method is implemented in MATLAB using the developed solver. Counterpart simulations are done in the ANSYS Maxwell software to validate the accuracy of the results generated by the developed solver.FindingsThe performance of the proposed method is studied on a 12/8 (500 W) SRM. Three scenarios are studied. The first one is the calculation of iron losses by uniform refinement, and the second one is by adaptive refinement, and the last one is by adaptive refinement started by particular initial points (switching points). According to the results, the proposed method substantially reduces the number of magnetostatic simulations without sacrificing accuracy.Originality/valueThe main novelty of this paper is introducing an error criterion to find the minimum number of magnetostatic simulations that are needed to calculate iron losses with the desired accuracy.

Permanent magnet shape optimization method for PMSM air gap flux density harmonics reduction

This paper proposed a permanent magnet optimization method to suppress the air gap flux density harmonic of permanent magnet synchronous motor (PMSM). The method corrected the effective air gap length of the motor, calculated the magnetization length of the permanent in the case of parallel magnetization, and took the influence of the permanent magnet relative permeability into consideration. Based on these works, for a given sinusoidal air gap flux density waveform, the corresponding structural parameters can be calculated, so as to achieve the optimization of the permanent magnet. By using this method to optimize the shape of the magnet, the fundamental wave of the air gap flux density can be retained to the greatest extent, so as to eliminate harmonics and maintain the output capacity at the same time. The feasibility and accuracy of the method have been verified by finite element analysis (FEA) and prototype machine experiment. This method is simple and time-saving, and has a satisfactory accuracy, which provides a reference method for permanent magnet optimization of PMSM.