Stator Core Research Articles

Loss And Temperature Rise Analysis of Permanent Magnet Motor Based on Magneto-thermal Coupling Field

Because of the situation of motor performance degradation caused by permanent magnet demagnetization and increased loss of built-in permanent magnet synchronous motor under high temperature working conditions, this paper optimizes the rotor magnetic circuit structure of the motor and uses amorphous alloys. The material stator core replaces the original ordinary silicon steel stator core to suppress the motor temperature increase and reduce the motor loss. Through simulation, comparative analysis and calculation, the result could show that losses and temperature increase are significantly reduced after optimization. Finally, temperature rise testing was conducted on the prototype, confirming the correctness of the improved model.

Pure sine wave generation in battery-less solar system using advanced control through single machine

Due to the reduction of conventional energy sources, humanity faces a critical challenge, forcing innovative solutions to bridge the growing gap between energy demand and supply. Solar energy has emerged as a promising alternative, owing to its efficiency and renewable nature. Despite their benefits, conventional solar power systems face many challenges, including their reliance on battery banks, which introduce complexities and inefficiencies, such as voltage fluctuations and harmonic content. To overcome these challenges, researchers propose a novel solution: the Dual Winding Machine (DWM). This innovative system integrates motor and generator functionalities within a single machine, operating on a dual stator core to achieve synchronous operation. In contrast to traditional setups, the DWM eliminates the need for batteries during periods of low solar energy. A crucial component in this novel approach is the utilization of a Zeta converter, which adjusts the switching frequency to regulate the DC voltage and machine terminals. By doing so, the DWM maintains a constant voltage supply without relying on a battery, mitigating the fluctuations observed in traditional solar power systems. The proposed solution offers several benefits over existing strategies. Firstly, by eliminating the need for a battery, the DWM reduces system complexity and enhances overall efficiency. The absence of a battery backup also minimizes the risk of fluctuations in the inverter's input voltage and mitigates potential increases in output harmonic content. This not only improves the reliability of the solar power system but also extends the lifespan of connected machinery, such as motors and electrical devices. Furthermore, simulations conducted using MATLAB and MAXWELL programs validate the effectiveness of the DWM, confirming its ability to generate harmonic-free sine waves without relying on a battery, thus representing a significant advancement towards more sustainable and reliable solar energy solutions. In summary, the DWM presents a promising solution to the challenges faced by conventional solar power systems, offering improved efficiency, reliability, and longevity.

Design and Analysis of a Linear Electric Generator for Harvesting Vibration Energy

This paper provides a proof of concept for a linear electric generator that can be used to harvest energy from various sources of linear motion, such as vibrations, free-piston engines and wave energy. The generator can be used to power small electronic devices, such as sensors, or charge household batteries. The literature was reviewed to develop an understanding about the applications, control methods, excitation methods and mechanics of rotating and linear electric machines. A bidirectional, two-sided linear machine was designed with two stator cores and a single mover core. The stator windings and mover winding can be independently excited, allowing for three modes: no mover excitation, a DC excited mover, and an AC excited mover. Simulation results showed that the magnetic flux generated by DC excited stator cores were concentrated in the centre of the mover core. The use of two stator cores eliminates lateral flux in the mover core when it is not excited, minimising attraction and repulsion forces. Parametric analysis showed that flux cutting occurred in all operation modes, verifying that the generator will produce power when operating. Hardware tests produced an output current when the machine was electrically and mechanically excited, verifying the proposed design.

Iron loss calculation model of high‐voltage multi‐pole asynchronous motors considering high harmonic flux density

AbstractA variable coefficient segmented iron loss calculation model is proposed for high‐voltage multi‐pole asynchronous motors, which fully considers the influence of high‐order harmonic magnetic density on such motors. This model introduces additional hysteresis loss, improved eddy current loss coefficients, and rotation magnetisation coefficients to account for changes in losses due to small hysteresis loops and skin effect, as well as rotation magnetisation losses. A 710 kW 10‐pole asynchronous motor is used as the research object. A full‐domain iron loss calculation model considering stator and rotor tooth top surface losses is developed. The model can be used to accurately calculate the overall and local harmonic iron losses in the stator and rotor cores of high‐voltage multi‐pole asynchronous motors. And quantitatively analyse the distribution pattern of any harmonic iron loss at any location in the motor core. It realises the refinement calculation and analysis of iron losses in the whole domain of high‐voltage multi‐pole asynchronous motor. Finally, no‐load and load tests were conducted on the 710 kW 10‐pole asynchronous motor. The iron losses of the 710 kW 10‐pole asynchronous motor at no load and load are calculated using the above mentioned model and the classical trinomial constant factor model. The results are compared with the measured iron loss values. It is proved that the iron loss model is more accurate in calculating the iron loss of high‐voltage multi‐pole asynchronous motor. The result helps researchers to calculate the iron loss distribution of high voltage motors more accurately. Thus, the design and operating parameters of the motor can be optimised to improve the efficiency and performance of the motor. It provides the necessary technical support and key basis for the reduction of loss and energy saving of high‐voltage motors and the optimisation of their core structure.

Influence of stator and rotor core material definition method on no‐load electromagnetic field calculation results for tubular hydrogenerator

AbstractIn this letter, the effects of various material definition approaches for stator and rotor cores on the no‐load electromagnetic field calculations of a 34 MW tubular hydrogenerator are investigated, utilizing the transient motion electromagnetic field time‐step finite element (FE) method. The findings indicate that employing a linear simplified definition for the stator core material maintains high accuracy and rationality in the calculation results of the no‐load electromagnetic field and voltage waveform while offering substantially greater computational efficiency than the non‐linear definition method. Conversely, using a linear simplified definition for the magnetic pole core material of the rotor significantly increases the error margin in the results, rendering them unacceptable.

Investigation and Suppression of Cogging Torque of Permanent Magnet Homopolar Inductor Machine

Cogging torque (CT) would cause the vibration and noise of the permanent magnet homopolar inductor machine (PMHIM), which should be suppressed. However, the unipolar air-gap flux density and the dual-segment stator and rotor cores of PMHIM make the characteristics of CT unclear, which leads to a lack of theoretical basis for suppressing the CT. Addressing this issue, the CT of PMHIM is investigated and suppressed. Firstly, the model of CT of PMHIM with integer and fractional slot configurations is developed, and the factors affecting the CT are revealed. Then, the methods for suppressing the CT are proposed based on changing rotor parameters. The influences of different rotor parameters on electromagnetic performance, including back electromagnetic force (EMF), output torque, current and efficiency are fully analyzed. In addition, the characteristics of the proposed method are highlighted by comparing the performance of the method proposed in this paper with the global optimization method in terms of CT suppression. Finally, the theoretical analyses are validated by experiments. The results show that the CT of PMHIM can be effectively suppressed by the proposed method in this work.

Simulations of Transients in a Four-Pole Magnetic Bearing with Permanent Magnets.

This paper presents the design of and transient time simulations for a four-pole magnetic bearing with permanent magnets. The usage of permanent magnets reduces the consumption of electric energy in comparison to a traditional active magnetic bearing. Permanent magnets are installed in the yoke of the stator core to limit the cross-coupling of the magnetic flux generated by the windings. The first part of this paper presents the design of the magnetic bearing and its finite-element model, while the second part describes the field-circuit indirectly coupled finite-element model for the transient time simulation. The presented simulation model was used to calculate the transient response for the rotor lifting from the starting position, the step change in the rotor position and the change in the rotor position under an external impact force applied along the y-axis.

Study on the Thermal Field of a Hydro-Generator under the Effect of a Plateau Climate

With the advancement in the developmental project on the lower reaches of the Yarlung Tsangpo River, the influence of the plateau climate environment on the performance of a hydro-generator has received more and more attention from researchers. This study numerically simulated the thermal field of a hydro-generator with a 20 MW capacity under the effect of a plateau climate. Ambient pressure and temperature are two main factors that affect the temperature distribution of the generator. In addition, temperature distributions with different speeds are also studied under a plateau climate. The results show that the generator temperature decreases with increasing air pressure and speed. The generator temperature increases linearly with increasing ambient temperature. Among them, when the pressure lies in the range of 25–85 kPa, the temperature change gradient of the stator structure is very large. The temperature difference gradually decreases with the increase in air pressure. The temperature gradient gradually slows down when the air pressure is above 85 kPa. When the pressure is located at 55–85 kPa, the average temperature difference of the stator windings is 6.325 °C, and the average temperature difference of the stator core is 3.815 °C. Finally, the temperature distribution pattern can provide a basis for staff in different barometric pressure regions. It can also improve the safety and reliability of the hydro-generator under the effect of a plateau climate, which is important for improving its integrated hydraulic performance.

Design and simulation of a superconducting machine excitation system taking into account the three-dimensional magnetic leakage

The optimized design of a new high-temperature superconducting rotating pole machine is presented. Its main structural feature is the use of a double stator core which separates the synchronous machine pole shoe from the pole body to rotate separately as the machine rotor, allowing the superconducting coil to operate in a stationary state. The inner stator core, the stationary dewar and the rotor core together form the excitation system of the machine. The excitation coil windings adopt a rectangular cross-section, with flux divertor strategically placed between the high-temperature superconducting coils. This configuration aims to modulate the background magnetic field, specifically reducing the perpendicular magnetic field component. This mitigation minimizes the impact of ambient magnetic fields on the superconducting coil’s current carrying capacity, ensuring an optimized magnetic field environment for its operation. Through the integration of these modifications, the technical and economic parameters of the enhanced high-temperature superconducting machine have been significantly improved. The optimization of design, coupled with detailed calculations of the 3D electromagnetic field, was achieved utilizing the commercial software Ansys EM module.

Performance Enhancement of Flux Switching Motor for Electric Vehicle Applications: An Overview

As the reduction of greenhouse gas emissions becomes crucial, electric vehicles (EVs) are expected to enter the market extensively in the coming years. The efficiency of the electrical motor used in EVs plays a significant role in their overall performance. This paper explores the flux switching motor (FSM) and its applications in EVs. The FSM is compared to other electrical motors, highlighting its potential as a suitable choice for EV traction. Various configurations and techniques are reviewed to enhance the performance of FSMs, including magnetic materials, torque ripple alleviation, and magnetic flux weakening. The advantages and disadvantages of these methods are discussed, providing valuable insights for designing FSMs for EVs. Generally, EV traction requires high torque density and high power density electrical motor. To achieve these goals, high electric and magnetic loading must be considered in design stage of the motor. Application of the FSM may be one of the appropriate option. For many reasons, three-phase FSM is preferred. Considering the base speed of machine in the EV and high electric loading, the FSM with 12 stator teeth and 10 rotor teeth may be the most appropriate choice in which the stator core is oriented and rotor core is nonoriented iron. To enhance the torque density and applied flux weakening method, combination of Nd and Al–Ni–Co magnets is preferred.

Improved calculation of core losses of high-speed motors with two different permanent magnets considering higher order current harmonics

In high-speed permanent magnet synchronous motor drives, time harmonics in the current occur owing to the carrier frequency of the inverter, which affects the core losses among the electromagnetic losses. According to Steinmetz’s equation, the core loss depends on the frequency and magnetic flux density, with each term influenced by harmonic currents. Therefore, to accurately predict core loss, it is necessary to consider harmonic currents. This study presents the effects of differences in the resistance, inductance, switching frequency, and harmonic current on the core loss for two models with different PMs at the same output power. Core losses are significantly affected by harmonic current content and magnetic field behavior, making the analysis of harmonic components and magnetic field behavior essential. To achieve this, the stator core was divided into segments to examine the magnetic field behavior owing to harmonic currents in each region, thus facilitating a comprehensive analysis of the core losses. When the results were compared with the experimental data, it was observed that the analysis of harmonic currents significantly improved the accuracy compared to the analysis based solely on sinusoidal currents; in particular, the error rate reduced from 37.8% to 4.1%. Furthermore, it was confirmed that ferrite PMs resulted in smaller core losses owing to harmonic currents than rare-earth PMs. This finding suggests that ferrite PMs are a suitable alternative to high-speed permanent-magnet synchronous motors.

Fast Calculation of Electromagnetic Vibration of Surface-Mounted PMSM Considering Teeth Saturation and Tangential Electromagnetic Force

In view of the shortcomings of the existing calculation methods of electromagnetic forces, this paper proposes an analytical method (AM) combining the magnetomotive force (MMF)-permeance method and the improved subdomain method. The amplitude of each force density component considering stator teeth saturation and current harmonics is calculated, and the specific order and frequency components in the radial and tangential electromagnetic force densities are analyzed and sorted out. In modal analysis, the stator core and the casing are regarded as cylindrical shells with axial ribs, the natural frequencies of the stator are obtained based on the energy method, and the accuracy is well verified by the modal test. Finally, the frequency response functions of low-order modes of the stator only related to the stator structure parameters are determined, and the vibration accelerations under different working conditions are obtained based on the linear superposition principle by only updating the electromagnetic forces. Compared with the multi-physical coupling finite element analysis, the total calculation time of the proposed AM is reduced by more than 92%, which facilitates the fast prediction and effective reduction of electromagnetic vibrations in the motor design stage.

Comparative Study of Yokeless and Segmented Armature Machines With Different Stator Cores for Electric Vehicle In-Wheel Applications

Comparative Study of Yokeless and Segmented Armature Machines With Different Stator Cores for Electric Vehicle In-Wheel Applications

Examination of auxiliary yoke and teeth heating technique for directly heating laminated stator cores by the secondary current heating method

Examination of auxiliary yoke and teeth heating technique for directly heating laminated stator cores by the secondary current heating method

Comprehensive Analysis of Dual-Rotor Yokeless Axial-Flux Motor with Surface-Mounted and Halbach Permanent Magnet Array for Urban Air Mobility

A dual-rotor yokeless and segmented armature (YASA)-type axial-flux permanent magnet (AFPM) motor with a surface-mounted permanent magnet (SPM) array type was developed for urban air mobility (UAM) aircraft in this work. The proposed AFPM motor had rated and peak output powers of 75.5 and 104 kW, respectively, with rated and peak rotational speeds of 1800 rpm. To achieve a high torque, a cobalt–iron alloy core material was used for the stator core. The prototype AFPM motor, developed by KSEP in the Republic of Korea, was successfully manufactured and verified through experimentation. Additionally, the thermal stability of the winding and permanent magnets (PMs) was confirmed with a water-cooling system. A structure analysis of the proposed AFPM motor was conducted due to the detachment of an uneven air-gap length in the prototype AFPM motor. An output performance comparison based on core materials for the stator and rotor was carried out to explore the material cost reduction. Subsequently, the design for performance improvement by applying a Halbach permanent magnet (HPM) array type was investigated for further research.

Numerical-field analysis of the magnetic conductivity of the slot dispersion of the stator winding of induction motors

Introduction. The magnetic fields and the corresponding magnetic conductivities of the slot dispersion of the stator winding of three-phase induction motors (IM) are studied. Such studies are relevant in their design and are one of the bases for calculating a number of energy parameters and characteristics of motors. In the classical design of an IM, which is still valid, the specified magnetic conductivities are determined analytically according to the simplified slot dispersion model, therefore they may not always provide sufficient accuracy due to a number of assumptions and conventions. Goal. Further development of the IM design system by means of a numerical-field calculation analysis of the magnetic conductivity of the slot dispersion of their stator winding, as well as a comparative check of the relevant analytical formulas from various methods of classical design. Results. The slot dispersion of IM is determined by numerical calculations using the FEMM program within the stator tooth steps. For the research, four variants of the shapes of the stator slots, which are common in modern IMs of small and medium power, are accepted. In the calculations, calculation models with strongly saturated and unsaturated in the magnetic relation with the stator core teeth are considered. The numerical-field method shows that the classical design method can give both sufficiently accurate results and unacceptable errors in determining the magnetic conductivities of slot dispersion of IM. Discussion and prospects for further development. The provided numerical-field analysis method and the obtained results of the calculation of slot dispersion of IM windings are recommended as a basis for improving the system of their design.

Ozone Transport in 311 MVA Hydrogenerator: Computational Fluid Dynamics Modelling of Three-Dimensional Electric Machine

In this paper, a three-dimensional turbulent fluid dynamics numerical model of a 311 MVA full hydroelectric power plant unit is made, using the finite element method, to study and understand the ozone transport mechanisms inside the enclosured electric machine structure. In the real world, ozone is produced by partial discharges related to faults on stator bars. In order to analyse ozone transport from localised sources, a 3D fluid dynamic model of a complete hydrogenerator in operation is developed and presented for the first time. The model has a high level of geometric detail. Furthermore, a new proposal to simplify the modelling of radiators is implemented and validated. The modelled structure is based on a Campos Novos hydrogenerator electric machine and it consists of 378 coil-type stator bars made of copper covered by mica and, more externally, by a semiconductor coating layer. Other parts are also represented, including the stator core and air directors made of stainless steel, copper radiators, the rotor with its epoxy surface, and the concrete floor and concrete external walls. In the fluid dynamics model, a finite element mesh was designed to represent the air regions inside the hydrogenerator and the material surfaces that react with ozone (with their respective reaction rates), where the airflow and ozone transport are modelled using the Navier–Stokes equations and the mass conservation law. Partial discharge sources are represented by ozone sources with prismatic shapes, placed on surfaces of stator bars. Ozone concentrations have been calculated inside and around the generator machine. The rotor radius is 3.8075 m and its rotation frequency is 200 RPM. Radial air velocity due to interpole ventilation is also considered (2.2 m/s, as experimentally verified in loco. The radial velocity in the vicinity of the radiators is 3 m/s. It has been concluded that the ozone transport profile is influenced by the source positioning on the stator bars in such a way that source pinpointing is possible and it depends on determining the local and global maxima areas of ozone concentration at the radiators.

ВИМІРЮВАННЯ ЗУСИЛЬ В СТЯГУВАЛЬНИХ ПРИЗМАХ ОСЕРДЯ СТАТОРА ПО-ТУЖНОГО ТУРБОГЕНЕРАТОРА З ВИКОРИСТАННЯМ ДАНИХ ПРО ХІД БЛОКУ ТАРІЛЧАСТИХ ПРУЖИН В СИЛОВИХ АКУМУЛЯТОРАХ

The advantages and features of the use of pressure accumulators (CA) with blocks of conic springs for restoring and stabilizing the pressing pressure of the stator core of a powerful turbogenerator (TG), which are installed under the tightening nuts or instead of them on the threaded ends of the tightening prisms of the core, are described. It is shown that the measurement of the displacement of the compression disc spring in the CA makes it possible to estimate the current state of the pressing pressure. The use of a capacitive sensor of linear displacements, placed outside the CA, to control the movement of the spring block in the caseless CA is substantiated. According to the specified design parame-ters of the caseless CA and the value of the maximum stroke of the plate springs in it, a capacitive sensor with its speci-fied characteristics was developed. The method of monitoring the state of the TG stator core using the CA system with capacitive sensors on each CA and the control method with the alternate use of one disk spring travel meter are de-scribed. Ref. 14, fig. 6. Key words: powerful turbogenerator, stator core, pressure, forces in the tightening prisms, power accumulator, displacement of block compression disc spring, capacitive sensor.

Orthotropic Material Parameters Identification Method of Stator Core and Windings in Electric Motors

The accurate equivalent orthotropic material parameters (OMPs) of stator core and windings are the basis of modal analysis in electric motors and the key to precisely predicting electromagnetic vibration and noise. A CNN (convolutional neural network)-MPGA (multi-population genetic algorithm) based OMPs identification method of stator core and windings for electric motors is proposed in this study. Firstly, the surrogate models between the material parameters and eigenmode frequencies are trained with CNN for stator core and windings. Then, MPGA is utilized to identify the equivalent OMPs of stator core and windings combined with tested eigenmode frequencies. Finally, two different classes of electric machines are selected to verify the method. The CNN-MPGA based method in this study can quickly and accurately identify OMPs of stator core and windings. It is significant for the calculation and suppression of electromagnetic noise for electric motors.

Characterization of an Axial Flux Machine With an Additively Manufactured Stator

Axial flux machines (AFM) are promising alternatives to radial flux machines for applications that benefit from high torque density and a large diameter to axial length ratio, such as in-wheel traction motors. However, the 3D flux paths in AFM present unique challenges to manufacturing laminated stator cores. This paper positions metal additive manufacturing (AM) technology as a potential solution to manufacture unconventional electric machine components such as AFM stators by investigating novel lamination emulating geometric structures and material silicon composition as design handles. In this paper, techniques to additively manufacture soft magnetic components for rotating electric machines are reviewed, and the Hilbert pattern is identified as a promising candidate to reduce eddy-current losses in these components. To further reduce the eddy current losses, this paper investigates the use of 6.5% silicon steel, which has higher resistivity compared to conventional steel laminations. The results in this paper show that the Hilbert structure is effective in reducing the eddy current losses by 50% compared to a solid structure with 3% silicon steel, and using 6.5% silicon steel further reduces the eddy current losses by 24%. Finally, a candidate AFM stator is designed with the Hilbert pattern and fabricated additively using 6.5% silicon steel. This machine is characterized and experimentally compared with an identical axial flux machine that uses a laminated stator. The results demonstrate the potential of metal AM technology to fabricate electric machine components with eddy current losses comparable to ultra-thin gauge laminations at frequencies up to 200Hz and conventional 29Ga laminations up to 480Hz.