Stator Iron Loss Research Articles

МОДЕЛЮВАННЯ АСИНХРОННИХ МАШИН У СКЛАДІ ЕЛЕКТРОМЕХАНІЧНИХ СИСТЕМ З УРАХУВАННЯМ ВТРАТ У СТАЛІ СТАТОРА

A comparative study has been conducted on methods for accounting for the influence of losses in the stator iron of squirrel-cage induction motors on the operating parameters. A comparison was made between reference data and calculation results of the nominal mode parameters of an asynchronous motor without considering losses in the stator iron and with their consideration using equivalent resistances connected in parallel to the motor, as well as equivalent circuits of losses in the stator. The effect of the ratio of active and inductive components of the load of equivalent stator loss circuits on the results of mathematical modeling has been investigated. The study was carried out based on a universal mathematical model of an asynchronous motor of electromechanical systems with an arbitrary stator winding scheme. An algorithm for determining and adjusting the parameters of the stator loss circuits during the integration of the differential equations of electrical and mechanical balance of the asynchronous motor to a steady-state value has been developed, based on the values of losses in the stator iron (depending on the induction and frequency) and the effective value of the current of the equivalent circuit. To ensure solution stability, the use of an iteration coefficient and discretization of resistance adjustment has been justified. The application of stator iron loss circuits in the mathematical model of an asynchronous machine in generator mode has been justified, when the use of parallel connected equivalent resistances contradicts the machine's energy diagram. References 10, figure 1, table 1.

Response Analysis and Stator Optimization of Ultrahigh-Speed PMSM for Fuel Cell Electric Air Compressor

For the requirement of the complex dynamic performance for the fuel cell vehicle (FCV), the wide operation range and rapid dynamic response ability are essential to the fuel cell electric air compressor, which are limited by the output torque of the permanent magnet synchronous motor (PMSM) commonly used in FCV. The purpose of this study is to improve the output torque of the stators and its rapid dynamic response capacity of PMSM using the mathematical model, multi-objective optimization and experimental validation. Firstly, a mathematical model of speed regulation response of ultra-high speed PMSM is established, which provides a basis for taguchi legal sub-optimization in this study. Secondly, stator parameters were selected as optimization variables based on Taguchi method, and the optimal combination of optimization variables was selected with the maximum electromagnetic torque, minimum cogging torque, minimum stator copper loss and minimum stator iron loss as optimization objectives. Finally, the effectiveness of the optimization method is verified by simulation analysis and bench test. At the target speed of 110652rpm, 124364rpm and 146876rpm, the overall response times before optimization are 1.9386s, 2.3902s, and 2.7844s. Respectively, the overall response times after optimization are 1.8604s, 2.2856s, and 2.6132s. The speed response time after optimization is 0.0782s, 0.1046s and 0.1712s less than before optimization, respectively.

Comparative Study of Various Slot Pitches for 2-Pole 6-Slot Ultra-high-Speed Permanent Magnet Synchronous Motors

The 2-pole 6-slot permanent magnet synchronous motor (PMSM) is an attractive option for ultra-high-speed (UHS) applications due to its excellent manufacturability and balanced magnetic force. UHS PMSMs should be designed with short stack lengths and end coil heights to address rotor dynamics issues. Additionally, given their high frequency, these PMSMs should be designed considering stator iron loss, rotor eddy current loss, and AC copper loss. The performance of the same pole-slot combination varies significantly based on the slot pitch. Hence, we compared the size and efficiency of the 2-pole 6-slot UHS PMSM based on the slot pitch. For a fair comparison, an optimal design was performed for each slot pitch. To reduce computation time, optimization was conducted in two stages: size minimization and efficiency maximization. It was confirmed that in terms of total axial length, the 1-slot pitch UHS PMSM is the shortest due to the advantage of having a short end coil height, even with the lowest winding factor and largest stack length. Furthermore, it was determined that the 2-slot pitch UHS PMSM offers an excellent trade-off between efficiency and size.

A real-time temperature rise prediction method for PM motor varying working conditions based on the reduced thermal model

Real-time and accurate temperature rise calculation can play a preventive role in preventing overheating motor damage. This article proposes a temperature rise calculation method for varying working conditions PM motors based on a reduced order model. The calculation model of this method consists of a thermal conductance matrix and a heat source matrix. The thermal conductance matrix is obtained by reducing the order of the detailed lumped parameter thermal network (DLPTN) conductance matrix, which significantly reduces the model order while retaining computational accuracy. A loss prediction function is introduced in acquiring the heat source matrix, which is constructed based on the relationship between motor loss and speed and power. It can predict the stator iron loss and PM loss with different speeds and powers in real-time, ensuring the accuracy of heat source loading. The experimental results show that this method can predict the temperature rise of critical nodes of the PM motor in real-time under varying working conditions. Its calculation results have high accuracy, providing an effective method for overheating PM motor protection.

Design and Analysis of a Novel High-Speed Permanent Magnet Machine With Dual Semi-Cage Winding

This article proposes a novel high-speed permanent magnet synchronous machine (HSPMSM) topology. The characteristics of the proposed machine are: 1) The stator winding is divided into two parts and each part is connected by the end ring at one end, which is helpful to solve the existing shortage of overlong end length in traditional HSPMSM. 2) The stator of the machine is designed with closed slot, which can greatly weaken the eddy current loss and the cogging torque of the machine. 3) The machine is driven by two separate three phase converter, which can improve the fault tolerance. In this article, the topology, and the corresponding control system is analyzed firstly. After that the electromagnetic performance, including back electromotive force, cogging torque, torque, etc. are analyzed with finite element analysis (FEA). In addition, the losses, including the stator copper loss, the stator iron loss and the eddy current loss of the permanent magnet and sleeve of the rotor, are calculated by FEA. The mechanical strength and dynamic performance of rotor is also checked. Finally, a prototype was designed and manufactured. The experimental results the validity of the topology.

A method for derating power of a MW directdrive wind turbine permanent magnet generator as over allowable working temperature

The use of direct-drive permanent magnet (PM) generators for MW wind application is increasing, because they have higher reliability and less maintenance than geared generators such as geared PM generators and geared induction generators. The price of the direct-drive PM generator is high, taking 10%-15% price of its overall system. Therefore, the generator mush be safely operated to have a long life. For a PM generator, its performance is sensitive to ambient and working temperature so that it needs to be monitored. In this paper, a method is proposed, combining the practical knowledge of a generator and theory to give permissible maximum generated power under certain ambient condition. The stator iron loss of a MW permanent magnet generator in direct-drive wind turbine application is presented as a function of rotor speed or frequency. The generator’s copper loss and electromagnetic torque versus winding temperature and current are investigated. The relationship of voltage, current and active power to the generator temperature is addressed. The given performances can be used to choose the generator’s working parameters such as voltage, current, output power for avoiding generator damaged by over temperature.

Investigation of Optimal Split Ratio of 6-Slot/2-pole High Speed Permanent Magnet Motor with Toroidal Winding

Split ratio, i.e. the ratio of stator inner diameter to outer diameter, has a closed relationship with electromagnetic performance of permanent magnet (PM) motors. In this paper, the toroidal windings with short end-winding axial length are employed in the 6-slot/2-pole (6s/2p) PM motor for high speed applications. The split ratio is optimized together with the ratio of inner slot to outer slot area, i.e. slot ratio, considering stator total loss (stator iron loss and copper loss). In addition, the influence of maximum stator iron flux density and tooth-tip on the optimal split ratio, slot ratio, and average torque is investigated. The analytical predictions show that when the slot ratio is 0.5, the maximum torque can be achieved, and the optimal split ratio increases with the decrease of slot ratio, as confirmed by the finite element (FE) analyses. Finally, some of predicted results are verified by the measured results of 6s/2p prototype motor with 0.5 slot ratio.

Estimation of losses and efficiency of double-stator switched flux permanent magnet machines

Losses such as rotor iron and stator iron losses, magnet eddy current loss, as well as efficiency of a double stator permanent magnet machine having varying rotor pole numbers is estimated and presented in this study. This current investigation would be vital for electrical machine designers in quantifying the amount of losses in the various sections of a given double stator electric machine and as well provide better insight on resulting output efficiency of the machine. Time-stepping finite element analysis (TS-FEA) procedure is adopted in the calculations using ANSYS-MAXWELL simulation software. The compared machines having the same stator teeth/pole number (Ps) and different rotor pole (Pr) numbers are designated as: 6Ps/10Pr, 6Ps/11Pr, 6Ps/13Pr and 6Ps/14Pr. The predicted total loss values at rated current and operating base speed is 13.02 Watts, 13.13 Watts, 13.539 Watts, 13.537 Watts, from the 6Ps/10Pr, 6Ps/11Pr, 6Ps/13Pr and 6Ps/14Pr machine types, respectively. The corresponding efficiency of the machine types at rated working conditions is: 81.76%, 88.17%, 86.95% and 78.61%, respectively. The results show that magnitude of losses in a given machine would largely depend upon factors such as number of rotor poles and hence, the machine’s operating speed, electric loading and angular rotor position of the machine, etc. It is also found that the number of loss waveform cycles (Nc) in an electric revolution of the investigated machine would depend upon its stator and rotor arrangements. The most performing compared machine types are the ones that have 11- and 13-rotor pole numbers, while the least amount of efficiency is obtained from the machine type that has 14-rotor pole number. Above all, the 6Ps/10Pr and 6Ps/14Pr are characterized with high amount of pulsations or ripples and this is detrimental to the overall performance of the machines.

Decoupled Estimation Scheme for PMSMs Toward Accurate Inductance Modeling

Parameter identification of permanent magnet synchronous machines (PMSMs) is critical toward building an accurate machine model, achieving precise control, and improving operational reliability. This article proposes a decoupled estimation scheme for interior PMSM with consideration of magnetic saturation as nonlinear functions of current to improve the inductance estimation accuracy. An improved machine model considering magnetic saturation and cross-coupling effects by utilizing a quadratic model in inductance calculation is developed. Furthermore, the decoupled estimation scheme with considering stator resistance and iron loss resistance can effectively reduce the interaction in the process of parameter identification, and the least square algorithm is employed to improve the computational efficiency. Moreover, this proposed method is especially dedicated to the modern testing solutions that require complex hardware and extensive machine operation while being noninvasive by nature.

Design and Analysis of New Modular Stator Hybrid Excitation Synchronous Motor

Hybrid excitation motor is a combination of permanent magnet motor and electric excitation motor, which can flexibly adjust the air gap magnetic field. At present, the traditional silicon steel sheet core material is widely used, but this material limits the further reduction of stator iron loss. In this paper, a new type of hybrid excitation synchronous motor with modular stator structure based on amorphous alloy material is proposed. The design power is 1kW, and the speed is 3000rpm. By placing the armature winding and electric excitation winding in the stator slot, the slip ring and brush are avoided, and the reliability of the motor is improved. The rotor adopts staggered magnetic pole structure, which has strong flux adjusting ability. The core loss is greatly reduced by using amorphous alloy. Firstly, the structure and working principle of the new motor are given; Secondly, the size parameters of the motor are given, and the principle of flux adjustment is verified and analyzed by three-dimensional finite element(3D-FEM); Finally, through theoretical analysis of the influence factors of the magnetic adjustment ability and 3D-FEM finite element computation, the flux adjustment ability and the torque lifting at low speed are verified, and the advantages of the motor are verified.

Study on performance of low-speed high-torque permanent magnet synchronous motor with dynamic eccentricity rotor

In actual production, errors in manufacturing and assembly may lead to misalignment of the stator and rotor and uneven air gap magnetic density, which affects the running performance of the motor. The influence of rotor dynamic eccentricity on air-gap flux density, cogging torque and loss is studied by combining analytical method and finite element analysis. The eccentric rotor model of low-speed high-torque permanent magnet synchronous motor (LHPMSM) is established on Maxwell 2D. The results show that with the increase of the rotor eccentricities, the back EMF and stator iron loss changeless, the cogging torque decreases slightly. The output torque increases slightly, but the harmonic distortion rate of air gap magnetic density and stator copper loss increase significantly.

High-Speed Synchronous Reluctance Machines: Materials Selection and Performance Boundaries

This paper presents a comprehensive comparative design exercise of Synchronous Reluctance (SyR) machines considering different soft magnetic materials and a wide range of speeds. First, a general design methodology able to consider all the consequences of selecting different materials is presented. In fact, magnetic non-linearities, rotor structural limitations and the rise of both stator and rotor iron losses are all considered. The adopted design approach allows achieving optimal stator and rotor geometries balancing all these competitive multi-physics aspects and keeping constant the cooling system capability. Both silicon-iron (SiFe) and cobalt-iron (CoFe) alloys with optimized magnetic and mechanical performance are examined to assess the maximum capabilities achievable with a SyR machine technology. The adoption of CoFe alloys leads to machines that outperform the SiFe counterparts up to a certain speed, above which, machines with SiFe provide better performance. Indeed, in the lower speed range, the effect of the higher saturation flux density of the CoFe materials is dominant, while for higher design speeds, their higher iron losses and lower yield strength, with respect to the SiFe ones, make the latter more convenient. All the design considerations are finally validated by comparing the predicted performance with the experimental test results on a 6.5kW, 80krpm SyR machine prototype.

Comparative Study of 6-Slot/2-Pole High-Speed Permanent Magnet Motors With Different Winding Configurations

In this article, three 6-slot/2-pole high-speed permanent magnet motors with 1, 2, and 3 coil-pitch windings are optimized by the finite element method taking into account stator copper loss and iron loss. Their electromagnetic performances are analyzed and compared, including air-gap flux density, back electromagnetic force, electromagnetic torque, winding inductances, and various loss components. For high-speed application, compared with 1 and 3 coil-pitch windings, the proposed 2 coil-pitch windings have a good tradeoff between winding factor and end-winding axial length which are attractive for improved torque density. Finally, the experimental results are given to validate some of the finite element predicted results.

Influence of Equivalent Circuit Resistances on Operating Parameters on Three-Phase Induction Motors with Powers up to 50 kW

This work shows the results obtained from studying the influence of equivalent circuit resistances on three-phase induction motors. The stator resistance, rotor resistance, and iron losses resistance affect the different motor operating variables (output power, current, speed, power factor, starting ratios, and maximum torque). These influences have been quantified, paying particular attention to the losses affected and their impact on efficiency. The study carried out does not apply optimization techniques. It evaluates the different influences of the equivalent circuit’s different resistances on its operation by evaluating applicable constructive modifications concerning available motors. The work has been limited to three-phase induction motors up to 50 kW and low voltage, with the nominal powers of the selected motors being 0.25 kW, 1.5 kW, 7.5 kW, 22 kW, and 45 kW. The tools used to carry out the study are analyzing the equivalent circuit and the simulation of the electromagnetic structure using a finite-element program. The variations proposed in each resistance for all the motors studied is not purely theoretical, as it is based on applying feasible constructive modifications, appropriately analyzed and simulated. These modifications are the variation of the conductor diameter in the stator coils, the change of the section of the rotor cage, and the selection of different ferromagnetic steel types.

Kriging Surrogate Model-Based Design of an Ultra-High-Speed Surface-Mounted Permanent-Magnet Synchronous Motor Considering Stator Iron Loss and Rotor Eddy Current Loss

Ultra-high-speed (UHS) surface-mounted permanent-magnet synchronous motors (SPMSMs) are widely used for driving air compressors. UHS SPMSMs can suffer from high stator iron loss and rotor eddy current loss due to their high rotational speed and changes in the magnetic flux density when loading. Since these losses do not have a linear trend but change according to the motor design parameters, mathematical models cannot always predict them. This study aims to design UHS SPMSMs based on a kriging surrogate model that takes into account the stator iron loss and rotor eddy current loss. Since the kriging surrogate model is highly predictive for nonlinear inputs, it is the perfect candidate to take into account the stator iron loss and rotor eddy current loss. The design proposed in this study allowed to minimize the size and losses of a motor that satisfied the power specification.

Impact of the Current Vector Angle on the Performance of a Synchronous Reluctance Motor With an Axially Laminated Anisotropic Rotor

The impact of the current vector angle on the performance of a synchronous reluctance motor (SynRM) with an axially laminated anisotropic (ALA) rotor intended for high-speed applications is studied. The paper shows that the current vector angle not only impacts on the stator winding Joule losses and iron losses, but also strongly influences eddy current losses in the rotor (when the rated torque is produced). The rotor eddy current losses are determined by the flux density harmonics produced by the stator. The air gap flux is affected both by the magnitude and angle of the current vector. However, the rotor surface harmonics are not directly related to the overall flux level (which can be quite low at a high current angle) but depend more on the values of the individual slot current linkages. Considering the dependence of rotor losses on the current vector angle, the most efficient operating point is suggested to be close to 45° or slightly larger, up to 65°, where a compromise between increasing rotor eddy current losses and winding Joule losses and decreasing stator iron losses is found. The eddy current loss distribution between the layers of an ALA rotor is analyzed in detail. With a larger current vector angle, the eddy current losses increase most in the layers close to the d-axis. This is explained by the largest current linkage in the stator slots that are in front of the layers close to the d-axis. The dependence of torque ripple on the current vector angle is also observed. An analysis of rotor and stator high-order harmonics, which determine the torque ripple, is performed.

Performance Comparisons of Fractional Slot Surface-Mounted Permanent Magnet Machines With Slot-Harmonic-Only Windings

Fractional-slot slot harmonic only windings (SHOW), featured by multi-layer and varied coil turn ratios, contain only the torque-generating component and its slot harmonics in stator magnetomotive force (MMF), which makes them attractive. This paper establishes general design principles of SHOW considering different slot/pole combinations and makes detailed comparisons between SHOW and double layer (DL) windings for surface-mounted permanent magnet (SPM) machines. Firstly, fractional slot windings are classified into several categories. Similarity in distribution factors of MMF harmonics is illustrated, based on which, harmonics elimination principle of SHOW is explained. Then, general equations for calculating optimal coil turn ratios for SHOW are derived. Practical ratios approximating the optimal ones are also presented and evaluated. Furthermore, in order to show the superiorities of SHOW, 12-slot/10-pole (12s10p) and 24S10P SPM machines with SHOW are comprehensively studied and compared with their DL counterparts in terms of torque ripple, overload capability, rotor magnet loss, stator iron loss and radial electromagnetic force harmonics. Finally, 12S10P and 24S10P prototypes with SHOW are fabricated and tested for verifications.

Loss-Optimization Method of Permanent-Magnet Synchronous Motor Based on Precise Stator Iron Loss Model

Traditional stator iron loss models lack precision when they are used for loss optimization of permanent-magnet synchronous motor (PMSM), because nonuniform distribution and nonsinusoidal waveform of the flux density in stator core are not fully considered. In this article, a new model is developed with a higher precision, in which the nonuniform flux density in stator core is observed through two virtual coils wounded on the yoke and tooth of a finite element model. Then, the stator iron loss is calculated depending on induced voltages of the coils. Moreover, nonsinusoidal waveform of the flux density is considered in the development. Based on this model, a loss-optimization method is proposed, in which the optimal current reference is determined by minimizing the stator loss under a constraint of ripple-free torque. Limitations of DC voltage supply and current amplitude are also considered to improve robustness of the method. Finally, precision of the iron loss model and performance of the loss-optimization method are validated experimentally on a 3.8-kW PMSM setup.

Implicit predictive flux control for high-performance induction motor drives

The paper aims to present a new formulation of a model predictive control for induction motor (IM) drives. The proposed control approach is based on utilizing the stator flux components as control variables; consequently, the cost function can be formulated in terms of only flux terms avoiding the use of weighting factor usually present in the model predictive direct torque control (MP DTC) techniques. The motor is modelled considering stator iron losses. An effective stator flux estimator is used to enhance the flux predictive control. A loss minimization criterion (LMC) is proposed in order to minimize the machine losses, especially at light load operation. In order to simplify the overall control scheme, the PWM strategy is eliminated and new model predictive flux control (MP FC) is implemented by the finite control set principle which enables the direct selection of voltage vectors among those (eight) delivered by the inverter. To prove the validity of the proposed MP FC, a detailed comparative study has been carried out between the performances of the IM drive under the classic MP DTC and the proposed MP FC control approaches (with and without the LMC). Dynamic performance of the drive is firstly tested by MATLAB/Simulink; then, a dSpace 1104 fast control prototyping board is used for the experimental verifications. The obtained results approve the improved dynamic performance of the IM drive under the proposed MP FC technique in comparison with the MP DTC.

Thermal and Electromagnetic Stator Vent Design Optimisation for Synchronous Generators

This article deals with the stator cooling of an air-cooled, synchronous generator with a power rating of 400 kVA, which has been improved by adding two radial vents to the stator. To ensure an optimal vent design, a novel combined thermal and electromagnetic modelling approach is developed. A parametric 3D Conjugate Heat Transfer Computational Fluid Dynamics (CFD) model is used for the thermal modelling. An electromagnetic 2D Finite Element Analysis determined the impact that venting the stator has on the loss distribution. The models are coupled by deriving analytical correlations between the combined vent width and rotor copper, rotor iron and stator iron losses. These correlations are implemented into the optimisation procedure of the parametric CFD model. Five design parameters are optimised simultaneously with the aim of minimising the peak stator winding temperature. The modeling approach was validated experimentally by thermal, torque and mass flow measurements on the benchmark machine, as well as the newly designed prototype.