Optimization of Electric Machine Designs - Part II

Through a systematic optimization study using high-fidelity finite-element (FE) models, torque capability of three common synchronous machine technologies, namely a permanent magnet (PM) synchronous machine (PMSM) with V-shaped rare-earth (RE) rotor magnets, a PMSM with deep V-shaped ferrite rotor magnets, and a synchronous reluctance machine (SynRM) with four layers of conforming flux barriers are compared for an application in a 48-V mild hybrid electric car. The optimization of the deep V-shaped ferrite PMSM automatically resulted in a spoke-type PM layout for maximum torque production. Yet, an optimized SynRM with conforming flux barriers was achieved that could produce a higher torque than ferrite PMSM. One machine technology is selected and is subsequently subjected to a large-scale FE model-based drive-cycle design optimization. Various pole-slot combinations are methodically compared in terms of drive-cycle losses, active material cost, torque ripple, and PM demagnetization level. More than 20,000 designs were analyzed over ten energy-centric torque-speed points to identify an optimal design solution. The results of multi-physics analysis incorporating electromagnetics, computational fluid dynamics (CFD), and structural analyses are provided, including a study on two different water jacket concepts. A final design is prototyped and initial experimental results are provided.

This paper presents an analysis of three different electrical machine topologies for a turbo circulator application. The electrical machines are designed to operate with 6 kW output power at 120 000 r/min. This paper demonstrates the design aspects of one solid rotor squirrel cage induction motor and two permanent magnet synchronous machines. The machines are compared using electromagnetic, thermal, and mechanical analyses. The benefits and disadvantages of each topology under study are discussed. For other high-speed applications presented, a comparative approach helps in selecting the suitable electrical machine topology by analyzing the performance criteria discussed. The prototype construction of one of the topologies is analyzed.

Offshore wind power generation has broad application prospects. The current single-unit capacity of offshore wind generators exceeds 20 MW. Superconducting (SC) armature permanent magnet (PM) generators have high current-carrying characteristics and can overcome the bottlenecks of the copper armature PM synchronous generator in terms of volume and weight. However, existing SC armature windings usually use an integrated dewar, which is difficult and costly to design and is not conducive to maintenance. In addition, SC armature windings are mostly three-phase windings, and the fault-tolerant operational capability of SC armature electrical machines is poor. In response to the above problems, this paper proposes a dual three-phase PM vernier SC armature electrical machine (DTVSM), which adopts an SC magnet with a static seal of the cooling medium. Each SC magnet used a modular dewar and contained two sets of SC coils. The SC magnets are connected externally to form a dual three-phase SC armature winding, which improves the fault-tolerant operational capability of the SC armature PM electrical machine. Compared with the 20 MW copper armature PM synchronous electrical machine, the unit volume torque density of the proposed DTVSM is about 108.22 kN• m/m3, which represents an improvement of about 60%, indicating significant application potential. This study designs and tests a 10 kW prototype, focusing on the electrical machine topology, working principle, and manufacture of SC magnets and prototype, and the related experimental tests verify the feasibility of the DTVSM technology route.

A strategy for interturn short-circuits and static eccentricity diagnosis in permanent magnet synchronous ma-chines (PMSM) is proposed in this paper. In several practical implementations, the PMSM faults produce similar behavior patterns on electrical signals. In these cases, robust diagnostic strategies are required in order to identify the fault, without being influenced by external disturbances. To achieve this goal, a 2D model of PMSM was designed and evaluated by using of a finite element method (FEM). The fault diagnosis is realized by analyzing the behavior pattern of a residual voltages (RV) in the αβ plane. A PMSM prototype with modified stator windings and bearings with eccentric bushings was used to evaluate the proposed diagnosis strategy. Experimental results obtained with this PMSM demonstrate the correct fault diagnosis of both, interturn short-circuits and static eccentricity.

Breakthrough innovations in electrical machines may be limited by parametric overlays and templates provided in commercial electromagnetic simulation software. Disruptive design spaces must therefore be explored using more flexible open-source software solutions. However, a significant scripting effort is necessary to define some new parametric geometries suitable for design optimization based on open source multiphysics solvers. This article illustrates the use of Pyleecan open-source simulation software under Python to more efficiently model, evaluate and optimize disruptive topologies of 2D or 3D electrical machines. The current status of Pyleecan initiative is first presented. Then, the principle and the advantages of the object-oriented approach of electrical machines are detailed. Some examples of complex innovative topologies that can be generated with Pyleecan are then introduced (e.g. complex winding, uneven slot types, multiple rotor and stators), as well as the optimization possibilities. Finally, the development roadmap of Pyleecan project is given.

This paper presents a simulation and a practical implementation for resolver based-vector control of Permanent Magnet Synchronous Machine (PMSM) using a dSPACE-1104. The rotor position is necessary to achieve the vector control drive system of the PMSM. In this paper, the resolver sensor detecting the rotor position of PMSM is focused. Resolver is the one of position sensors that can measure the initial rotor position at standstill. The resolver algorithm is proposed and implemented in the vector control drive system of PMSM. The proposed scheme has been verified by both simulation and experiment using MATLAB/Simulink and the dSP1104 based digital controller, respectively. Simulations and experimental results well demonstrate the effectiveness of the proposed control scheme.

In recent years, a lot of attentions have been paid to the less rare-earth permanent magnet synchronous machine (LRE-PMSM). The LRE-PMSM combines the features of two machine types: high energy density, high efficiency of the permanent magnet synchronous machine and the lower cost of the synchronous reluctance machine. The design optimization of the less rare-earth interior U permanent magnet synchronous machine (LRE-IUPMSM) is investigated in this paper. And a general approach for the analysis of noise is presented.

The increasing complexity associated with many modern engineering applications, including autonomous robot guidance and navigation, process control in sensor-rich environments, and control of biological systems, has far-reaching implications for control system design. As an example, reactive, embedded software systems, interacting among themselves and remote users over communication networks, introduce a whole new set of system-level challenges, and classic control design objectives such as stability, performance, and robustness are being complemented with a number of new questions. These include the cost of hardware implementation, measured for example not only by computational requirements such as speed and memory, but also by communication requirements such as available communication bandwidth. Moreover, the complexity associated with specifying the control procedures and with verifying the behavior of the closed-loop system increasingly plays a fundamental role, especially in safety-critical control systems arising in energy and transportation networks, and in medical applications.

For integrated on-board battery chargers (IOBCs) using permanent magnet synchronous machines (PMSMs), it is not desirable to use the winding inductance measured from the motor in a stationary state to evaluate the equivalent filter inductance during charging operation. This is because the magnetic circuit is coupled when the motor windings are reused as the grid current filters. In addition, the grid current flowing through the parameter-unoptimized PMSM makes it difficult to satisfy the charging standards, which even causes a system crash. The current of the charging system is lower compared with the propulsion mode, which means that the motor usually operates in the linear zone. On this basis, this article proposes a filter inductance model for the dynamic charging process of IOBCs. The method for evaluating the grid current ripple and current symmetry based on the inductance model is given. Then, an iterative design optimization method is used to optimize a PMSM, which enables the PMSM to balance propulsion performance and dynamic charging stability. At last, a control algorithm is proposed based on the inductance model to make the IOBCs further satisfy the charging standard. The theoretical analysis and control algorithm are verified by experiments.

Structural design optimization in precise or imprecise environment plays an important role in civil engineering as well as in mathematics. Conventionally in most of the situation structural designs are treated as single objective optimization problem with cost as objective function. Practically there exists some real life problems where multiple and conflicting objects frequently exist.So a methodology known as Multi-objective Four Valued Refined Neutrosophic Optimization (MOFVRNO) technique has been introduced in this paper.This optimization technique is generalization of fuzzy set (FS)theory,Intuitionistic Fuzzy Set (IFO)Theory and above all Single Valued  Neutrosophic Set Optimization (SVNSO)theory.In this problem cost and deflection of the beam have been considered as objective functions. Also in this welded beam design problem maximum shear stress in the weld group, maximum bending stress in the beam, buckling load of the beam have been considered as constraints. The design variables are length ,depth ,height,width in this optimization problem.Now from the mathematical point of view indeterminacy is again refined as uncertain(U),Contradiction(Truth∧Falsity,T) in Four valued Refined Neutrosophic Optimization technique.The results obtained by different methods like nonlinear optimization technique,Fuzzy optimization technique ,Intuitionistic Fuzzy Optimization technique ,Single Valued Neutrosophic Optimization technique andFour Valued Refined Neutrosophic Optimization technique have been discussed in the perspective of welded beam design problem in this paper. It helps to make comparison among them to find most cost effective method.

The modular slip‐synchronous permanent magnet generator (SSPMG) is viewed as an induction‐synchronous machine pair that is electromagnetically decoupled by a free‐rotating rotor that in turn houses two different sets of permanent magnets. This machine pair combines the advantages of both conventional induction and permanent magnet synchronous machines. It therefore has the potential to realize a new path in reliable, robust and cost‐effective wind turbine drivetrains. However, which electromagnetic SSPMG topology is best and how does it compare with conventional drivetrain designs for various capacities? To date, the most published SSPMG advances are specific to winding design, torque quality and performance optimization in the small capacity range. This paper presents optimized analytic electrical designs of modular, radially and axially separable, radial flux SSPMG topologies of capacities ranging from 100 kW to 5 MW. Designs are based on lumped analytic models and are optimized for minimum specific active mass (mass/torque). A rated efficiency of 95 % and an inductive power factor of 0.95 are applied to all designs. The analytic models are validated with transient two‐dimensional finite element analysis results. The best SSPMG topologies are determined and compared with conventional drivetrain designs. The axially separable topology seems to be the best SSPMG design. Copyright © 2014 John Wiley & Sons, Ltd.

There is recognized interest in in-wheel motors for vehicle traction. Studies have gradually focused the design of in-wheel motors on electro-mechanical vibration, subject to the demand of driving comfort. It is crucial to model, analyze, and minimize the air-gap exciting force, the dominant source of vibration. In order to qualitatively and quantitatively study the air-gap vibrational exciting force and evaluate its characteristic for an in-wheel outer-runner permanent magnet synchronous machine (PMSM), this research proposes an air-gap permeance model (APM) and a unique adaptive reluctance network model (ARNM). In the process of motor design, APM is a quick means of determining dominant radial force density (RFD) harmonics and minimizing specific components that may produce considerable vibration. Morphing surface-mounted magnets and nonuniform air-gap length are guided by design optimization which complicates the analysis. Yet, proposed ARNM can account for this geometry variation and handle deformed gap geometry by using modified equation-based local permeance and residual flux. The speed and accuracy of proposed model are verified through the comparison of flux density and force mapping data between the calculation by proposed analytical model and the simulation by finite element tools. A 3-kW prototype is fabricated and tested to explore the effectiveness of ARNM-based performance prediction.

A large-scale finite element model-based design optimization algorithm is developed for improving the drive-cycle efficiency of permanent magnet (PM) synchronous machines with wide operating ranges such as those used in traction propulsion motors. The load operating cycle is efficiently modeled by using a systematic k -means clustering method to identify the operating points representing the high-energy-throughput zones in the torque–speed plane. The machine performance is evaluated over these cyclic representative points using a recently introduced computationally efficient finite element analysis, which is upgraded to include both constant torque and field-weakening operations in the evaluation of the machine performance metrics. In contrast with the common practice, which aims at enhancing the rated performance, the entire range of operation is considered in the present design optimization method. Practical operational constraints imposed by the voltage and current limits of the motor-drive system, excessive PM demagnetization, and torque ripple are accounted for during the optimization process. The convergence to the optimal design solutions is expedited by utilizing a new stochastic optimizer. The developed design algorithm is applicable to any configuration of sinewave-drive PM and synchronous reluctance motors over any conceivable load profile. Its effectiveness is demonstrated by optimizing the well-established benchmark design represented by the Toyota Prius Gen. 2 interior PM motor configuration over a compound operating cycle consisting of common U.S. driving schedules. Multiphysics electromagnetic, thermal, and mechanical performance of the optimized design solutions is discussed in a postdesign optimization stage.

This paper concerns the design optimization of an outer-rotor permanent magnet synchronous machine (PMSM) with fractional-slot and concentrated-winding (FSCW) configuration for a lightweight direct-drive electric vehicle. Based on the rigid space envelope limits and performance specifications required by the vehicle, four candidate versions of a FSCW PMSM have been determined by initial machine sizing analysis. All versions share the same rotor outer diameter, rotor back iron thickness, permanent magnet thickness, air gap length, and magnet pole arc width ratio. A window-zoom-in response surface method based on two-dimensional parametric finite element analysis is proposed for comprehensive electromagnetic optimization for maximum torque density. Additionally, the machine losses at rated torque output including copper joule loss, rotor eddy current loss, and stator core loss maintain the same in all the candidates. It is found that significant correlation exists between stator slot depth and active axial length in the optimal outer-rotor PMSMs. Finally, the performance characteristics of the four optimal machines are comprehensively evaluated and compared to confirm the best candidate, and its utility for the vehicle's mission.

This paper presents an implementation of zero speed sensorless control for permanent magnet synchronous machines (PMSM). The paper focuses on the principles and practical implementation of high frequency injection technology in a salient PMSM. The method using rotating vector, carrier frequency excitation and heterodyning, tracking observers for position estimation is discussed. A DSP-based drive system for this purpose is developed The experimental results for the case of a buried PM machine are shown in the paper. It was demonstrated that acceptable results could be obtained from the buried PM machine using the simplest, single saliency-tracking method and a digital solution (DSP system based) is feasible for low speed operation, including zero speed.