Design Optimization and Comparison of Direct-Drive Outer-Rotor SRMs Based on Fast Current Profile Estimation and Transient FEA

Outer-rotor switched reluctance machines (SRMs) have drawn much attention as promising candidates for in-wheel direct-drive motors of future electric vehicles. This article presents a systematic performance comparison of three outer-rotor SRM topologies for in-wheel traction applications in terms of the specific torque, electromagnetic efficiency, torque ripple, radial force, and mechanical aspects. A generalized design optimization framework for SRMs is proposed to enable the fast evaluation of large numbers of designs generated from the differential evolution by incorporating an analytical current profile estimation into the transient finite element analysis. The relationship between the saliency ratio and converter volt-ampere rating is also discussed. The calculations are then benchmarked with the experimental results from an existing prototype. The effectiveness of the performance prediction method and the proposed optimization approach is validated

Critical Aspects of Electric Motor Drive Controllers and Mitigation of Torque Ripple - Review

Electric vehicles (EVs) are playing a vital role in sustainable transportation. It is estimated that by 2030, Battery EVs will become mainstream for passenger car transportation. Even though EVs are gaining interest in sustainable transportation, the future of EV power transmission is facing vital concerns and open research challenges. Considering the case of torque ripple mitigation and improved reliability control techniques in motors, many motor drive control algorithms fail to provide efficient control. To efficiently address this issue, control techniques such as Field Orientation Control (FOC), Direct Torque Control (DTC), Model Predictive Control (MPC), Sliding Mode Control (SMC), and Intelligent Control (IC) techniques are used in the motor drive control algorithms. This literature survey exclusively compares the various advanced control techniques for conventionally used EV motors such as Permanent Magnet Synchronous Motor (PMSM), Brushless Direct Current Motor (BLDC), Switched Reluctance Motor (SRM), and Induction Motors (IM). Furthermore, this paper discusses the EV-motors history, types of EVmotors, EV-motor drives powertrain mathematical modelling, and design procedure of EV-motors. The hardware results have also been compared with different control techniques for BLDC and SRM hub motors. Future direction towards the design of EV by critical selection of motors and their control techniques to minimize the torque ripple and other research opportunities to enhance the performance of EVs are also presented.publishedVersio

Comparison of Switched Reluctance Motor and Double Stator Switched Reluctance Motor

This thesis is concerned with the design and analysis of Switched Reluctance Motor (SRM) and its improved structure Double Stator Switched Reluctance Motor (DSSRM). Three configurations of SRM viz. Inner Stator, Outer stator and Double Stator are designed and simulated in ANSYS Maxwell Suite. Design parameters are chosen by aiming optimum performance of motor after literature review and analytical study of the motor. SRM is not a line start machine, so power converter circuit is required to excite the motor. Without proper switching of current, desired torque is not obtained in SRM. The converter circuit and switching unit is built in Maxwell Circuit Editor Tools. Both magnetostatics and transient analysis is performed to investigate motion torque, torque ripple, normal force and radial force. A good comprehensive comparison of three different types of SRMs based on their torque profile and force densities is presented. Simulation performed verified better performance of DSSRM

Comparison of Switched Reluctance Motor and Double Stator Switched Reluctance Motor

This thesis is concerned with the design and analysis of Switched Reluctance Motor (SRM) and its improved structure Double Stator Switched Reluctance Motor (DSSRM). Three configurations of SRM viz. Inner Stator, Outer stator and Double Stator are designed and simulated in ANSYS Maxwell Suite. Design parameters are chosen by aiming optimum performance of motor after literature review and analytical study of the motor. SRM is not a line start machine, so power converter circuit is required to excite the motor. Without proper switching of current, desired torque is not obtained in SRM. The converter circuit and switching unit is built in Maxwell Circuit Editor Tools. Both magnetostatics and transient analysis is performed to investigate motion torque, torque ripple, normal force and radial force. A good comprehensive comparison of three different types of SRMs based on their torque profile and force densities is presented. Simulation performed verified better performance of DSSRM

Mitigation of Torque Ripple and Vibration in Switched Reluctance Motor Drives: A Switching Optimization

Switched reluctance motor (SRM) drives represents an attractive solution for industrial, transportation and domestic applications due to their rugged structure, independence from rare earth metals, modular design, wide speed range, and tolerance to harsh environments. Despite these advantages, the adequacy of SRM drives for many applications has been overshadowed by its relative high levels of torque pulsation and vibration/acoustic noise. This research aims to investigate and propose control strategies to mitigate these adverse features. To reach this goal the current shaping and switching optimization have been proposed. Two modeling methods were used in this process: i) field reconstruction method (FRM) to model the electromagnetic behavior; and ii) mechanical impulse response to model the structural behavior. This two-modeling procedure are the key innovative tools in this dissertation, since those are techniques recently proposed in the literature. Moreover, these two methods have been combined to simultaneously mitigation of torque ripple and radial vibration. Firstly, the structural vibration was investigated in detail for an 8/6 SRM. The modal analysis is carried out experimentally and through finite element model in ANSYS. Then, the mechanical impulse response concept was applied to develop a vibration prediction model that, after validated, was introduced in an optimization algorithm developed in MATLAB to design the precise switching instants to have active vibration cancellation. The method is focused on SRM operating under current control (low speed region). The experimental results show a significantly reduction. This technique is sensitive to timing without adverse impact on productivity and efficiency of the SRM drive. Moreover, the vibration mitigation also has contributed to acoustic noise reduction. In a second approach, an optimization based on the SRM model using the FRM is used to find the optimal current profile that mitigates the torque ripple. The percentage reduction reached is about 44%. Furthermore, the effect of the new current profile in the structural response is also investigated and a negative impact in the vibration has been observed. To deal with this shortcoming, an adaptive hysteresis band is implemented over the optimized current profile for torque ripple mitigation. The obtained results demonstrated a good compromise between the torque ripple and vibration mitigation

Comparative Study of Torque Production in Conventional and Mutually Coupled SRMs Using Frozen Permeability

This paper investigates the influence of mutual fluxes (inductances) on the resultant torque in three-phase conventional switched-reluctance machine (CSRM) and mutually coupled SRM (MCSRM) using the frozen permeability (FP) method. Under saturation conditions, the FP method allows accurately separating the torques due to self-flux and mutual flux, hence quantifying their contributions to torque generation. Then, appropriate current waveforms (unipolar or bipolar, square wave or sinewave) can be established to maximize the output torques. It is well known that the mutual torque of CSRM can be negligible. However, this paper has shown that when sinewave current is employed and under full or overload conditions, the torque will be significantly reduced due to non-negligible negative mutual torques. Different from CSRM, the self-torque and the mutual torque of MCSRM can be added if current waveform is properly chosen, e.g., sinewave currents. This can significantly boost the resultant torque. The predictions have been validated by experiments

Mathematical Approaches to Modeling, Optimally Designing, and Controlling Electric Machine

Optimal performance of the electric machine/drive system is mandatory to improve the energy consumption and reliability. To achieve this goal, mathematical models of the electric machine/drive system are necessary. Hence, this motivated the editors to instigate the Special Issue “Mathematical Approaches to Modeling, Optimally Designing, and Controlling Electric Machine”, aiming to collect novel publications that push the state-of-the art towards optimal performance for the electric machine/drive system. Seventeen papers have been published in this Special Issue. The published papers focus on several aspects of the electric machine/drive system with respect to the mathematical modelling. Novel optimization methods, control approaches, and comparative analysis for electric drive system based on various electric machines were discussed in the published papers

Design, fabrication and testing of a stacked variable-reluctance motor

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (page 107).A new type of variable-reluctance motor with axially stacked stator and rotor plates is explored in this thesis. This stacked variable-reluctance motor (SVRM) has mechanically parallel air gaps, carrying magnetic flux in series. Magnetic models are developed to predict the maximum and minimum flux linkage of the motor, as well as the average torque over an electrical cycle. A geometric optimization is carried out using a combination of the Monte Carlo method and the simulated annealing method on a prototype, designed as a hip motor for a cheetah like robot. A one-phase 56 polepair prototype is designed and constructed to confirm the theory. The prototype can maintain its two 100 pm axial air gaps over a 5 inch diameter. The prototype, given all its practical constraints, produces 2 Nm of torque at 30 A phase current. After material property adjustments, the model predictions match well with the experimental performance of the prototype. Another round of optimization is done using the modified material properties, the best torque-to-mass ratio found for a ferrite motor with no more than 100 pole pairs is 8.4 Nm/kg. It is concluded that ferrite's flux carrying capacity is insufficient for high toque-to-mass ratio motors, given the requirements of the hip motor. A steel SVRM can have torque-to-mass ratio as high as 35.7 Nm/kg, but is restricted to low speed operation due to the slow magnetic diffusion.by Kai Cao.M. Eng

Optimal Design of Special High Torque Density Electric Machines based on Electromagnetic FEA

Electric machines with high torque density are essential for many low-speed direct-drive systems, such as wind turbines, electric vehicles, and industrial automation. Permanent magnet (PM) machines that incorporate a magnetic gearing effect are particularly useful for these applications due to their potential for achieving extremely high torque density. However, when the number of rotor polarities is increased, there is a corresponding need to increase the number of stator slots and coils proportionally. This can result in manufacturing challenges. A new topology of an axial-flux vernier-type machine of MAGNUS type has been presented to address the mentioned limitation. These machines can attain high electrical frequency using only a few stator coils and teeth, which can simplify construction and manufacturing under certain conditions. Additionally, the inclusion of auxiliary small teeth within the stator main teeth can generate a noteworthy increase in output torque, making it a unique characteristic of this motor. By analyzing the operating principle of the proposed VTFM PM machine, possible pole-slot combinations have been derived. The process of designing an electric machine is complicated and involves several variables and factors that must be balanced by the designer, such as efficiency, cost, and performance requirements. To achieve a successful design, it is crucial to employ multi-objective optimization. Using a 3D FEA model can consider the impact of magnetic saturation, leakage flux, and end effects, which are not accounted for in 2D. Optimization using a 3D parametric model can offer a more precise analysis. Validating the machine\u27s performance requires prototyping a model and testing it under different operating conditions, such as speed and load, which is a crucial step. This approach provides valuable insights into the machine\u27s behavior, allowing the identification of any areas for improvement or weaknesses. A large-scale multi-objective optimization study has been conducted for an axial-flux vernier-type PM machine with a 3-dimensional (3D) finite element analysis (FEA) to minimize the material cost and maximize the electromagnetic efficiency. A detailed study for torque contribution has indicated that auxiliary teeth on each stator main teeth amplify net torque production. A prototype of optimal design has been built and tested