Sai Sudheer Reddy Bonthu

Optimal design of five-phase permanent magnet assisted synchronous reluctance motor for low output torque ripple

This paper presents the optimal design of five-phase permanent magnet assisted synchronous reluctance motor (PMa-SynRM) for low torque ripple. PMa-SynRMs are similar to interior permanent magnet (IPM) motors in structure but with reduced permanent magnets, PMa-SynRMs are more economical. In this study, lumped parameter model (LPM) is used in the approach to initially design the five-phase PMa-SynRM. Thousands of models are designed by LPM, which are then converged to optimized model using differential evolution strategy (DES). Optimization is done with maximum efficiency and minimum torque ripple as objective. The optimized 3 kW five-phase PMa-SynRM is then analyzed by finite element method (FEM) for fine tuning. Simulation results for back electromotive force (EMF), developed torque, torque ripple, cogging torque, and other necessary motor parameters such as d and q-axis inductances variation over respective axis currents are verified by fabricated prototype.

Comparison of optimized permanent magnet assisted synchronous reluctance motors with three-phase and five-phase systems

This paper presents comparison of optimized permanent magnet assisted synchronous reluctance motor (PMa-SynRM) with three-phase and five-phase architectures. The three-phase and five-phase PMa-SynRMs are designed with magnetic equivalent circuits (lumped parameter model (LPM)) and 2D finite element analysis (FEA) approach. Objective function with torque ripple, motor cost and efficiency is used to derive optimal design of each motor. Multiple parametric simulations are done to minimize the objective function through differential evolution strategy (DES). Both PMa-SynRMs are fabricated with same power rating (3kW) and same volume. Torque pulsation, back electromotive force (EMF), flux linkage, d- and q-axis inductances versus their respective currents and cogging torque are intensively simulated through FEA and are experimentally tested on the prototypes.

Obtaining optimized designs of multi-phase PMa-SynRM using lumped parameter model based optimizer

This paper focuses on multi-objective optimization of multi-phase Permanent Magnet Assisted Synchronous Reluctance Motor (PMa-SynRM) using Lumped Parameter Model based Optimizer (LPO). Optimized PMa-SynRM are cost efficient compared to Interior Permanent Magnet Motor (IPM). Five-phase PMa-SynRMs offer lower torque ripple and higher fault tolerant capability. Depending on various industry application and their application environment, PMa-SynRMs should be customized with appropriate design specification including different current rating, torque ripple, converter cost, magnet cost and overall machine cost. The developed LPO can efficiently extract optimized multi-phase PMa-SynRM models from different design families through defined Objective Functions (OFs). To prove the accuracy of developed LPO for different OFs, four PMa-SynRM models have been obtained while minimizing torque ripple, phase current, machine cost, and magnet costs respectively. Finally, Finite Element Analysis (FEA) of these models has been performed to validate accuracy of the LPO by comparing predicted performances through LPO and FEA.

Design procedure for multi-phase external rotor permanent magnet assisted synchronous reluctance machines

This paper presents the optimal design procedure to develop multi-phase external rotor permanent magnet assisted synchronous reluctance machines (EPMa-SynRMs). With its higher torque density and higher power density compared to the internal rotor PMa-SynRM, external rotor PMa-SynRM is best suitable in applications to electric bikes and aircrafts. Enormous amount of research has been done in optimizing internal rotor PM machines. However, an efficient optimization technique to develop a five-phase EPMa-SynRM is not presented in the literature. The optimization of the EPMa-SynRMs is important to provide better performance characteristics and controllability in terms of lower back-EMF harmonics and cogging torque for critical applications. In this study, a detailed analysis on developing magnetic equivalent circuit for the multi-phase EPMa-SynRM is presented. Differential evolution (DE) optimization algorithm is utilized to develop the optimal models for five-phase EPMa-SynRM. The effects of rotational forces on the rotor in both internal and external rotor PMa-SynRMs are analytically studied. A thermal model for the proposed EPMa-SynRM structure is presented. Initial simulation results for stress and thermal heat flow for the proposed designs are presented. Furthermore, electromagnetic finite element simulation results such as back-EMF, flux linkage, cogging torque, and their harmonics are presented for the developed five-phase EPMa-SynRM model. The best design which has lower back-EMF harmonics and cogging torque is chosen to fabricate and conduct experimental tests.

Design of permanent magnet assisted synchronous reluctance motor with external rotor architecture

This paper proposes an external rotor Permanent Magnet assisted Synchronous Reluctance Motor (PMa-SynRM). Due to the high material cost of PM machine, there was a continuous effort to reduce the amount of permanent magnets (PM) in manufacturing an electric machine. PMa-SynRM has reduced great amount of PM usage by hybridizing the architectures between Synchronous Reluctance Motor and Permanent Magnet Motor. To further reduce the PM usage and to further increase of torque density, design of PMa-SynRM has been investigated through external rotor architecture. With best of authors knowledge, external rotor has not been properly researched even with great advantage and design flexibility with PMa-SynRM architecture. Analytical comparison between two different types of motor (internal and external) has been investigated to prove the superior design flexibility and performance of proposed method. Performance characteristics such as average torque developed and variation of torque with respect to variation in speed have been analyzed in finite element atmosphere (FEA) to validate the proposed design. A lower torque ripple model with distributed winding structure has been modeled and its FEA simulation results for developed torque have been compared with the concentrated type external rotor PMa-SynRM model.

Optimal design of five phase permanent magnet assisted synchronous reluctance motor for integrated starter generator application

This paper presents the design of optimal five-phase permanent magnet assisted synchronous reluctance motor (PMa-SynRM) for integrated starter generator (ISG) application. PMa-SynRM is the hybrid structure of interior permanent magnet (IPM) motor and synchronous reluctance motor (SynRM). In this study, an optimized 15kW five-phase PMa-SynRM has been proposed as a better substitute for three-phase IPM motor for ISG operation in Honda Civic Hybrid car. A new reverse engineering technique (RET) has been applied to model the Honda IPM ISG. In order to develop a better PMa-SynRM ISG, the model developed using RET has been used as reference. Thorough analytical and finite element analysis have been performed to obtain the optimal PMa-SynRM design which has better performance characteristics compared to the Honda IPM ISG. Lumped parameter modeling (LPM) has been utilized with differential evolution (DE) optimizer to extract the best optimal design for the five-phase PMa-SynRM ISG. For the same power and volume, five-phase PMa-SynRM design has shown better performance characteristics in terms of cogging torque and torque developed.

Design Optimization With Multiphysics Analysis on External Rotor Permanent Magnet-Assisted Synchronous Reluctance Motors

Multiphase permanent magnet-assisted synchronous reluctance motor (PMa-SynRM) is proposed as one of the optimal machine designs for vehicular applications such as electric vehicles due to their fault tolerant operation capability. However, optimization of the multiphase PMa-SynRMs for in-wheel applications in EVs and aircrafts require more research efforts to increase their power density with the size constraint. In addition, optimization of the machine design with multiphysics structural and thermal analysis has not been intensively discussed in the literature. In this paper, an optimal design procedure which includes multiphysics analysis to design the multiphase external rotor PMa-SynRMs is presented. In specific, a five-phase external rotor PMa-SynRM with neodymium-based magnets has been proposed as a solution to produce higher power density compared to the conventional internal rotor PMa-SynRMs. Multiphysics analysis is included in the optimization procedure to determine the effects due to rotational forces and heat flow on the proposed optimal five-phase external rotor PMa-SynRM design. Detailed electromagnetic finite element simulations are carried out to depict the performance characteristics. A 3.8-kW prototype is fabricated and the experimental results are compared with same volume 3-kW five-phase internal rotor PMa-SynRM.

Eccentricity fault detection in multiphase permanent magnet assisted synchronous reluctance motor

This paper presents fault detection and its analysis for permanent magnet assisted synchronous reluctance motor (PMa-SynRM). The PMa-SynRM has been increasingly studied for critical service application where high efficiency and reliability is required in industry. However, the research on the fault in a PMa-SynRM has been limitedly studied, and no study on the eccentricity fault diagnosis for multiphase PMa-SynRM has been documented so far. The three-phase and five-phase PMa-SynRM has been comparatively analyzed under eccentricity condition to identify a fault diagnosis index which is independent from phase numbers. The simulation model for PMa-SynRM has been developed using finite element method (FEM). Through FEM, static eccentricity (SE), dynamic eccentricity (DE) and mixed eccentricity (ME) are designed to evaluate the performance of the multiphase PMa-SynRM motors under faulty conditions. The fault features have been extracted through average torque, torque ripple, and back-EMF harmonics. Theoretical analysis with designed motors has been done to evaluate extracted features under eccentricity condition.

Design of a rare earth free external rotor permanent magnet assisted synchornous reluctance motor

This paper presents the design of a low-cost rare-earth free external rotor permanent magnet assisted synchronous reluctance motor (EFa-SynRM) for traction motor applications. In recent design innovations, rare-earth free permanent magnet (PM) motors have been proposed as an alternative to the rare-earth based PM motors. However, rare-earth free PM motors exhibit lower power density, lower torque, lower efficiency, and higher prone to demagnetization issues. With proper design of flux barrier and PM shapes, the Fe PM based electric motor design can be optimized to overcome the above mentioned drawbacks. In this study, an optimal five-phase ferrite PM based EFa-SynRM is developed to achieve high power density and no demagnetization effect. Extensive finite element simulations are carried out to depict the higher average torque developed, lower torque pulsations, and higher efficiency. The proposed EFa-SynRM design has shown no demagnetization effect at three times of rated input current. A 3.7kW design prototype is fabricated and experimentally tested under no load conditions. Results are compared with a same size five-phase internal rotor 3kW Fa-SynRM.

Torque ripple minimization under unbalanced phase resistance in a five-phase permanent magnet assisted synchronous reluctance motor

This paper presents an analysis of the torque ripple minimization under unbalanced phase resistance (UPR) in a five-phase permanent magnet assisted synchronous reluctance motor (PMa-SynRM). There are many reasons for arising UPR conditions in a motor. One of the key reasons can be the shortening winding turns of the motor which significantly reduces the winding insulations. Therefore, over the times, the torque ripple increase gradually. Excessive torque ripple leads to early degradation of the drive train components with an increased acoustic noise that reduces the performances of a PMa-SynRM. Especially, under UPR conditions, the torque ripple becomes prominent which require smart and easy mitigation approach to retain the advantages of a PMa-SynRM. This paper investigates three different UPR conditions that commonly arise a five-phase PMa-SynRM. A simple phase voltage compensation technique has been utilized to improve the torque ripple under different UPR conditions. Extensive theoretical analysis has been carried out through finite element analysis (FEA) to verify the proposed idea. The effectiveness of the method has been evaluated by the experimental tests that are conducted by utilizing 3.7 kW dynamo system.