Permanent Magnet Assisted Synchronous Reluctance Motor Research Articles

Design of a Robust Five-Phase Ferrite-Assisted Synchronous Reluctance Motor With Low Demagnetization and Mechanical Deformation

This study presents the design of a robust five-phase ferrite (Fe) permanent-magnet-assisted synchronous reluctance motor (PMaSynRM) to mitigate two major design challenges: irreversible demagnetization and mechanical deformation. Recently, rare-earth magnet-based five-phase PMaSynRMs have been proposed for vehicular applications due to their better fault tolerance, higher torque density, and low torque ripple compared to their three-phase counterparts. However, rare-earth magnets are expensive and, their supplies were disrupted multiple times in past few years. Therefore, to avoid rare-earth magnets in traction motors, this study proposes a five-phase PMaSynRM with Fe magnet. Special attention is paid to avoid irreversible demagnetization and deformation as these are two major concerns in any Fe-based machine. The rotor structure is uniquely optimized with additional geometrical parameters to reduce the risk of irreversible demagnetization. To increase the structural stability of the rotor, optimal center post and weight reduction notches are adopted. The proposed Fe-based five-phase PMaSynRM has been comparatively studied over a rare-earth magnet-based PMaSynRM. The lumped parameter model and finite element model have been utilized for design optimization and performance analysis. Finally, A 3 kW prototype of the proposed five-phase Fe PMaSynRM has been fabricated, experimentally tested, and compared with the benchmark rare-earth PMaSynRM to validate the proposed design and simulations results.

A Hardware-in-the-Loop Realization of a Robust Discrete-Time Current Control of PMa-SynRM for Aerospace Vehicle Applications

The hardware-in-the-loop (HIL) realization platform significantly supports the advance of control techniques in secure, precise, and low-cost design. Innovative control techniques are anticipated to ensure aerospace vehicle drive controllability. This paper presents a novel robust discrete-time (RDT) predictive current control (PCC) strategy of a permanent-magnet-assisted synchronous reluctance motor (PMa-SynRM) implemented using the HIL tool and the experimental setup. The proposed RDT controller has a discrete-time integral term added to the conventional deadbeat (DB) current predictive control to improve the robustness and stability of the current control. The PMa-SynRM mathematical model with parameter uncertainties is theoretically derived. Conventional PCC techniques are constructed utilizing the DB framework. Although this controller has a good dynamic response, it still suffers from unmodeled transient changes as well as parametric motor uncertainties. A 6-kW PMa-SynRM machine drive system is built and tested using DS1104 R&D Controller Board. Typhoon HIL is used to emulate the PMa-SynRM and the inverter connected to a dSPACE MicroLabBox. The performance of the proposed RDT technique is assessed and compared with traditional DB using the HIL and experimental results under different speed commands, electrical and mechanical motor parameters variations, and rated speed reversal conditions.

Transient Overload Characteristics of PM-Assisted Synchronous Reluctance Machines, Including Sensorless Control Feasibility

Synchronous reluctance (SyR) machines are a high-efficiency alternative to induction motors for variable-speed applications. To mitigate the well known downside of their lower power factor, permanent-magnet-assisted topologies, in which either rare-earth or ferrite magnets are inserted into the rotor in suitable quantities, are often adopted. The design and optimization procedures for PM-assisted topologies have been thoroughly discussed in the related literature. This paper compares SyR machines assisted with NdFeB and ferrite magnets, focusing on torque overload capability and feasibility of saliency-based position estimation algorithms. Three prototypes were realized and tested. They all have the stator of a commercial induction motor and the same custom-designed SyR rotor laminations. Among the three prototypes, one is a pure SyR motor, and the other two have NdFeB and ferrite magnets, respectively; both are designed to give the same torque at rated current. Results from simulations and experiments are presented comparing the transient overload capability of the three machines, in terms of torque capability and de-magnetization limit. A dynamic thermal model of the machines was developed within this scope. Moreover, the feasibility of saliency-based sensorless methods was investigated and is presented here for the three machines, both at high- and low-current loads. The results of the paper suggest that the ferrite-assisted solution is the best candidate for replacing induction motors in variable-speed applications, for its optimal tradeoff between performance and cost.

Performance assessment of triple redundant nine‐phase delta‐ and wye‐connected permanent magnet‐assisted synchronous reluctance motor under healthy and fault conditions

In this study, the performance of a triple redundant nine-phase permanent magnet-assisted synchronous reluctance motor with delta-connected windings is comprehensively assessed and compared with that of wye-connected winding under healthy and fault conditions, including open circuit, inter-turn short-circuit and terminal short circuit. The steady-state torque behaviour, loss, efficiency and temperature distribution of the two winding configurations are analysed and compared. It is shown that the delta-connected winding has higher output torque under one phase open-circuit fault and lower inter-turn short-circuit current with three-phase terminal short circuit.

Design and analysis of a high-performance dual-rotor PM synchronous reluctance machine with toroidal windings

This paper presents a dual-rotor permanent magnet synchronous reluctance machine (PM-SynRM) with toroidal windings to improve the magnetic torque and the utilization of two torque components, thus to obtain high electromagnetic performance, such as torque, efficiency, and power factor. To highlight the advantages of the proposed dual-rotor PM-SynRM, all of its machine characteristics, including airgap flux density, back electromotive force (EMF), torque, power, efficiency, and flux weakening capability are compared to those of a conventional PM assisted SynRM (PMA-SynRM) with the same machine size and operating conditions, with the aid of a finite element method (FEM) using the JMAG-Designer. Furthermore, the proposed dual-rotor PM-SynRM is verified to have superior endurance against the magnet irreversible demagnetization within five times of the rated current excitation.

Active Current Harmonic Suppression for Torque Ripple Minimization at Open-Phase Faults in a Five-Phase PMa-SynRM

This paper presents an active phase current harmonic suppression method to smartly and adaptively perform torque ripple minimization (TRM) under open-phase fault conditions in a five-phase permanent-magnet-assisted synchronous reluctance motor (PMa-SynRM). The five-phase machine is gaining increasing attention due to its promising fault-tolerant and wide-speed operation capabilities. However, during the fault-tolerant operation, the torque ripple is substantially increased with dangerous vibrations. Until now, most TRMs have been primarily performed to maintain the constant magnetomotive force while only analyzing its fundamental harmonic. However, large torque variations are also caused by unexpectedly modulated high-order harmonic fluctuations that are challenging to predict. This fluctuation in current harmonics is highly destructive to reluctance machines due to its higher nonlinearity. To address this critical challenge, a real-time active TRM technique has been proposed that will be smartly adaptive to identified harmonic fluctuations. To achieve this, the proposed TRM solution systematically consists of three major steps: first, active harmonic identification; second, harmonic injection; and third, vector rotation of phases. To precisely identify fluctuating harmonics in a real time, a high precision but compact correlation-based monitoring algorithm has been proposed. A detailed theoretical analysis has been carried out through a finite-element analysis. The experimental tests are conducted to validate the proposed theory through a five-phase PMa-SynRM drive controlled by Texas Instruments DSP F28335.

Improvement of PMa-SynRM Output Characteristics by Optimizing the Rib Structure

In this paper, we have studied the optimization of the rib thickness in the design of a Permanent Magnet assisted Synchronous Reluctance Motor (PMa-SynRM). In the case of PMa;-SynRM, mechanical stress is concentrated on the rib structure supporting the segment at high rotation speeds, and the stiffness analysis results in the largest mechanical stress on the rib of the q-axis. On the other hand, it was confirmed that relatively low mechanical stresses were distributed in the case of the d-axis rib. Therefore, it is confirmed that the thickness of the whole rib should be equal to the thickness that can support the maximum stress. In addition, we find that it increases the magnetic flux leakage and is an inappropriate design method for reducing the output power. To prevent this phenomenon, concentrations of mechanical stress on each of the ribs were investigated, and a method was developed for designing the ribs with the optimized rib thickness. In addition, the thickness of the ribs that satisfies both the electromagnetic output and the mechanical safety factor was derived using the response surface method. Finally, we confirmed the improvement of the output using FEM analysis.

Experimental Assessments of a Triple Redundant Nine-Phase Fault-Tolerant PMA SynRM Drive

Fault-tolerant machine drives are key enabling technologies in safety critical applications. The machine drives are expected to exhibit high performance in healthy conditions and accommodate as many faults as possible, namely open circuit or short circuit in the machine and inverter or even an interturn short circuit. This paper aims to assess a triple redundant nine-phase (3 × 3-phase) permanent magnet assisted synchronous reluctance machine (PMASynRM) drive by comprehensive experimental tests under both healthy and fault conditions on a 35 kW machine drive prototype. The healthy performance, fault behavior, fault detection, and mitigation strategy are presented and assessed by extensive tests which demonstrate that the machine drive exhibits high performance and excellent fault tolerance with simple and cost-effective implementation. Therefore, the proposed machine drive has proven to be a practical candidate for safety critical applications.

Life cycle assessment of permanent magnet electric traction motors

Ongoing development of electrified road vehicles entails a risk of conflict between resource issues and the reduction of greenhouse gas emissions. In this study, the environmental impact of the core design and magnet material for three electric vehicle traction motors was explored with life cycle assessment (LCA): two permanent magnet synchronous machines with neodymium-dysprosium-iron-boron or samarium-cobalt magnets, and a permanent magnet-assisted synchronous reluctance machine (PM-assisted SynRM) with strontium-ferrite magnets. These combinations of motor types and magnets, although highly relevant for vehicles, are new subjects for LCA. The study included substantial data compilation, machine design and drive-cycle calculations. All motors handle equal take-off, top speed, and driving conditions. The production (except of magnets) and use phases are modeled for two countries – Sweden and the USA – to exemplify the effects of different electricity supply. Impacts on climate change and human toxicity were found to be most important. Complete manufacturing range within 1.7–2.0 g CO2-eq./km for all options. The PM-assisted SynRM has the highest efficiency and lowest emissions of CO2. Copper production is significant for toxicity impacts and effects on human health, with problematic emissions from mining. Resource depletion results are divergent depending on evaluation method, but a sensitivity analysis proved other results to be robust. Key motor design targets are identified: high energy efficiency, slender housings, compact end-windings, segmented laminates to reduce production scrap, and easy disassembly.

Computationally Efficient Design and Optimization Approach of PMa-SynRM in Frequent Operating Torque–Speed Range

This paper proposes a design process of permanent magnet assisted synchronous reluctance motors (PMa-SynRM) intended for vehicular propulsion. This approach takes into account range optimization and a multiphysics evaluation without the use of finite element analysis during the electro-magnetic-thermal optimization stage. The design process is based on a predesign stage to calculate a first approximation of the motor dimensions. The geometry obtained in the predesign step is used to initialize a genetic algorithm during the optimization process, which evaluates different motor designs by means of coupled magnetic, thermal, and electrical models. The magnetic model is based on a nonlinear reluctance network, which calculates the inductances and magnet flux linkages. The temperature dependence of the phase resistance and the temperature distribution in the main parts of the machine are obtained from a lumped thermal network. Once obtained the electrical parameters of the machine, its behavior can be assessed considering current and voltage restrictions, by means of a dq model that evaluates the iron and copper losses. The optimization process is based on a multiobjective cost function within a torque–speed interval.

An Investigation Into the Effect of PM Arrangements on PMa-SynRM Performance

The paper aims to provide a guideline for rotor design of permanent magnet (PM) assisted synchronous reluctance machine (PMa-SynRM). Unlike interior PM machines, the PMa-SynRM is essentially an SynRM with dominant reluctance torque. The PMa-SynRM is often designed by directly embedding magnets into an SynRM rotor to improve the performance. However, how the PMs can be arranged in the rotor to enhance motor performance has not been fully discussed. This paper investigates the influence of several key factors concerning the PM arrangements, including number of PM layers, inserted positions, and PM sizes. The torque, flux linkages, power factor, and motor performance are comprehensively evaluated. Based on the analysis, a brief guideline is suggested for PMa-SynRM rotor design. Finite element analysis is used for evaluation and experiments are conducted to validate the analysis.

Investigation of Losses for a Concentrated Winding High-Speed Permanent Magnet-Assisted Synchronous Reluctance Motor for Washing Machine Application

In this paper, improvement of torque quality and magnetic losses of a concentrated winding high-speed permanent magnet (PM)-assisted synchronous reluctance motor (PMaSRM) that can operate in the wide speed range are investigated. Optimization studies have been carried out to enhance the torque quality. In addition, ac copper losses in the stator coils and iron losses in laminations at high frequencies have been investigated. Since the PMaSRM can operate in a wide constant power-speed range, the field weakening performance has also been investigated. The motor performance results of the PMaSRM at both no-load and on-load conditions are examined by using Flux 2-D FEA software. A prototype motor based on the simulations has been built and validated in order to show the feasibility of such technology for white good applications.

Optimal Design of an Ultra-Premium-Efficiency PMA-Synchronous Reluctance Motor With the Winding Method and Stator Parameters to Reduce Flux Leakage and Minimize Torque Pulsations

In this paper, the optimal design for a permanent magnet-assisted synchronous reluctance motor (PMA-SynRM) is proposed in terms of efficiency, maximum torque, and minimum torque pulsations. Design variables, objective functions, and constraints are selected for this optimal design, which is divided into two steps. Step I utilizes the pole/slot combination of the PMA-SynRM and winding methods. The chosen 4-pole/36-slot model with distributed winding maximizes the rated efficiency. In Step II, the optimal design of the stator parameters is obtained using the response surface method and the precise torque and torque ripple are calculated using the finite-element analysis (FEA). The proposed stator slot openings are minimized to minimize the air-gap flux leakage, and consequently, realize a smooth electromagnetic torque. Finally, a few FEA results are validated by experimental results.

Electromagnetic Force and Vibration Analysis of Permanent-Magnet-Assisted Synchronous Reluctance Machines

This paper first studies the electromagnetic force and vibration characteristics of the permanent-magnet-assisted synchronous reluctance machines (PM-SynRMs). First, an analytical method to calculate the radial force is proposed based on the Maxwell stress tensor method. The temporal and spatial orders of radial force are obtained by two-dimensional fast Fourier transform, then the combination of stator slots and rotor virtual slots of PM-SynRMs is proposed to give a guideline for the initial design of PM-SynRM to achieve low noise and vibration. A PM-SynRM is designed and a multiphysics model for electromagnetic vibration is established. The radial and tangential force under no-load and load conditions are calculated by finite element method, and then compared with the analysis results. Modal analysis is implemented to capture the structural parameters of the stator. Based on the proposed multiphysics model, the vibration responses under both no-load and load conditions are calculated through modal superposition method. Finally, a PM-SynRM is built and vibration test is performed to investigate its vibration characteristics.

Comprehensive design and analysis of a PMaSynRM for washing machine applications

This study presents a comprehensive design procedure of a permanent magnet assisted synchronous reluctance machine (PMaSynRM) for replacing a permanent magnet synchronous motor (PMSM) in a commercial washer. The motors used in these applications have to perform efficiently on a wide speed range with constant-torque region for washing, and field-weakening region for spinning. A design methodology is determined consisting of electromagnetic design, thermal/mechanical stress analysis, optimisation and prototyping. There are limitations and decisions on the initial design steps, considering the volume allocated for the machine, magnetic material and permanent magnet (PM) selection and the electromagnetic parameters for constant-torque and field-weakening regions. Design process is carried out following the initial parameter selection then the motor is produced and tested. Test results show that the PMaSynRM is 8.26% higher in volume and lower in power density than those of PMSM with a better field-weakening characteristic and fault tolerance. As a result, the authors proposed a methodology to design a PMaSynRM which becomes a good alternative for the mass produced home appliance motors since the materials' amount are decreased in 20% for silicon steel and 50% for PMs consequently decreasing the total cost and offering nearly the same efficiency and power density for the application.

Design and optimisation of a novel asymmetric rotor structure for a PM‐assisted synchronous reluctance machine

This study proposes a novel asymmetric rotor structure with tuning-fork flux barriers for a permanent magnet (PM)-assisted synchronous reluctance machine (PMA-SynRM) to improve the torque characteristics. The proposed asymmetrical rotor structure can effectively decrease the flux leakage inside the rotor, as well as ensure the maximum values of the magnetic torque and the reluctance torque are near the same current phase angle as each other to achieve better utility. To realise this, the frozen permeability method is implemented to separate the total torque into the reluctance torque and the magnetic torque via a two-dimensional finite-element method – JMAG-Designer. To achieve the optimal torque characteristics in the proposed model, the Kriging method and a genetic algorithm are used for getting the optimised model. The contribution of this investigation into motor performance is validated by comparing the proposed model with a conventional PMA-SynRM with a symmetric rotor structure. Beyond that, all machine models are the same size, have the same number of magnets and are operated under the same conditions. A prototype of the proposed model is experimentally verified, i.e. the simulation results agree with the experimental results.

Adaptive sliding mode backstepping control - based maximum torque per ampere control of permanent magnet-assisted synchronous reluctance motor via nonlinear disturbance observer

Combined with two approaches of sliding mode control and backstepping control, an adaptive sliding mode–based backstepping control scenario on the basis of nonlinear disturbance observer is proposed to complete maximum torque per ampere control for permanent magnet–assisted synchronous reluctance motor. The constraint relation of permanent magnet–assisted synchronous reluctance motor under maximum torque per ampere control is built, and the design of the controller is elaborated in detail. The uncertainties of modeling errors considering unmatched items are estimated through a presented nonlinear disturbance observer. The adaptive law reflecting the modeling error of the system is constructed. Globally asymptotic stability and convergence of the tracking error for the system are validated through Lyapunov stability criterion. Simulation and experimental results illustrate that external disturbances and uncertainties are observed correctly by nonlinear disturbance observer; the close-loop system controlled by the proposed controller can track the references rapidly and precisely, and the designed controller has a good robust ability.

Performance Analysis of Permanent Magnet Motors for Electric Vehicles (EV) Traction Considering Driving Cycles

This paper evaluates the electromagnetic and thermal performance of several traction motors for electric vehicles (EVs). Two different driving cycles are employed for the evaluation of the motors, one for urban and the other for highway driving. The electromagnetic performance to be assessed includes maximum motor torque output for vehicle acceleration and the flux weakening capability for wide operating range under current and voltage limits. Thermal analysis is performed to evaluate the health status of the magnets and windings for the prescribed driving cycles. Two types of traction motors are investigated: two interior permanent magnet motors and one permanent magnet-assisted synchronous reluctance motor. The analysis results demonstrate the benefits and disadvantages of these motors for EV traction and provide suggestions for traction motor design. Finally, experiments are conducted to validate the analysis.

Sensorless control strategy for light-duty EVs and efficiency loss evaluation of high frequency injection under standardized urban driving cycles

Sensorless control of Electric Vehicle (EV) drives is considered to be an effective approach to improve system reliability and to reduce component costs. In this paper, relevant aspects relating to the sensorless operation of EVs are reported. As an initial contribution, a hybrid sensorless control algorithm is presented that is suitable for a variety of synchronous machines. The proposed method is simple to implement and its relatively low computational cost is a desirable feature for automotive microprocessors with limited computational capabilities. An experimental validation of the proposal is performed on a full-scale automotive grade platform housing a 51 kW Permanent Magnet assisted Synchronous Reluctance Machine (PM-assisted SynRM). Due to the operational requirements of EVs, both the strategy presented in this paper and other hybrid sensorless control strategies rely on High Frequency Injection (HFI) techniques, to determine the rotor position at standstill and at low speeds. The introduction of additional high frequency perturbations increases the power losses, thereby reducing the overall efficiency of the drive. Hence, a second contribution of this work is a simulation platform for the characterization of power losses in both synchronous machines and a Voltage Source Inverters (VSI). Finally, as a third contribution and considering the central concerns of efficiency and autonomy in EV applications, the impact of power losses are analyzed. The operational requirements of High Frequency Injection (HFI) are experimentally obtained and, using state-of-the-art digital simulation, a detailed loss analysis is performed during real automotive driving cycles. Based on the results, practical considerations are presented in the conclusions relating to EV sensorless control.

Optimal Phase Advance Under Fault-Tolerant Control of a Five-Phase Permanent Magnet Assisted Synchronous Reluctance Motor

In this paper, optimal phase advances under fault-tolerant control (FTC) of a five-phase permanent magnet assisted synchronous reluctance motor (PMa-SynRM) have been proposed under different fault conditions. Critical applications where the consistency and safety are the major concerns in automotive and aerospace industries require reliable control systems. The multiphase motor is considered a promising candidate for these applications as it has redundant phases primarily for fault-tolerant operation. However, advanced FTC for a PMa-SynRM with maximization of reluctance torque has been limitedly studied until now. In the conventional approach, to maintain constant magnetomotive force under fault conditions, phase currents of a motor need to increase significantly. However, this will easily saturate the PMa-SynRM resulting in significantly reduced reluctance torque. To overcome this issue, this paper proposes a novel phase current control method that maximizes the reluctance torque with minimum phase current. Here, a phase current control with a novel phase advance has been proposed under various fault conditions. Extensive theoretical and experimental analysis has been carried out to verify the effectiveness of the proposed idea with 5-hp dynamo system controlled by TI DSP F28335.