Magnet-assisted Synchronous Reluctance Motor Research Articles

Electromagnetic-Thermal Coupled Simulation Under Various Fault Conditions of a Triple Redundant 9-phase PMASynRM

This article performs electromagnetic (EM) and thermal coupled simulation based on two-dimensional (2-D) transient electromagnetic and 3-D thermal model of a triple redundant nine-phase permanent magnet-assisted synchronous reluctance motor under various fault conditions at different speeds. The coupled simulation process is controlled by a scripting file. The resultant temperatures under EM-thermal coupled simulation will be comprehensively compared with those under thermal-only simulation. The predicted current waveforms under fault conditions by the 2-D EM model and predicted temperatures by the 3-D thermal model will be compared with the test results for validation. The outcomes of the study not only gives a better understanding of the thermal behavior, but also provides a guidance to the necessity of the EM-thermal coupled simulation under different fault conditions as well as to determination of the maximum permissible fault detection time before permanent damage due to the fault may occur.

Detection of Inter-Turn Faults in Multi-Phase Ferrite-PM Assisted Synchronous Reluctance Machines

Inter-turn winding faults in five-phase ferrite-permanent magnet-assisted synchronous reluctance motors (fPMa-SynRMs) can lead to catastrophic consequences if not detected in a timely manner, since they can quickly progress into more severe short-circuit faults, such as coil-to-coil, phase-to-ground or phase-to-phase faults. This paper analyzes the feasibility of detecting such harmful faults in their early stage, with only one short-circuited turn, since there is a lack of works related to this topic in multi-phase fPMa-SynRMs. Two methods are tested for this purpose, the analysis of the spectral content of the zero-sequence voltage component (ZSVC) and the analysis of the stator current spectra, also known as motor current signature analysis (MCSA), which is a well-known fault diagnosis method. This paper compares the performance and sensitivity of both methods under different operating conditions. It is proven that inter-turn faults can be detected in the early stage, with the ZSVC providing more sensitivity than the MCSA method. It is also proven that the working conditions have little effect on the sensitivity of both methods. To conclude, this paper proposes two inter-turn fault indicators and the threshold values to detect such faults in the early stage, which are calculated from the spectral information of the ZSVC and the line currents.

Torque Enhancement for a Novel Flux Intensifying PMa-SynRM Using Surface-Inset Permanent Magnet

This paper proposes a flux-intensifying permanent magnet-assisted synchronous reluctance motor (FI-PMa-SynRM) using surface-inset permanent magnet (PM) instead of embedded PM in the rotor. The proposed FI-PMa-SynRM employs a small amount of PM that is inset on the rotor surface facing $d$ -axis instead of facing $q$ -axis as in common PMa-SynRMs. It also differs from conventional flux-intensifying interior PM motor, where the PM is embedded inside the rotor. The proposed motor enables making use of the arrangements of two types of flux barriers (FBs): the cutoff FB and the magnet FB, collectively referred to the outer FBs, to enhance the torque output and reduce the torque ripple. The first objective in this paper is to explain the principles of the proposed FI-PMa-SynRM, and the second is to analyze the proposed technique for enhancement of the torque output with small PM volume while keeping the lowest possible torque ripple. The finite-element analysis is employed to validate the proposed motor and analyses, and the results demonstrate their advantages and effectiveness.

Irreversible Demagnetization Analysis for Multilayer Magnets of Permanent Magnet-Assisted Synchronous Reluctance Machines Considering Current Phase Angle

This paper investigates the demagnetization problem of permanent magnets for permanent magnet-assisted synchronous reluctance motors (PMa-SynRM) and applies “demagnetization ratio” as an index to evaluate demagnetization of permanent magnet (PM). The PMa-SynRM is often designed with multilayer flux barriers to improve saliency and reluctance torque in the rotor. Weaker or less PM (than that for interior PM motors) is embedded into the rotor which could be demagnetized in high-performance operation. PM demagnetization involves temperature, current magnitude, current phase angle, designed PM operating point, or combined effect of the above factors. This work investigates the demagnetization risk for PMs in all the layers of PMa-SynRM rotor considering these factors. In particular, the current phase angle for flux weakening operation is often omitted in demagnetization analysis. First, the motor performance to satisfy the operation condition over a wide speed range is analyzed and the proportion of motor torque components, i.e., reluctance torque and electromagnetic torque, considering temperature is investigated. Then, the flux density distributions on PMs at each position/layer are studied and the PM operating points are obtained based on the variation of excitation current, current phase angle, and temperature in order to evaluate the demagnetization risk. The analysis suggests that the high current phase angle combining the effect of high temperature is the major cause of irreversible demagnetization. Finally, a method incorporating the index “demagnetization ratio” is proposed to redesign the PMa-SynRM to avoid demagnetization. Experiments are conducted to validate the simulation.

Hybrid Adopted Materials in Permanent Magnet-Assisted Synchronous Reluctance Motor With Rotating Losses Computation

This paper presents an optimized design in the permanent magnet-assisted synchronous reluctance motor (PMa-SynRM) rotor structure design with hybrid adopted materials for enhancing the motor characteristics and operation. Two types of permanent magnet (PM) materials are embraced in the PMa-SynRM rotor of rare-earth and ferrite PMs. The optimized design for the PMa-SynRM rotor structure considers the motor magnetic equivalent circuit for reducing the reluctance of the hybrid PMs to improve the motor performance. Moreover, the irreversible demagnetization of the ferrite PM which occurs due to the reversing of the magnetic field of the rare-earth PM is presented. The analytical rotating losses computation with the hybrid adopted materials at the design process is introduced. The rotating losses of the PMa-SynRM are investigated as core, magnet, proximity, ohmic, and friction losses. The core loss in the PMa-SynRM occurs due to the altering of the flux densities in numerous fragments of the iron structures. The loss measurements can be accomplished by measuring the electric parameters of the PMa-SynRM at a defined operating point. The magnetic modeling of the improved 6 KW PMa-SynRM manufactured prototype structure is derived and rotational losses are computed, validated, and compared with the finite element analysis (FEA).

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.

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.

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.

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.

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.

Adaptive Backstepping Based MTPA Sensorless Control of PM-Assisted SynRM with Fully Uncertain Parameters

A nonlinear and robust adaptive backstepping based maximum torque per ampere speed sensorless control scheme with fully uncertain parameters is proposed for a permanent magnet-assisted synchronous reluctance motor. In the design of the controller, the relation to d-q-axis currents constrained by maximum torque per ampere control is firstly derived. Then, a fully adaptive backstepping control method is employed to design control scenario and the stability of the proposed control scenario is proven through a proper Lyapunov function candidate. The derived controller guarantees tracking the reference signals of change asymptotically and has good robustness against the uncertainties of motor parameters and the perturbation of load torque. Moreover, in allusion to the strong nonlinearity of permanent magnet-assisted synchronous reluctance motor, an active flux based improved reduced-order Luenberger speed observer is presented to estimate the speed. Digital simulations testify the feasibility and applicability of the presented control scheme.

Design of Permanent Magnet-Assisted Synchronous Reluctance Motor for Maximized Back-EMF and Torque Ripple Reduction

This paper proposes the optimization of the shape and size of a ferrite magnet and the arrangements necessary to reduce torque ripple and maximize back electromotive force (B-EMF) in a permanent-magnet-assisted synchronous reluctance motor. First, four different models of general magnet arrangements were selected, and analysis using the finite-element method was performed under open circuit and load operations for each of the four models. Next, the relationship between the cogging torque and the torque ripple was analyzed, considering the segment saturation phenomenon. Then, based on the initial model, the design was optimized for maximum B-EMF and minimum torque ripple, and the total harmonic distortion was measured. Finally, the validity and superiority of the optimized design were confirmed by manufacturing a prototype motor and performing the experiment.

Robust Speed Sensorless Control to Estimated Error for PMa-SynRM

Recently, the permanent magnet-assisted synchronous reluctance motor (PMa-SynRM) that can replace induction motor has been more studying because of the needs of the high efficiency motor development for minimum energy performance standard. PMa-SynRM requires the speed and position information of rotor to control motor correctly. However, sensor for rotor information has many problems such as mounting space shortage and the additional system cost. Therefore, in this paper, the speed-sensorless control based on reference model adaptive control is introduced to eliminate the sensor. And mechanical design is improved for control. The proposed method is verified by simulation.

Optimum design and operation analysis of permanent magnet-assisted synchronous reluctance motor

Optimum design and operation analysis of permanent magnet-assisted synchronous reluctance motor

Research of Parameters and Antidemagnetization of Rare-Earth-Less Permanent Magnet-Assisted Synchronous Reluctance Motor

The parameters and antidemagnetization ability of permanent magnet-assisted synchronous reluctance motor (PMaSynRM), with concentrated and distributed windings, was analyzed by the finite-element analysis. The reason that concentrated winding PMaSynRM has worse performance in the utilization of reluctance torque and antidemagnetization ability was pointed out, compared with the distributed one. A method was proposed to further improve the antidemagnetization ability of distributed winding PMaSynRM. The magnetic circuit model of multilayer PM structure, in demagnetization case, was established. The operating point formulation, which can reach the consistency of PM layers, was deduced by solving this model. The main optimal parameters were obtained, and a prototype was made according to this method. Finally, the experimental verification of this proposed method was given.

Energy efficiency improvement adopting synchronous motors

Purpose – The purpose of this paper is to compare different types of electric motor drives for high-efficiency applications: an induction motor (IM) drive, a synchronous reluctance motor drive and a permanent magnet-assisted synchronous reluctance motor drive. An innovative field-oriented analysis technique is applied to estimate the performance of the IM drive. This method of analysis is particularly advantageous in comparing the IM performance to those of synchronous machines. Design/methodology/approach – The comparison among the capabilities of the three electric drives is carried out combining both analytical and finite element methods. Findings – From the analysis, it results that the REL motor exhibits higher torque density than IM, but lower losses since there are no Joule losses in the rotor. On the contrary, the REL motor exhibits a very power factor, which corresponds to a high-volt-ampere ratings of the inverter that supplies the motor itself. Originality/value – A new analysis technique is adopted to investigate and compare the energy efficiency performance of different machines.

Line back-EMF oriented 6/4 pole PMA-SynRM drive based on third harmonic current injection

This paper presents a line back-EMF oriented current vector drive (LBOCVD) that increases torque density and reduces acoustic noise in a three-phase 6/4 pole permanent magnet-assisted synchronous reluctance motor (PMA-SynRM). To implement LBOCVD, three-phase Y-connected windings are excited by three-phase sinusoidal currents with third harmonic component. Torque angle measurement (TAM) is used to control the motor's space current vector, thereby regulate its loading and increase the system's overall efficiency. To verify the high-performance of the proposed drive, a 400 W three-phase 6/4 pole SRM and a PMA-SynRM were operated at the rated load and below 2500 rpm. Experimental results showed that the SRM drive generated maxima of 96 dB acoustic noise, 16 kg cm torque, and 65% system efficiency. In contrast, the PMA-SynRM drive yielded maxima of 70 dB acoustic noise, 30 kg cm torque, 93% system efficiency, and 0.8% steady speed error. The proposed drive is thus very useful for industrial products geared toward energy saving. Copyright © 2010 John Wiley & Sons, Ltd.

Study of Permanent Magnet Optimum Design on the Permanent Magnet assisted-Synchronous Reluctance Motor

Average torque of PMa-SynRM(Permanent Magnet-assisted Synchronous Reluctance Motor) is changed by magnet form inserted to the barrier. Because the magnet structure inserted to the barrier influences to the magnet-torque and reluctance torque. Therefore, this paper present a suitable permanent magnet form design for maximum torque when the magnet quantites are always fixed. And each motor characteristic such as average torque, torque ripple, cogging torque and back-EMF are analyzed by FEM(Finite Element Method) for optimal design.

Comparison of torque capability of three-phase permanent magnet synchronous motors with different permanent magnet arrangement

The paper presents a comparison of torque capability of three-phase permanent magnet synchronous motors with different permanent magnet arrangement. Motors with the following permanent magnet topologies were accounted for in the comparison: the surface-mounted permanent magnet synchronous motor (SMPMSM), the interior permanent magnet synchronous motor (IPMSM), the permanent magnet-assisted synchronous reluctance motor (PMASRM) and the flux reversal permanent magnet motor (FRPMM). Finite element method analysis is employed to determine the performance of each motor. Calculated performance of four-pole IPMSM determined by finite element method calculation is confirmed with the measurements at nearly constant nominal output power in the range of speed 3000–10,000 rpm.