Line-start Permanent Magnet Synchronous Motor Research Articles

Effect of Permanent Magnet Structure on The Performance of LSPMSM with a Power of 22 kW and 3000 rpm

Energy efficiency and sustainability are important goals for countries all over the world. With the advancement of material technology, many new generations of high-efficiency motors are being researched and developed to replace induction motors (IM) to save energy. Line-start permanent-magnet synchronous motors (LSPMSM) are high-performance and ultra-high-performance motors that are emerging as an alternative to squirrel-rotor induction motors. Constructing the permanent magnets in the rotor is critically important in ensuring LSPMSM performance. The study uses the finite element method to analyze the characteristics of the motor. The study presented the influence of the permanent magnet structure in the rotor of the LSPMSM with a power of 22 kW and a speed of 3000 rpm on the electromagnetic field distribution in the motor, as well as the motor’s working characteristics to optimize the permanent magnet structure to optimize the performance of the LSPMSM. The analysis results show that the proposed LSPMSM has a 92.6% higher efficiency than the same-type induction motor. This is a suitable replacement for high-power and high-speed IM, which contributes to energy efficiency, so using fewer fossil fuels to reduce environmental impact is a sustainable development solution.

Design of high-performance explosion proof motor of 3,000 rpm for local exhaust ventilation in underground mining

The power consumption of mine ventilation in general and local exhaust ventilation in particular accounts for a large proportion of the whole mine. Saving energy for the local exhaust ventilation that leads to the reduction of the overall power consumption of the entire mining enterprise is one of the necessary requirements. With the rapid development of rare earth, permanent magnet technology with high magnetic field density, line-start permanent magnet synchronous motor (LSPMSM) is becoming a suggestion of partially replacing for squirrel cage induction motors (IM) to save energy. The present results are a calculation of designing for the LSPMSM of 15 kW, 660/1,140 VAC, 3 phases, 3,000 rpm, and simulation of operating characteristics of the LSPMSM with the rated load of the exhaust ventilation of mine to replace the IM in practice.

Bond graph model of line-start permanent-magnet synchronous motors

The bond-graph (BG) enables to model multi-physics systems in the energy domains. This paper shows that BG models are an alternative, more intuitive and simpler to interpret, graphical tool as compared to existing dynamic models for performance prediction of the line-start permanent-magnet synchronous motors (LSPMSMs). It includes electrical, magnetic, and mechanical energy domains where the stator windings, rotor bars, and permanent magnets are the main components of the model. The dynamical equations of the proposed BG are extracted and solved using the MATLAB ordinary differential equation solver for a sample LSPMSM. The dynamics of the studied LSPMSM is investigated under two operating conditions (1) a healthy motor and (2) a motor with broken rotor bars. The simulation results are compared with the finite-element analysis (FEA) as the most accurate method to simulate the electric motor behaviour. It is shown that the proposed BG model accurately predicts the performance parameters of the motor such as current, torque, and speed under various operating conditions. In addition to the modelling validation, the transient behavior of the LSPMSM are discussed to describe the possible reasons for its behaviour during transient and steady-state operating conditions.

Modelling and experimental verification of temperature effects on back electromotive force waveforms in a line start permanent magnet synchronous motor

PurposeThis paper aims to elaborate the method and algorithm for the analysis of the influence of temperature on back electromotive force (BEMF) waveforms in a line start permanent magnet synchronous motor (LSPMSM).Design/methodology/approachThe paper presents a finite element analysis of temperature influence on BEMF and back electromotive coefficient in a LSPMSM. In this paper, a two-dimensional field model of coupled electromagnetic and thermal phenomena in the LSPMSM was presented. The influence of temperature on magnetic properties of the permanent magnets as well as on electric and thermal properties of the materials has been taken into account. Simulation results have been compared to measurements. The selected results have been presented and discussed.FindingsThe simulations results are compared with measurements to confirm the adequacy of this approach to the analysis of coupled electromagnetic-thermal problems.Originality/valueThe paper offers appropriate author’s software for the transient and steady-state analysis of coupled electromagnetic and thermal problems in LSPMS motor.

Indirect Efficiency Measurement Method for Line-Start Permanent Magnet Synchronous Motors

Despite the great potential and the high performance of energy-efficient line-start permanent magnet synchronous motors (LSPMSMs), their developers face a great deal of difficulties, one of which is the lack of reliable and accurate testing methods for such electrical machines. In this paper, we propose a new method for indirectly determining the efficiency of LSPMSM through the summation of individual loss components. The standard input-output method usually used for these machines is based on torque measurement, requires expensive measuring equipment, and, as a rule, has great uncertainty. Contrarily, the proposed method does not require direct measurement of torque and mechanical power on the shaft and is less sensitive to measurement uncertainties. The theoretical substantiation of the proposed method and its experimental verification using a commercially available four-pole LSPMSM with a rated power of 0.55 kW are presented. Satisfactory convergence of the experimental results obtained using the standard input-output method and using the proposed indirect method is shown.

Sizing by optimization of line-start synchronous motor

PurposeThe purpose of this paper is to develop an algorithm and software for determining the size of a line-start permanent magnet synchronous motor (LSPMSMs) based on its optimization.Design/methodology/approachThe software consists of an optimization procedure that cooperates with a FEM model to provide the desired behavior of the motor under consideration. The proposed improved version of the genetic algorithm has modifications enabling efficient optimization of LSPMSMs. The objective function consists of three important functional parameters describing the designed machine. The 2-D field-circuit mathematical model of the dynamics operation of the LSPMSMs consists of transient electromagnetic field equations, equations describing electric windings and mechanical motion equations. The model has been developed in the ANSYS Maxwell environment.FindingsIn this proposed approach, the set of design variables contains the variables describing the stator and rotor structure. The improved procedure of the optimization algorithm makes it possible to find an optimal motor structure with correct synchronization properties. The proposed modifications make the optimization procedure faster and moreOriginality/valueThis proposed approach can be successfully applied to solve the design problems of LSPMSMs.

Experimental and Simulation Studies of Partial Demagnetization Process of Permanent Magnets in Electric Motors

For the analysis of the process of partial demagnetization of permanent magnets (PMs) in electric machines, a field model of coupled electromagnetic and thermal phenomena was proposed. In the proposed approach the non-linearity of the magnetic circuit, the effect of temperature on the magnetic, electrical and thermal properties of the materials as well as the developed method for modeling the process of partial demagnetization of the PMs were taken into account. In order to verify the usefulness and effectiveness of the developed algorithm as well as software for analyzing the impact of temperature and the process of partial demagnetization of the magnets on the operation of a PM motor, the results of calculations were compared with the results of experimental studies. The experimental tests were carried out on a specially designed and constructed measuring test stand. The results of the research on the process of partial demagnetization of magnets in the line start permanent magnet synchronous motor (LSPMSM) are presented and the conclusions resulting therefrom have been formulated.

Performance verification of novel rotor line start PMSM

In this study, 5.5-kW 1500 rpm IEC-60034-30-1:2014-IE4 super premium efficiency class Line Start Permanent Magnet Synchronous Motor (LS-PMSM) was presented with an innovative rotor design utilizing two different slot types have been used. The slots offered in two different geometries make a significant contribution to the motor in the form of a high starting torque thus increasing the synchronization ability. The prototype was manufactured for the optimal model obtained via analytical methods and Finite Element Software. Torque ripples that pose an important issue for permanent magnet motors were tried to be reduced by way of a skewed stator structure. In addition, motor frame and stator main dimensions were acquired from a standard IE2 induction motor design during the manufacturing of the prototype. Experimental studies for the suggested LS-PMSM topology put forth a 6 % higher efficiency in comparison with low efficiency IE2 standard induction motors with the same shaft power. Results for the starting performance, torque ripples and back-EMF were presented for the prototype motor under a constant load of 0-1.25 p.u. It was verified as a result of the study that LS-PMSMs can be used as an alternative to induction motors in pump and fan industrial applications.

Design and Optimization Techniques in Performance Improvement of Line-Start Permanent Magnet Synchronous Motors: A Review

This article covers the design methodologies and optimization techniques studied in the performance improvement of line-start permanent magnet synchronous motors (LSPMSMs). LSPMSM performance improvement using design techniques are chiefly limited to either the transient or the steady-state performance improvement, and a focus on only the transient performance improvement may degrade the steady-state performance of the LSPMSM and vice versa. Optimization studies of LSPMSMs can be categorized in terms of optimization aim in three classifications: transient performance improvement, steady-state performance improvement, and simultaneous improvement of both transient and steady-state performances. This study indicates the impact of various variables on the LSPMSM performance improvement. The optimization review shows that starting cage optimization without considering the steady-state characteristics as constraints results in synchronous performance degradation. The steady-state performance optimization with transient characteristics as constraints results in a minor synchronous performance improvement though there is the lowest transient performance sacrifice. Multi-objective optimization, including a transient and a steady-state characteristic as individual objectives, resulted in a more optimum LSPMSM with overall performance improvement. Finally, suggestions for optimization implementation of LSPMSMs are presented for future research work.

Motor Current Signature Analysis-based Non-invasive Recognition of Mixed Eccentricity Fault in Line Start Permanent Magnet Synchronous Motor

— In this study, a cost-effective and non-invasive detection strategy is proposed for three-phase line start permanent magnet synchronous motor (LSPMSM) under mixed eccentricity fault using motor current signature analysis. In this respect, theory of air gap magnetic field in eccentric LSPMSM is presented. The detection strategy is examined through modeling and experimental studies. Two-dimensional time stepping finite element method is employed to calculate the motor parameters. Effects of mechanical load and fault severity on eccentric LSPMSM are also investigated. Different fault-related components are scrutinized and the most effective features are identified for this new type of electrical motor. The results indicate that amplitudes of fault-related components at rotor frequency are precise for early detection of mixed eccentricity in LSPMSM. Finally, an efficient frequency pattern as well as detection criterion is specified.

Simultaneous Efficiency and Starting Torque Optimization of a Line-Start Permanent-Magnet Synchronous Motor Using Two Different Optimization Approaches

Line-start permanent-magnet synchronous motors (LSPMSMs) have poorer starting performance than induction motors. Optimization focusing only on transient performance improvement of the LSPMSM may degrade steady-state performance, and vice versa. In fact, an optimization focusing on maximizing starting torque may reduce efficiency by up to approximately 7% and optimizing efficiency may cause degradation in starting torque by 5%. Hence, simultaneous steady-state and transient performance optimization of a 4-kW LSPMSM under a multi-objective function is examined in this study. Efficiency maximization and starting torque maximization are nominated as objective functions. Two different optimization approaches, a gradient-based algorithm and gradient-free algorithm, are employed to optimize the LSPMSM. Sequential nonlinear programming is used as the gradient-based algorithm in this study, and the gradient-free algorithm used is the genetic algorithm (GA). A comparative study of the algorithms’ performance is presented. To provide an inclusive comparison of both algorithms’ performance, a similar optimization study is implemented for a baseline induction motor. The results demonstrate that the multi-objective optimization improves steady-state and start-up performance of both motors. Results indicate that both algorithms converge reliably to almost the same optimum (objective) value. Depending on the nature of the optimization problem, number of design variables, and degree of convergence, the genetic algorithm requires many more evaluations than the gradient-based algorithm. Accordingly, optimization time required by the GA is more than the gradient-based algorithm under similar conditions.

Analysis of rotor asymmetry fault in three-phase line start permanent magnet synchronous motor

This article proposed a detection scheme for three-phase Line start permanent magnet synchronous motor (LSPMSM) under different levels of static eccentricity fault. Finite element method is used to simulate the healthy and faulty LSPMSM with different percentages of static eccentricity. An accurate laboratory test experiment is performed to evaluate the proposed index. Effects of loading condition on LSPMSM are also investigated. The fault related signatures in the stator current are identified and an effective index for LSPMSM is proposed. The simulation and experimental results indicate that the low frequency components are an effective index for detection of the static eccentricity in LSPMSM.

Diagnosis of Inter-Turn Faults Based on Fault Harmonic Component Tracking in LSPMSMs Working Under Nonstationary Conditions

Inter-turn faults are one of the most important issues in line-start permanent magnet synchronous motors (LSPMSMs). To date, steady-state operating conditions of LSPMSMs have been analyzed in studies focusing on diagnosing this fault. However, no studies have been conducted for nonstationary operating conditions, such as variable speed or variable load conditions, which are common in the industry. This paper presents a novel approach for fault harmonic component (FHC) tracking based on transient-MCSA to diagnose inter-turn faults in an LSPMSM operating under nonstationary conditions. First, the inter-turn failure model of LSPMS was analyzed to show the fault effect on motor current, and the most dominant inter-turn FHC in the order and frequency domains were determined. Then, using Gabor-OT, inter-turn FHC signals were extracted from motor current signals in the frequency domain and reconstructed in the time domain. Intrinsic mode functions (IMFs) were calculated by decomposing the reconstructed FHC signals (RFHCSs) via ensemble empirical mode decomposition. Using the energies of RFHCSs, calculated based on Gabor coefficients, and the Kullback–Leibler divergences of the selected IMFs, diagnosis of the inter-turn faults and detection of the severity of the faults was performed. The results are in agreement with the results in the literature, thus showing that the proposed method is a successful and useful means for detecting inter-turn faults in LSPMSMs.

Performance Enhancement of Line Start Permanent Magnet Synchronous Motor With a Special Consequent Pole Rotor

This paper presents the development of line start permanent magnet synchronous motor (LSPMSM) employing a special consequent pole rotor. The proposed rotor structure uses both circumferentially magnetized spoke shape and radially magnetized arc shape magnets. The combination of spoke and arc shape is arranged to provide consequent magnetic poles. This new rotor structure improves the motor performance and consumes less magnet volume. The time-stepping finite element analysis (FEA) is used to evaluate transient and steady state performances. Extensive simulation studies are performed to establish the supremacy of proposed rotor structure over benchmarked spoke and some other known rotor structures. For experimental validation, prototypes of machine are built using (a) proposed magnet configuration, and (b) spoke type configuration having circumferentially magnetized magnets which is used as baseline motor. Rigorous experimental studies are carried out and it is observed that the proposed structure offers 4% improvement in the full load efficiency over the benchmarked spoke rotor LSPMSM yet by saving 10% magnet volume. Further, it is observed that the performance of the proposed machine is enhanced for direct online (DOL) as well as variable frequency drive (VFD) fed supply operation.

Comparison of minimum energy consumption indicators for electric motors powered directly from the mains at part loads

The article presents a comparison of minimum energy consumption indicators for motors powered directly from the mains at part load conditions. The energy characteristics of induction motors and line-start permanent magnet synchronous motors of different energy efficiency classes are compared. As an example, the calculations of proposed energy consumption indicators are provided for the throttle-controlled 2.2 kW pump unit with variable flow-time profile. It is shown that if a motor is used mostly at part load conditions and was chosen by its energy efficiency class only, minimum energy consumption might not be achieved. Universal average efficiency indicator is suggested for motors running at variable loads with output power much lower than the rated power. The comparison shows that the proposed average efficiency does not depend on a specific application or load profile and describes the motor energy consumption enough for practical goals. Thus, this indicator can be used for fast evaluation and selection of a motor by the lowest energy consumption criterion, especially without detailed information about load profile. Calculation of this indicator requires only motor efficiency data per 4 points 25, 50, 75, 100% of rated load.

Analysis of the Partial Demagnetization Process of Magnets in a Line Start Permanent Magnet Synchronous Motor

The paper justifies the validity of analyzing the impact of temperature and the process of partial demagnetization of magnets on the operating parameters of machines. To analyze this impact, a field model of coupled electromagnetic and thermal phenomena in a permanent magnet synchronous motor was proposed. The non-linearity of the magnetic circuit, the effect of temperature on the magnetic, electrical and thermal properties of the materials as well as the developed method of modeling the process of partial demagnetization of the magnet were taken into account. Based on this model, an algorithm and software were developed to analyze the effect of temperature and the process of partial demagnetization of magnets on the work of the line start permanent magnet synchronous motor (LSPMSM). The elaborated software was used to study the effect of temperature during the motor starting phase on the magnetization state of the magnets after the start-up process. The calculation results were compared to the results of experimental studies. The experimental tests were carried out on a specially constructed test stand. The results of the research on the process of partial demagnetization of the magnets are presented and the conclusions resulting therefrom formulated.

An efficient acoustic-based diagnosis of inter-turn fault in interior mount LSPMSM

This paper investigates the use of acoustic signals in diagnosing stator inter-turn faults in Line Start Permanent Magnet Synchronous Motors (LSPMSMs). Singular spectrum analysis (SSA) is proposed to analyze the acoustic signal for fault detection. The proposed methodology involves collection of experimental acoustic data using a smartphone from an interior mount LSPMSM under different loading levels, healthy as well as faulty motor cases where different number of turns are shorted to emulate different fault levels. Acoustic signal for each case is analyzed using SSA, which results in decomposition of the signal into periodic components and noise. Fast Fourier Transform (FFT) of each component is carried out to find the unique frequency representative for each case. The results with the proposed methodology show that it is capable to detect the occurrence of inter-turn fault under different loading levels with the capability of distinguishing fault severity with readily available acoustic sensor of a smart phone. In addition, it is possible to differentiate between the load and no-load modes of operation.

Analytical Calculation of Performance of Line-Start Permanent-Magnet Synchronous Motors Based on Multidamping-Circuit Model

This article presents a new analytical method for calculating performance of line-start permanent-magnet synchronous motor (LSPMSM) based on multidamping-circuit model (MDCM) to take spatial harmonic components of LSPMSM into account. First, MDCM of damping bar in the rotor is established according to Kirchhoff's current law. Second, an eleven-order system of LSPMSM is deduced from a group of differential equations according to the equations of flux linkage, voltage, torque, and motion. Then, starting process of LSPMSM is simulated with the proposed analytical method, including speed, current, and electromagnetic torque waveforms versus time, respectively. The starting performance and synchronization capability are analyzed and compared under different effective value of input phase voltage, moment of inertia, and load torque. The simulation time with finite element method is about 1235 times longer than the simulation time with the proposed analytical method to calculate the starting process of LSPMSM with the same computer. Finally, the validation of the developed analytical method based on MDCM is verified by comparing simulating results with experimental results and direct axis and quadrature axis (DQ) model. The results based on this new method are reliable. It is conducive to calculate, analyze, and design LSPMSM with less time.

Recognition of Stator Winding Inter-Turn Fault in Interior-Mount LSPMSM Using Acoustic Signals

This paper presents a novel stator inter-turn fault diagnosis method for Line Start Permanent Magnet Synchronous Motors (LSPMSMs) using the frequency analysis of acoustic signals resulting from asymmetrical faults. In this method, acoustic data are experimentally collected from a 1 hp interior mount LSPMSM for different inter-turn fault cases and motor loading levels, while including the background noise. The signals are collected using a smartphone at a sampling rate of 48,000 samples per second. The signal for each case is analyzed using fast Fourier transform (FFT), which results in the decomposition of the signal into its frequency components. The results indicate that, for both no-load and full-load conditions, 39 components are observed to be affected by the faults, whereby their amplitudes increase with the fault severity. The 40-turns fault shows the highest difference in the component amplitudes compared with the healthy condition acoustic signal. Therefore, this diagnostic method is able to detect the stator inter-turn fault for interior mount LSPMSMs. Moreover, the method is simple and cheap since it uses a readily available sensor.

Design of a Large Capacity Line-Start Permanent Magnet Synchronous Motor Equipped With Hybrid Salient Rotor

This article presents a successful design of a three-phase large capacity line-start permanent magnet synchro nous motor (LSPMSM) developed for industrial applications. A hybrid rotor containing both slotted solid steels and cage bars is included in the designed LSPMSM to enhance the motor starting and synchronizing abilities. A salient rotor periphery making air-gap length, which maximizes at the quadrature axis and minimizes at the direct axis, is employed to reduce the harmonics of air-gap flux density and motor losses. The implementation of a genetic algorithm coupled with a neural network optimizes the rotor-periphery saliency ratio and other crucial dimensions for further performance improvement. Finite-element analyses highlight the advantages of the designed LSPMSM by comparing its performance indexes with those of a conventional cage-rotor LSPMSM. The effectiveness of the designed motor is validated by a series of prototype tests.