Line-start Permanent Magnet Motor Research Articles

Notice of Violation of IEEE Publication Principles: Performance Improvement of a Line-Start Permanent-Magnet Synchronous Motor

Notice of Violation of IEEE Publication Principles Performance Improvement of a Line-Start Permanent-Magnet Synchronous Motor by Solmaz Kahourzade, Amin Mahmoudi and Wooi Ping Hew, in the IEEE Transactions on Industrial Electronics After careful and considered review of the content of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE's Publication Principles. This paper was submitted with significant similarity to ideas and applications presented in the thesis listed below. The paper includes a reference to the thesis, but there was no clear delineation between their work and previous work presented in the thesis. Two of the authors, Solmaz Kahourzade and Amin Mahmoudi were found to be responsible for the misconduct. Line Start Permanent Magnet Motors, by Arash Hassanpour Isfahani, in Ph.D dissertation, Department of Electrical Engineering, Tehran University, Iran, 2011. This paper presents the design and performance analysis of a line-start permanent-magnet synchronous motor to overcome the efficiency and power factor deficiencies of induction motors. Proper start-up and synchronization are considered. An optimization algorithm is applied to improve the rotor bar resistance for the smooth line start of the motor. Dynamic d-q modeling and finite element analysis are performed to predict the transient and steady-state performances of the motor. Based on the presented optimized design, a 3-phase, 4-pole, 2 kW line-start permanent-magnet synchronous motor is fabricated and tested. Simulation and experimental results validate the improved performance of the proposed optimized motor.

Exploring the Effects of Voltage Variation and Load on the Electrical and Thermal Performance of Permanent-Magnet Synchronous Motors

Europe has initiated the transition process toward IE4 efficiency motor classes, setting an example for other regions to follow in adopting higher-efficiency motor standards. However, in some regions, the operating voltage may differ from the nominal voltage according to the IEC 60038-2009. Therefore, the performance of new technologies under conditions of voltage variations (VVs) must also be assessed. This study presents a comprehensive analysis of a 0.75 kW line-start permanent-magnet motor (LSPMM) under different VV magnitudes, including undervoltage and overvoltage, while considering different load conditions. The study incorporates technical, economic, statistical, and thermal analyses to obtain important indicators related to power consumption, efficiency, power factor, and temperature. This study provides valuable insights to specialists regarding the technical and economic impacts of voltage-magnitude variation on LSPMMs.

Investigation of the Effect of the Voltage Drop and Cable Length on the Success of Starting the Line-Start Permanent Magnet Motor in the Drive of a Centrifugal Pump Unit

The use of Line-Start Permanent Magnet Synchronous Motors (LSPMSM) improves the efficiency of conventional direct-on-line electric motor-driven fluid machinery such as pumps and fans. Such motors have increased efficiency compared to induction motors and do not have an excitation winding compared to classical synchronous motors with an excitation winding. However, LSPMSMs have difficulty in starting mechanisms with a high moment of inertia. This problem can be exacerbated by a reduced supply network voltage and a voltage drop on the cable. This article investigates the transients during the startup of an industrial centrifugal pump with a line-start permanent magnet synchronous motor. The simulation results showed that when the voltage on the motor terminals is reduced by 10%, the synchronization is delayed. The use of the cable also leads to a reduction in the voltage at the motor terminals in a steady state, but the time synchronization delay is more significant than that with a corresponding reduction in the supply voltage. The considered simulation example shows that the line-start permanent magnet synchronous motor has no problems with starting the pumping unit, even with a reduced supply voltage. The conclusions of this paper support a wider use of energy-efficient electric motors and can be used when selecting an electric motor to drive a centrifugal pump.

Virtual Modeling and Experimental Validation of the Line-Start Permanent Magnet Motor in the Presence of Harmonics

The world is experiencing an accelerated energy transition that is driven by the climate goals to be met and that has driven the growth of different potential sectors such as electric mobility powered by electric motors, which continue to be the largest load globally. However, new needs in relation to power density, weight, and efficiency have led manufacturers to experiment with new technologies, such as rare earth elements (REEs). The permanent magnet motor is a candidate to be the substitute for the conventional induction motor considering the new editions of the IEC 60034-30-1, for which study and evaluation continue to be focused on identifying the weaknesses and benefits of its application on a large scale in industry and electric mobility. This work presents a FEM model to assess the line-start permanent magnet motor (LSPMM), aiming to simulate the behavior of the LSPMM under supply conditions with distorted voltages (harmonic content) and evaluate its thermal and magnetic performance. The model created in the FEM software is then validated by bench tests in order to constitute an alternative analysis tool that can be used for studies in previous project phases and even to implement predictive maintenance schemes in industries.

Analysis and Prediction of Cogging Torque and ripples in output Torque of Permanent Magnet Synchronous Motor and Line Start Permanent Magnet Synchronous Motor

Permanent magnet (PM) motors are rapidly replacing the squirrel cage induction motors for its energy efficient operation, smooth control and high power density. Although PM Motors are energy efficient, they are inherently affected by cogging torque and torque ripple. Magnetic alignment between teeth of stator and permanent magnet of rotors produce cogging torque. Torque ripple is a dynamic oscillation during steady-steady operation which leads to various mechanical anomalies like vibration, noise and rotor stress. Torque ripple is produced in PM motors because of non-sinusoidal distribution of flux, saturation, improper selection of slots etc., these ill effects will deteriorate the starting and steady-state performance of motors. So it is very vital to make analysis and prediction of cogging torque and torque ripples to make the motor more effective. Now a day's minimizing the torque ripples and cogging torque are gaining importance in PM motor designs. In this proposed work, the cogging torque analysis and torque ripple analysis of permanent magnet motor and line start permanent magnet motor has been done and reported.

Assessing Energy Efficiency and Power Quality Impacts Due to High-Efficiency Motors Operating Under Nonideal Energy Supply

The search for more competitive equipment in the global market has led to the implementation of new materials and technologies in the search for greater energy efficiency. This is certainly a guideline followed by the electric motor industry that has introduced new technologies in rotating machines, such as the permanent magnet motor, evolving into increasingly efficient motor classes. However, subjecting these efficient motors under nonideal electric grid power conditions, such as voltage unbalance, can cause these efficient machines to generate additional distortions in the voltage and current waveforms, which in turn not only affect the performance of electric motors themselves but also that of the electrical system in general. This work presents a comparison between energy efficiency gain and the corresponding power quality degradation through a detailed harmonic analysis of the effects of voltage harmonics and voltage unbalance in three 0.75-kW electric motors classes: IE2, IE3, and IE4, The results show that for increasing percentages of a specific harmonic distortion, other harmonics are also increased in the higher efficiency electric motors sample analyzed, and similar responses were also observed for large percentages of voltage unbalance, mainly in the line-start permanent magnet motor class IE4. The results achieved are interesting but rigorously reflect only the tested motor sample and cannot be generalized to all motors, in other power ranges, of the respective motor classes tested. For generalization, exhaustive tests must be accomplished to formulate general conclusions according to the electric motors’ classes commercially available.

Optimal Design of Line-Start Permanent Magnet Synchronous Motor Based on Magnetic Equivalent Parameters

This paper used a lumped magnetic parametric approach-based analytical technique to design the 7.5 kW, three-phase line start permanent magnet (LSPM) motor. In order to enhance the efficiency and power factor (PF) of the prototype LSPM machine, an optimized slot shape of rotor permanent magnet (PM) was selected. The lumped magnetic circuit model is developed to present the magnetic characteristics, and analytical expressions are derived under the open circuit condition. The impact of the design variables on the analytical model air gap flux density distribution and magnetic flux leakage is studied for the LSPM. The design variables have a significant influence on the steady-state performance characteristics of the LSPM motor. Therefore, to verify the output results of the purposed model, the two-dimensional finite element analysis (FEA) was evaluated for the numerical solution of the analytical model.

Improvement of Starting Performance for Line-Start Permanent Magnet Motors by Winding Reconfiguration

Line-start permanent magnet (LSPM) machines have significant advantages in efficiency and power factor compared with regular induction motors; however, the poor starting torque and synchronization capability prevent the widespread of LSPM machines. In this article, winding reconfiguration methods are proposed to improve the starting performance and steady-state performance of LSPM machines. The turns-changing method is to increase asynchronous torque by reducing coil turns in starting, and the pole-changing method is to reduce and even eliminate the permanent magnet (PM) braking torque by changing the pole pair number of stator windings in the early starting period. Both of them can be adopted for an LSPM machine simultaneously to improve average torque in the starting stage. The starting performance is also compared between the turns-pole-changing LSPM machine and pole-increasing LSPM machine. Finite-element analysis is carried out to show the performance differences of LSPM machines using different starting strategies. A turns-changing LSPM machine is also manufactured and tested to validate the starting improvement.

Analytical Modeling for Optimal Rotor Shape to Design Highly Efficient Line-Start Permanent Magnet Synchronous Motor

In this study, an analytical technique for the rotor geometry optimization based on lumped magnetic parametric approach is used to design a two-pole, three-phase, 7.5-kW line-start permanent magnet (LSPM) synchronous motor. The permanent magnet shape substantially affects the air-gap flux density distribution, back electromotive force (EMF) as well as the copper loss, which have a great impact on the performance characteristics of the permanent magnet synchronous motors. Principal advantages involve in adjusting the rotor shape are to achieve the effective air-gap flux density and optimize the fundamental component of the back EMF with low harmonic content for minimum ripple torque. Therefore, to enhance the efficiency (η) and power factor, an optimized slot shape considering various design parameters is selected for the permanent magnet of the rotor in the prototype LSPM machine. A linear saturated lumped magnetic parametric model is developed to exhibit magnetic characteristics, and analytical equations are acquired under the open-circuit condition without considering the slotting effect for design simplicity. The influence of design variables on the air-gap flux density distribution and the flux leakage is investigated precisely using an analytical circuit model. A parametric study of the prototype model demonstrates that the steady-state performance of the LSPM motor are significantly influenced by the design variables. The inductance saliency ratio and electromagnetic torque components are carefully analyzed in terms of their effects on the load characteristics of the LSPM motor in order to determine the optimal shape of the PM slots and the magnetic flux barriers. The validity of the proposed method has been checked by evaluating the numerical solution of the analytical model using a two-dimensional finite element method.

Irreversible Demagnetization analysis of the Line Start Permanent Magnet Motor Using Time Stepping Finite Element Method

In recent years Line Start Permanent Magnet (LSPM) motor has attracted a lot of attention thanks to many advantages, such as high efficiency, high power factor, and high power density. In this motor, at the start, the risk of irreversible demagnetization in Permanent Magnet (PM) is essential due to the large inrush current. So in this paper using Finite Element Method (FEM) the effective factors on demagnetization of this motor structure at various temperatures will be investigated. In addition, the sensitivity analysis will be carried out. Finally, the electromagnetic torque of this motor using a modified FEM algorithm will be calculated and compared to the conventional FEM algorithm.

Investigation of the transient and steady state operations of two Line Start Permanent Magnet Motors (LSPMMS) with different rotor configurations

This paper investigates the transient and steady state operations of two Line Start Permanent Magnet Motors (LSPMMs) with different rotor types. The calculations showed that both designs can reach a higher efficiency than comparable induction motorsof the same size. The loading capability of the Surface Permanent Magnet (SPM) rotor is better than the Interior Permanent Magnet (IPM) rotor on asynchronous rotation as it has lesser torque ripples. However, IPM rotor had less flux leakage and copper losses at the synchronous operation under the same loading conditions.The results of the investigation also show that IPM motor attains a higher speed responses than SPM motor but SPM motor synchronizes faster than the IPM motor under the same loading conditions. During the asynchronous period, the chracteristics of both machines display similar features at a lower load torque less than 50N-m. The ripple contents of IPM is greater than that of SPM as can be observed in the run-up speed characteristics where IPM shows spontaneous overshoot. The pull out torque for SPM and IPM occurred at the time of 6 and 10 second respectively with same load increments. Keywords: synchronous, asynchronous, motor, permanent magnet, torque

An Improved Analysis Method of Irreversible Demagnetization for a Single-Phase Line-Start Permanent Magnet Motor

This paper presents an effective analysis method of irreversible demagnetization for a line-start permanent magnet (PM) motor considering the magnetic field produced by secondary conductor bars. The magnetic field produced by the secondary conductor bars opposes the variation of the magnetic field caused by the primary part, and these result in the reduced magnetic field acting on the PM. By using finite element analysis in the transient magnetic field, currents in the primary and secondary conductors are estimated and used for demagnetization analysis of the magneto-static field. Therefore, conditions closer to actual situations can be achieved. Both the general demagnetization analysis method, using only primary currents, and presented analysis method are compared and the results are verified by experiments. General demagnetization analysis leads to over-estimation of the magnetic field acting on the PM, and results in excessive PM usage.

Design Procedure and Optimal Guidelines for Overall Enhancement of Steady-State and Transient Performances of Line Start Permanent Magnet Motors

This paper proposes a design procedure in addition to some optimal design guidelines for line start permanent magnet (LSPM) motors, independent from their ratings. Major transient and steady-state characteristics of LSPM motors, including magnet braking torque, synchronizing torque, efficiency, and power factor, are analyzed with respect to the main motor design parameters, i.e., motor back electromotive force, reactances, and saliency ratio. The contradicting behaviors of the motor characteristics with respect to the motor parameters are fully investigated. Design guidelines are developed to wisely compromise the performance characteristics by selecting optimal parameters. A design procedure considering the guidelines is proposed. By following the procedure and guidelines, an LSPM motor is designed and optimal values of the motor parameters are determined. Accordingly, a prototype LSPM motor is built and tested. The finite element method (FEM)-based simulation results in close agreement with the experimental results confirm superior steady-state and transient performance characteristics of the motor, thus validating the developed guidelines and the proposed design procedure.

Line start permanent magnet motors with double‐barrier configuration for magnet conservation and performance improvement

This study proposes a new configuration for line start permanent magnet (PM) motors with low consumption of PM material, providing improved performance. The configuration is developed by analysing PM flux density distribution in the machine airgap and focusing on the d-axis armature reaction flux path and also different magnetisation types in the PM poles. It features double flux barriers for each rotor pole to facilitate near sinusoidal flux density distribution. Main characteristics of a motor with the proposed configuration are analysed by finite element method (FEM) and compared with the characteristics of a motor with the conventional configuration. Finally, the motor is built and tested. The FEM and experimental results verify the advantages of the proposed configuration. The results show that the required PM material reduces by one-third, while desirable performance is provided. The machine is capable of working with delta connection causing negligible circulating current and low torque ripples.

Influence of the shape of squirrel-cage bars on the dimensions of permanent magnets in an optimized line-start permanent magnet synchronous motor

PurposeThe purpose of this paper is to compare parameters and properties of optimal structures of a line-start permanent magnet synchronous motor (LSPMSM) for the cage winding of a different rotor bar shape.Design/methodology/approachThe mathematical model of the considered motor includes the equation of the electromagnetic field, the electric circuit equations and equation of mechanical equilibrium. The numerical implementation is based on finite element method (FEM) and step-by-step algorithm. To improve the particle swarm optimization (PSO) algorithm convergence, the velocity equation in the classical PSO method is supplemented by an additional term. This term represents the location of the center of mass of the swarm. The modified particle swarm algorithm (PSO-MC) has been used in the optimization calculations.FindingsThe LSPMSM with drop type bars has better performance and synchronization parameters than motors with circular bars. It is also proved that the used modification of the classical PSO procedure ensures faster convergence for solving the problem of optimization LSPMSM. This modification is particularly useful when the field model of phenomena is used.Originality/valueThe authors noticed that to obtain the maximum power factor and efficiency of the LSPMSM, the designer should take into account dimensions and the placement of the magnets in the designing process. In the authors’ opinion, the equivalent circuit models can be used only at the preliminary stage of the designing of line-start permanent magnet motors.

Optimum design of a line‐start permanent‐magnet motor with slotted solid rotor using neural network and imperialist competitive algorithm

Slotted solid-rotor line-start permanent-magnet motors have good synchronisation capability for high load torques and moment of inertia. This study presents the impacts of rotor-slot parameters such as the slot depth and width to obtain better synchronisation capability. Therefore, the starting torque and the torque near synchronisation speed are considered. For high synchronisation capability these torques should have higher values. To obtain optimum parameters, the artificial neural network and the imperialist competitive algorithm are used. The results obtained show that the values of parameters are very close to the outcomes of the sensitivity analysis. Finally, a four-pole, 1500 rpm, 1050 W, three-phase line-start synchronous motor with an optimised slotted solid rotor is prototyped to confirm the validity of the results.

Comparison of Protection Requirements in IE2-, IE3-, and IE4-Class Motors

In this paper, an overview of the main motor features influencing the protection devices settings is presented, pointing out key differences between three-phase direct-on-line (DOL) motors of different efficiency classes. The results of experimental tests and simulations are presented and discussed in the scope of the motor protection against overload, short-circuit, current unbalance, and locked-rotor conditions, for 7.5-kW, four-pole, IE2- and IE3-class squirrel-cage induction motors (SCIMs) and for IE4-class line-start permanent-magnet motors (LSPMs), offering important data related to their electrical and thermal behaviors. Two commercial digital thermal-magnetic motor protection devices, whose thermal models were designed for IE1- and IE2-class motors, are evaluated in terms of operation effectiveness in the tested motors. This paper is important for industry due to the significant penetration of IE3-class induction motors, as well as to the recent introduction into the market of IE4-class induction motors and LSPMs.

Design and Analysis of a Two-Speed Line Start Synchronous Motor: Scheme One

Line-start permanent magnet motors have many advantages, such as high efficiency, high power factor, high power density, and good thermal performances. Also, they do not need to use an inverter in comparison with brushless dc motors. The mentioned advantages have introduced these motors as a good alternative for induction motors in industry. However, there are some drawbacks that limit the use of them. One of these drawbacks is that line start permanent magnet (LSPM) motors could only rotate at one speed due to the fixed polarity of permanent magnets. This matter limits the implementation of LSPM motor for some applications that need two rotating speeds, such as fans and pumps. This paper presents a good scheme that enables LSPM motors to rotate at two different speeds. This scheme is based on combining LSPM motor with synchronous reluctance motor. To validate the proposed scheme, the designed motor has been analyzed by using finite-element method. Simulation results verify the theoretical findings, and show that the proposed scheme leads to good performances at both low- and high-speed operation of the motor.

Modelo de capas para motores encapsulados de imán permanente con arranque en línea

This paper describes the concept of ‘canned pump’ and the analysis of the canned motor. The motor is integrated directly into the pump and operates as a line-start permanent-magnet motor. It has two cans one in the stator and the other in the rotor. The rotor containment can provide a dual function: acting as the induction element to provide the line-start capability and provides a protection to the rotor against the fluid being pumped. The paper describes the development of an analytical pseudo-3D model based on the layer theory and demonstrates how the conventional approach can be modified to accommodate voltage-forced solutions and synchronous operation. The model is validated experimentally using a 10kW prototype pump motor and the model is used to examine the influence of certain design features such as the thickness of the rotor containment, the rotor magnets strength and the overhang length of the stator containment can.

ANALYTICAL SYNCHRONIZATION ANALYSIS OF LINE-START PERMANENT MAGNET SYNCHRONOUS MOTORS

A main challenge in designing line-start permanent magnet synchronous motors is synchronization analysis and determination. The transient time-step finite element simulations are often required in the design process, which is computationally expensive. An attractive alternative is to use an analytical synchronization model, which is time efficient and thus viable to be included in an optimization procedure. In this paper, two variants of the energy-based analytical synchronization model are proposed. Their viability and performance are compared with those of the existing analytical method and validated by transient finite element simulations. It is shown that the proposed methods have a better resolution and accuracy in determining the synchronization status of line-start permanent magnet motors.