Line-start Permanent Magnet Synchronous Motor Research Articles

A New Method of Reducing the Inrush Current and Improving the Starting Performance of a Line-Start Permanent-Magnet Synchronous Motor

This paper presents a new method of reducing the inrush current and improving the starting performance of a line-start permanent-magnet synchronous motor (LSPMSM). The novelty of the proposed method relies on the selection of the time instant of the connection of the stator winding to the grid, for which the smallest values of the amplitudes of inrush currents are obtained. To confirm the effectiveness of the developed method of limiting the inrush current, simulations and experimental studies were carried out. The algorithm and dedicated computer code developed by the authors for the analysis of transient coupled phenomena in the LSPMSM were used to study the impact of the time instant of connection of the winding to the grid on the motor start-up process. The algorithm was based on a field model of coupled electromagnetic and thermal phenomena in the studied motor. To verify the developed model of the phenomena and the proposed method, experimental research was carried out on a purpose-built computerised test stand. Good concordance between the results of the experiments and simulations confirmed the high reliability of the proposed model, as well as the effectiveness of the developed approach in limiting the inrush current and improving the starting performance of LSPMSMs.

Coil short-circuit in the stator winding of Line-Start Permanent Magnet Synchronous Motor

Coil short-circuit in the stator winding of Line-Start Permanent Magnet Synchronous Motor

Dynamic Model of a Line-Start Permanent Magnet Synchronous Motor Equipped with Hybrid Rotor

Dynamic Model of a Line-Start Permanent Magnet Synchronous Motor Equipped with Hybrid Rotor

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.

Line-Start Permanent Magnet Synchronous Motor Supplied with Voltage Containing Negative-Sequence Subharmonics

In some power systems, the voltage waveform contains frequency components less than fundamental, called subharmonics or subsynchronous interharmonics. Voltage subharmonics can be both positive- and negative-sequence, independent of their frequency (order). Subharmonics exert harmful effects on sundry electrical equipment, especially on rotating machinery; they cause various noxious phenomena, such as a local saturation of the magnetic circuit, increases in power losses and windings temperature, and torque pulsations leading to vibration of unacceptable severity. Notably, previous works reported excessive vibration of rotating machinery only under no-load, while under full load, rather moderate vibration occurred. This study deals with vibration analysis of a line-start permanent magnet synchronous motor (LSPMSM) supplied with the voltage containing negative-sentence subharmonics. Experimental investigations were conducted for a 3 kW, four-pole production LSPMSM for subharmonics of various values and frequencies. Voltage subharmonics of values significantly less than reported in real power systems were found to cause unacceptable vibration, especially under full load.

Effect of Permanent Magnet Structure on Working Characteristics of LSPMSM 3000 rpm

Reducing the cost of electricity to improve production efficiency is one of the urgent tasks. Nowadays, the rapid development of Neodymium rare earth (NdFeB) permanent magnet technology has promoted the creation of high-efficiency motors to replace low-efficiency induction motors to save electricity. One of them is a line-start permanent magnet synchronous motor (LSPMSM). The permanent magnet configuration significantly affects the operating characteristics of the LSPMSM, such as working current characteristics, pulsating torque, working efficiency, and starting speed. The content of the article focuses on investigating and evaluating some permanent magnet configurations affecting the working characteristics of the LSPMSM based on the finite element method through Ansys/Maxwell software. The research results are suggested for the design and manufacture of LSPMSM used in mining to save electricity.

Quantitative assessment on synchronisation capability of a line‐start permanent magnet synchronous motor with hybrid rotor

AbstractThe authors devote a quantitative assessment on the synchronisation capability of a line‐start permanent magnet synchronous motor (LSPMSM) equipped with a hybrid rotor. The quantitative assessment is realised by determining a load criterion consisting of load torques and inertias under which the motor will just synchronise. During the process of load‐criterion determination, close attention is paid to parameters governing the motor synchronisation behaviour. Following the principle of stator‐current error minimisation, the time‐variant magnetising inductances and permanent magnet (PM) flux linkages of the analysed LSPMSM are simplified into slip‐dependent constants via the simple and robust genetic algorithm (GA). The load criterion is then obtained after the establishment of a dynamic motor model involving the simplified parameters. Prototyping tests focused on motor speed‐time responses under different mechanical loads are carried out to validate the obtained load criterion and the paper analyses.

End Effect Equivalence in the 2-D Finite Element Analysis of a Line-Start Permanent Magnet Synchronous Motor with Hybrid Solid Rotor

Reasonable end effect equivalence is of vital importance in the 2-D finite element analysis (FEA) for a line-start permanent magnet synchronous motor (LSPMSM) equipped with a hybrid solid rotor for improved starting and synchronous capabilities. In this work, a series of correction factors are applied to the rotor conductivity to include the end effect in the 2-D FEA model. Derivation of these correction factors completes after the separation of different torque components. A dynamic motor model of the LSPMSM is established with some parameters extracted from the 2-D FEA using the conductivity correction. Outcomes of this model exhibit good agreements with the 3-D FEA results, by which the introduced correction factors are validated to possess the acceptable precision and effectiveness.

An Improved 2-D Subdomain Method Toward Electromagnetic-Performance Analysis of Line-Start Permanent Magnet Synchronous Motor

The 2-D subdomain method (SDM) has proven to be a time-efficient approach suited for determining the magnetic field of permanent magnet synchronous motor (PMSM). However, further application of this method into the field analysis for the line-start PMSM (LSPMSM) is limited by its natural defects including (a) inability to consider the saturation effect of iron material and (b) failure to deal with the rotor eddy currents allowing self-start. In this work, the step-by-step or iterative numerical calculation using the finite difference method (FDM) is embedded into the execution of conventional 2-D SDM, through which an enhanced version addressing all issues as stated above is obtained. The improved SDM avoids limitations of pure analytical method and possesses higher calculation efficiency than that of pure numerical method. Reliability of the presented method is validated by the finite element analysis (FEA) and tests.

Irreversible Demagnetization of a Large Capacity Line-Start Permanent Magnet Synchronous Motors considering Influence of Permanent Magnet Temperature

This paper investigates the irreversible demagnetization (ID) of a large capacity line-start permanent magnet synchronous motor (LSPMSM) considering influence of permanent magnets’ (PMs) temperature. The phenomenon of ID occurs on the pull-in stage and close to the cusp of magnet on the direct-axis direction. The PMs’ temperature causes the demagnetization curve to move down and the knee point to shift up. The extensive area ID of magnet will lead to pulling in synchronism failure and operation at the asynchronous state. A prototype is fabricated to validate the analysis that temperature of PMs will bring more serious ID risk and degradation of motor performance.

Stator Inter-Turn Short-Circuits Fault Diagnostics in Three-Phase Line-Start Permanent Magnet Synchronous Motors Fed by Unbalanced Voltages

This paper addresses the diagnostics of stator faults in three-phase line-start permanent magnet synchronous motors. More traditional fault diagnostic methodologies are unable to properly diagnose stator inter-turn short-circuit faults in three-phase motors under unbalanced supply voltage conditions, since both conditions impact the fault indicators used for inter-turn short-circuit fault diagnostics in a similar way. In this paper, the relation between the symmetrical components of the three-phase quantities and the harmonic components of the Extended Park’s Vector Approach (EPVA) is established. It is proved that the negative component and the EPVA harmonic component at a frequency twice the supply frequency are directly related to the fault occurrence. It is also proved that the healthy motor negative impedance is constant and not load-dependent. Based on this, the negative impedance/admittance is indirectly analyzed, through the combined use of the Extended Park´s Vector Approach of both voltage and current, and is explored for the fault diagnostics. Experimental results, obtained for different load torques, unbalanced supply voltage values, and fault severity levels, show that inter-turn short-circuit fault diagnostics can be achieved even under unbalanced supply voltage conditions based on the analysis of the motor admittance, at a frequency twice the supply frequency, that is the negative sequence admittance.

Comparison of Differential Evolution and Nelder–Mead Algorithms for Identification of Line-Start Permanent Magnet Synchronous Motor Parameters

Line-start permanent magnet synchronous motors (LSPMSMs) are of great interest to researchers because of their high energy efficiency, due to the growing interest of manufacturers in energy-efficient units. However, LSPMSMs face some difficulties in starting and synchronization processes. The LSPMSM lumped parameter model is applicable to estimating the successfulness of starting and further synchronization. The parameters of such a model can be determined using computer-aided identification algorithms applied to real motor transient processes’ curves. This problem demands significant computational time. A comparison between two algorithms, differential evolution and Nelder–Mead, is presented in this article. The algorithms were used for 0.55 kW, 1500 rpm LSPMSM parameter identification. Moreover, to increase computational speed, it is proposed to stop and restart the algorithms’ procedures, changing their parameters after a certain number of iterations. A significant advantage of the Nelder–Mead algorithm is shown for the solving of the considered problem.

A new approach to design line start permanent magnet synchronous motors

<span lang="EN-US">The article describes a new approach to line start permanent magnet synchronous motors (LSPMSM) design process. This different, novel approach is based on the modification of mass-produced induction motors. The presented method facilitates and expedites the electrical motor design process. A field-circuit model of the motor has been created to expound the methodology of the process. Then, the machine's geometry was changed to apply permanent magnets. The problems and benefits associated with the use of permanent magnets were described. The created model was tested. The authors examined the operation of the LSPMSM motor in different states, such as starting, no-load, and blocked-rotor tests. Electromechanical characteristics have been plotted. The simulation results were compared with the parameters and characteristics of the induction motor. The conducted tests proved the correctness of the design process. The operational properties of the motor have been improved. Moreover, the validity of using LSPMSM motors instead of induction motors has also been demonstrated.</span>

Calculation of no‐load induced electromotive force of pole changing line‐start permanent magnet synchronous motor

AbstractPole changing line‐start permanent magnet synchronous motor (LSPMSM) can significantly improve the starting capability of LSPMSM by decreasing the braking torque and pulsating torque during starting process. The fundamental reason for the elimination of braking torque is that there is no generating effect during minor‐pole starting process. That is to say, induced electromotive force (EMF) does not exist when the magnetic field generated by multi‐pole rotor PMs cut the minor‐pole stator winding. Therefore, the induced EMF of pole changing LSPMSM is analysed theoretically and calculated analytically. Considering that the magnetic flux per pole of the coils under the adjacent pole are different, the induced EMFs of a conductor, a full‐pitch coil, a coil group in minor‐pole stator winding are, respectively, calculated, and then the general analytical expression of the induced EMF of a phase winding with different rotor/stator pole ratio is derived. Then, the motors with different rotor/stator pole ratios are simulated based on finite element method to obtain the corresponding EMFs. Meanwhile, a 6/8 pole changing LSPMSM is taken as prototype. The consistency of the simulation, experiment, and the analytical calculation results effectively verify the validity of the derived general analytical expression and theoretical analysis.

Fluid-thermal characteristics of high-voltage line-start permanent magnet synchronous motor based on bidirectional hydraulic-thermal network coupling

This paper concerns the fluid-thermal characteristics of a high-voltage line-start permanent magnet synchronous motor (LSPMSM). A bidirectional hydraulic-thermal network coupling methodology is proposed and applied to the fluid-thermal characteristics calculation. The proposed method can fully account for fluid-thermal interactions to achieve an accurate prediction. According to the structural features of the motor with axial and radial mixed ventilation cooling, the global hydraulic network is established by connecting the local indenter elements and hydraulic resistances. The global thermal network is established based on heat source distribution and heat transfer paths. The temperature rise of the motor ranges from 45.8 K to 84.9 K. The hotspot appears at the lower end-winding on the drive side, and the lowest temperature rise occurs on the nondrive side of the shaft. Moreover, the experimental platform is built to verify the accuracy of the proposed method, and the relative error is 2.2% and 2.9%.

Magnetic Field Prediction for Line-Start Permanent Magnet Synchronous Motor via Incorporating Geometry Approximation and Finite Difference Method Into Subdomain Model

A hybrid computing method for predicting the magnetic field of line-start permanent magnet synchronous motor is presented in this article. The vector magnetic potential (VMP) is selected to be the primary objective of the calculation. For the convenience of expressing the VMP in the polar coordinate system, the topology of each motor component is replaced by the assembly of radial sectors. Along with the topology approximation, the VMPs of the stator and air gap are determined analytically, whereas the finite difference method is used to calculate the VMP of the rotor with the eddy current. Combining the numerical technique with the analytical method not only enables solution efficiency higher than using the former one merely but also keeps away from the inefficacy of using the latter one solely to predict magnetic fields with complex geometry. The presented approach is validated by the finite-element analysis and prototyping tests.

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.

Analytical and FEM Methods for Line Start Permanent Magnet Synchronous Motor of 2.2kW

This paper has developed electromagnetic equations based an analytical model to design a three-phase line start permanent magnet synchronous motor (LSPMSM) of 2.2 kW. In order to enhance the torque and efficiency of this machine, an optimized slot shape of rotor permanent magnet is proposed. The analytical model is first presented to evaluate the magnetic characteristics, and then analytical expressions are derived under the open circuit condition. The influence of the magnet size variables on the analytical model is considered to investigate the magnetic leakage flux and flux density distribution in air gaps. Moreover, the variation of design has a significant impact on the steady-state performance characteristics of this motor. In addition, in order to check the output results from the analytical model, a finite element method is developed to evaluate these solutions. Finally, experimental and simulation results have been compared and analyzed to validate the development of method.

A Study on a Design Considering the Transient State of a Line-Start Permanent Magnet Synchronous Motor Satisfying the Requirements of the IE4 Efficiency Class

In this paper, the transient state analysis of a Line-Start Permanent Magnet Synchronous Motor (LSPMSM) and the optimum design for high efficiency were studied. In the case of an LSPMSM, aluminum bars and permanent magnets are inserted in the rotor. Since it has aluminum bars, it can be directly started on-line without closed-loop control at the time of starting, like an induction motor. Furthermore, once driven, it rotates at a synchronous speed due to the permanent magnets in the steady state. Theoretically, since the rotor bars have no induced current, copper loss does not occur in the rotor bars. Further, because of the inserted permanent magnets, an LSPMSM has a higher power density than an induction motor with the same output power. However, since it is driven directly on-line, the transient state is longer than that of a synchronous motor driven by an inverter. Therefore, it is important to analyze the characteristics of the transient state depending on the rotor shape in the LSPMSM design. In this study, an LSPMSM that has the same outer diameter of a 7.5 kW IE3 efficiency class induction motor currently used for the industry was designed. The optimal design of the motor was designed using Finite-Element Analysis (FEA) and Design of Experiment (D.O.E). In the design process, the velocity ripple was minimized in the transient state, and the steady state was quickly reached. Finally, the efficiency of the motor satisfies the requirements of the IE4 efficiency class, an efficiency standard described in IEC 60034-30, which is an international standard.

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.