Design and starting process analysis of multipolar line-start PMSM

When the line-start permanent magnet synchronous motor (LSPMSM) operates stably, sudden change of load torque may result in out-of-step and supersynchronous faults. The currents in stator windings and rotor bars will increase under the two faults, so will the strength of demagnetization field, which is likely to cause the irreversible demagnetization of permanent magnets in LSPMSM. This paper adopts two-dimensional finite-element method (2-D FEM) to analyze the demagnetization characteristics of LSPMSM under out-of-step and supersynchronous faults. The operating points of all positions in permanent magnets are not exactly the same, and the variation of magnets' minimum operating point, which is the minimum value of operating points of all positions in permanent magnets, is used to reflect the variation of demagnetization field strength. The influences of initial load condition, load torque change time as well as the load torque after change are studied, and corresponding conclusions are drawn.

High-efficiency motors are being gradually introduced in many industrial applications because of their positive impacts on the environment by reducing energy consumption and CO2 emission. In this respect, line start permanent magnet synchronous motors (LS-PMSMs) have been introduced recently. Due to their unique configuration, LS-PMSMs allow the obtaining of super premium efficiency levels, accompanied with a high torque and power factor. However, since the use of LS-PMSMs in the industry is in its infancy, no efficient scheme has yet been reported for broken rotor bar (BRB) fault detection in this type of motor. Accordingly, the main aim of this research is to investigate the fault-related feature for BRB faults on LS-PMSMs. In this regard, a simulation model and experimental setup for the investigation of BRB in LS-PMSM are implemented. The detection strategy for BRB in LS-PMSM proposed here is based on the monitoring of the start-up current signal and discrete wavelet transform. The entropy features are used as fault-related features for BRB faults. Finally, the ability of these features is validated for the detection of BRB in LS-PMSM through statistical analysis. In this research, the importance of the starting load is also considered for BRB detection in LS-PMSMs.

This paper attempts to present an optimal design strategy and characteristics of high-power permanent magnet synchronous motor(PMSM) for direct-drive oil drilling mud pump. The structures of stator lamination, rotor lamination and stator winding are analyzed. And how temperature influences the performance of the motor is presented. Moreover, how to calculate air-gap length and the size of permanent magnet of high-power PMSM are discussed. The structure and design method of this motor can be used on other high-power PMSM.

The variation of stator winding turns will directly affect the key parameters of a motor, such as winding resistance and winding reactance, which further affect the steady-state performance of the motor. In order to get excellent steady-state performance from line-start permanent magnet synchronous motors (LSPMSMs) under different load powers, taking an 11 kW LSPMSM as an example, the finite element method (FEM), combined with the steady-state phasor diagram and torque angle characteristic, are used in this paper for the optimal design of the stator winding turns of the prototype. The correctness of the model is verified by comparing the experimental data with the calculated data. First, the influences of different stator winding turns on the no-load, back-induced electromotive force (EMF), as well as on inductance and overload ability are studied, and the variation mechanism is obtained. In addition, from the perspective of the torque angle characteristic, the influence of the change in synchronous inductance caused by the number of turns on the steady-state power angle is studied. Second, the variation of the current and power factors with turn number is obtained by studying the steady-state power angle and end voltage. Based on the coupling relationship between the no-load back EMF and the power angle, the mechanism of non-linear variation of current and power factor is revealed. Finally, the variation of the number of turns on the core loss and eddy current loss is analyzed under various operating conditions, and the variation mechanism is revealed, based on the armature reaction theory.

Pole 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.

A comprehensive comparison of the dynamic and steady state performance characteristics of permanent magnet synchronous motors (PMSM) with interior and surface rotor magnets for line-start operation is presented. The dynamic model equations of the PMSM, with damper windings, are utilized for dynamic studies. Two typical loading scenarios are examined: step and ramp loading. The interior permanent magnet synchronous motor (IPMSM) showed superior asynchronous performance under no load, attaining faster synchronism compared to the surface permanent magnet synchronous motor (SPMSM). With step load of 10 Nm at 2 s the combined effect of the excitation and the reluctance torque forced the IPMSM to pull into synchronism faster than the SPMSM which lacks saliency. The ability of the motors to withstand gradual load increase, in the synchronous mode, was examined using ramp loading starting from zero at 2 s. SPMSM lost synchronism at 12 s under 11 Nm load while the IPMSM sustained synchronism until 41 seconds under 40 Nm load. This clearly suggests that the IPMSM has superior load-withstand capability. The superiority is further buttressed with the steady state torque analysis where airgap torque in IPMSM is enhanced by the reluctance torque within 90° to 180° torque angle.

Purpose. Analysis of the rotor configuration of line start permanent magnet synchronous motor (LSPMSM) when using 3-bar magnet structure with two cases: one with a separating magnetic steel bridge and one without it. Research results allow selecting the appropriate rotor configuration to obtain the best starting characteristics, current, torque, and performance. Thereby, it is possible to replace high efficiency LSPMSM with low efficiency induction motors used in ventilation and water pumping loads to improve the efficiency of electricity use in mining. Methodology. The article uses analytical methods and simulation methods on Ansys/Maxwell software and conducts a laboratory test evaluation to determine the effect of rotor configuration on the starting characteristics, working current, torque ripple, and working efficiency of an LSPMSM for mining applications. Findings. An LSPMSM model was built based on a 15 kW–3,000 rpm induction motor with two rotor configurations: one with a separating magnetic steel bridge and one without it. The results of the study show that when a rotor configuration has no separating magnetic steel bridge, the LSPMSM reaches its maximum speed in 0.45 seconds, a synchronous speed of 3,000 rpm in around 0.75 seconds, a torque ripple of 23.1 %, a current total harmonic distortion of 14.3 %, and a performance of 93.3 %. In contrast, when a rotor structure has a separating magnetic steel bridge, starting the motor is more difficult, taking 1.14 seconds to reach synchronous speed and having a lower starting torque, a current total harmonic distortion of 16.1 %, and a performance of 92.5 %. Originality. Research rotor configurations of LSPMSM based on the 15 kW–3,000 rpm induction motor with and without a separating magnetic steel bridge. The research results allow choosing the appropriate rotor configuration to obtain the best starting characteristics, current, operating torque and performance efficiency. Practical value. The research results are important scientific guidance in the design and manufacture of LSPMSM for application in underground mining to improve the efficiency of electricity use in mining.

Under the crane's working conditions, a Wound Rotor Line-start Permanent Magnet Synchronous Motor (WRLSPMSM) is designed in this paper. Rotor external resistance can be connected to the prototype, and rotor resistance determines when the maximum torque appears. So this paper puts forward a method to improve the starting performance, which PWM chopping is adopted to control rotor external DC fixed resistance. Because the number of rotor external AC resistance is limited, the starting torque has fluctuation when rotor external AC resistance is switched. Rotor external DC fixed resistance is controlled by PWM chopper technology. Regulate the rotor external DC fixed resistance rapidly to reduce torque ripple and realize speed stepless. Detailed theoretical analysis shows that starting torque is mainly affected by asynchronous torque and generated braking torque, and also according the analysis determines the value of rotor external DC fixed resistance. Meanwhile considering the influence of slots per pole per phase q on cogging torque, which easily disturbs the system's precise controlling during the low speed running, the fraction-slot winding is adopted in the prototype. The PWM chopping control method makes the starting process safer and more convenient than asynchronous motor.

With the appearance of high-performance permanent magnet (PM) materials as well as the development of computer technology and nanotechnology and electricity machine theory, scholars have done a lot of research on the self-starting permanent magnet synchronous motor and have made many achievements. Although the starting permanent magnet synchronous motor has many advantages compared with the induction motor, there are also many problems. Since the self-starting motor needs to realise the self-starting and maintaining the synchronous speed operation, its rotor structure design is more complex. The rotor requires the starting winding and the magnets coexist, so there is 'space competition', especially the small motors with high power density. Nowadays, nano-materials are applied on a motor to improve its electromagnetic performance. In this paper, the electromagnetic performance of a PM motor with different metal nano-material bars is researched by finite element analysis (FEA). In this paper, the electromagnetic performance of a PM motor is researched when the rotor bars are with different sizes metal nano-palladium by FEA. The magnetic field distribution, the dynamic speed and torque variation and the eddy current losses are analysed respectively.

Line Start Permanent Magnet Synchronous Motor (LSPMSM) has been proved as an economically feasible, high efficiency alternative to an induction motor where constant speed is desirable. These motors are having the properties of an induction motor during starting and synchronous motor during steady state period. The need of line starting, calls for a cage winding in addition to permanent magnets in the rotor, which increases the complications in rotor design, and restricts the choice of rotor geometries. There is always conflict in the rotor design of this machine. This conflict is in between synchronous and asynchronous performance of the machine which in turn is a conflict between cage and magnet placement in the rotor. This paper reports an attempt in the direction of removing this conflict and optimizes both synchronous and asynchronous performances of the machine. A new two-part rotor geometry is suggested and analyzed using the dynamic model of LSPMSM prepared in Simulink.

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.

This report provides background information on various fractional-horsepower electric motor technologies used for evaporator fan applications in commercial refrigeration and summarizes data from a DOE-sponsored evaporator fan motor laboratory and field demonstration project. This report also extrapolates that data to project the potential economic and environmental benefits resulting from upgrading the current installed base of commercial refrigeration evaporator fan motors to permanent magnet synchronous (PMS) motors.Evaporator fan motors used in commercial refrigeration applications are fractional horsepower in size, responsible for moving air across the evaporator coil, and typically run at one speed. Historically, shaded-pole induction motors have been the most commonly used evaporator fan motors in commercial refrigeration equipment and beverage vending machines. These are the simplest and least expensive type of fractional-horsepower motor, with an efficiency of approximately 20%. Electronically commutated (EC) permanent magnet motors, also known as brushless DC motors, were initially commercialized in the late 1980s, and their use in commercial refrigeration applications has increased within the last 10 to 15 years because of economic incentives and regulatory requirements. State-of-the-art EC motors are approximately 66% efficient. Another induction motor type, the permanent split capacitor (PSC) motor, offers a mid-point between shaded-pole and EC motor price and efficiency levels. PSC motors are typically about 29% efficient.A permanent magnet synchronous (PMS) AC motor that can directly use grid-supplied AC current without the need to rectify to DC has recently been commercialized. This new motor exhibits a peak efficiency of 75% and has the potential to significantly reduce the energy consumption of evaporator fan motors in commercial refrigeration equipment. Laboratory evaluation of evaporator fan motor technologies was performed to quantify and compare the performance of shaded-pole, PSC, EC, and PMS evaporator fan motors in a controlled environment, so as to minimize the influence of external factors and anomalies. The laboratory evaluation included dynamometer testing of the fan motors and airflow testing of the motor/fan assemblies. It was found that the 6–12 W PMS motor exhibited a peak efficiency of 75% with a power factor of approximately 0.9 at a power output of 11 W. It was also found that a 38–50 W PMS motor exhibited a peak efficiency of 82% with a power factor of approximately 0.9 at a power output of 35 W.Airflow testing of shaded-pole, PSC, EC, and PMS motor/fan assemblies was performed using an airflow test chamber, which was designed in accordance with ANSI/AMCA Standard 210-16/ASHRAE Standard 51-16, to measure the performance of the subject motor/fan assembly and to determine the incumbent display case system impedance (AMCA 2016). A family of fan curves (static pressure vs airflow rate and electrical power input vs airflow rate) was generated for the 6–12 W PMS motor/fan assemblies with 8-inch fan blades pitched from 17 to 32 degrees. A similar set of curves was generated for the 38–50 W motors paired with 10 and 12-inch blades. Various incumbent motor/fan assemblies were also tested in the laboratory airflow test chamber and their fan curves were generated.Field evaluation of refrigerated display case evaporator fan motors was accomplished by performing side-by-side comparisons of 6–12 W PMS motors to 6–12 W shaded-pole and EC evaporator fan motors. It was found that, on average, a PMS motor consumes 79% less power and draws 82% less current than a shaded pole motor, and on average, 34% less power and 49% less current than an EC motor. In addition, the PMS motor exhibits an average power factor of approximately 0.82, which is on average 40% greater than that of existing evaporator fan motors.Two field test sites were selected to evaluate the performance of the larger 38 to 50 W PMS evaporator fan motors in walk-in cooler/freezer applications. At each supermarket, two walk-in units were selected for investigation: one walk-in dairy cooler and one walk-in freezer. A 61% decrease in fan motor power was measured when retrofitting existing evaporator fan motors with PMS motors in the walk-in cooler. In addition, a 48% decrease in fan motor power was measured when retrofitting existing evaporator fan motors with PMS motors in the walk-in freezer.The culmination of the field evaluation of fan motor technologies was a whole-store retrofit conducted at a supermarket. Pre- and post-retrofit measurement of evaporator fan motor power in medium- and low-temperature refrigerated display cases and walk-in coolers/freezers was performed. Overall for the whole-store retrofit, the current supplied to all monitored evaporator fan motors was reduced by 52%, the real power was reduced by 46% and the apparent power was reduced by 51% following the retrofit of the 262 evaporator fan motors that w

A new instantaneous torque-control strategy is presented for high-performance control of a permanent magnet (PM) synchronous motor. In order to deal with the torque pulsating problem of a PM synchronous motor in a low-speed region, new torque estimation and control techniques are proposed. The linkage flux of a PM synchronous motor is estimated using a model reference adaptive system technique, and the developed torque is instantaneously controlled by the proposed torque controller combining a variable structure control (VSC) with a space-vector pulse-width modulation (PWM). The proposed control provides the advantage of reducing the torque pulsation caused by the nonsinusoidal flux distribution. This control strategy is applied to the high-torque PM synchronous motor drive system for direct-drive applications and implemented by using a software of the digital signal processor (DSP) TMS320C30. The simulations and experiments are carried out for this system, and the results demonstrate the effectiveness of the proposed control.

In order to estimate the vibration and acoustic noise in a permanent magnet (PM) synchronous motor, the natural frequencies of the stator structure should be determined during the design stage. In this paper, analytical formulas to predict the natural frequencies of the stator are derived. The analytical model of the stator includes stator teeth, winding, stator core, and stator case. It is observed that the natural frequencies calculated with the integrated components exceed those based on the stator core alone only. In order to verify this analytical model, numerical simulation and experimental measurement are carried out using a PM synchronous motor which has 5 pole-pairs and 12 slots structure configuration. Good agreements are observed among the results obtained by analytical formula, simulation and experiment.

This article presents a design improvement of the dual‐pole, two‐speed line start permanent magnet (LSPM) synchronous motor. For this purpose, the operational performance of the motor with dual‐pole structure is first compared with the conventional single‐pole motor to identify its performance limitations. Next, the structure of the dual‐pole rotor is modified accordingly to address the related limitations. The proposed, modified design reduces the number of PMs in the rotor structure and offers a better steady state and transient performance. The motor is analysed using 2D finite element analysis (FEA), and results are verified by experimental tests on the motor prototype.