Surface Permanent Magnet Motor Research Articles

Topology Optimization of a Surface Permanent Magnet Motor With High Torque Density

Topology Optimization of a Surface Permanent Magnet Motor With High Torque Density

Study on Decreasing the Rotor Eddy Current Loss of Surface Permanent-Magnet Motors with Copper Sleeves

Study on Decreasing the Rotor Eddy Current Loss of Surface Permanent-Magnet Motors with Copper Sleeves

Study on Decreasing the Rotor Eddy Current Loss of Surface Permanent-Magnet Motors with Copper Sleeves

Study on Decreasing the Rotor Eddy Current Loss of Surface Permanent-Magnet Motors with Copper Sleeves

A Period Energy Method for Demagnetization Detection in Surface Permanent Magnet Motors with Search Coils

Irreversible demagnetization of permanent magnets (PMs) in PM synchronous motors (PMSMs) degrades the performance and efficiency of a machine and its drive system. There are numerous fault diagnosis methods for detecting demagnetization under steady-state conditions. However, only a few works could be found on fault diagnosis under dynamic conditions, whereas the dynamic operation of a motor is a very common scenario, e.g., electric vehicles. The voltage and current signal-based traditional fault detection method is not only affected by the structure of the motor, but it also becomes complicated to extract signals involving fault characteristics. Hence, this paper proposes a search coil-based online method for detecting demagnetization faults in PMSMs under dynamic conditions, which are not affected by the motor structure. To gather the flux of the stator tooth, flexible Printed circuit board (FPCB) search coils are positioned at the stator slot. The search coil is made up of two branches that are one pole apart and arranged in reverse sequence. In this installation option, the output signal in the fault state cannot be eliminated, and the output signal in the health state is zero. This paper defines only that characteristic value related to the position angle of the rotor. Further, the aim was to simultaneously eliminate the influence of elements like the search coil installation error and the inherent dispersion of the permanent magnet on the detection results. To characterize the fault degree, the measurement differential between the health state and the fault state is further integrated according to a predetermined angle range. Last but not least, speed-independent detection of individual permanent magnet demagnetization faults is possible using rotor position and stator tooth flux. A six-phase PMSM was used in experiments to show the efficiency of the suggested approach. The findings of the experiment demonstrate that the suggested strategy may precisely ascertain when a defect will occur.

The development of a high-efficiency aquaculture water pump using self-adhesive electrical steel

Traditional water pump use AC motor combines with gearbox to achieve high torque and low speed to protect fish form injury by blades, which will shorten the life of waterwheel. Besides, the efficiency of the gearbox is about 40 ∼ 50%, resulting in low efficiency of whole system, and translated into poor reliability. The waterwheel in this study uses surface permanent magnet (SPM) motor instead of AC motor. However, the design of conventional waterwheel PM motor has the following drawbacks: (a) the slot fill factor cannot be too low; (b) the spacing between the rotor magnet grooves is too large, which affect the efficiency of the motor. To improve the motor efficiency without changing the shape of the stator core, this study developed an assembled stator core to improve the slot fill rate of motor winding. However, if the stack length of the stator core is too high, there will be a problem of core breakage. Therefore, this study introduced the self-adhesive steel to develop a self-adhesive assembled stator core to improve the breakage situation, and also to take advantage of the higher slot fill rate of the assembled core. Furthermore, in order to solve the problem of large spacing between the rotor magnet grooves, we optimize the magnetic circuit design by using simulation to improve the motor performance, such as magnet size, slot opening size, etc, to make the back electromotive force waveform as a sine wave. In addition, this design also reduces the thickness of magnets to reduce the cogging torque of the motor, and effectively reduces magnet usage to reduce the cost. As a result, this study developed a high-efficiency waterwheel SPM motor about 86.32% at 123 rpm, by using self-adhesive assembled stator core to increase the slot fill factor. The overall efficiency of system reaches about 78.72%.

Performance analysis of various rotor topologies of surface PM synchronous motor

Abstract Surface mounted permanent magnet synchronous motors can be found in several designs regarding configuration of magnets on the rotor. Finding the most optimal design in terms of the high efficiency and power factor, small cogging torque and material consumption along with good overloading capability could be a challenging task. This paper analyzes three different rotor designs of surface permanent magnet motors regarding their magnet shapes. All three motors have the same outer dimensions, output power, torque and the material properties. The comparison of all three models is performed and advantages and drawbacks of each model are pointed out. Four design variables are selected to be varied within prescribed limits for each motor model in order the best combination of number of conductors per slot, magnet thickness, the magnet length and shape to be fond, which result with the highest efficiency, small cogging torque and good overloading capability of the motor. The impact of each varied parameter on motor efficiency and cogging torque is presented. All three optimized model are compared and the most optimal model in terms of the above-mentioned characteristics is analyzed by finite element method (FEM) and with the Simulink. The model in Simulink allows motor transient characteristics to be obtained. The performed analysis is useful for determining the most optimal and cost-effective solution among presented three types of surface mounted permanent magnet motors in terms of the high efficiency and power factor, small cogging torque and material consumption.

Analytical model of electromagnetic torque of surface PM motors considering current harmonicsin electric vehicles

The modeling of the magnetic field, as well as the amplitude prediction and source analysis of torque ripple, are the theoretical basis to reduce the vibration and noise of electric motors. An analytical model of electromagnetic torque of surface permanent magnet motors considering current harmonics, which is capable of purely analytical calculation and theoretical analysis, is proposed in this paper. The open-circuit magnetic field solution considering the stator slot is performed by using the analytical conformal mapping along the deformed solving path, allowing more accurate prediction of the cogging torque. The armature reaction field is derived under any current condition with current harmonics. So far, the analytical model of electromagnetic torque is established, and the purely analytical calculation of torque value and the theoretical analysis of torque ripple characteristics are implemented in an 8-pole-24-slot surface permanent magnet motor used for the propulsion of light electric vehicles. The generation mechanism of constant torque and torque ripple is clarified both under sinusoidal current and harmonic current. Furthermore, the effect of the stator skew slot on the motor torque is well explained to demonstrate the utility of the proposed model. It is found that the skew slot is almost ineffective in mitigating the torque ripple caused by current harmonics.

Mathematical Model Derivation and Experimental Verification of Novel Consequent-Pole Adjustable Speed PM Motor

This paper proposes a novel consequent-pole-type PM motor having a structure different from that of conventional consequent-pole-type PM motors. The proposed rotor structure is composed of a magnetic pole pair using a permanent magnet and an image-pole pair using a high permeability core. The windings facing the magnetic pole pair and the image-pole pair are connected in series in the rotor structure, the three-phase synchronous impedance is balanced, and the d-axis inductance is increased. Therefore, compared with the conventional consequent-pole type, the field weakening operation can be performed efficiently with a lower d-axis current. These advantages make it possible to expand the operating range during field weakening. Furthermore, to fix the driving control method of the proposed consequent-pole PM motor, the voltage equation of the proposed motor is derived and verified by analysis and experiment. In addition, the essential characteristics of the proposed motor were compared with that of a standard surface permanent magnet (SPM) motor and a conventional consequent-pole PM motor.

Performance Analysis of Permanent Magnet Vernier Motor with Surface and Halbach Magnets

Background: Surface permanent magnet motors (SPMVM) and dual permanent magnet motors (DPMVM) have broad prospects in direct drive systems, but some problems occur with large magnetic leakage, large torque ripple and large amount of permanent magnets (PMs). Objective: In order to reduce the torque ripple and magnetic flux leakage of SPMVM and DPMVM, and improve the torque density, a dual permanent magnet vernier machine with Halbach PM array (DHPMVM) is proposed. Method: By air gap permeance method, flux density analysis of three kinds of motors was analyzed, and the main harmonics of SPMVM and DHPMVM are investigated with structure parameters. Electromagnetic characteristics of three motors such as no-load back, electromotive force (EMF), torque, and inductance are compared and analyzed by finite element method (FEM). Results: The study found that under the same size, winding distribution, electrical load and speed conditions, DHPMVM uses Halbach PM array and consequent pole structures to reduce magnetic flux leakage and torque ripple, increase torque density, PM utilization and torque per unit PM volume. Compared with SPMVM and DPMVM, the DHPMVM proposed in this paper has better electromagnetic performance. Conclusion: The DHPMVM topology is the better choice in terms of torque density, torque ripple, and magnet usage among the investigated topologies.

Nonlinear Modeling of MGSPMs Based on Hybrid Subdomain and Magnetic Equivalent Circuitry

The need for combining two mechanical powers with electrical power is a vital part of many applications, such as hybrid electric vehicles. The magnetic geared surface permanent magnet (MGSPM) motor is a compact and efficient way of achieving this goal. However, their complex structure demands time-consuming optimizations, which requires a large number of simulations. In this context, a fast and accurate simulation method is required to reduce the design and optimization time. In addition to speed and accuracy in considering the complex structures of the machine, as the saturation effect has a major impact on the accuracy of the simulations in these machines, it must be included in the method. To tackle this problem, in this article, a hybrid subdomain (SD) and magnetic equivalent circuit (MEC) model is proposed, considering the saturation effect of the iron parts using current distributions in the SD model on the surfaces of modulators and rotor core, as well as in the stator slots. These currents are calculated using the MEC model of the respective parts and Ampere’s law. Furthermore, an example motor is simulated both using the proposed method and the FE method, and the accuracy of the method both for prediction of magnetic flux density inside iron parts and prediction of flux linkages of the machine for a variety of designs and excitations is verified.

Torque imporvement of IPM motors with skewing magnetic designs

In this paper, a type interior permanent magnet synchronous motor designs is proposed for sport scooter application to improve constant torque wide speed performance. Interior Permanent Magnet machines are widely used in automotive applications for their wide-speed range operation and low maintenance cost. An existing permanent magnet motor (commercial QS Motor) is 3 kW-3000 rpm. In order to improve torque and power in wide speed range, a IPM electric motor 5.5 kW -5000 rpm can run up to 100 km/h: An Step-Skewing Interior Permanent Magnet motor alternatives is designed and optimized in detail with optimal magnetic segment V shape. The electromagnetic charateristics of Interior Permanent Magnet motors with V shape are compared with the reference Surface Permanent Magnet motor for the same geometry parameter requirements. Detailed loss and efficiency result is also analyzed at rate and maximum speeds. A prototype motor is manufactured, and initial experimental tests are performed. Detailed comparison between Finite Element Analysis and test data are also presented. It is shown that it is possible to have an optimized Interior Permanent Magnet motor for such high-speed traction application. This paper will figure out optimal angle of magnetic V shape for maximum torque and minimum torque ripple.

Development of Axial-Flux Single-Drive Bearingless Motor With One-Axis Active Positioning

This study proposes a novel axial-flux bearingless permanent magnet motor with one-axis active positioning. This bearingless motor consists of an axial-flux surface permanent magnet motor with coreless coils and a repulsive permanent magnet coupling located at its center. Therefore, it has a single three-phase winding and needs only one three-phase inverter for both rotation and magnetic suspension; it is, thus, referred to as a single-drive bearingless motor. The axial position of the rotor is actively controlled, whereas the radial and tilting motions are passively stabilized. The suspension force and torque are regulated by the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis currents, respectively. The structure of the proposed axial-flux single-drive bearingless motor is presented, and its torque and suspension force are obtained by both theoretical derivation and numerical modeling (using the finite-element method). A prototype machine is fabricated, and the obtained experimental results are presented and discussed.

The Mechanism for Suppressing High-Frequency Vibration of Multiphase Surface Permanent Magnet Motors via PWM Carrier Phase Shifting

Switching-frequency vibration caused by pulsewidth modulation (PWM) is a critical shortcoming of permanent magnet synchronous motor (PMSM) drives in certain applications. This article reveals the mechanism for suppressing high-frequency vibration of multiphase surface permanent magnet (SPM) motors via PWM carrier phase shifting (CPS). The article first introduces a 12-phase SPM drive with three different modes of CPS. Then, it presents an analytical method to calculate high-frequency current harmonics as well as flux and force distributions along stator boundaries. By analyzing the calculated current harmonics and flux distributions under different CPS modes and parameters, the article discovers that CPS greatly alters the spatial distribution of high-frequency stator electromagnetic forces and, thus, significantly changes their zero-order components, which are the major contributors to high-frequency motor vibrations. Finally, the optimal CPS mode and parameter are determined analytically and are validated by experimental results.

Optimization Methodology of PMSM Cooled by External Convection in Aircraft Propulsion

Nowadays, the reduction of aircraft emissions is one of the industrial targets with a horizon time until 2050. The recent progresses in electrical drives give the opportunity to modify the aircraft propulsion based on thermal engine or gas turbine to a hybrid/full electric one. Some problems must be solved: weight, reliability, and the choice of the best configuration for the electric propulsion. One of the most important aspects to solve is the thermal behavior of power converters and electric motors. This paper proposes an optimization procedure for the design of surface permanent magnet motors used for the aircraft propulsion: the aim of the paper is to investigate the possibility of cooling the motor with only the air flow due to the aircraft speed. The optimization procedure has been solved with the integration of analytical model and finite element analysis and using a differential evolution algorithm.

Multidisciplinary analysis of a 750 kW PMSM for marine propulsion including shock loading response

This study presents the electromagnetic, thermal and mechanical analysis of a 750 kW, 1200 rpm, 690 V surface permanent magnet motor aimed at marine propulsion (azimuth thruster). Based on a preliminary machine design, key electromagnetic design aspects including magnet demagnetisation and magnet loss reduction by tangential and axial segmentation are assessed. Then, three different cooling solutions are evaluated via computational fluid dynamics simulations combining the use of a water-jacket surrounding the stator, wafters attached to the rotor structure and the addition of an inner fan. Subsequently, the dynamic design analysis method is applied in order to check the machine's response to shock loadings due to underwater explosions. Finally, a machine prototype is successfully manufactured and tested, showing the proper fulfilment of the design requirements.

Novel Empirical Model for Calculation of Core Losses in Permanent Magnet Machines

This article presents a simple model for the calculation of core losses in permanent magnet machines based on the total flux linkage of the stator winding. In reality, the total core losses will vary as a function of permanent magnet field and the combination of $d-q$ current components even in the case when different $d-q$ currents produce the same amount of stator winding flux linkage at a given speed. The classical model with constant equivalent core loss resistance predicts constant core losses for constant flux linkage which leads to incorrect results. The model presented in this paper expands the classical core loss resistance based model with a novel additional term which corrects the classical model and calculates an additional core loss component as a function of $d$ axis current, total flux linkage of the stator winding, and two constant parameters. The accuracy of the model is confirmed by finite element simulations and core loss measurements for the cases of an interior permanent magnet traction motor and an industrial surface permanent magnet motor (only simulations).

Deadbeat Direct Flux Vector Control of Surface Permanent Magnet Motor Drives

The predictive control algorithms for electrical drives are currently subject to considerable interest and development. In particular, the predictive torque control is a competitive solution that may replace in the future the conventional control schemes based on linear controllers. Therefore, this article proposes a predictive torque control for surface permanent magnet motor drives requiring a wide constant power range. The predictive algorithm uses a deadbeat direct flux vector control approach for the simultaneous control of the stator flux amplitude and torque-producing current component. The proposed control scheme is suitable for applications requiring a wide speed range with current and voltage constraints. The proposed deadbeat torque controller has been tested on a fractional slot permanent magnet machine and the experimental results demonstrate the full drive controllability, including deep flux-weakening operation with limitation of the load-angle.

Permeance Distribution Function: A Powerful Tool to Analyze Electromagnetic Forces Induced by PWM Current Harmonics in Multiphase Surface Permanent-Magnet Motors

This article introduces a new method to analyze electromagnetic forces induced by pulsewidth modulation current harmonics in inverter-fed surface permanent-magnet motors. The concept of the permeance distribution function (PDF) is first introduced with its properties and relation to machine inductances fully explained. Utilizing the concept of PDFs, two methods are proposed to calculate the flux distribution on stator boundaries by armature currents and rotor permanent magnets, respectively. By superposing the stator flux distributions from both sources, the final stator electromagnetic force distribution is obtained. The method is validated by finite-element analysis, demonstrating good accuracy and very fast computation time.

Design and Control Method for a Surface-Mounted Permanent Magnet Motor Drive System With Passive Output Power Network

This article proposes a method to extend the operating area of the surface permanent magnet motor by inserting the passive power networks between the motor and the voltage source inverter (VSI). In the conventional motor drive system, since the operating area is limited by the maximum voltage, which is synthesized by the inverter, the output torque capability is reduced in the high-speed region. In order to extend the operating area, two types of passive power networks are proposed in this article. The power networks supply the reactive power to the motor for amplifying the motor terminal voltage. Due to the actions, the proposed motor drive system can utilize a higher maximum motor terminal voltage than that in the conventional drive systems. Depending on the network types, the operating point at which the maximum power or torque is generated is shifted to a high speed. The design, control, and analysis methods of the proposed system are presented in this article. The effectiveness of the proposed system is verified through the experimental results.

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