Tow Leong Tiang

A Comprehensive Analytical Subdomain Model and Its Field Solutions for Surface-Mounted Permanent Magnet Machines

This paper presents a comprehensive analytical subdomain model together with its field solutions for predicting the magnetic field distributions in surface-mounted permanent magnet (PM) machines. The tooth tips and slotting effects during open-circuit, armature reaction, and on-load conditions are considered when deriving the model and developing its solutions. The model derivations and field solutions are extended from a previous model, and can be applied to PM machines with any combinations of slot and pole numbers and any magnetization patterns in the magnets. This model is initially formulated according to Laplaces and Poissons equations in 2-D polar coordinates by the separation of variables technique in four subdomains, such as magnet, airgap, winding slots, and slot-openings. The field solution of each subdomain is obtained applying the appropriate boundary conditions and interface conditions between every two subdomains, respectively, which can precisely account for the mutual influence between slots. Finite element analysis (FEA) is later deployed to validate the analytical results in a surface-mounted PM machine that has nonoverlapping winding arrangement. For validation purposes, PM machines having 3-slot/2-pole with parallel magnetization and 12-slot/10-pole with either parallel or radial magnetizations are used for comparisons. Computation of global quantities for the motor which include the phase back-EMF and cogging torque is also included. The results indicate that the proposed analytical model can accurately predict the magnetic field distributions in each subdomain and the motors global quantities, which are in good agreement with those obtained from the FEA.

Novel MPPT Control in Permanent Magnet Synchronous Generator System for Battery Energy Storage

This paper presents a novel sensorless maximum power point tracking (MPPT) control strategy for capturing the maximum energy from the fluctuating wind speed that being used in the stand-alone small scale variable speed wind turbine generator system (VSWTGS). The generated electricity from the wind turbine systems is used to charge battery energy storage. The whole system including the wind turbine, permanent magnet synchronous generator (PMSG), power converter, filter and lead acid battery has been simulated in Matlab/SimPowerSystem simulation software. The MPPT controller is developed to function as a wind speed estimator to generate an appropriate duty cycle for controlling power MOSFET switch in of the boost converter in order to capture maximum power in variable wind speed. From the simulation results, the power converters and filters are showing good performance in charging the lead acid battery. Besides, the novel MPPT controller is capable of extracting the maximum power from the fluctuating wind speed and exhibits good performance in both steady state and transient condition.

A novel analytical method using virtual PM blocks to optimize magnet segmentations in surface-mounted PM synchronous machines

Infinite numbers of virtual permanent magnet (PM) blocks can be used to represent the segmented magnets per magnet pole in any combination of slot and pole numbers of the semi-closed surface-mounted permanent magnet synchronous machines (PMSMs). This concept is exploited and developed in the two-dimensional (2D) analytical subdomain model to predict the motor performances. The model is able to facilitate the analytical investigation to determine the optimum magnet pole-arcs of each magnet segment and the optimum spacing between the magnet segments. This novel method is then applied to a three-phase, 12s/8p surface-mounted PMSM. It is found that for two segmented magnets (2SM) per magnet pole machine, the optimum settings are 147.6° elect. in each magnet pole and 11.2° elect. of airgap spacing between the magnet segments. By comparing the results to the optimum magnet pole-arc of one magnet segment (1SM) per magnet pole machine, the cogging torque and the total harmonic distortion of the phase back-EMF are significantly reduced by 89 % and 25 %, respectively, where both machines utilize the same PM volume. These analytical results are also validated by the 2D finite element method (FEM), where good agreement has been achieved.

Complete subdomain model for surface-mounted permanent magnet machines

This paper presents a complete and improved analytical subdomain model for predicting the magnetic field distributions in surface-mounted permanent magnet (PM) machines accounting for tooth-tips and slotting effect, during open-circuit, armature reaction and on-load conditions. The model analytical derivations and field solutions are extended to overcome the shortcoming in previous subdomain model, and can be applied on PM machines having any combination of slots and pole numbers and any magnetization pattern in the magnets. This model is initially derived based on Laplaces and Poissons equations in polar coordinates by the separation of variables technique in four subdomains, i.e., magnet region, airgap, winding slots, and slot-openings. The field solutions in each subdomain are obtained by applying the appropriate boundary conditions and interface conditions. Finite element analysis (FEA) is later deployed to validate the analytical results in surface-mounted PM machine having a non-overlapping winding arrangement. The results show that the proposed analytical model can accurately predict the magnetic field distributions in each subdomain in PM machines.

Performance evaluation of permanent split-capacitor single-phase induction motor for ceiling fan application

The parameters of a permanent split-capacitor single-phase induction motor can be estimated by conducting the DC test, blocked rotor test and no-load test which later can be used to facilitate the prediction of motor torque-speed characteristics. To improve further its performance, an exact motor model is simulated and investigated in 2D finite element analysis under influence of different capacitor values, winding turn ratio and impedance ratio. A prototype is built and tested. Experimental results are compared with those obtained in 2D finite element analysis.

Analytical assessment of optimum magnet pole-arc for PMSM under influence of different magnetization patterns

This study aims to predict the optimum value of magnetic pole-arc in designing a surface-mounted permanent magnet synchronous machine (PMSM) under the influence of four different magnetization patterns. Parametric characteristics of the PMSM are evaluated using analytical subdomain model and fast Fourier transform.

ANALYTICAL METHOD USING VIRTUAL PM BLOCKS TO REPRESENT MAGNET SEGMENTATIONS IN SURFACE-MOUNTED PM SYNCHRONOUS MACHINES

This paper describes an analytical subdomain model to predict the magnetic field distributions in the semi-closed surface-mounted permanent magnet synchronous machines (PMSMs) due to magnet segmentations with radial magnetization (RM). The magnet segments per pole can be virtually represented by finite number of permanent magnet (PM) blocks and Fourier decompositions. The model can also determine the optimum magnet pole-arcs for each segment and the optimum airgap spacing between the segments. The analytical model is then applied to evaluate the performance of a three-phase, 12-slot/8-pole, surface-mounted PMSM having two segmented magnets per pole with RM. With design objective for minimum cogging torque and minimum total harmonic distortion in phase back-emf waveforms, we obtain that the optimum settings are 147.6◦ elect. for magnet segment pole-arc and 11.2◦ elect. for airgap spacing between the magnet segments. These analytical results are further compared and validated by 2-D finite element analysis (FEA). Additionally, we also compare the results with those from the optimum magnet pole-arc of one magnet segment per pole machine. It is observed that the cogging torque and total harmonic distortion THDv of the phase back-EMF are significantly reduced by 89% and 25%, respectively, with constraint and assumption that both machines utilize similar total magnet volume.

Analytical Subdomain Model of Surface-Mounted PM Synchronous Machine Using Virtual PM Blocks to Optimize Magnet Segmentations for Underwater Vehicle Applications

This paper presents an analytical subdomain model which can consider infinite numbers of virtual permanent magnet (PM) blocks to represent the segmented magnets per pole in any combination of slot and pole numbers of the semi-closed surface-mounted permanent magnet synchronous machines. From the case study discussed in this paper for a three-phase, 6 s/4p surface-mounted PMSM designed specifically for the underwater vehicle applications, the optimum magnet pole-arcs of the two segmented magnets per pole are 147.0° elect. for each magnet pole and 11.3° elect. for the airgap spacing between the magnet segments. The cogging torque and the total harmonic distortion of the phase back-EMF are drastically reduced by 88 % and 26 %, respectively, when comparing the results to the optimum magnet pole-arc of one magnet segment per pole machine, under similar constraint of PM volume. These analytical results are validated by 2D finite element analysis, where good agreement has been achieved.

Fourier decomposition of segmented magnets with radial magnetization in surface-mounted PM machines

Abstract This paper presents a generic field model of radial magnetization (RM) pattern produced by multiple segmented magnets per rotor pole in surface-mounted permanent magnet (PM) machines. The magnetization vectors from either odd- or even-number of magnet blocks per pole are described. Fourier decomposition is first employed to derive the field model, and later integrated with the exact 2D analytical subdomain method to predict the magnetic field distributions and other motor global quantities. For the assessment purpose, a 12-slot/8-pole surface-mounted PM motor with two segmented magnets per pole is investigated by using the proposed field model. The electromagnetic performances of the PM machines are intensively predicted by the proposed magnet field model which include the magnetic field distributions, airgap flux density, phase back-EMF, cogging torque, and output torque during either open-circuit or on-load operating conditions. The analytical results are evaluated and compared with those obtained from both 2D and 3D finite element analyses (FEA) where an excellent agreement has been achieved.

Influence of magnet pole arc variation on the performance of external rotor permanent magnet synchronous machine based on finite element analysis

Cogging torque is a common design issue in Permanent Magnet Synchronous Machines (PMSMs). Altering the magnet shape is one of the solutions in reducing the cogging torque. This paper addresses the variation in the rotor magnet pole arc which would affect the cogging torque of the external rotor permanent magnet synchronous motor (ERPMSM). Analytical calculations to design a three-phase, 12slot/8pole (12s/8p) ERPMSM with consideration of major parameters and material properties are presented. A two-dimensional (2D) layout of the ERPMSM is constructed and analysed. The variation in reducing the magnet pole arc is modelled and simulated in a commercial finite element software i.e. OPERA 2D, to illustrate its effects on the cogging torque generated in the machine. After which, the paper describes the possible reasons behind the trend of the changing cogging torque exhibited by variation of the magnet pole arc, and its effects on the phase-back electromotive force (EMF) produced by the ERPMSM.