INVESTIGATING INFLUENCES OF TAPPED SHOE ROTOR POLES ON ELECTROMAGNETIC TORQUES AND RADIAL FORCES OF SWITCHED RELUCTANCE MOTORS

The shape of rotor poles has a significant influence on the performance of electromagnetic torques and radial forces, because the air-gap flux density is depent on the stator and rotor areas and surfaces. Serveral articles have studied influences of the stator/rotor designs on radial forces and electromagnetic torque waveforms as well. Moreover, the electromangetic characteristics of switched reluctance motors are also defined by tapped-shoe-skewing of the stator and rotor poles with the inner holes. However, the total solution designs of the tapped-shoe rotor with diferent tapped angles have not yet implemented by those papers so far. For that, in this paper, the tapped shoe rotor pole design is proposed by different angles for the high speed switched reluctance motor of 30 kW and 18000 rpm.

Electromagnetic Torque Improvement of Doubly Salient Permanent Magnet Machine Using Pole Ratio Adjustment Technique

This paper introduces the pole ratio adjustment technique to improve the torque characteristics of the doubly salient permanent magnetic machine (DSPM). The electrical characteristics of the machine, namely the magnetic field distribution, flux linkage, back-electromotive force (EMF), and cogging torque, were obtained under open-circuit conditions. The electromagnetic torque and ripple torque were examined under the loaded condition. The simulations, based on the 2D-finite element method, show that the optimal pole ratio for the DSPM structure is with 18 stator teeth and 15 rotor poles. This optimal structure achieves a larger phase back-EMF than the conventional structure, as well as had a better magnetic flux path with a reasonable cogging torque. The on-load test also confirmes that the proposed optimal structure can produce a significantly higher electromagnetic torque than the conventional machine while maintaining a satisfactory torque ripple. Furthermore, an experimental prototype of the DSPM structure having 18/15 stator/rotor poles was fabricated and tested to verify the simulations. The experimental results were in good agreement with the simulations. The design technique and the fabricated prototype demonstrate the DSPM utilization for low-speed/high torque applications.

2-D Steady-State Heat Transfer Prediction in Rotating Electrical Machines Taking into account Materials Anisotropy: Thermal Resistances Network, Exact Analytical and Hybrid Methods

This paper presents two-dimensional (2-D) thermal resistances network (TRNM), exact analytical (AM) and hybrid (HM) methods for calculating steady-state temperature and heat flux distribution in rotating electrical machines considering materials anisotropy (i.e., different thermal conductivities in both directions). They are based on the thermal equivalent circuit (TEC), the improved exact subdomain (SD) technique where the solution and thermal conductivities depend on both directions (r, theta) and the coupling between the two methods. TRNM is known as a semi-analytical method that can predict the heat transfer in the machine in less time than finite element method (Fem). The implementation of TRNM by considering the difference between the thermalconductivities in (r, theta) using its equivalence with Fem is presented. The SD technique is improved to consider the difference between thermal conductivities in the directions (r, theta). It is known that the SD technique with non-homogeneous boundary conditions (BCs) is very sensitive to the dimensions of SDs where the harmonics number and the accuracy are lower in small subdomains. Hence, the HM from the TRNM and AM is given to answer these inaccuracies especially in electrical machines with a high number of stator slots and rotor poles. The heat sources are volumetric power losses due to hysteresis, eddy-current, Joule losses and windage losses in all the regions of the machine obtained by a simplified method. The studied problem is conductive with conductive interface conditions (ICs) and convective heat transfer between the machine and the external air and at the rotor internal air. The semi-analytical results are compared between them as well as with those obtained by Fem.

Design and Analysis of the 45kW-Class Magnetic Geared Permanent Magnet Synchronous Motor for Traction of Tram Vehicles

The magnetic geared permanent magnet synchronous motor (MG-PMSM) is a PMSM that has two rotors with different rotation speeds and includes the function of magnetic gear. The design studies of the 45kW-class MG-PMSM are conducted for the application of the driving system for a tram. In this research, first, to derive the detailed model of the 45kW-class MG-PMSM for the tram, the analysis of the characteristics according to the stator winding method was performed. After selecting the winding method that can reduce the size of the MG-PMSM, two design topologies were applied to determine the number of stator poles, the number of outer rotor pole pieces, and the number of inner rotor poles of the MG-PMSM. A 45kW-class MG-PMSM detailed model was derived by applying a design topology that can minimize the size of the MG-PMSM, and it was confirmed that the required performance is satisfied through electromagnetic characteristics analysis. In addition, the 4.5kW-class small-scaled MG-PMSM prototype with concentrated winding was manufactured to verify the validity of the analytical model, and performance verification was performed.

Analysis of Stator-Slot Circumferentially Magnetized PM Machines with Full-Pitched Windings

Stator-slot circumferentially magnetized PM machines (SSCMPMMs) have high fault-tolerant capability. In this paper, the SSCMPMMs with full-pitched windings and different stator slot/rotor pole numbers are investigated, together with the influence of key geometric parameters. It shows that the 12 stator-slots 7 rotor-poles (12S7R) machine delivers the highest torque. It is then compared with the SSCMPMM with tooth-coil windings. The results show that when they have the same active length, the 12S7R machine delivers significantly higher torque and higher efficiency. Furthermore, when the machine length is over around 140 mm, the 12S7R machine is more advantageous in producing high torque and high efficiency. A prototype is manufactured and tested to validate the theoretical analyses.

Procedure for Detection of Stator Inter-Turn Short Circuit in AC Machines Measuring the External Magnetic Field

This paper presents a non-invasive procedure to detect inter-turn short circuit faults in the stator windings of AC electrical machines. It proposes the use of the stray external magnetic field measured in the vicinity of the machine to determine stator faults. The originality introduced by this procedure is the analysis method presented in the paper, which when compared to usual diagnosis methods, does not require any data on the healthy state of the machine. The procedure uses the magnetic unbalance created by the rotor poles and the load variation in faulty cases. The presented method can be applied to induction and synchronous machines used as a motor or generator. It is based on the variation of sensitive spectral lines obtained from the external magnetic field when the load changes. Analytical relationships are developed in the paper to justify the proposed method and to explain the physical phenomenon. To illustrate these theoretical considerations, practical experiments are also presented.

Sinusoidal PWM Techniques in Rotor Pole Segmentation to Reduce Permanent Magnet Synchronous Machine Torque Ripple

Torque ripples can cause mechanical stress in electrical machines, among otherproblems. The present paper proposes three methods to reduce these ripples in the permanent magnets synchronous machine considering rotor poles design. These methods consist in segmenting the rotor poles, with width and distances between segments obtained by SPWM techniques. The modulating wave is a sinwave which has the same frequency as the air gap flux density fundamental harmonic. Method 1 contemplates the unipolar SPWM technique, whereas methods 1 and 2 used the bipolar SWPM technique. Furthermore, the equations used to predict the cogging torque behavior are presented and verified by means of a finite element analysis. The torque ripple reduction is achieved due to the elimination of back-electromotive force harmonics and the decrease in the cogging torque peak. Method 1 has proved to be the most effective, reducing the torque ripple by 51.38% and 76.61% for the 4-pole and 8-pole machines, respectively. In addition, the magnet volume utilized has been reduced by 22.55% for the 4-pole machine, but the average torque value has been reduced by 18.7%. It is worth mentioning that the proposed methods do not require skewing to reduce the torque ripple.

ANN-based optimization approach devoted to the sizing of arbitrary rotor pole geometries of permanent magnet motors for electric motorcycle

Various design approaches have been studied for performance improvement of permanent magnet motors, especially for electric vehicles application. This paper deals with an effective concept that is based on adopting non-traditional geometries for permanent magnet poles. The study focuses on a general methodology for optimal sizing of the rotor poles’ pre-defined geometrical parameters considering certain objectives. For this purpose, the artificial neural network is employed for creating an accurate and simple model to be used in a multi-objective optimization procedure. An interior crescent-shaped permanent magnet motor for an electric motorcycle is studied as a typical case study to prove the performance of the proposed method. Finite element models are developed to create the required dataset for the modeling stage as well as to verify the results.