Javier Ojeda

Comparative Studies Between Classical and Mutually Coupled Switched Reluctance Motors Using Thermal-Electromagnetic Analysis for Driving Cycles

This paper presents copper and iron loss models of a classical switched reluctance motor (SRM) and a mutually coupled switched reluctance motor (MCSRM). The iron losses in different parts of machines are then detailed. Based on the power losses model, a lumped parameter (LP) transient thermal model during driving cycles is performed, the analytical results are validated by the finite-element (FE) transient thermal model. Special attention has been paid to model the salient rotor and a method to transform the salient rotor into a nonsalient one has been proposed. A comparison between the maximum temperatures obtained by using different heat source (average power losses or instantaneous power losses during driving cycles) is given. The experimental tests are also realized to verify the analytical and numerical results.

Modification in Rotor Pole Geometry of Mutually Coupled Switched Reluctance Machine for Torque Ripple Mitigating

This paper presents a new method to minimize the torque ripple of a 3-phase, 6-slot, and 4-pole mutually coupled switched reluctance motor (MCSRM 6/4). The difference between a MCSRM and a classical SRM is their winding configuration. In a MCSRM, the mutual inductances are no longer neglectable when compared to self inductance. On the contrary, due to mutual inductances, the MCSRM can produce higher average torque than a classical SRM. A literature review is firstly performed to identify the source of high torque ripple level of a MCSRM. Then, the method using punching holes in rotor poles to modify the waveforms of flux as well as derivatives of inductances with respect to rotor position (dL/d and dM/d ) is proposed. Using the 2-D finite-element method (FEM), the influence of dimensions of punching hole on the electromagnetic performances (average torque and torque ripple) is analyzed. The two MCSRM are supplied by three-phase sine wave currents, and comparisons in terms of average torque and torque ripple versus RMS current density are also carried out. In order to make sure that the presence of punching holes does not cause mechanical problems, some mechanical studies are performed. Finally, experimental tests are also realized to validate numerical results obtained by 2-D FEM.

Thermal–Electromagnetic Analysis for Driving Cycles of Embedded Flux-Switching Permanent-Magnet Motors

This paper presents a fast and precise electromagnetic-thermal model of a redundant dual-star flux-switching permanent-magnet (FSPM) motor for embedded applications with driving cycles, e.g., hybrid electrical vehicle (HEV) and aerospace. This model is based on a prior steady characterization by finite-element method (FEM) 2-D of the FSPM motor via calculating the instantaneous torque and the normal and tangential components of the magnetic flux density (Br and Bθ) of each element of the stator and the rotor for different root-mean-square (RMS) current densities and different rotor positions. These results are then used in the analytical copper and iron loss models for calculating the instantaneous copper and rotor and stator iron losses during one driving cycle. The lumped-parameter (LP) and finite-element 2-D transient thermal models are then carried out, in which the previously obtained instantaneous power losses are used as heat sources for calculating the temperatures of different motor parts during driving cycles. In the thermal studies, a transformation of an irregular slot structure into a regular (rectangular) one is applied to simplify the calculation of the winding thermal resistance. The thermal-electromagnetic analysis method in this paper can also be extended for all the other applications with driving cycles. The experimental tests are carried out to validate the analytical and numerical results.

Design of a Flux-Switching Electrical Generator for Wind Turbine Systems

This paper proposes a parametric optimization of a flux-switching electrical machine customized for a wind turbine application with a typical operating range for average and low-power wind energy sites. Statistics of wind resources are taken into consideration for the machine design for definition of the turbine power envelope. Both copper and iron losses for three different machine designs are evaluated. A very important consideration taken in this design is the elimination of gearbox requirements for coupling to the turbine. Although the developed approach makes the machine somewhat voluminous, the overall performance is highly improved because a direct-drive flux-switching electrical generator becomes very competitive for small-scale wind turbines. The design methodology presented in this paper will support widespread application of small-scale wind turbines for rural systems, farms, and villages. This paper concludes by demonstrating that a very cost-effective distributed wind system can be approached with this design.

Comparative Study of Classical and Mutually Coupled Switched Reluctance Motors Using Multiphysics Finite-Element Modeling

This paper presents the numerical modeling of a classical switched reluctance motor (SRM) and a mutually coupled SRM (MCSRM); both have three phases with 12 slots and 8 poles. The multiphysics models have been developed, which can take into account the electromagnetic characteristics, mechanical vibration, and acoustic noise of the foregoing machines. A 2-D electromagnetic model has been used to calculate the magnetic force which is the main source of vibration of the entire motor system. The vibration of the motor is calculated by a mode superposition method, while the acoustic noise is predicted by a 3-D finite-element acoustic model. In order to validate the numerical models, experiments have been carried out. A good agreement between measured and numerical results has been observed, and it is found that the vibration and the noise levels of MCSRM are considerably lower than those of classical SRM.

Fault-Tolerant Control Using the GA Optimization Considering the Reluctance Torque of a Five-Phase Flux Switching Machine

This paper deals with the fault tolerance of a five-phase flux switching machine. Short-circuit currents calculation considering inductances variation is developed. Machine behavior (torque quality, copper losses, and homopolar current) under a single short-circuit phase fault, two consecutive and nonconsecutive phases short-circuited, is simulated with a two-dimensional finite elements (2-D FE) model and validated experimentally. Then, a new method is developed to improve its performances in faulty mode, by reconfiguring reference currents. In fact, an accurate torque model is established and then used in a genetic algorithm to optimize reference currents in faulty mode. In this approach of reference currents computation, the used algorithm has multiobjectives and multiconstraints, thereby allowing choosing the appropriate fault-tolerant current solution according to our application. The torque model is considered to be more accurate and closer to the 2-D FE results in both healthy and faulty modes. Then, a comparison of machine performances in healthy, degraded, and reconfigured modes is presented. Experimental results corroborate the analysis.

Analytical Approach for Mechanical Resonance Frequencies of High-Speed Machines

This paper presents an analytical approach for the determination of the mechanical eigenfrequencies of an electrical machine stator. This model is based on the calculation and the minimization of Rayleighs quotient. It uses an energetic approach from beam theory applied to stators with a Timoshenko kinematic model. This model is very specially adapted for stators with a thick yoke as the high-speed machines. This approach is validated by finite-element simulations and experimental measurements.

Double and single layers flux-switching permanent magnet motors: Fault tolerant model for critical applications

This paper deals a double layer and a single layer Flux-Switching Permanent Magnet (FSPM) motors for a fault tolerant application. The self and mutual inductances of these two machines are calculated, which are then applied for establishing a faulty model. A three phase short-circuit problem is simulated for these two motors. A comparison between these two machines is carried out, which is in terms of normal phase currents and the output torque before and after the failure as well as the short-circuit peak currents against the rotor velocity.

Excitation Winding Short-Circuits in Hybrid Excitation Permanent Magnet Motor

This paper presents two short-circuit fault models of a hybrid excitation flux switching permanent magnet machine, i.e., excitation phase short-circuit and interturn short-circuit in excitation windings. Two-dimensional finite element (FE) method is used to calculate the major parameters, such as armature and excitation inductances, which are not only functions of rotor position, but also of armature and excitation currents. Moreover, in case of short-circuits, the variations of armature and excitation currents are often significant. This in turn leads to an important change in winding inductances. Therefore, in order to precisely predict machine performance under short-circuit conditions, the use of inductances versus rotor position and RMS currents is essential. With the obtained FE results, two MATLAB/Simulink-based models are established. Then, the previously mentioned short-circuits have been studied and their influences on electromagnetic performances, such as armature and excitation currents, speed and torque, armature and excitation copper losses, stator and rotor core iron losses, as well as permanent magnet (PM) eddy current losses are analyzed. Experiments have been carried out to validate the simulations.

Low Computational-cost determination of Vibrational Behavior: Application to Five-phase Flux-Switching Permanent-Magnet Motor

This paper presents a study of the vibrational behavior of a five-phase flux-switching permanent-magnet (FSPM) motor with a low computational-cost. Magnetic and mechanical models are sequentially considered to predict the acoustic noise generated by the structure. After the description of the motor, stress due to magnetic source is obtained by finite element simulations, particularly at the interface between the air-gap and the stator. Then, the most significant eigenmodes of the stator structure, obtained by finite element simulation and by experimental measurements, are presented to determine how the motor is then excited. Finally, from the knowledge of the magnetic excitations and the modal basis, an analytical model is proposed to determine the dynamic behavior of the stator outer surface, instead of a costly dynamic finite element analysis. This model is applied to the five-phase FSPM motor and validated by experimental measurements.