Wasi Uddin

Design Methodology of a Switched Reluctance Machine for Off-Road Vehicle Applications

This paper presents the design of a switched reluctance machine (SRM) for off-road hybrid electric vehicle applications. SRMs are ideally suited for this application for their low cost, fault tolerance, and reliable operations. A multistage fast design methodology for SRM is presented in this paper. The process aims to determine the best speed at which the SRM would start single-pulse mode operation. This ensures the best efficiencies over the specified operating range. The machine is initially designed at that operating point using analytical design tools and then further optimized through finite-element analysis (FEA). The designed machine has been prototyped and then experimentally tested.

Analytical modeling of a novel transverse flux machine for direct drive wind turbine applications

This paper presents a nonlinear analytical model of a novel double sided flux concentrating Transverse Flux Machine (TFM) based on the Magnetic Equivalent Circuit (MEC) model. The analytical model uses a series-parallel combination of flux tubes to predict the flux paths through different parts of the machine including air gaps, permanent magnets (PM), stator, and rotor. The two-dimensional MEC model approximates the complex three-dimensional flux paths of the TFM and includes the effects of magnetic saturation. The model is capable of adapting to any geometry which makes it a good alternative for evaluating prospective designs of TFM as compared to finite element solvers which are numerically intensive and require more computation time. A single phase, 1 kW, 400 rpm machine is analytically modeled and its resulting flux distribution, no-load EMF and torque, verified with Finite Element Analysis (FEA). The results are found to be in agreement with less than 5% error, while reducing the computation time by 25 times.

Design of a switched reluctance machine for off-road vehicle applications based on torque-speed curve optimization

Design of a Switched Reluctance Machine (SRM) for off-road hybrid electric vehicle applications is presented in this paper. SRMs are ideally suited for this application for their low cost, fault tolerance and reliable operations. A methodology to get an optimized design for meeting the torque-speed requirements is developed. The process aims in determining the best speed at which the SRM would start single pulse mode operation for a given set of specifications while delivering the best efficiencies over the specified operating range. The designed machine has been prototyped and then experimentally tested.

Analytical modeling of mutually coupled switched reluctance machines under saturation based on design geometry

An analytical calculation of the winding flux linkages and torque is proposed for fully pitched mutual coupled switched reluctance motors to develop a machine model without using numerical methods. The proposed technique is not empirical and does not require any finite-element analysis (FEA). The design parameters and the material properties of the machine are the only inputs to the model, which can predict the winding flux linkages and torque at any phase currents and rotor positions. The model is applicable for the rotor positions where the stator and rotor poles overlap. Initial assumptions and then the step-by-step procedure for flux linkage, co-energy, and torque calculations are provided. The flux linkages and torque predicted through the proposed modeling technique are compared with the FEA results. Finally, experimental results of flux linkage and torque are provided to verify the accuracy of the proposed modeling technique.

Dual rotor mutually coupled switched reluctance machine for wide speed operating range

A new dual rotor mutually coupled switched reluctance machine (DR-MCSRM) is proposed. The proposed machine has a magnetic circuit similar to the full pitched mutual coupled switched reluctance machine (FP-MCSRM) without short end windings. FP-MCSRMs have higher torque and power density, but they have longer end windings leading to unwanted copper loss. The construction of the proposed machine is similar to the merging version of the outer rotor and inner rotor FP-MCSRMs. An example machine is designed to meet specifications developed for automotive applications. A finite element model is developed and the machine is optimized to meet the performance targets. The machine performance is compared with a FP-MCSRM designed for the similar specifications.

Transverse Flux Machines with rotary transformer concept for wide speed operations without using Permanent Magnet material

This paper presents a new concept of Transverse Flux Machine (TFM) design that uses rotary transformers to replace the Permanent Magnet (PM) field excitation in the rotor. The rotary transformer has an inductive interface that allows for contactless transfer of energy to the field windings embedded in the rotor core. In order to achieve high magnetic coupling, a highly permeable ferrite core is selected for the transformer which is excited with high electrical frequency of 100 kHz. A field power converter is used to regulate the transformer secondary winding voltage to maintain constant DC field in the rotor. The proposed TFM has a modular structure that is free of PM, which makes it cost-effective, without sacrificing its peak torque and power when compared to a similar sized PM based TFM.

Modeling of mutually coupled switched reluctance motors for torque ripple minimization

A model of Mutually Coupled Switched Reluctance Machine (MCSRM) which includes the effect of multiple phase current excitations using a single lookup table is developed. The model can predict the MCSRM flux linkage and electromagnetic torque. The current waveform for low torque ripple is determined with the help of this model. The optimum current waveforms vary with the torque and speed levels. This increases the memory requirement of the control system. A memory efficient method for determining the optimum current waveform responsible for low torque ripple is proposed in this paper. With the proposed method Fourier series coefficients of the current shapes at some specific operating points are determined. Parameters for other operating points are determined through bi-cubic spline interpolation. The proposed modeling and torque ripple minimization approach is studied for a 30 kW MCSRM design. Finite Element Analysis (FEA) coupled with circuit simulations are presented along with Matlab/Simulink simulations for verification of the proposed modeling and ripple minimization methods.

A chirp PWM scheme for brushless DC motor drives

A novel chirp pulse width modulation (CPWM) scheme is proposed to improve the performance of AC motor drives by reducing electromagnetic interference. The proposed CPWM is operated on the chirped waveform that has a specified bandwidth defined within a minimum and a maximum switching frequency. The design procedure of CPWM that includes selecting the chirp bandwidth and the PWM frequency sweeping time period is presented and analyzed. Then the theoretical analysis is done for both the chirped and non-chirped waveforms. Optimum EMI reduction scheme is developed from the theory. The computer simulation and experimental results verify that the proposed CPWM method has better performance in comparison to PWM with fixed frequency.

Continuous conduction operation for mutually coupled switched reluctance machines

This paper introduces the benefits of using continuous conduction to improve the operation of a mutually coupled switched reluctance machine. Conventionally switch reluctance machines do not have a wide speed range; however, when continuous conduction control methods are used they provide an increased speed range in addition to increased torque per volume in the high-speed region. This paper discusses the benefits of continuous conduction control for motoring operation and shows these benefits through finite element analysis simulations.

Analytical Modeling of Mutually Coupled Switched Reluctance Machines Under Saturation Based on Design Geometry

An analytical model of the winding flux linkage is proposed for fully pitched mutual coupled switched reluctance motors (MCSRM). Basic magnetic field laws are used for the derivation phase winding fluxes of the machine. The model is not empirical and does not require any finite element analysis (FEA) data. The model only takes in the dimensions of the machine as inputs and then calculates the winding flux linkage at any current and rotor position. The model is applicable for the rotor positions where the stator and rotor poles overlap. There are some assumptions which are described initially. Then the step by step procedure of flux linkage calculation is provided. The flux linkages predicted through the model is compared with the FEA results.