Design And Analysis Of Flux Reversal Machine (FRM)

Abstract

Flux Reversal Machine (FRM) is a doubly salient singly excited stator – permanent magnet (PM) machine with a windingless rotor, where the flux reverses polarities in the stator concentrated coils. FRM is a new generation machine, which combines the advantages of both Switch Reluctance Machine and Permanent Magnet Brushless DC Machine. The power capacity of this machine is higher than compared to other machines. This is because of the bipolar flux and bipolar back EMF which results into power generation when rate of chance of the inductance with respect to the angle theta is positive as well as negative. Torque capability of this machine is also higher than others. Thus, volume of machine required for producing same amount of torque and power would be less as compared to Switch Reluctance Machine. Due to doubly salient structure and windingless rotor, construction wise FRM is very robust. FRM has magnet placed on stator pole face, so restriction of speed is removed. FRM is capable of going up to around 35,000 RPM easily without any mechanical constraints. This works compiles some basic information regarding construction, operation and performance of FRM. Apart from these listed advantages, this machine has the inherent high amount of torque ripple. Torque ripple is main factor influencing the performance of machine under loaded and unloaded condition. Researchers tried out various combinations for reducing this torque ripple. Design combinations like rotor pole face variation (like rotor pole dummy slots, rotor pole champhering, magnet champhering, magnet pole height, etc.) and control strategies are employed to reduce this torque ripple. This DOE was performed and performance parameters (as average torque, maximum torque, minimum torque and torque ripple) are observed. Best combination is employed for design optimization in the further design section. During this DOE not only the performance parameters were improved but also the inductance of machine winding was reduced which would help in reducing the response time. FRM has a unique characteristic of being robust to rotor eccentricity. Performance of the machine is unchanged for normal and also eccentric rotor condition. First cut design of FRM proposed by Nasar and Boldea, takes into consideration, most of factors influencing machine design. But there are some thumb rules which can be optimized by electromagnetic formulations. FRM design, governed and optimized using such formulation with upgraded performance is presented in this thesis. Finite Element Analysis (FEA) using ANSYS is the fundamental approach used for the analysis of various combinations and design validation. Time taken for acquiring these results using FEA is huge. Same model can be solved faster with some approximation using Magnetic Circuit Model (MCM) which is macro level FEA. Full cycle results are obtained by solving MCM of FRM for different rotor positions. Results for the MCM are validated using FEA. Later part of the thesis compiles the way for solving MCM and results from MCM. But, upfront, FRM is having a bright future and ready to be implemented for common applications.