Performance of torus-type brushless DC motor with winding connected in two and three-phase system

A torus-type permanent magnet brushless DC motor is the object of this thesis. The motor can operate with the winding connected either in two - phase or three - phase system. A comparative study of performance of the motor operating in these two systems is the objective of the thesis. To analyze the motor performance, the dynamic models of the motors operating with two - phase and three - phase motors have been proposed. The simulation of motor operation was carried out using the MATLAB/SIMULINK software package. A study of motors operation in steady state conditions has been done by applying simpler models which were based on brush DC motor equivalent circuit. It is observed that the electromechanical characteristics of these two motors are similar and the motor with three - phase winding has lesser quantity of torque ripples. Since the motors operating in the two types winding connection systems are supplied from voltage - type inverters, switching conditions have a significant influence on motor performance. This was also studied in the thesis project using the dynamic motor model. The results of this study show that by advancing the commutation angle, the efficiencies could be improved greatly

Modular switched reluctance machines to be used in automotive applications

In the last decades industry, including also that of electrical machines and drives, was pushed near to its limits by the high market demands and fierce competition. As a response to the demanding challenges, improvements were made both in the design and manufacturing of electrical machines and drives. One of the introduced advanced technological solutions was the modular construction. This approach enables on a hand easier and higher productivity manufacturing, and on the other hand fast repairing in exploitation. Switched reluctance machines (SRMs) are very well fitted for modular construction, since the magnetic insulation of the phases is a basic design requirement. The paper is a survey of the main achievements in the field of modular electrical machines, (especially SRMs), setting the focus on the machines designed to be used in automotive applications

Optimal Design of Special High Torque Density Electric Machines based on Electromagnetic FEA

Electric machines with high torque density are essential for many low-speed direct-drive systems, such as wind turbines, electric vehicles, and industrial automation. Permanent magnet (PM) machines that incorporate a magnetic gearing effect are particularly useful for these applications due to their potential for achieving extremely high torque density. However, when the number of rotor polarities is increased, there is a corresponding need to increase the number of stator slots and coils proportionally. This can result in manufacturing challenges. A new topology of an axial-flux vernier-type machine of MAGNUS type has been presented to address the mentioned limitation. These machines can attain high electrical frequency using only a few stator coils and teeth, which can simplify construction and manufacturing under certain conditions. Additionally, the inclusion of auxiliary small teeth within the stator main teeth can generate a noteworthy increase in output torque, making it a unique characteristic of this motor. By analyzing the operating principle of the proposed VTFM PM machine, possible pole-slot combinations have been derived. The process of designing an electric machine is complicated and involves several variables and factors that must be balanced by the designer, such as efficiency, cost, and performance requirements. To achieve a successful design, it is crucial to employ multi-objective optimization. Using a 3D FEA model can consider the impact of magnetic saturation, leakage flux, and end effects, which are not accounted for in 2D. Optimization using a 3D parametric model can offer a more precise analysis. Validating the machine\u27s performance requires prototyping a model and testing it under different operating conditions, such as speed and load, which is a crucial step. This approach provides valuable insights into the machine\u27s behavior, allowing the identification of any areas for improvement or weaknesses. A large-scale multi-objective optimization study has been conducted for an axial-flux vernier-type PM machine with a 3-dimensional (3D) finite element analysis (FEA) to minimize the material cost and maximize the electromagnetic efficiency. A detailed study for torque contribution has indicated that auxiliary teeth on each stator main teeth amplify net torque production. A prototype of optimal design has been built and tested

Design Optimization of a Very High Power Density Motor with a Reluctance Rotor and a Modular Stator Having PMs and Toroidal Windings

This paper proposes a new high power density permanent magnet (PM) motor design for traction applications to achieve the 50kW/L target set by the US Department of Energy by increasing the torque capability and operating speed compared to conventional PM machine topologies. A large-scale multi-objective design optimization based on 2D finite element analysis (FEA) and differential evolution algorithm was conducted to achieve the best trade-off among high efficiency, high power density and high power factor. The torque-speed envelopes are also checked for the Pareto front designs to make sure they have a constant power speed ratio of at least 3:1. An open frame lab prototype (OFLP) motor has been fabricated and tested to validate the principle of operation and design optimization approach, and to identify the potential challenges in manufacturing and testing. Ongoing work on further pushing the electromagnetic performance to the limit and improving the manufacturing and cooling techniques are also discussed

Flux switching machine design for high-speed geared drives

Electrical machines capable of high-speed operation are key technology used in many modern applications, such as gas turbine electrical systems, high-speed fly-wheels, turbochargers, and computer numerical control (CNC) machines. The use of geared high-speed machines to replace low-speed high torque drives has not been adequately researched to-date. The rationale of this thesis is to investigate a candidate high speed machine, namely flux switching machines to be used together with new types of core material with mechanical gearing to deliver high-torque and low speeds. Modern developments in advanced material technology have produced new magnetic materials capable of dealing with high resulting in very low losses in high speed machines. However, such metals typically have low mechanical strength, and they are found to be brittle. In order to manufacture electromechanical device with such new materials, it has to be reinforced with a mechanically strong structure. The use of multiple types of magnetic materials referred as a MMLC has been proposed in this thesis for high-speed machine design. In this research, a generic method using magnetic equivalent circuit to model flux switching machines (FSMs) is investigated. Moreover modeling, based on machine dimensions for multiphase FSMs having any pole and slot number has been introduced. The air-gap permeance modeling to simplify the magnetic circuit calculation of FSMs was also investigated in this thesis. It is shown that the permeability of magnetic material can be adjusted with the use of MMLC material. Using this feature, the FSM mathematical model is used to show the impact on electromagnetic performance using MMLCs and is shown to be beneficial. In order the evaluate the weight benefits of using geared high speed FSMs, the planetary gear systems are studies and their design constraints have been identified. An abstract form of weight estimation for given torque and speed requirements has been developed and validated using commercially available planetary gear specifications. FSMs together with gear boxes have been considered and it is shown that significant weight savings can be achieved at higher diameter and at high speeds

Traction axial flux motor-generator for hybrid electric bus application

Tato dizertační práce se zabývá návrhem původního motor-generátoru s axiálním tokem a buzením permanetními magnety, zkonstruovaným specificky pro hybridní elektrický autobus. Návrhové zadání pro tento stroj přineslo požadavky, které vedly k této unikátní topologii tak, aby byl dosažen výkon, účinnost a rozměry stroje. Tato partikulární topologie motor-generátoru s axiálním tokem je výsledkem literární rešerše, kterou následoval výběr koncepce stroje s představeným návrhem jako výsledkem těchto procesů. Přístup k návrhu stroje s axiálním tokem sledoval „multi-fyzikální“ koncepci, která pracuje s návrhem elektromagnetickým, tepelným, mechanickým, včetně návrhu řízení, v jedné iteraci. Tím je v konečném návrhu zajištěna rovnováha mezi těmito inženýrskými disciplínami. Pro samotný návrh stroje byla vyvinuta sada výpočtových a analytických nástrojů, které byly podloženy metodou konečných prvků tak, aby samotný návrh stroje byl přesnější a spolehlivější. Modelování somtného elektrického stroje a celého pohonu poskytlo představu o výkonnosti a účinnosti celého subsytému v rozmanitých operačních podmínkách. Rovněž poukázal na optimizační potenciál pro návrh řízení subsystému ve smyslu maximalizace účinnosti celého pohonu. Bylo postaveno několik prototypů tohoto stroje, které prošly intensivním testováním jak na úrovni sybsytému, tak systému. Samotné výsledky testů jsou diskutovány a porovnány s analytickými výpočty parametrů stroje. Poznatky získané z prvního prototypu stroje pak sloužily k představení možností, jak zjednodušit výrobu a montáž stroje v příští generaci. Tato práce zaznamenává jednotlivé kroky během všech fází vývoje elektrického stroje s axiálním tokem, počínaje výběrem konceptu stroje, konče sumarizací zkušeností získaných z první generace prototypu tohoto stroje.This thesis deals with a design of a novel Axial-Flux Permanent Magnet Motor-Generator for a hybrid electric bus application. Thus, the design specification represents a set of requirements, which leads toward a concept of a unique topology meeting performance, efficiency and dimensional targets. The particular topology of the Axial-Flux Permanent Magnet Motor-Generator discussed in this work is an outcome of deep literature survey, followed by the concept selection stage with the layout of the machine as an outcome of this processes. The design approach behind this so-called Spoke Axial-Flux Machine follows an idea of multiphysics iterations, including electromagnetic, thermal, mechanical and controls design. Such a process behind the eventually proposed design ensured a right balance in between all of these engineering disciplines. A set of bespoke design and analysis tools was developed for that reason, and was backed up by extensive use of Finite-Element Analysis and Computational Fluid Dynamics. Therefore, the actual machine design gained higher level of confidence and fidelity. Modelling of the machine and its drive provided understanding of performance and efficiency of the whole subsystem at various operational conditions. Moreover, it has illustrated an optimization potential for the controls design, so that efficiency of the machine and power electronics might be maximized. Several prototypes of this machine have been built and passed through extensive testing both on the subsystem and system level. Actual test results are discussed, and compared to analytical predictions in terms of the machine's parameters. As a lesson learned from the first prototype of this machine, a set of redesign proposals aiming for simplification of manufacturing and assembly processes, are introduced. This work records steps behind all phases of development of the Axial Flux Machine from a basic idea as an outcome of concept selection stage, up to testing and wrap-up of experience gained from the first generation of the machine.

Design Optimization of a Direct-drive Wind Generator with Non-rare-earth PM Flux Intensifying Stator and Reluctance Rotor

This paper presents a multi-objective design optimization for a novel direct-drive wind turbine generator. The proposed electric machine topology employs an outer rotor of the reluctance type and a special modular stator including three phase-windings and spoke-type permanent magnets (PMs). Each stator module includes a single coil toroidally wound around the ferromagnetic core. Consecutive stator modules are separated by PMs and include coils belonging to a different phase. An optimization method with three objectives: total power loss, weight, and torque ripple, and with one constraint for a minimum acceptable value for the power factor, is described. The design examples are for a direct-drive generator rated at 3 MW and 15 rpm. The simulation results show that with the proposed topology, which greatly benefits from PM flux concentration and special coils, performance, such as specific thrust, efficiency, “goodness”, etc, can be comparable to more traditional synchronous PM designs, but without the need to use rare earth-magnets that have high cost and critical supply. Furthermore, options for using aluminum instead of copper wire to further reduce the weight and cost of winding are investigated and comparative results are discussed

Linear Machines for Long Stroke Applications: a review

This document reviews the current state of the art in the linear machine technology. First,the recent advancements in linear induction, switched reluctance and permanent magnet machines arepresented. The ladder slit secondary configuration is identified as an interesting configuration for linearinduction machines. In the case of switched reluctance machines, the mutually-coupled configuration hasbeen found to equate the thrust capability of conventional permanent magnet machines. The capabilities ofthe so called linear primary permanent magnet, viz. switched-flux, flux-reversal, doubly-salient and verniermachines are presented afterwards. A guide of different options to enhance several characteristics of linearmachines is also listed. A qualitative comparison of the capabilities of linear primary permanent magnetmachines is given later, where linear vernier and switched-flux machines are identified as the most interestingconfigurations for long stroke applications. In order to demonstrate the validity of the presented comparison,three machines are selected from the literature, and their capabilities are compared under the same conditionsto a conventional linear permanent magnet machine. It is found that the flux-reversal machines suffer froma very poor power factor, whereas the thrust capability of both vernier and switched-flux machines isconfirmed. However, the overload capability of these machines is found to be substantially lower than theone from the conventional machine. Finally, some different research topics are identified and suggested foreach type of machine

Permanent Magnet Vernier Machine: A Review

Permanent magnet vernier machines (PMVMs) gained a lot of interest over the past couple of decades. This is mainly due to their high torque density enabled by the magnetic gearing effect. This study will provide a thorough review of recent advances in PMVMs. This review will cover the principle of operation and nature of magnetic gearing in PMVMs, and a better understanding of novel PMVM topologies using different winding configuration as well as different modulation poles and rotor structures. Detailed discussions on the choice of gear ratio, slot-pole combinations, design optimisation and role of advanced materials in PMVMs will be presented. This will provide an update on the current state-of-the art as well as future areas of research. Furthermore, the power factor issue, fault tolerance as well as cost reduction will be discussed highlighting the gap between the current state-of-the art and what is needed in practical applications