Advances in Rotating Electric Machines

It is difficult to imagine a modern society without rotating electric machines. Their use has been increasing not only in the traditional fields of application but also in more contemporary fields, including renewable energy conversion systems, electric aircraft, aerospace, electric vehicles, unmanned propulsion systems, robotics, etc. This has contributed to advances in the materials, design methodologies, modeling tools, and manufacturing processes of current electric machines, which are characterized by high compactness, low weight, high power density, high torque density, and high reliability. On the other hand, the growing use of electric machines and drives in more critical applications has pushed forward the research in the area of condition monitoring and fault tolerance, leading to the development of more reliable diagnostic techniques and more fault-tolerant machines. This book presents and disseminates the most recent advances related to the theory, design, modeling, application, control, and condition monitoring of all types of rotating electric machines

Torque Control

This book is the result of inspirations and contributions from many researchers, a collection of 9 works, which are, in majority, focalised around the Direct Torque Control and may be comprised of three sections: different techniques for the control of asynchronous motors and double feed or double star induction machines, oriented approach of recent developments relating to the control of the Permanent Magnet Synchronous Motors, and special controller design and torque control of switched reluctance machine

Induction Motors

AC motors play a major role in modern industrial applications. Squirrel-cage induction motors (SCIMs) are probably the most frequently used when compared to other AC motors because of their low cost, ruggedness, and low maintenance. The material presented in this book is organized into four sections, covering the applications and structural properties of induction motors (IMs), fault detection and diagnostics, control strategies, and the more recently developed topology based on the multiphase (more than three phases) induction motors. This material should be of specific interest to engineers and researchers who are engaged in the modeling, design, and implementation of control algorithms applied to induction motors and, more generally, to readers broadly interested in nonlinear control, health condition monitoring, and fault diagnosis

Efficiency optimal control of interior permanent magnet synchronous motor / by Fasil Abera.

There has been a growing concern over energy consumption since the past decade mainly because of the soaring cost of energy and tight environmental laws and regulations. In this thesis a model based efficiency optimization for speed control of interior permanent magnet synchronous motor (IPMSM) is proposed to improve the efficiency of the motor drive which usually operates at different load and speed conditions. Recently, the IPMSM has been becoming popular due to some of its advantages such as high efficiency, high power density, low noise and robustness as compared to the conventional induction and other ac motors. Thus, the IPMSM is considered in this work. The proposed energy optimization algorithm is developed based on motor model. In order to minimize the controllable losses, the air gap flux level should be optimized. In an LPMSM the flux level can only be optimized by controlling the d-axis armature current as the field flux is supplied by the rotor permanent magnet. For the proposed work the vector control technique is used in order to achieve fast and accurate speed response, quick recovery of speed from any disturbance and insensitivity to parameter variations etc. A simulation model for the complete closed loop vector control of IPMSM incorporating the proposed energy optimization algorithm has been developed using Matlab/Simulink software. The performance of the drive has been tested extensively for different dynamic operating conditions such as sudden load, command speed and parameter changes. An efficiency gain of about 4% is obtained from the proposed optimization algorithm from simulation. After the satisfactory simulation results are found a realtime implementation of the complete drive system using DSP board (DS1104) for a laboratory 5 hp motor performed and the real time responses confirms with the simulation results as expected

Control of a fractional-slot, concentrated-wound interior permanent magnet generator for direct-drive wind generation applications

This thesis assesses improvements to two types of control for a novel interior permanent magnet (PM) synchronous generator with fractional-slot, concentrated-wound stator designed for direct-drive wind energy conversion. The two control techniques assessed are a) field oriented control using a back-to-back converter arrangement and b) a current controller with a rectifier-connected boost converter. These were chosen to understand the potential and the limitations of the generator and its control. Modifications to the control techniques are proposed to improve the generator efficiency, the dynamic performance in the flux-weakening range and the torque ripple performance. The adequacy of the distributed-wound PM synchronous machine model for steady-state and dynamic control of this generator was experimentally validated under field oriented control using a back-to-back converter connected to the grid. The effectiveness of the existing current trajectory controls on the efficiency of the new generator was evaluated. A new flux-prioritized maximum torque per ampere technique which is independent of speed-dependent predefined trajectories was introduced, and a similar efficiency improvement was gained as the conventional loss minimization method in the partial load range. Thus, the control model validation and efficiency imrpovement of the new generator are the primary contributions. The dynamic performance of the generator, directly driven by a non-pitchable wind turbine emulator was investigated from cut-in speed to cut-out speed using maximum power point tracking and then constant power control above rated speed. A significant contribution was done in the power control above base wind speed that was achieved by utilizing the extended flux-weakening capability of the machine with its wide constant power-speed range. High torque ripple was observed when operated with a rectifier and boost converter using boost converter inductor current control. A new direct torque control technique using a machine rotor position based torque estimator was proposed to minimize this torque ripple. Eventhough the reduced torque ripple is still higher than that with back-to-back converter, the achieved ripple reduction is significant. The control of generator speed under each method is also demonstrated. Although the new method gives a faster speed dynamics than the conventional method, it shows slower speed response than that of back-to-back converter control. However, the significance of the study using a diode rectifier-connected boost converter control is highlighted with the achieved torque ripple minimization and performance enhancement of the generator. This study is expected to open new investigations in flux-weakening control of the PM generators using rectifier-connected boost converter. In this thesis, back to back converter control is demonstrated in order to optimally control the novel generator under the field oriented control, energy efficient current control and power control together with voltage control operating above rated speed. Torque ripple minimization of the generator is also presented when used with a diode rectifier-connected boost converter control

New optimal PWM strategies for a VSI induction motor drive

The applications of robust squirrel-cage induction motors in variable speed inverter drive systems have increased considerably due to the availability of easily controlled semiconductor switching devices. One problem encountered in inverter drives is the non-sinusoidal nature of the supply voltage, which results in increased motor losses and harmful torque pulsations producing undesirable speed oscillations. The latter effects are negligible at high frequency operation, due to the damping effect of the rotor and load inertia. However, torque pulsations and speed ripple may be appreciable at low frequency, wore they may result in abnormal wear of gear-teeth or torsional shaft failure. Hence, in applications where constant or precise speed control is important, eg; machine tool, antenna positioning, traction drives etc., it is essential to establish a method for determining the magnitudes of these torque pulsations and speed ripple, as a first stage in minimizing or eliminating them. When a voltage source inverter is used in such applications, pulse width modulation (PWM) techniques are usually employed, whereby the quasi square waveshape is modulated so as to minimize or eliminate the low order harmonic voltage components and thereby reduce the torque pulsations. Recent investigations have shown that total elimination of low order components does not produce optimal efficiency or torque pulsations and speed ripple. minimization. This thesis describes new PWM strategies which does not rely on complete elimination of low order harmonics, but on controlling the magnitude and phase of these components to achieve a smooth rotor motion. Initially, a mathematical model for the inverter/induction motor drive was developed, based on numerical integration of the system differential equations. The changing topology of the inverter bridge was simulated using tensor techniques. Then an analytical method, based on harmonic equivalent circuit analysis was proposed for calculating the induction motor pulsating torque components under steady-state operating conditions, in terms of stator and rotor current harmonics. The accuracy of this method was verified by comparing its results with those obtained from the mathematical model developed earlier. This provided an extremely rapid, numerically stable and efficient means for evaluating harmonic current and torque components with balanced non-sinusoidal applied voltages. This method was then used to formulate the torque performance function necessary to determine the new optimal PWM switching strategies. Throughout the work, the predicted performance was extensively validated and supported by practical results obtained from an experimental rig specifically designed to drive the machine under different PWM techniques

A Review of Transverse Flux Machines Topologies and Design

High torque and power density are unique merits of transverse flux machines (TFMs). TFMs are particularly suitable for use in direct-drive systems, that is, those power systems with no gearbox between the electric machine and the prime mover or load. Variable speed wind turbines and in-wheel traction seem to be great-potential applications for TFMs. Nevertheless, the cogging torque, efficiency, power factor and manufacturing of TFMs should still be improved. In this paper, a comprehensive review of TFMs topologies and design is made, dealing with TFM applications, topologies, operation, design and modeling

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.