Development and Analysis of Interior Permanent Magnet Synchronous Motor with Field Excitation Structure

Throughout the years Hybrid Electric Vehicles (HEV) require an electric motor which has high power density, high efficiency, and wide constant power operating region as well as low manufacturing cost. For these purposes, a new Interior Permanent Magnet Synchronous Motor (IPMSM) with brushless field excitation (BFE) is designed and analyzed. This unique BFE structure is devised to control the amount of the air-gap flux for the purpose of achieving higher torque by increasing the air-gap flux at low speed and wider operating speed range by weakening the flux at high speed. On the process of developing the new IPMSM, the following analysis results are presented. Firstly, a new analytical method of output torque calculations for IPMSM is shown. This method works well when using a 2-dimensional magnetic equivalent circuit of a machine by omitting the step of calculating the inductance values which are required for the calculation of the reluctance torque. Secondly, there is a research about the slanted air-gap shape. This structure is intended to maximize the ratio of the back-emf of a machine that is controllable by BFE as well as increase the output torque. The study of various slanted air-gap shapes suggests a new method to increase torque density of IPMSM. Lastly, the conventional two-axis IPMSM model is modified to include the cross saturation effect by adding the cross-coupled inductance terms for calculating the power factor and output torque in comparing different saturated conditions. The results suggest that the effect of cross-coupled inductance is increase when d-axis current is high on the negative direction

FY 2005 Oak Ridge National Laboratory Annual Progress Report for the Power Electronics and Electric Machinery Program

The U.S. Department of Energy (DOE) and the U.S. Council for Automotive Research (composed of automakers Ford, General Motors, and DaimlerChrysler) announced in January 2002 a new cooperative research effort. Known as FreedomCAR (derived from ''Freedom'' and ''Cooperative Automotive Research''), it represents DOE's commitment to developing public/private partnerships to fund high-risk, high-payoff research into advanced automotive technologies. Efficient fuel cell technology, which uses hydrogen to power automobiles without air pollution, is a very promising pathway to achieve the ultimate vision. The new partnership replaces and builds upon the Partnership for a New Generation of Vehicles initiative that ran from 1993 through 2001. The Vehicle Systems subprogram within the FreedomCAR and Vehicle Technologies Program provides support and guidance for many cutting-edge automotive and heavy truck technologies now under development. Research is focused on understanding and improving the way the various new components of tomorrow's automobiles and heavy trucks will function as a unified system to improve fuel efficiency. This work also supports the development of advanced automotive accessories and the reduction of parasitic losses (e.g., aerodynamic drag, thermal management, friction and wear, and rolling resistance). In supporting the development of hybrid propulsion systems, the Vehicle Systems subprogram has enabled the development of technologies that will significantly improve fuel economy, comply with projected emissions and safety regulations, and use fuels produced domestically. The Vehicle Systems subprogram supports the efforts of the FreedomCAR and Fuel and the 21st Century Truck Partnerships through a three-phase approach intended to: (1) Identify overall propulsion and vehicle-related needs by analyzing programmatic goals and reviewing industry's recommendations and requirements, then develop the appropriate technical targets for systems, subsystems, and component research and development activities; (2) Develop and validate individual subsystems and components, including electric motors, emission control devices, battery systems, power electronics, accessories, and devices to reduce parasitic losses; and (3) Determine how well the components and subsystems work together in a vehicle environment or as a complete propulsion system and whether the efficiency and performance targets at the vehicle level have been achieved. The research performed under the Vehicle Systems subprogram will help remove technical and cost barriers to enable technology for use in such advanced vehicles as hybrid and fuel-cell-powered automobiles that meet the goals of the FreedomCAR Program. A key element in making hybrid electric vehicles practical is providing an affordable electric traction drive system. This will require attaining weight, volume, and cost targets for the power electronics and electrical machines subsystems of the traction drive system. Areas of development include: (1) Novel traction motor designs that result in increased power density and lower cost; (2) Inverter technologies involving new topologies to achieve higher efficiency and the ability to accommodate higher-temperature environments; (3) Converter concepts that employ means of reducing the component count and integrating functionality to decrease size, weight, and cost; (4) More effective thermal control and packaging technologies; and (5) Integrated motor/inverter concepts. The Oak Ridge National Laboratory's (ORNL's) Power Electronics and Electric Machinery Research Center conducts fundamental research, evaluates hardware, and assists in the technical direction of the DOE Office of FreedomCAR and Vehicle Technologies Program, Power Electronics and Electric Machinery Program. In this role, ORNL serves on the FreedomCAR Electrical and Electronics Technical Team, evaluates proposals for DOE, and lends its technological expertise to the direction of projects and evaluation of developing technologies. ORNL also executes specific projects for DOE. The following report discusses those projects carried out in FY 2004 and conveys highlights of their accomplishments. Numerous project reviews, technical reports, and papers have been published for these efforts, if the reader is interested in pursuing details of the work

Modeling and Design Optimization of Permanent Magnet Variable Flux Machines

Permanent magnet synchronous machines (PMSMs) with rare-earth magnets are widely used especially in traction applications as a result of their higher efficiency and torque density in comparison with other electrical motors. Due to price fluctuations and limited production of rare-earth materials, it is essential to find alternatives to the rare-earth PMSMs for different applications. This thesis focuses on the application of Aluminum-Nickel-Cobalt (AlNiCo) magnets in PMSMs. AlNiCo magnets can theoretically provide torque densities comparable to rare-earth magnets in electrical machines. The application of AlNiCo magnets in electrical machines can improve the field-weakening performance, due to the possibility of varying their magnetic flux density using armature current pulses. As a result, these machines are named variable flux machines (VFMs). This thesis presents an analytical model for the VFM to calculate the no-load air gap flux density and consequently, the no-load back-EMF, torque peak to peak value, average torque, and magnetization current. The proposed model is used to develop an analytical design criterion for spoke type AlNiCo-based VFMs. An experimental characterization of an existing spoke type VFM at different magnetization levels is done of the torque waveform, the torque-angle characteristics, the no-load back-EMF and the magnetization/demagnetization energy. An optimization procedure to reduce the torque ripple and the magnetization current of the spoke type AlNiCo-based VFM is then proposed. A new VFM design with radially magnetized interior magnets is presented to enhance the torque density in the field-weakening operating condition. The torque-speed and power-speed characteristics of the VFM are calculated considering the demagnetization of the AlNiCo magnets in the field-weakening region. The proposed design keeps the fully magnetized condition at both no-load and full-load conditions and provides high power densities at a wider speed range. This design is also optimized to have reduced torque ripple. An improved core loss model is proposed and implemented in the finite element software, and an experimental method based on the flux controllability of the VFM is developed to measure the mechanical and core losses at the no-load condition. These results are then used to verify the proposed core loss model