Study on Ultra High-Speed Electric Drive of Automotive Turbocharger to Improve Environmental Compatibility and Drive Performance

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During the financial support by this research project (fiscal year 2004-2005), grant-in-aid for scientific research, Ultra High-Speed Electric Drive of Automotive Turbocharger to Improve Environmental Compatibility and Drive Performance were studied and the following knowledge and results were obtained :(1) Development of Ultra High-Speed Electric Drive for TurbochargerA prototype of an ultra high-speed permanent-magnet motor/generator for an electrically assisted turbocharger was developed. 6-slot concentrated winding structure was employed in the stator core, which was made of 0.15-mm super thin electromagnetic steel plates. The rotor was composed with a cylindrical Neodymium permanent-magnet, which was reinforced with a carbon fiber and a metal alloy sleeve. This ultra high-speed machine was fed by a pseudo current-source inverter with 72-V DC bus voltage, and the inverter power circuit and its drive circuit were implemented with a 4-layer large-current printed wire board. From expe … More rimental results of the system, regenerative power of 1.3 kW at 120,000 r/min was confirmed and inverter output power of 2.2 kW at 220,000 r/min was obtained in a motoring operation. In addition, turbo lag was improved by 45 % compared with a conventional mechanical turbocharger, using this electrically assisted system.(2) Development of Ultra High-Speed Electric Drive for SuperchargerA prototype of an electrically driven supercharger was developed, which employed an ultra high-speed permanent-magnet motor. The motor has three-slot stator core structure with concentrated windings and Samarium-Cobalt permanent-magnet on the rotor. A pseudo current-source inverter was used to drive the motor as well as an electrically assisted turbocharger. As a result of experimental tests, 2.7-kW inverter output power was confirmed at 160,000 r/min and boost pressure response (turbo lag) was shortened to 0.5 s.(3) Efficiency Measurement and Losses Analysis of Ultra High-Speed MotorA motor-generator set composed with 2 ultra high-speed permanent-magnet motors was set up on the basis of the electrically driven supercharger. As a result of motor operation using this experimental setup, the maximum efficiency and the power factor was 79 % and 62 %, respectively. Also, it was found from FEM based losses analysis that eddy-current loss on the permanent-magnet was dominant and 38 % of the total loss. Less