| Summary: | 碩士 === 國立雲林科技大學 === 電機工程技術研究所 === 86 === Zero-Voltage-Transition techniques which combine PWM with the soft-switching characteristics make all semiconductor devices be operated at constant frequency. ZVT structure also has very low voltage and current stress and the soft-switching characteristic of the rectifier diode. Therefore, ZVT converters have the minimum conduction loss. This thesis will analyze and discuss the characteristics of the ZVT-PWM technique applied to the dc and ac motor drives. First, the effects of switching frequency and duty cycle on efficiency,speed characteristics and ripple current of the various dc motor are investig ated. Comparison of ZVT-PWM converter-fed dc motor with the traditional hard-switching PWM topology shows the ZVT-PWM converter-fed dc motor can reduce switching loss, ripple current and improve the efficiency even the load variation is very large. In tradition, the hard-switching inverter applied to the three phase induction motor is subject to high switching loss and consequently reduces the performance and efficiency of the inverter system. Therefore, This thesis applied a new type of Parallel Resonant DC Link ﹙PRDCL﹚topology which can provide the zero voltage switching of switches of the inverter and minimize the peak voltage stress of the switches. In addition, The Space Voltage Vector Pulse-Width-Modulation }SVPWM﹚strategy is applied to the inverter. It can reduce the voltage and current harmonics in the inverter output and consequently provide the operation of induction motor smoothly. Digital Signal Processor TM S320C14﹙T.I.﹚is used to implement the SVPWM strategy. Experimental results show that the new PRDCL combines with SVPWM can reduce the switching loss and the current harmonic. The structure can also minimize the voltage stresses and improve the efficiency while it is applied to induction motor drives system.
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