Browsing by Subject "Common-mode voltage"
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Item Common-mode Noise Reduction in Wide Band Gap Device Based Motor Drives(2015-11) Narasimhan, SnehaWide band gap (WBG) devices are the latest trend in the power electronics industry. MOSFETs built using WBG materials offer numerous benefits to power electronic circuits. The benefit of using WBG MOSFETs over conventional Si IGBTs is the ability to operate at higher switching frequencies and lower dead times, which reduces the switching losses. This thesis will explore the application of WBG MOSFETs to motor drives, where higher switching frequencies reduce harmonic losses and torque ripple and allow higher control bandwidth, Two-level voltage source inverters (VSI) utilizing Silicon Carbide (SiC) MOSFETs are constructed to operate a 1 HP induction motor. Experimental results are presented which show that the short turn-ON and turn-OFF times as well as high switching frequencies lead to increased shaft voltage and ground currents. Mitigation techniques of open-end winding drive and clamp-on ferrite chokes are evaluated in this thesis. The shaft voltage and ground currents are found to be eliminated when an open-end winding drive combines with the clamp-on ferrites. Simulation results of loss analysis is presented for a conventional two-level VSI and dual two-level VSI to understand the thermal requirements of the Si and SiC based drives. The advantages and disadvantages of WBG based conventional two-level inverter and the various mitigation techniques are discussed.Item Power electronic transformer based three-phase PWM AC drives(2013-01) Basu, KaushikA Transformer is used to provide galvanic isolation and to connect systems at different voltage levels. It is one of the largest and most expensive component in most of the high voltage and high power systems. Its size is inversely proportional to the operating frequency. The central idea behind a power electronic transformer (PET) also known as solid state transformer is to reduce the size of the transformer by increasing the frequency. Power electronic converters are used to change the frequency of operation. Steady reduction in the cost of the semiconductor switches and the advent of advanced magnetic materials with very low loss density and high saturation flux density implies economic viability and feasibility of a design with high power density. Application of PET is in generation of power from renewable energy sources, especially wind and solar. Other important application include grid tied inverters, UPS e.t.c. In this thesis non-resonant, single stage, bi-directional PET is considered. The main objective of this converter is to generate adjustable speed and magnitude pulse width modulated (PWM) ac waveforms from an ac or dc grid with a high frequency ac link. The windings of a high frequency transformer contains leakage inductance. Any switching transition of the power electronic converter connecting the inductive load and the transformer requires commutation of leakage energy. Commutation by passive means results in power loss, decrease in the frequency of operation, distortion in the output voltage waveform, reduction in reliability and power density.