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OPERATION ANALYSIS AND LOSS REDUCTION OF MAGNETIC GEAR
Title
OPERATION ANALYSIS AND LOSS REDUCTION OF MAGNETIC GEAR
Creator
Feng, Yanjun
Date
2015, 2015-12
Description
In the first part of this thesis, analysis of magnetic gears which includes operation analysis and loss analysis is introduced. With these...
Show moreIn the first part of this thesis, analysis of magnetic gears which includes operation analysis and loss analysis is introduced. With these analysis, the behavior of magnetic gears are deeply studied for their advantages and disadvantages. Their performance in terms of torque transfer, speed transfer, and the loss are the main focus. With different properties setting for magnetic gear, the influence of these properties to the final performance are also studied. By comparing results from different simulation software and different methods, the results are analyzed more accuracy and detailed. For loss analysis, FFT are utilized for harmonics analysis. This analysis was done by Matlab. All these analysis processes and results lead to the next part of this thesis which is optimization for magnetic gear. The second portion of this thesis focuses on core loss reduction in magnetic gears. Pole shaping similar to what is used in electric machines to reduce electromagnetic torque ripple is introduced to attempt to reduce higher order harmonic flux components in the magnetic gears without reducing power density. In this part, lots of simulation shows the work analysis of magnetic gear to verify the working principle and optimizations results. Large ripple problems of magnetic gear are also found during this part.
M.S. in Electrical Engineering, December 2015
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Electronically Assisted Direct Current Circuit Breakers
Title
Electronically Assisted Direct Current Circuit Breakers
Creator
Feng, Yanjun
Date
2019
Description
DC power is gaining tractions recently, however, DC fault protection remains a major technical challenge. Popular and cost-effective AC...
Show moreDC power is gaining tractions recently, however, DC fault protection remains a major technical challenge. Popular and cost-effective AC mechanical circuit breakers do not offer sufficient DC interruption capability. Solid state circuit breakers have drawbacks of high cost and high conduction loss. The reported hybrid circuit breakers solutions require fast responding current sensors and mechanical actuation mechanism vastly different from and far more complex than the conventional AC circuit breakers.This thesis introduces a new DC hybrid circuit breaker concept termed Electronically Assisted Circuit Breaker (EACB). A conventional AC mechanical circuit breaker (MCB) is used to interrupt DC fault currents with the assistance of an electronic commutation circuit, which is activated for a short time period only during the late phase of the breaking process. Unlike other prior art HCB concepts, an EACB uses (1) a conventional thermal-magnetic AC baseline breaker design with minimal modification; and (2) an electronic commutation circuit which only needs to commutate a fault current already reduced from its peak for a very short duration (~100µs), both contributing to significant cost savings. While an EACB does not facilitate arc-free or ultrafast breaking, it does provide a simple and cost-effective way to enhance the DC current interruption capability of conventional thermal-magnetic AC circuit breakers currently dominating the low voltage circuit breaker market. The EACB concept has been validated both experimentally and by simulation. A 600VDC/250A (nominal) EACB prototype is designed and tested. It has experimentally demonstrated a fault current interruption capability of over 8kA at a DC voltage of 600V within 6 milliseconds.
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