Study of static transfer switches

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Faculty of Electronics, Communications and Automation | Master's thesis
Power Electronics
Degree programme
Elektroniikan ja sähkötekniikan tutkinto-ohjelma
x, 92
Quality and reliability of electrical power have become a must for many industries and applications. Airports, hospitals, data centers and financial institutions are just a few of the locations where an unpredicted loss of power could bring fatal consequences ranging from massive economic losses to life casualties. The risk of not having such power calls for electrical equipment capable of assuring the quality and reliability of the power source under the hardest conditions and on the most unpredictable events. One of those equipments is a power electronics-based switch called Static Transfer Switch (STS). This document analyzes the technical design of such a switch focusing on the power electronics of the device. For this purpose, a thorough study of semiconductors is carried out. Additionally, the report addresses the STS applications and market niches. The breakdown of the report is as follows; Chapter 2 reviews the background, applications and market niches of the STS; Chapter 3 is a theoretical study on the semiconductors that are applicable for the STS; and Chapter 4 presents an in-deep analysis of the STS design, stressing its limitations and giving guidelines of how to design it in the case that is required as a further project. The main conclusion of this work is that the most cost-efficient design of an STS should be based on Silicon Controlled Rectifiers (SCRs). Even when other power semiconductors like Gate Tum Off Thyristors (GTOs) and Integrate Gate Commutated Thyristors (IGCTs) can provide a solution for high power requirements, and better in teams of commutation times; the limitations that they impose in other areas like thermal management, availability and cost make them commercially unfeasible at the moment. Maybe with the advent of new semiconductor materials and the consequent improvement of semiconductor devices in a near future this landscape could change, but at the moment the SCR still stands out as the ultimate solution for the STS.
Kyyrä, Jorma; Prof.
Thesis advisor
Mustonen, Heikki; DI
STS, critical power, thyristor, SCR, GTO, IGCT
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