Browsing by Author "Tekgün, Didem"

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Design and Control of a Single Phase DC/Rectified AC/AC Inverter for low THD Applications
(IEEE, 2018) Tekgün, Burak; Tekgün, Didem; Alan, Irfan; Badawy, Mohamed; AGÜ, Mühendislik Fakültesi, Elektrik & Elektronik Mühendisliği Bölümü;
In this paper, a single phase DC/Rectified AC/AC (DC/RAC/AC) inverter is analyzed and compared to classical single phase PWM inverters. A traditional AC power supply (PS) system consists of a DC/DC converter, a cascaded H-bridge inverter, and a passive filter to generate the sinusoidal output voltage. The presented DC/RAC/AC inverter has a similar structure; however, the control of the cascaded units differ. The presented method generates rectified sine wave at the output of the DC/DC converter unit and the H-bridge inverter alternates the rectified sine wave to generate the full sine wave without having an additional output filter; hence, the switching losses at the Hbridge inverter is limited to the line frequency (50-60 Hz). Moreover, the bulk DC bus capacity at the output of the DC/DC converter is reduced significantly. Therefore, the power consumed by the passive elements are minimized. The circuit modes of operation are analyzed and the system is simulated in Matlab/Simulink environment for both traditional and proposed topologies. Results show that the proposed system is superior to the traditional one in terms of efficiency, generated THD with a simplified control structure, and it offers a reduced system size and cost.
Systematic design optimization and implementation of line-start synchronous reluctance machine for down-hole submersible water pump applications
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2022) Tekgün, Didem; AGÜ, Fen Bilimleri Enstitüsü, Elektrik ve Bilgisayar Mühendisliği Ana Bilim Dalı
Considering the electric drive systems constitute roughly 40% of global energy production, improving electric machine efficiencies provides important nationwide and global scale advantages. Among the electric motors used in the industry, a major portion of them are pump motors used for pumping underground waters and petroleum products. Especially the motors for submersible pump applications run at very low-efficiency levels because of the motor design issues and wrong selection of motor-pump configurations. Due to the features like robustness, low cost, and line start capability, induction machines (IM) are generally the first choice for pump applications. However, IMs work with low efficiency, especially at low and medium power levels. Line start synchronous reluctance machines (LS-SynRM) come to the scene as a reasonable alternative by having the line start capability and not having rare earth permanent magnets as well. The working principle of these machines is a combination of a reluctance machine and an IM. In LS-SynRM, a rotor cage is inserted in the rotor for the machine to start with the line voltage, but the rotor copper losses become zero when the machine operates at synchronous speed. Moreover, SynRMs have higher power and torque density. In this thesis study, it is aimed to reduce the overall cost of the submersible water pump system by designing and optimizing a LS-SynRM as a submersible pump motor with higher efficiency compared to conventional IMs. Increasing the efficiency of the pump motor used in industry will improve the overall system performance. Accordingly, it lowers energy and maintenance costs, and easy process control will be achieved. This way, while reducing energy consumption nationwide significantly, not only the natural resources will be protected, but also huge amounts of money will be saved.