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Design and Implement of an Ultra Low Ripple Power Supply for Cathode of Microwave Tube
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahryar (Supervisor)
Abstract
The purpose of this Thesis is designing and constructing of high voltage power supply with very low ripple. Proposed method of this thesis is formed of two sections. In this proposed structure, in first section, structure is on basis of diodes rectifier that has been used for producing main portion of output load energy. Second section uses with aim of regulating of first stage voltage. In attention to existence of noises and available offsets in different sections of proposed circuits, model is basis of two stages structure. Sampling of output voltage by using of resistance divider for main loop of circuit has been done. So noises and offsets available in circuit act as prevented factor...
Analysis of the Challenges in the Design of High Power and High Frequency Inverters
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahryar (Supervisor)
Abstract
Power Inverter or DC to AC voltage converter is one of the most important and widely discussed topics in the world of power electronics and systems such as DC/DC converters. Increasing the switching frequency of the inverter, in addition to its many advantages, also creates challenges that will be addressed in this dissertation. To build a high frequency yet reliable inverter, you need accurate and comprehensive information about the inverter circuitry, parasitic elements, switches and their behavior against fault conditions such as short circuit, protection requirements and etc.In this dissertation, several MOSFET transistors is shorted under various test conditions while parameters...
Improving the Performormance of an Ultra Narrow Pulse Generator based on Transmission Lines
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahryar (Supervisor)
Abstract
The ultra-narrow pulse generator have being used for direct production of pulsed power. One of these structures is being used to make a bipolar pulse and its main feature is the utilization of the real transmission lines (not PFN) with an intricate structure that caused volume to be compressed. It is desired to reach an appropriate design by analyzing the output waveform and its relation to the transmission line parameters. A little piece of work has been done in the past but there were some differences from our anticipations in the waveforms, like pre-pulse, long rise and fall times and overshoot that caused by some non-idealities in the structure. What we have done in this project is to...
Analysis and Improvement of Output Voltage Ripple in High Voltage DC Power Supply
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahryar (Supervisor)
Abstract
The TWT is highly sensitive to the ripple amplitude of its power supply output voltage. If the amplitude of the output voltage's ripple exceeds a certain limit, the amplitude of the undesired harmonics in the power spectrum of the TWT is greatly increased. Increasing the amplitude of undesired harmonics in the TWT output power spectrum reduces the accuracy and performance of the TWT. Therefore, for optimum TWT performance, a low-ripple power supply is essential. Typically, a low-frequency rectifier or high-frequency switching structure is used to build a high-voltage DC power supply. In this thesis, the different structures of high voltage DC power supplies are studied. Next, by focusing on...
Design and Implement of Voltage Ripple Measuring System for Power Supply of Microwave Tubes
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahryar (Supervisor)
Abstract
Mostly, the high voltage DC power supplies have output voltage ripple. In such an applications like power supply of microwave lamps in radar systems, low output voltage ripple is an important point of operational characteristics. On the other hand, measuring the low voltage ripple will be a challenge that can lead to recognize of its reasons and reduce its amplitude. In this thesis, different ways of ripple measurement constraints is described, then a method based on high pass filters for output voltage ripple measurement is implemented. The impact of components tolerance and their parasitic components like shunt parasitic resistance of a capacitor in filter operational characteristics is...
Investigation and modeling of the thermal conductivity of PP/clay nanocomposites and PP/MWCNT nanocomposites
, Article E-Polymers ; Dec , 2010 ; 16187229 (ISSN) ; Golzary, A ; Sharif University of Technology
2010
Abstract
In this study, polypropylene/clay nanocomposites were prepared by melt blending method and their thermal conductivity and the thermal conductivity of polypropylene/multi-wall carbon nanotube (MWCNT) nanocomposites were investigated and modeled. It is found that the thermal conductivity of the PP/Clay and PP/MWCNT nanocomposites is increased with increasing temperature. The thermal conductivity of the nanocomposites is improved due to incorporation of nanoclay and MWCNT compared with pure PP matrix
Twin growth in RF window ceramic as a criterion for the response time of protection system in high power vacuum tubes
, Article 2019 International Vacuum Electronics Conference, IVEC 2019, 28 April 2019 through 1 May 2019 ; 2019 ; 9781538675342 (ISBN) ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
The ceramic fracture in output RF window is one of the most important failure factors in high power microwave sources. Fast protection systems are used to protect the source. The methods for determining the required protection response time are conservative and rough. In this paper, an investigation is presented about the twin growth in the ceramic of RF window in faulty condition. It is shown that the twin growth in ceramic can be a reliable figure of merit for the response time calculation of the microwave source protection system
A microscopic assessment about the fracture of alumina in the pillbox-type rf window of high-power electron tubes
, Article IEEE Transactions on Plasma Science ; Volume 49, Issue 4 , April , 2021 , Pages 1414-1421 ; 00933813 (ISSN) ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
Alumina is widely used as a vacuum ceramic separator in the pillbox-type output window of high-power electron tubes. The fracture of alumina is one of the most important factors in the failure of these tubes. In this article, the fracture process of alumina in the pillbox-type window of high-power electron tubes is assessed microscopically. The investigation shows the twinning phenomenon in the fractured alumina. The reason for initiating and propagating twins is also investigated. An increase in the alumina temperature decreases the required stress level for generating twins. The overheating condition occurs due to an impedance mismatch in the pillbox-type window. Experimental and numerical...
Heat trap detection in the stator bar of large turbogenerators during the fault of cooling water channels blockage
, Article IECON Proceedings (Industrial Electronics Conference), 24 October 2016 through 27 October 2016 ; 2016 , Pages 1501-1506 ; 9781509034741 (ISBN) ; Oraee, H ; Sharif University of Technology
IEEE Computer Society
2016
Abstract
Cooling water is used to remove the heat from stator bar of large turbogenerators and prevent additional temperature rise. Blockage of these channels leads to heat traps along the stator bar and its temperature failure. In addition, transposition of strands in a bar causes accumulation of heat in some parts of stator bar because of non-uniform arrangement of cooling channels especially when some of channels are blocked. In this paper, effect of cooling water channels blockage is studied using a precise thermal model. It is shown that such heat traps cause additional temperature rise in stator bars and this phenomenon can not be detected by thermal sensors of turbogenerator. Laboratory and...
Application of z-source inverter in improving cross regulation of multiple output full-bridge based DC-DC converter
, Article IECON Proceedings (Industrial Electronics Conference), 24 October 2016 through 27 October 2016 ; 2016 , Pages 3265-3269 ; 9781509034741 (ISBN) ; Karimi, Y ; Sharif University of Technology
IEEE Computer Society
2016
Abstract
This paper investigates the multiple output full bridge based DC-DC converter and derives the analytical expression for its cross regulation. The effect of input voltage is studied and a topology is proposed that boosts the input voltage by a single stage structure. The proposed converter is based on Z-Source Inverter. In addition, the modulation scheme of the converter is presented. Simulation and experimental results are presented to verify the analytical study
Research on the effect of transients of high-voltage power supplies on the lifetime of high-power vacuum tubes: A microscopic assessment
, Article IEEE Transactions on Plasma Science ; Volume 50, Issue 11 , 2022 , Pages 4700-4708 ; 00933813 (ISSN) ; Ziaoddini, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
Electron guns are used as the electron sources in high-power electron tubes. The generated electron beam in electric guns passes through an aperture at the center of the anode. Since the electron beam has considerable kinetic energy, any collision between the electron beam and the anode aperture edge damages the electron gun. Therefore, electron guns are designed to meet the compatibility between the diameters of the electron beam and the anode aperture. However, this compatibility is disrupted during the transient time interval of the gun's power supply. In this article, the cause of failure of the electron gun of high-power electron tubes is investigated for the transient interval of the...
Analysis of the Effects of Parasitic Elements of Pulse Transformer on Output Voltage in High Voltage DC Sources
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
Today, in different industries,as the use of high voltage DC power supplies is increasing, the need of output voltage precision also is increasing. One way to make High DC voltage is to use a multi-output DC-DC converter and makethe output series.Existing problems in measuring high voltages, results in this idea That in these converters, we measure and regulate only one of the outputs and estimate the others by circuit elements. In this estimatin, differences between the transformer parasitic elements are very effectiveon transformer various output voltages. In this thesis after a comprehensive study on the pulse transformer parasitic elements and choose a suitable model for it, the...
Direct Torque Control in Brushless Doubly-Fed Induction Motor
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
Common induction motors are controlled with the stator voltage and so all the power passes throw the converter. In the Brushless Doubly-fed Induction Motor (BDFM) a converter with smaller size and lower cost can be used. Also its brushless operation and cage rotor are advantages in comparison with doubly-fed induction motors with rotor excitation. Direct Torque Control is a method to control induction motors. Its advantages include fast responses to flux and torque commands, not requiring to know machine parameters except winding resistors, and easy implementation. In this thesis application of this method to control the BDFM is studied. At the first, electromagnetic mechanism and coupling...
Application of Z-Source Inverter in High Voltage and Multiple Output dc-dc Power Supplies
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
High voltage dc-dc converters are widely used in industrial applications. One of the methods for generating the high voltage is series connection of isolated voltage sources which can be produced by a multiple output converter. One major problem of multiple output converters is their cross regulation. In this project, the operation of a full-bridge based dc-dc converter (FBBC) is investigated in both single output and multiple output cases and analytical expressions for its output voltage and cross regulation are derived. Then, the effect of different parameters of the converter on the cross regulation is studied. It has been shown that increasing the input voltage of the converter improves...
Design and Implement a Short Time Ultra High Voltage Pulser
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
In various industries as a solution to energy production for a short period of time in order to have a high instantanuse power pulsed sources are widely used. This resource is a relatively long period of energy stored in the energy storage element and then this energy in a short period of time the exhaust. Among the most important applications of these resources can be used in radar systems, linear accelerators, pulsed lasers, nuclear fusion, medical applications, etc. Among the most important targets are the following sources can be output pulse quality, reliability and longevity of these resources, efficiency and cost them. From the perspective of the quality of the output pulse, rise time...
Design and Construction of High-voltage Linear Regulator with Minimal Losses for Power Supply of Microwave Tube Cathode
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
Microwave tubes are widely used in the telecommunications transmitters. high voltage power supplies are used to feed them. According to the specifications that arises for microwave tubes, To take advantage of these tubes need to maintain and stabilize voltage in a certain amount to be felt. If the tube supply voltage changes, the desired output parameters such as RF output power quality will change. To stabilize the voltage is within acceptable limits provided in different ways. One common method is the use of switching regulators due to the high efficiency compared to linear regulators considered. But it also will bring problems. Some of these problems can be pointed to electromagnetic...
Analysis of Pulse to Pulse Regulation in the High Voltage Pulse Generators
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
High voltage pulse generators are widely used in the radar systems, laser, medical, food processing and etc. One of the pulse quality criteria that was analysed in this thesis is the pulse to pulse regulation. Pulse to pulse regulation is important in various fields. In the radar applications pulse to pulse instability caused undesired errors in the signal processing and limitations in the tracking of the targets. In Free Electron Lasers (FELs) non identical pulses cause RF phase shift in the each pulsed power supply and creates instabilities in the electron beam. Pulse quality is essential in medical application so that in the treatment of cancer an improved precision in delivering the...
Design and Implement a High Voltage Switching DC Power Supply Based on Voltage Multiplier for High Regulation and Controllable Output Voltage
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
High DC voltage is widely used in many applications such as X-Ray machines ,CRT , photocopy machines and etc. One idea to produce this high DC voltage is to use transformers, but it will be large in volume. We can increase frequency to reduce the volume of transformers but high voltage of primary and secondary winding will limited this volume reduction. Furthermore high turn ratio in transformers increases non idealities that cause voltage and current spike, and increase loss and noise. The main goal of this thesis is to reduce differential mode voltages on transformers to reduce the volume of power supply. Voltage multiplier will be used to reduce differential mode voltage. Voltage...
Effect of Cathode Voltage Waveform on the Output Power of Magnetrons
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
In industial applications such as linear accelerators, pulsed lasers, nuclear fusion, radar systems, medical applications and etc. that need great ratio of instantanuse to the average power, pulsed power supplies are used. These power supplies store energy in an energy storage element and discharge this energy to load in a short period of time. The most important characterisitics of them are output pulse quality, reliability and longevity of the resource, efficiency and cost. One of the devices that produce high instantaneous RF power is magnetron tube. In some applications such as radar systems, quality of the output RF is very important and the most important factor that affect the quality...
Analysis of High Voltage Switching Power Supply With Minimum Switching Frequency Considerations for Constant and Pulsed Load
,
M.Sc. Thesis
Sharif University of Technology
;
Kaboli, Shahriyar
(Supervisor)
Abstract
The growth of high voltage dc-dc switching power supplies in various applications such as medical, industrial and laboratory research is undeniable. Design of these power supplies, respect to their expectation have some restrictions. Among the main characteristics, appropriate output voltage regulation, high efficiency, fast dynamic response and low EMI problems, are expected. Transformers constraints as one of the key components of high voltage dc-dc switching power supplies, plays essential role in the selection of converter topology and its control algorithm. In this thesis, first, with regard to issues of high frequency and high voltage transformers, provides a good approximation model...