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X-WR-CALDESC:Events for EE
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TZID:Asia/Kolkata
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TZOFFSETFROM:+0530
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DTSTART:20240101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240508T103000
DTEND;TZID=Asia/Kolkata:20240508T113000
DTSTAMP:20260527T065415
CREATED:20240507T042856Z
LAST-MODIFIED:20240507T042941Z
UID:241466-1715164200-1715167800@ee.iisc.ac.in
SUMMARY:Open  Ph.D. Thesis Defense of Mr. Ranashree Ram
DESCRIPTION:Ph.D. Thesis Open Defense \nStudent Name          :     Ranashree Ram \nThesis Title              :     Developmental Studies on a Multistage Induction Coilgun-Based Electromagnetic  \n                                        Launcher \nPlace                        :     High Voltage Lab Seminar Hall / MS Teams \nDate & Time           :     8th May 2024\, 10.30 AM \nMicrosoft Teams Link  \nAbstract \nThe archetypal chemical propellant-based launchers (e.g.\, guns\, missiles\, spacecraft launchers\, etc.) with their hot trailing plume has been widely deployed over the decades for various applications. However\, because of certain disadvantages of these systems and the physical limitations associated with their designs\, electromagnetic launchers (EMLs) seem to offer an alternative way forward as the next-generation hypervelocity (>3 km/s) launchers. The multistage induction coilgun is one such futuristic class of EMLs that works on the principle of electromagnetic induction between an array of coils (or drive coils)\, which are wound on a long barrel of appropriate length\, and an electrically conducting projectile (or armature) placed inside the barrel. Previously charged high-voltage capacitor banks are sequentially discharged into the coils through solid-state switches leading to the generation and flow of very high pulsed currents (kA) through the coils. Time-varying magnetic flux thus produced by the pulsed currents through the coils interact with the projectile inside and induce a resultant current on it. The propulsive electromagnetic force exerted on the projectile is a product of the current through the coil\, the induced current on the projectile\, and the mutual inductance. The “turn on” and “turn off” of the coils of the various stages must be precisely and appropriately synchronized during the multistage operation to achieve a higher projectile velocity and this makes its successful design and operation a challenge. Owing to its high confidentiality in defense and space applications\, not much can be known from the published works. In the present work a four-stage induction coilgun has been designed and developed in the laboratory. The research work presented in the thesis aims to understand the factors contributing to achieving a higher muzzle velocity for a projectile of a given mass while launching a payload with the coilgun. The projectile of a coilgun can be either sleeve-type (ring-shaped projectile) or solenoid-type (multi-turn projectile). \nThe author also designed and fabricated a high-speed infrared transmitter-receiver-based sensor (with 25 ns rise and fall time) to quickly sense the moving projectile (or armature) inside the barrel. The triggering instant of the subsequent stage coils of a multistage coilgun critically depends on the projectile’s position inside the barrel. The projectile will fail to achieve the highest muzzle velocity if the subsequent stage coils are not optimally triggered in a sequence. The fast-moving projectile through the barrel necessitates the fast sensing of its position inside the barrel. In addition\, the author has also designed\, developed\, and fabricated a high-speed gate driver circuit with a peak 25 kV DC isolation for the signal circuit from the high voltage power circuit within a compact space of the printed circuit board (PCB) to trigger the high-voltage SCRs used for triggering the pulsed power source of each stage of the coilgun.. \nThe large current flowing through each stage coil creates EMI problems in the coilgun. The EMI issues corrupt the sensor data\, which prevents successful sensing of the projectile’s position. Also\, EMI causes the SCRs to trigger the coils spuriously even when the projectile has not reached its optimal triggering position inside the coil. Synchronizing the triggering of stages by preventing the EMI issues is a significant challenge and is very important in successfully operating a multistage induction coilgun. The author could successfully synchronize the stages of the coilgun by preventing spurious triggering of the SCRs using appropriate EMI mitigation techniques. \n The influence of the capacitance of the capacitor bank used in the high voltage pulsed power supply on the optimum triggering position of the projectile inside the drive coil of the coilgun has been analyzed. An empirical relationship between the projectile velocity and the charging voltage of the capacitor bank has been formulated for the first time in this thesis. The subject of the study presented in this thesis also focuses on analyzing the parameters on which the efficiency of an induction coilgun depends and how it can be optimized. Study has been performed to optimize the shape and dimensions of the projectile to achieve the highest muzzle velocity. The dependency of the projectile motion on the flow of induced current in the subsequent stages has been analyzed. The study also focuses on establishing an approach to choosing a proper distance between the stages in a multistage induction coilgun. \nA comprehensive and explicit analysis has been performed to study and explain the reasons behind the differences in the optimum triggering positions of the projectile inside each stage coil and the achieved muzzle velocities for different arrangements of the drive coil current directions in a multistage induction coilgun.
URL:https://ee.iisc.ac.in/event/open-ph-d-thesis-defense-of-mr-ranashree-ram/
LOCATION:High Voltage Lab Seminar Hall (Hybrid mode)
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DTSTART;TZID=Asia/Kolkata:20240520T110000
DTEND;TZID=Asia/Kolkata:20240520T130000
DTSTAMP:20260527T065415
CREATED:20240520T110840Z
LAST-MODIFIED:20240520T110840Z
UID:241473-1716202800-1716210000@ee.iisc.ac.in
SUMMARY:PhD Colloquium
DESCRIPTION:Title of Thesis:   Frequent Episode Mining: Efficient Discovery Algorithms and Significance Analysis \nSpeaker:     Mr. Santhosh B. Gandreti \nDate/Time:     Monday 20th May 2024\n11:00 AM \nVenue:    MMCR\, EE Department \nResearch Supervisor:   Prof. P. S. Sastry \nAbstract: \nFrequent Pattern Mining is a popular area of data mining aimed at discovering interesting patterns that occur often in a given data. These patterns represent structures encapsulating correlations and dependencies among data elements. This thesis focuses on frequent episode mining which is aimed at discovering temporal patterns known as episodes in sequential data of event sequences. \nEpisodes are collections of event-types constrained by a partial order.  An episode is frequent if its number of occurrences exceeds a user-defined threshold.  Techniques for mining episodes employ either Breadth-First Search (BFS) or Depth-First Search (DFS) approaches to navigate the episode space. The talk begins by giving a brief introduction to frequent episode mining and various algorithms dealing with discovery of frequent episodes. \nThe talk next discusses a novel DFS algorithm for discovering injective general episodes and chain episodes\, which are two broad subclasses of episodes. The proposed algorithms are more efficient compared to the state-of-art as demonstrated by empirical results. The talk next considers more complex patterns called episodes with simultaneous events\, where the episodes contain multiple event-types at the same time instant. A novel BFS algorithm is presented for discovering serial episodes with simultaneous events. Through simulations on both synthetic and real data sets\, the effectiveness and efficiency of the proposed algorithm is demonstrated. \nThe next part of the talk discusses significance analysis that assesses the statistical relevance of episodes and presents two novel approaches for significance analysis; one for non-overlapped occurrences under Markov-null hypothesis and the other for minimal occurrences under IID-null hypothesis. This analysis helps determine an episode-specific frequency threshold for the episode to be statistically  significant\, providing a more nuanced understanding of pattern relevance. For both the above mentioned cases\, specialized Markov chains capturing the occurrences of interest are derived for a given episode\, which help in computing episode-specific thresholds on frequency\, to access its significance. Effectiveness of the proposed methods is confirmed through empirical studies.
URL:https://ee.iisc.ac.in/event/phd-colloquium/
LOCATION:MMCR\, Hall C 241\, 1st floor\, EE department
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240524T100000
DTEND;TZID=Asia/Kolkata:20240524T120000
DTSTAMP:20260527T065415
CREATED:20240520T110420Z
LAST-MODIFIED:20240520T110420Z
UID:241470-1716544800-1716552000@ee.iisc.ac.in
SUMMARY:Ph.D. Thesis Colloquium of Baby Sindhu A. V.
DESCRIPTION:Colloquium \n\nCandidate’s Name       :  BABY SINDHU A V \nDegree Registered      :  Ph.D. \nDate  & Time                :   24th May 2024 @ 10.00 AM \nVenue                            :   Seminar Hall\, High Voltage Lab and in Teams Link \nTitle                               :  Developmental Studies on Polymeric Nano/Micro Composite \n                                      Insulation  for Various High Voltage  Power Applications \n\nAbstract \n  \nThe  demand for electrical  power is increasing  day by day  necessitating a higher voltage level for power transmission. Also the development of high speed rails \, electric vehicles\, more electric aircrafts and all electric ships  call  for improvement in electric motor capacity in those vehicles. Also the use of cast resin type dry transformers in high moisture area and confined area is increasing since it is more reliable in extreme conditions and also they require less maintenance. All these applications demand for  better insulating materials which can address all the above issues cost effectively. In  recent years\,  the use of  polymeric insulating material  in HV power apparatus is increasing. Hence this study focuses on the development of polymeric  composite insulating  material  with better performance for various electrical power applications. \nSilicone rubber is a  preferred  material for use as weathershed material in outdoor polymeric insulators used in high voltage power transmission lines.   The tracking & erosion on the insulator surface due to the electrical discharges  and corona cutting  of the insulator surface  are the main issues related to outdoor polymeric insulators and these are  addressed in this study.   Tracking and erosion performance of silicone rubber filled with nano/micro fillers of different loadings is  analysed using Inclined Plane Test (IPT) as per IEC 60587.  A computational study on the behavior of the samples subjected to  tracking  is also done and the same is verified with the experimental results obtained in this work. Corona ageing studies are done by ageing the samples in a corona chamber for 25 hours. Hydrophobicity changes\, crack width formation and erosion performance after corona ageing are evaluated. An effort is made to correlate the value of leakage current to the eroded mass and a reliable online condition monitoring tool is also developed as a part of the thesis work. \n   Again\, epoxy is extensively used in  many  electrical  power apparatus such as ground wall insulation of the high voltage rotating machines\, as spacer material  in Gas Insulated Substations (GIS)\, as solid insulation in dry type transformers etc. Heat dissipation is an important area of concern when using  epoxy as ground wall insulation in rotating machines and as an insulation in  cast resin dry type transformer. The performance of epoxy filled with nano/ micron sized fillers are  investigated in this study in terms of their heat removal capacity and at the same time  retaining their dielectric properties. The improvement in thermal conductivity is correlated with the performance of various composites developed. The formation of track in the ground wall insulation and the failure of the machine is a major issue as far as rotating machines are considered. Hence the tracking time of various epoxy composites are observed and compared. The initiation of a faint track on the surface of the insulator is monitored with the help of a ratio of third harmonic component to the fundamental component. This ratio can be used as an efficient condition monitoring tool for rotating machines by measuring the leakage current online. \n    In summary polymeric composite insulating  materials based on silicone rubber and epoxy with different fillers and loadings and having   better electrical and thermal performance than the conventional materials  are developed in this study.
URL:https://ee.iisc.ac.in/event/ph-d-thesis-colloquium-of-baby-sindhu-a-v/
LOCATION:High Voltage Lab Seminar Hall (Hybrid mode)
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