BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//EE - ECPv5.10.0//NONSGML v1.0//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
X-WR-CALNAME:EE
X-ORIGINAL-URL:https://ee.iisc.ac.in
X-WR-CALDESC:Events for EE
BEGIN:VTIMEZONE
TZID:Asia/Kolkata
BEGIN:STANDARD
TZOFFSETFROM:+0530
TZOFFSETTO:+0530
TZNAME:IST
DTSTART:20240101T000000
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240508T103000
DTEND;TZID=Asia/Kolkata:20240508T113000
DTSTAMP:20260415T185921
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)
END:VEVENT
END:VCALENDAR