RESONANT BASED SOLID STATE MARX GENERATOR 1 RESONANT BASED SOLID STATE MARX GENERATOR 1

OVERVIEW OBJECTIVES INTRODUCTION CONVENTIONAL MARX GENERATOR RESONANT BASED MARX GENRATOR CIRCUIT ANALYSIS CONCLUSION 2

OBJECTIVES To give a small introduction about PULSED POWER TECHNOLOGY To study about the MARX GENERATOR To introduce the concept of RESONANCE in MARX GENERATOR 3

4 INTRODUCTION Accumulates energy over a long period and releases it quickly Increases instantaneous power Pulsed Power Technology evolved during WWII Developed mainly for radars Further developments in Sandia National Laboratories Sandia National Laboratories house the largest X-ray machine – Z machine Basic Power supply of Z machine: Marx Generator 4

The Z machine at Sandia Laboratories 5 Cylindrical in layout Houses huge capacitors discharging in Marx Generator Uses the principle of Z pinch Fast discharge of capacitors in a tube causes it to collapse towards the centerline under the influence of Lorentz Force Due to the production high voltages the power feeding equipment submerged in transformer oil and deionized water which acts as insulators. The Z machine at Sandia Laboratories 5

Conventional Marx Generator 6

First described by Ervin Otto in 1942 A number of capacitors are charged in parallel And then discharged in series via spark gap switches Ideally produces a voltage of n x V, n being the number of stages Performance of the Marx generator depends upon selection of capacitor and the discharge timing Doping of electrodes in spark gap with radioactive isotopes improves switching performance 7

Resonant Switch Converters Basically divided into two: Zero Current Switching Topology in which the switch turns on and off at zero current Zero Voltage Switching Topology in which the switch turns on and off at zero voltage Resonance phenomenon in power electronics reduces the switching losses The switches are turned on or off at zero current or voltage 8

Resonant based Marx Generator 9

Marx Topology With Reduced Components 10

General configuration Consists of an ac-dc converter, voltage regulator, dc-ac converter and the Marx Topology The large capacitor provides the rest of the topology with a smooth and continuous voltage level Single leg inverter is used so as to utilize fewer active power switches Three levels of voltage applied to the inductor Each two stage of the topology consists of two capacitors, two diodes and two power switches Has three switching states Positive charging mode Negative charging mode Load supplying mode 11

(a) positive charging mode Switches S1 andS3 are turned on As S1 is on positive voltage appears at the output of inverter Diodes D1, D3 and DS3 are forward biases and C1 and C3 are being charged Reverse energy transmission prevented by the diodes Therefore the capacitors keep the charge till the load supplying mode (a) positive charging mode 12

S2 and S3 are turned ON As S2 is ON negative voltage appears at the output of inverter Diodes D2 and D4 are forward biased Hence capacitors C2 and C4 are charged with reverse polarity The capacitors keep the charge till the load supplying mode (b)Negative charging mode 13

All the switches except S4 are turned OFF S4 connects the capacitors in series All the diodes are bypassed The output high voltage pulse will be eight times the input voltage Breakdown phenomenon at he load side due to high voltage (c) Load Supplying Mode 14

Current and Voltage Waveforms Accompanied By Relevant Switching signal patterns Gate switching signals and voltage current waveforms 15

Circuit Analysis Analysis of the circuit done in two modes Single shunt operation Done initially To test the capability of the Generator in producing the pulses Repetitive mode operation The single shut operation is extended to get this mode The component behavior during resonance is expressed as follows during the positive charging mode 16

Simulation Results For (A)Single Shunt Mode (b) Repetitive Mode 17

Switching frequency cannot be more than the resonant frequency unless inverter switches have antiparallel diodes 18

19 Capacitor charge and inductor charge different in two half cycles Generated voltage levels are impossible to control Causes malfunction to the normal operation of the converter Bidirectional switching state installed to give feasibility 19

Triggered just for voltage adjustability Bidirectional solid state switching path provides a reserve path for current when the inverter switches are off during resonant cycle Stored current in the inductor has sufficient time to be delivered to the capacitors Triggered just for voltage adjustability Bidirectional Solid State Switching Path 20

Conclusions Generated voltage is twice the supply voltage The number of diodes and switches are reduced Power loss reduction in capacitors charging process Pulse generation frequency restricted by resonant frequency Smaller values of inductor and equivalent capacitor higher repetition rate achieved Single leg inverter used inorder to reduce the switching and conduction losses 21

THANK YOU.. 22