REPETITIVE ALL SOLID-STATE PULSE MARX TYPE GENERATOR WITH ENERGY RECOVERY CLAMP CIRCUIT FOR INDUTIVE LOADS ∗ L. M. Redondo 1,2,ξ, M. T. Pereira 3 1 Instituto Superior de Engenharia de Lisboa ISEL/CEEI, Rua Conselheiro Emídio Navarro 1, Lisbon, Portugal 2 Centro de Física Nuclear da Universidade de Lisboa, Portugal 3 Lusoforma Comércio e Indústria de Embalagens, S.A,. Rua do Mercado, S. Carlos, Mem Martins, Portugal ∗ Work supported by ISEL and Lusoforma S.A. under a scientific contract. ξ email: lmredondo@deea.isel.ipl.pt Abstract A newly developed Marx type circuit topology that achieves both output-voltage multiplication and energy recovery, which has been developed for inductive load applications, namely Electromagnetic metal Forming (EMF), based on an all-solid-state Marx type generator, is described. The proposed circuit takes advantage on the power semiconductor switches intensive use, replacing the conventional Marx Bank passive elements, to increase the performance, strongly reducing losses and increasing the pulse repetition frequency. Additionally, the generator is designed with an energy reset circuit that enables the use of inductive loads, recovering the inductive energy during the semiconductor switches off-state, back to the energy storage capacitors. Preliminary results from this EMF modulator prototype are presented and discussed. I. INTRODUCTION In the last decade, repetitive high-voltage pulses have been used extensively in industrial applications, like Food Sterilization and Surface Engineering, which increased the need of efficient, flexible and suitable power supplies, based on solid-state switches [1, 2]. To deal with this, a number of techniques have been used in order to generate high-voltage pulses from generators with optimised performance and characteristics, taking the best of solid-state technology, regarding the fact that semiconductors are still, compared with hard-tube switches, relatively low power devices, and very sensitive to voltage and current instabilities, needing auxiliary protection circuits. Due to its innovation, it’s worth mention the techniques based on power-electronic circuit topologies that were developed for switching power supplies, which with different operating conditions and small circuit changes were adapted for high-voltage pulsed generation [3, 4]. Also recent is the important technological upgrading done in the mature Marx generator concept that as has been intensively used through the years, in order to increase the performance of the original circuit [5, 6]. Nowadays, one of the most challenging pulse power application is Electromagnetic Metal Forming (EMF), were electromagnetic forces are used to form metal in two very broad implementations, radial and sheet forming [7]. Briefly, EMF works by the magnetic induction effect. When a coil or solenoid is placed near a metallic conductor and pulsed (kV and kA), a magnetic field is generated between the coil and the workpiece. If done quickly enough, the magnetic field is excluded from penetrating into the workpiece for a short period of time. During this time, a pressure is generated on the workpiece that is proportional to the magnetic flux density squared. This "magnetic" pressure is what provides the forming energy. The energy is usually supplied to the workpiece in the form of kinetic energy. The magnetic pressure pulse accelerates the workpiece up to a certain velocity (such as 200-300 m/s). This kinetic energy drives the material into the die, causing forming on impact [7]. We will report on a newly developed all-solid-state Marx type circuit topology, to achieve both output- voltage multiplication and energy recovery, developed for inductive load applications, in particular EMF. In this circuit, the conventional passive elements that were present in the original Marx Bank generator, for charging the energy storing capacitors and limit their self- discharge current during the pulse period, were replaced by power semiconductors, diodes and IGBTs (Isolated Gate Bipolar Transistors), used intensively, in order to increase the performance, strongly reducing losses and increasing the pulse repetition frequency. Additionally, the generator is designed with an energy reset circuit that enables the use of inductive loads, recovering the inductive energy during the power semiconductors off-state, back to the energy storage capacitors. This decreases the charging time, and enables higher frequency operation, increasing the pulse generator yield. Preliminary experimental high-voltage measurements, voltage and current, taken from an assembled prototype will be presented and compared with the results of circuit simulations. This will assist the discussion on circuit performance and launch hints for further improvements, to construct an industrial modulator.