Development of a high power modulator for a linear induction launcher[LIL]

T. Podlesak, R. Pastore, H. Singh, Z. Zabar, R. Uhlrich, J. Creedon

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The conditioning of power for inductive launchers is one of the most challenging applications of power modulators. This paper deals with the supply of electrical energy to a particular type of launcher, a linear induction launcher (LIL). The LIL consists of an array of coils, forming the barrel, and a conducting cylinder (sleeve) enveloping the payload. The coils of the barrel are grouped into sections and are energized in polyphase fashion by capacitor banks, through appropriate switch gear. The polyphase excitation is designed to create an electromagnetic wave packet that travels with fixed velocity in each section, but with increasing velocity down the barrel. The relative motion (slip) of the wave packet with respect to the sleeve induces in it azimuthal currents that interact with the exciting magnetic field to product propulsion and levitation (centering) force. The development of the power modulator is based on the following specifications: projectile mass of 250 gr., muzzle velocity of 2 W s , and peak voltage of 40 kV. These specifications lead to performance requirements for the most stressed components, the switches, as listed in Table 1. The design of the power modulator for the gun is based ON imparting short duration increments of pulse energy to the projectile at precise times during its travel down the barrel. This design requires 24 individual modulators that are charged in parallel and then programmed to discharge at selected times. Development of such a modulator can be met by using 24 eparate RLC circuits that are individually switched. Currently, we are evaluating components and circuits for such a pulser. A universal test module has been constructed which enables us to evaluate state of the art components over a wide range of voltages, currents, and energies. Since component cost and commercial availability will have a strong bearing on the construction of the system in the 1993-1994 time frame the evaluation concentrated on components that offer a compromise between cost and life while meeting the technical requirements and operation constraints. The single shot test module is resistively charged and can be operated from 0-40 kV. Capacitance can be varied from 25- 1225 microfarads by series and or parallel connection of 7 each 175 microfarads capacitors rated for 22 kV. Inductance can be varied from 3 to 1200 microhenries by series and or parallel connection of ten (10) 60 microhenry inductors. Switches evaluated to date include ignitrons models BK-514 and NL 8900 and the ST-300 spark gap. Circuit designs for terminating a current pulse are also being investigated. Results obtained at voltages up to 20 kV and peak currents up to 30 kA for underdamped oscillations at frequencies up to 10 kilohertz will be presented.

Original languageEnglish (US)
Title of host publication20th Conference Record on Power Modulator Symposium, MODSYM 1992
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages4
ISBN (Electronic)0780307186, 9780780307186
StatePublished - 1992
Event20th Conference on Power Modulator Symposium, MODSYM 1992 - Myrtle Beach, United States
Duration: Jun 23 1992Jun 25 1992

Publication series

Name20th Conference Record on Power Modulator Symposium, MODSYM 1992


Conference20th Conference on Power Modulator Symposium, MODSYM 1992
Country/TerritoryUnited States
CityMyrtle Beach

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering
  • Control and Optimization


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