In-Bore Magnetic Field Management

Report No. ARL-TR-1914
Authors: Zielinski, Alex
Date/Pages: March 1999; 45 pages
Abstract: The turbine/alternator T/A) in the M734A1 Multi-Option Fuze for Mortar (MOFM) was identified as a component whose performance was altered by exposure to the in-bore magnetic induction produced by the armature in an electromagnetic railgun. Passive shielding techniques were developed to attenuate the exposure field. A model, based on the experimental results, was used to predict shielding effectiveness. Results were verified by subjecting T/ As to the exposure field. No statistically significant changes in T/A output were observed for magnetic induction less than 0.06 T. Significant degradation in performance was observed for magnetic induction greater than 0.1 T. Active shielding was also demonstrated. This technique was implemented with coil windings mounted in the bore insulators and powered by an external power supply. The in-bore magnetic induction produced by the armature was canceled down-bore of the armature. The technique provides for mitigation of large magnitude exposure fields where otherwise passive shielding may become unwieldy.
Distribution: Approved for public release
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Last Update / Reviewed: March 1, 1999