A Supersonic Linear Motor Accelerator For An Introduction To Pulse Power

Educational pulse power concepts are presented through the construction and demonstration of a linear motor accelerator. Multi-student projects typically begin with a 50 cm long accelerator which launches 2.2 g, 3.8 cm wide split aluminum wire loop armatures (split to allow radial magnetic forces which ensure brush contact in this low voltage system) once every 6 seconds (the manual reload and surge charging time). Energy is supplied by a 280 V, 0.25 F electrolytic capacitor bank (9,800 J, 70 C) yielding 40 kA peak, critically damped pulses with an effective time width of 1.8 ins (70C). A thin gap (0.3 cm) flux meter technique was employed to determine the flux between the permanent magnets over the acceleration distance. The projects are utilized to introduce fundamental concepts of pulse power. The magnetic force is determined by current * width * magnetic flux density. The work done is determined by the previous magnetic force * length = maximum kinetic energy. The theoretical maximum velocity = (2 * current * flux/mass)/sup 0.5/ = 700 m/s with a supplemental one turn loop. Experimentally, velocities of 540 m/s (320 J) were determined by the sequential breaking of two foil contacts. This would result from a force of 630 N and an acceleration of 290,000 m/s/sup 2/ .