Linear Electromagnetic Accelerator Nick Rainsford and Alex Seiger

Design Two Main Parts Energy Storage Bank Coils and Switching

Capacitor Bank Approximately 3kJ of Energy Storage Controllable and Repeatable Charge/Discharge High Saftey Margin This is a lethal amount of energy! Numerous Safety Interlocks

Coils Generates strong electric field when current is run through them. In this case, Currents of 200A or more. Sophisticated switching is needed to control quick dI/dt shifts in inductive loads. Collapsing magnetic field creates high voltage spikes Timing is delicate, Coil remaining on longer than necessary will slow the projectile.

Implementation All Capacitors were measured for their exact capacitance using a velleman K8055 USB Interface Board

Implementation Capacitor Bank was then assembled with Low-Resistance “wiring” made of flattened copper pipe.

Implementation Next Steps for capacitor bank are to construct a robust charging and safety mechanism. Microprocessor charge control Digispark “micro” arduino Easy-to-read display of charge-to voltage, current capacitor bank voltage, and charging circuit output voltage LCD display or Multiple Analog Panel Meters Emergency Discharge resistor 3-Ohm 1000-watt wirewound ceramic resistor Remains across capacitors unless charging is occurring, actuated by 20A Automotive relay. When Charging circuit is powered off, resistor will remain across capacitors.

Implementation Coil switching will be accomplished with IR 104X125DA125 Silicon-Controlled Rectifiers

Implementation Coils will be constructed out of either Litz wire or common household electrical wiring Litz wire allows for higher quality factor of inductors, and thus a higher dI/dt Household wiring, however, is cheap and readily avaliable Coil Geometry is dependent on projectile size and the desired on-time during switching.

Implementation To implement the needed precise timing for triggering the current in the various stages, optical sensors and designed discrete real time circuitry will be used. To fabricate some of the essential control circuitry we will use basic mixed signal components and PCBs fabricated on a CNC router.

Testing (what we have done) We have tested the exact capacitance values using the Vellman K8055 board and Matlab. This was done by measuring discharge times or the RC time constant across a known resistance. The SCRs were also tested, and were found to have a current rise time of 1.75 A/μS.

Testing(what we will do) Using a current shunt resistor, we will test the whole capacitor banks ESL and ESR. Using an optical coronagraph we will test the muzzle velocity. Comparing this to the energy left in the capacitors we can determine the overall efficiency. We will also find the high currents using a hall-effect sensor and ferrite ring. We will either fabricate a sensor or simply use a commercially-available device.