Minimizing the mass of a potential railgun power supply

A pulsed power supply is being designed to deliver 5 MJ at 1 MA at 1 shot per second to a railgun. The supply stores energy at low current in the primary of a hydrogen-cooled transformer. A switch opens the primary circuit to transfer energy to the secondary, stepping the current up to 1 MA. The relationship between the transformer and switch is being studied to determine how the total power supply mass can be minimized. Vacuum interrupters and gate-turn-off (GTO) thyristors are used in the switch. Switch mass dominates the system, accounting for 85% of the total mass. The switch must absorb the uncoupled energy of the transformer. Low transformer coupling requires large capacitors. Even with high coupling, capacitors account for 75 to 85% of the switch mass. If transformer coupling increases, the uncoupled energy decreases, resulting in lower capacitor mass. At high transformer coupling, switch mass also depends on the turns ratio of the transformer. At lower turns ratio, a lower voltage is placed across the switch capacitors. Lighter capacitors can be used, reducing system mass. The combined transformer and switch (system) mass is minimized when transformer coupling is 0.97 to 0.99 and the turns ratio is as low as possible