Nearly all of the railgun designs I've seen have arranged the capacitors in parallel. Why is this? If one arranged the capacitors in series, couldn't they achieve a higher voltage (and thus more current and a larger force on the projectile) while still maintaining the same capacity for energy in the capacitors? What advantage does adding capacitance provide for the railgun?

Wikipedia - Railgun

enter image description here

  • 2
    \$\begingroup\$ Caps in series reduce C and increase ESR so current reduces. \$\endgroup\$ Jun 15 '19 at 0:52
  • 1
    \$\begingroup\$ Rail guns need more capacitance and less voltage typically, because they need to sustain a huge power output for a non trivial amount of time as the projectile moves down the rails. \$\endgroup\$
    – MadHatter
    Jun 15 '19 at 1:23
  • 1
    \$\begingroup\$ If by railgun you mean railgun (ie the proper version with a sliding payload between two busbars, then the requirement is to maximise current. As the resistance of the path is about zero Ohms what you want is the lowest impedance highest current capability source you can. At a given voltage, if you halve R you double I so I^2R doubles. The aim is to increase power delivered by reducing R rather than by increasing V. Two caps that can each deliver I amps will deliver about 2I in parallel but I at best in series. . \$\endgroup\$
    – Russell McMahon
    Jun 15 '19 at 3:21
  • \$\begingroup\$ @Russell McMahon wouldn't ohm's law say otherwise? When you hook up a bunch of batteries in parallel, the current doesn't increase. Why is this different for capacitors? \$\endgroup\$ Jun 15 '19 at 4:30
  • \$\begingroup\$ @PeterBlood I think you are conflating two different scenarios. If the current is limited by the load, such as by Ohm's Law, then putting voltage sources in parallel will not increase current. However, if the current is limited by the real-life resistance (ESR) of those voltage sources, rather than by the load, then putting sources (or capacitors) in parallel does increase the current. \$\endgroup\$ Jun 15 '19 at 13:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.