How to choose a power run capacitor

I know what a real capacitor does. It stores up ten of thousands of volts at about 20000 microfarads and can be used to power a huge rail gun electrode assembly. Or it is like a storage batry which will store millions of joules in a space less than the size of a basketball. Most capacitors you will run into will have energy ratings far less than any of these. Here we will discuss the various types of capacitor elzet

A capacitor made up of tantalum metal as the anode it stores up a lot of charge per volume size. They are be harvested from SMT technology breadboards and throw away electronics like cell phones. Companies such as KYOCERA use a lot of these capacitors

Mylar~ polyester

Polyester capacitors can be those tiny blue rolled deals up to an infinite size. Tables for calculating polyester ac ripple is done here. Mylar capacitors are terrble for ac applications because polyester has a high electrical hysterisis meaning it heats up when exposed to alternating currents. An industry secret has been to make each rolled plate a combination of three layers each layer 1/3 of the thickness required for the voltage. This eliminates microscopic holes that naturally occur during manufacture an elzet capacitor works a similar way. You can also use these type of capacitors in how to build a marx generators and voltage multipliers plans. Way cheaper than surplus high voltage capacitors

Doorknob capacitor
Doorknob capacitors look like doorknobs. The have screw in inserts and range in voltage from 10kv to 50kv. They are usefull for marx generators and diode cockcroft Walton multipliers. How to build a billon joule bank out of capacitors

AC Run capacitor
Run capacitors are 4 wire start capacitors made by aerovox they are used to shunt the inrush current to a ac motor or am alternator