I just noticed a better pic of the schematic. And now see it does not have any capacitor(s) in the circuit. I do see a choke, L1, so that brown cylinder thing is probably the choke. Whatever DC motor you try to run with this VSD, note that some DC motors have a permanent magnet field and do not need a DC source for the field. In this situation you just supply DC to the armature and it can be fixed or variable voltage for variable speed. And another note, the armature supply is typically of a higher current demand that the field current…Dave.