▁and ▁Build ings ▁Phot ograph ▁of ▁the ▁castle ▁in ▁its ▁original ▁state ▁at ▁Bry n ▁M aw r ▁College ▁ ▁Category : H ouses ▁on ▁the ▁National ▁Register ▁of ▁Historic ▁Places ▁in ▁Pennsylvania ▁Category : Sh ing le ▁Style ▁architecture ▁in ▁Pennsylvania ▁Category : Ne igh bor hood s ▁in ▁Philadelphia ▁Category : History ▁of ▁Philadelphia ▁Category : H istor ic ▁districts ▁in ▁Philadelphia ▁Category : Ch est nut ▁Hill , ▁Philadelphia ▁Category : H istor ic ▁district ▁contrib uting ▁properties ▁in ▁Pennsylvania ▁Category : H ouses ▁in ▁Philadelphia ▁Category : H istor ic ▁districts ▁on ▁the ▁National ▁Register ▁of ▁Historic ▁Places ▁in ▁Pennsylvania ▁Category : National ▁Register ▁of ▁Historic ▁Places ▁in ▁Philadelphia <0x0A> </s> ▁A ▁multi - level ▁converter ▁( ML C ) ▁is ▁a ▁method ▁of ▁generating ▁high - vol t age ▁wave - forms ▁from ▁lower - vol t age ▁components . ▁M LC ▁orig ins ▁go ▁back ▁over ▁a ▁hundred ▁years , ▁when ▁in ▁the ▁ 1 8 8 0 s , ▁the ▁advantages ▁of ▁DC ▁long - distance ▁transmission ▁became ▁evident . ▁ ▁Mod ular ▁multi - level ▁conver ters ▁( MM C ) ▁were ▁investig ated ▁by ▁Tr ic oli ▁et ▁al ▁in ▁ 2 0 1 7 . ▁Although ▁their ▁vi ability ▁for ▁electric ▁vehicles ▁( EV ) ▁was ▁established , ▁suitable ▁low - cost ▁sem icon duct ors ▁to ▁make ▁this ▁topology ▁compet itive ▁are ▁not ▁currently ▁available ▁( as ▁of ▁ 2 0 1 9 ). ▁ ▁In ▁ 1 9 9 9 ,