▁ 3 2 R - 2 0 0 ▁DC ▁tra ction ▁mot ors , ▁two ▁per ▁bog ie . ▁ ▁The ▁mot ors ▁can ▁be ▁connected ▁in ▁three ▁combinations : ▁series , ▁series - parallel ▁and ▁parallel ; ▁each ▁combination ▁provides ▁a ▁progress ively ▁higher ▁voltage ▁to ▁the ▁mot ors , ▁therefore ▁increasing ▁the ▁current . ▁ ▁Their ▁set - up ▁is ▁the ▁following : ▁ ▁The ▁r he ost at ▁( connected ▁in ▁series ▁to ▁the ▁tra ction ▁mot ors ) ▁is ▁necessary ▁because ▁the ▁DC ▁motor ▁has ▁the ▁intr insic ▁characteristic ▁of ▁absor bing ▁a ▁current ▁in vers ely ▁proportional ▁to ▁its ▁rot ating ▁speed ; ▁at ▁high ▁spe eds , ▁it ▁absor bs ▁less ▁current . ▁ ▁This ▁means ▁that ▁on ▁start ▁the ▁current ▁would ▁be ▁very ▁high , ▁because ▁the ▁only ▁resistance ▁encountered ▁would ▁be ▁only ▁the ▁one ▁offered ▁by ▁mot ors ▁and ▁internal ▁conduct ors , ▁which ▁is ▁very ▁low ▁( a ▁short ▁circuit , ▁in ▁practice ). ▁The ▁r he ost at ▁increases ▁the ▁overall ▁resistance ▁when ▁starting ▁the ▁locomot ive , ▁lower ing ▁the ▁current ▁and ▁allowing ▁a ▁sm o other ▁start . ▁ ▁In ▁S - P ▁and ▁P ▁combinations , ▁the ▁r he ost at ▁is ▁divided ▁in ▁three ▁branches ▁connected ▁in ▁parallel ; ▁this ▁low ers ▁the ▁overall ▁r he ost at ▁equivalent ▁resistance ▁to ▁about ▁ 3 . 5   oh m , ▁while ▁in ▁S ▁combination ▁its ▁elements ▁are ▁all ▁connected ▁in ▁series . ▁ ▁Like ▁almost ▁every ▁Italian ▁locomot ive