Page - 17 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 1217 Figure21.Drive trainofseries-parallelhybridsystemusingplanetarygearunit. Theplanetarygear unit combines theengine, thegeneratorandthemotor [30]. Figure22.Drive trainofseries-parallelhybridsystemusingtransmotor. Theplanetarygearsystemis absent in thisarrangement [30]. 3.2.4.ComplexHybrid Thissystemhasonemajordifferencewiththeseries-parallel system, that is, itallowsbidirectional flowof powerwhereas the series-parallel canprovide only unidirectional power flow. However, usingcurrentmarket terminologies, thisconfiguration isdenotedasseries-parallel systemtoo.High complexityandcostaredrawbacksof this system,but it isadoptedbysomevehicles tousedual-axle propulsion[4].Constantlyvariable transmission(CVT)canbeusedforpowersplitting inacomplex hybridsystemorchoosingbetweenthepowersources todrive thewheels. Electricarrangementscan beusedforsuchprocessesandthis isdubbedase-CVT,whichhasbeendevelopedandintroduced byToyotaMotorCo. (ToyotaCity, Aichi Prefecture 471-8571, Japan). CVTs can be implemented hydraulically,mechanically,hydro-mechanicallyorelectromechanically [32]. Twomethodsofpower splitting—input splittingandcomplex splittingare shown in [32]. Input splittinggot thenameas ithasapower splitdeviceplacedat the transmission input. This systemisusedbycertainToyota 17