Page - 272 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 437 3.1. PELoss TheMG1 andMG2 losseswere calculated from the efficiencymap. The efficiency ofMG1 orMG2canbedetermined fromtheoperationpoint for thegiven torqueand speed (Figure 8a,b). Thehigh-voltageDC/DCconverter (HDC)boosts thebatteryvoltage inconsiderationof theoperating conditionsofMG1orMG2.WhentheHDCboosts thebatteryvoltage,aboost lossoccurs. TheHDC losswasdeterminedfromtheHDCefficiencywithrespect tothebatterypower(Figure8c). Inaddition, thebattery losswasobtainedfromthecharge (discharge)efficiency. In thisstudy, thebatterycharge (discharge)efficiencywasassumedtobe98.5%[21]. (a) (b) (c) 0* VSHHG USP 0* VSHHG USP %DWWHU\ SRZHU N: Figure8.Theefficiencymapderivedfromtheexperimental result for: (a)motorgenerator1 (MG1); (b)MG2; (c)high-voltageDC/DCconverter (HDC). 3.2.DrivetrainLoss Thedrivetrain losseshavebeendescribed indetail in the literature [22].Ashort summaryof the drivetrain losses isas follows: Gear loss:Gear losswasassumedtobe1%of the transmittedtorque[23],which iswidelyused in theautomotive industry. Planetarygear loss:Whenthesun,pinion, andringgeararemeshing, theplanetarygear loss occursdueto thegear teeth friction. Theplanetarygear loss is representedas [24,25]: Tloss_PG= ⎧⎪⎪⎨ ⎪⎪⎩ kPG×Tin_PG, whenthecarrier isfixed kPG× ( Zr Zr+Zs ) ×Tin_PG, whentheringgear isfixed kPG× ( Zs Zr+Zs ) ×Tin_PG, whenthesungear isfixed, (4) whereTloss is the torque loss,Tin is the input torque,andk is thecoefficientof frictionforPG. Bearingloss:Thereare loadedandunloadedlosses in thebearing. Loadedloss isproportional to thebearing load. The loadedloss iscalculatedas follows[26,27]: Tloss_BRGload= f1×P1a×dmb×10−3, (5) wherea,b, and f1 are thecoefficientsaccordingto thebearingtype,P1 is theequivalentbearing load andisdeterminedfromtheaxialandradialbearingreactionforce,anddm is thebearingmeandiameter. Bearingunloadedloss iscausedbytheslipbetweentherotatingsurfaceandthe lubricationoil film.Thebearingunloadedloss is representedas Tloss_BRGunload= { 1.6×10−8× f0×dm3, if (υoil×n)< 2000mm2s·min 10−10× f0×(υoil×n) 2 3×dm3, if (υoil×n)≥ 2000mm2s·min , (6) where f0 is thecoefficient for thebearingunloaded loss,υoil is thekinematicviscosity, andn is the bearingrotational speed. 272