Environmental Engineering Reference
In-Depth Information
Figure 9.6 Illustration of HV to LV automotive dc/dc converter (and power
inverter)
surprising because electric drive air conditioning used in electric vehicles is sized
for 6.5 kW during pull-down and approximately 4 kW for sustaining. Current
estimates are that electric power assist steering (EPS) will be approaching 100%
penetration in 2012, partly for facile packaging of this function and in part to meet
more stringent emission regulations. There appears to be a de jure standard for
EPS system voltage versus steering rack load. At rack loads above approximately
9-11 kN translating force a higher EPS voltage is required. Consider, for example,
that at 14 V the EPS will require from 85 to 130 A peak demand on such systems.
Second, in hybrid electric vehicles it is feasible to operate the EPS from the traction
battery via a dedicated dc/dc converter. For example, Toyota does this in the
Lexus RX series using a 288 to 42 V converter just to support that vehicle's EPS.
Figure 9.6 illustrates a Denso power converter (lower right in figure) of an HV to
42 V converter. Note the planar transformer in the cutaway.
Figure 9.7 illustrates the breakpoints in EPS voltage versus rack load for var-
ious EPS architectures. The installation costs follow the same trend as the EPS
power level with rack integrated being the most costly.
Electrically heated seats take 1.5 kW. Should electromechanical engine valve
actuation technology meet the business conditions for deployment then there is an
additional load of 3.2 kW [2]. Vehicle characterization requires set values of
electrical load. As more functionality is electrified, this additional burden must be
included and accounted for in the performance and efficiency predictions.
The FCHV has more M/G system losses due to battery system than the FCV,
and transmission losses are about the same. However, energy supplied to the
wheels is higher in the FCHV case due to recuperated energy that is stored in the
