IEEE Electrification Magazine - March 2018 - 31

The drivetrains are
the heart and soul
of any vehicle used
in transportation,
especially fourwheel-drive vehicles.

Solid-Oxide FC

the solid-oxide fc (sofc) uses a hard
ceramic compound of metal (e.g., calcium and zirconium) oxides as an
electrolyte and is suitable for hightemperature conditions of approximately 600-1,000 °c. the anode is
made of porous nickel and a cathode
and uses a metal oxide such as indium oxide. the exhaust heat can be
reused in a combined heat power
plant to further boost the overall efficiency of the plant. the explanation of an sofc on the
basis of chemical equations is shown in figure 7.

Series-Hybrid EVs

a series-hybrid ev is fundamentally an ev with an onboard battery
charger. an ice is generally run at a
desired efficiency point to drive the
generator and charge the onboard
battery. series-hybrid evs would run
at their optimal torque and speed to
save fuel and improve the efficiency
of the system. however, some of the
energy is lost because of the twostage power conversion process.
Moreover, the engine/generator set maintains the battery
charge at roughly 65-75%. a series-hybrid ev is more useful for city driving.

Topologies of Drivetrains of EVs
the drivetrains are the heart and soul of any vehicle used
in transportation, especially four-wheel-drive vehicles.
advances in drivetrains are playing a key role in peMfc
vehicles because of the new techniques to control the
acceleration and deceleration of the drivetrains by using
front-wheel drive. Rear-wheel drive and all-wheel drives
are being developed to achieve a more effective use of fuel
and to improve the efficiency of fc vehicles. a comprehensive analysis of complete drivetrains for evs is shown
in figure 8 and described in the following sections.

Battery EVs
a purely electric drive system principally replaces the
internal combustion engine (ice) and the various transmission systems with an all-electric system (power electronics and super batteries). the practical evs still use
lead-acid batteries, while the more sophisticated ones use
nickel metal-hydrate batteries.

Parallel-Hybrid EVs
in the parallel-hybrid ev, the traction motor and system
generator are mechanically connected through the
torque coupler. the parallel-hybrid ev has various modes
of operation based on the use of the generator and traction motor. furthermore, the torque coupler is designed
using digital concepts such as the continuous variable
transmission system rather than the conventional fixed
variable transmission system for efficient use of fuel and
optimal operation. the transmission losses are less compared to the series-hybrid evs, but parallel-hybrid evs
are much bigger and require more complex operation
and control.

Series-Parallel-Hybrid EVs
it is possible to combine the advantages of both the
series and parallel-hybrid ev configurations. when acceleration is required, the electric traction motor is used in

Electron Flow
Syngas
(Hydrogen and Carbon
Monoxide)

Oxygen

AGDL

CGDL

Oxygen Ions

Carbon
Bipolar Plates
Dioxide and (Metalic Plates)
Water

AGDL Plus
Anode Catalyst

Electrolyte
(Ceramic)

CGDL Plus
Cathode Catalyst

Bipolar Plates
(Metalic Plates)

Excess
Oxygen

Figure 7. A portrayal of the internal operation of an SOFC.

IEEE Electrific ation Magazine / ma r c h 201 8

Table of Contents for the Digital Edition of IEEE Electrification Magazine - March 2018