Environmental Engineering Reference
In-Depth Information
Fig. 5.1 Electric and
mechanical connections
between the main compo-
nents of a BEV
T
RASMISSIO
N
BATTERY
PACK
Electric Drive
Nowadays the worldwide market offers a range of electric vehicles which
fundamentally use the configuration described in Fig.
5.1
. For example, from the
smallest to the biggest ones it is possible to mention: electric bicycles, electric
wheel chairs, tricycles, small commuter vehicles, delivery vehicles, electric golf
buggies, electric cars, delivery trucks and buses. The fact of the matter is that
private electric cars do not play an important role in the field of BEVs, but each of
the above types of vehicles fills a different niche in its specific market.
The scheme of Fig.
5.1
represents the base of all other types of electric vehi-
cles, both those using an additional traction engine on board (HTEV) and those
adopting alternative storage/generation electric energy systems to power the
electric drive (hydrogen fuel cell electric vehicles, HFCEV, solar vehicles and
vehicles using flywheels and supercapacitors).
5.2 Electric Drives for Road Vehicles
The main characteristics of electrical drives are reported in this section from the
point of view of the application of these components to road electric vehicles.
Electrical drives are composed of rotating electric machines (which transform
electric energy into mechanical energy or viceversa), power electronic converters
and controllers connected together in order to operate the whole electrical drive in
steady state or variable speed working operations.
Rotating electric machines fundamentally can be subdivided in two main types:
direct current (DC) machines and alternating-current (AC) machines. All types of
rotating electric machines have a stationary part, called stator, and a rotating part,
called rotor. Generally the rotor is connected to a shaft which the mechanical
torque acts on.
In rotating electrical machines, several conductors are distributed along the
inner and outer sides of the air gap between rotor and stator, which are electrically
excited. These conductors carry currents in the rotor and stator conductors creating
resultant magnetic fields, which vary in space and time. The interaction between
the two magnetic fields causes a resultant electromagnetic torque, which have a
very important effect on the steady-state and transient behavior of the machine.
