Energy Efficiency of Electric Vehicles

2. Electrical losses reduction in EV
2.1. Energy efficiency of the converters
Increasing of the energy efficiency of the convertors can be achieved by optimizing their
configuration and control, as well as choosing the adequate component. Converter configu‐
ration depends on the type of the electric motor (DC or AC), possible recovery energy braking,
drive dynamics etc.
For DC motor supply there are mostly used chopper voltage reducers, so they will be consid‐
ered here. Figure 7 shows simplified presentation of the chopper supply of a DC motor.
Chopper is shown as ideal breaker controlled by voltage (U
up
), so it can control switching on
(T
ON
) and switch-off (T
off
) exiting voltage (U
do
). For all four quadrant operation transistor bridge
as shown in fig. 1 can be used [1].
Figure 1. Transistor Bridge
By switching on transistor pairs T
1
-T
2
or T
3
-T
4
positive or negative polarity of motor voltage
u
d
is provided. To close motor current at null or reverse polarization, diodes D
1
to D
4
are
provided. Converter part of the AC drive of the vehicle consists of the inverters, regulators
and control set. The inverter is part of the drive inverter that inverts DC voltage to AC voltage
necessary waveform to ensure the required control electric motors. Three-phase inverter
consists of three inverter bridges with two switching elements in each bridge, therefore, a total
of six switches. By controlling the moments of switching of the particular switches, and by
controlling the length of their involvement, the appropriate waveforms at the output of
inverter are achieved.
Energy Efficiency of Electric Vehicles
http://dx.doi.org/10.5772/55237
95

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General modern circuit for speed regulation of DC motor is shown in figure 2. Reference rotary
speed W
ref
is set and also maximum armature current I
amax
and their actual values are monitored
and also brought into regulator which outputs present command values for excitation
actuators and inductor [1-2].