Environmental Engineering Reference
In-Depth Information
Flux
Paths
Flux
Paths
Field
Winding
N
N
Armature
Winding
Rotor
S
S
Stator
(a)
(b)
Fig. 5.6 Schematic illustration of synchronous machines of a round or cylindrical rotor and
b salient rotor structures
Variable reluctance synchronous AC machines represent other types of syn-
chronous machines which do not require any excitation system on the rotor [
3
].
5.2.3 Control and Power Electronics
DC machines are simpler and cheaper, because their speed regulation is based on
scalar controls. For that reason they need simple electronic boards to control the
DC electric drive operations. Moreover, they have the advantage that they can be
fed by the DC supply already on board. On the other hand, the principal disad-
vantage is represented by the maintenance required, since for instance brushes
need to be periodically checked and changed. Another point to take in consider-
ation is that fuel cell electric vehicles equipped with brushed electric machines
would require specific safety devices to avoid that sparks of the collector during
the commutation might interact with the hydrogen used as fuel on board.
Asynchronous machines have the great advantage to be mechanically robust,
because of their simple rotor windings. Nevertheless, AC electric drives require
sophisticate control algorithms, based on vector relationships between the regu-
lation parameters and the cost of their implementation is quite high. Although,
nowadays electronic components and especially microcontrollers are becoming
cheaper than in the past and for this reason AC drives are now more competitive
than DC drives also in terms of cost.
