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current component that lags behind the applied voltage. The sta-
tor has winding coils (distributed or concentrated). The rotor also
consists of a number of laminated segments that are connected
by non-magnetic elements. Rotor windings and magnets are not
required. The synchronous reluctance machine has a simple de-
sign and is extremely robust. High torque yield, however, is asso-
ciated with noise development, because the torque is achieved
through pulse currents that also induce radially acting forces and
thus induce noise development. This must be resolved in the de-
sign. A high level of intrinsic safety occurs due to the shape. To
compensate for the lack of permanent magnetization, possibilities
for combining the reluctance principle and permanent excitation
are offered. In this regard, special forms, such as a pre-magne-
tized reluctance motor or hybrid reluctance motor, are possible.
The hybrid-excited machine contains significantly fewer magnet
materials than does the PSM. Nevertheless, an rpm range inde-
pendent power is achieved as is the case with the asynchronous
machine, however with higher efficiency in the lower rpm range.
Peak overload does not approach the characteristics of a PMS.
For a high quadrature reactance, extremely precise and small air
gaps must be maintained, as is the case with ASM. Extremely high
requirements are also imposed on the reduced material, and the
motor topology has complex regulation.
REQUIREMENTS AND CHALLENGES
In the selection of an optimal propulsion concept for electric ve-
hicles and hybrid vehicles, the emphasis is on system coordina-
tion of motor, power electronics and transmission, to achieve an
optimum in terms of cost, weight, power density and efficiency, as
well as safety and reliability.
It should be noted that widely varying requirements from the in-
dustry sector, as well as automotive manufacturing will be impo-
sed on the production of electric machines. Examples that can be
cited from automobile manufacturing are a higher delivery quality
(100 parts per million, i.e. number of defective parts for 1 million
produced units) and delivery reliability (100 percent), as well as
a higher level of automation (wage fraction approximately 5 per-
cent), and also a reduced service life (approx. 4,000 hours) [Franke
(2011a)]. Through the different motor concepts, new requirements
and new challenges are arising for the companies and new requi-
rements for manufacturing processes that must now be developed
for mass production of automobiles.
Currently, several automobile manufacturers are already active
in developing and manufacturing electric motors on their own,
(BMW is one example), or in collaboration with a supplier (Daimler
and Bosch). Thus manufacturing of electric motors could become
a core competence of automobile manufacturers. For example,
automobile manufacturers could manufacture machine compo-
nents, such as rotors and stators, on their own, buy-in the power
electronics and take over assembly and integration in the vehicle
[Schäfer (2010)].
Chapter 2