Environmental Engineering Reference
In-Depth Information
SyncRel increases, thereby diminishing the efficiency advantage it held over the
IM. This means that for machine ratings suitable for hybrid propulsion systems the
SyncRel really has no efficiency advantage even given its inert rotor. The other
drawback of the machine technology is the fact that its axial laminated rotor
structure has real issues at higher speeds where rotor retention becomes a major
concern.
5.5.3 Radial laminated structures
Radial laminated SyncRel machines are generally not as widely used as axial
laminated designs because with multiple flux barriers the mechanical constraints on
ribs and posts to support the soft iron pole shoes above and in between the flux
barriers become major design challenges. It has been shown that for the same total
losses a SyncRel machine can have 20% more torque than a corresponding IM.
However, losses in the SyncRel machine increase substantially with increasing pole
number, so these machines are restricted to pole numbers of less than 4.
There is strong interest in SyncRel for machine tool applications because it can
deliver overload torque ratings of
>
3:1. It is also recommended to drive the radial
laminated designs with current controlled inverters and to avoid delta connected
stator windings.
In general, this design has not found much favour with hybrid propulsion
designs because it cannot compete with its cousin, the IPM.
5.6 Relative merits of electric machine technologies
This chapter has reviewed a great many electric machine technologies and several
methods of controlling such machines. It is now important that this vast amount of
material on electric machines be summarized into a more cohesive framework from
which hybrid propulsion system designers can choose. For this summary, two
seminal papers will be cited that give clear insights into machine comparisons for
the two important categories of ac drives: battery electric vehicles and hybrid
propulsion systems.
The next two subsections will summarize the material in this chapter in the
context of machine technology comparisons of the leading three major categories:
IM, IPM machine and the VRM. Furthermore, each of these machine types was
compared based on a representative vehicle and performance specifications. The
interested reader is referred to the appropriate reference at the end of this chapter.
5.6.1 Dynamic performance comparisons
Volumes have been written on the topic of electric machine comparisons, so this
section will be brief. In Reference 36 Melfi
et al.
look at industrial induction and
permanent magnet machines from the view of power density and energy savings.
Their findings cover salient pole PM machines of the inset magnet design (similar
to what Honda Motor used in early IMA systems), plus single buried magnet to
