Environmental Engineering Reference
In-Depth Information
permanent magnet systems, though not specifically stated, is considerably higher
than either the IM or the VRM based on permanent magnet costs of $120/kg for
NdFeB. In this comparison, there is not so great a difference between the IM and
the IPM (and SPM) in terms of critical attributes for hybrid propulsion systems.
The last attribute to compare is the CPSR for each of the ac drive system types.
All of the ac drives are able to meet the transient response requirements. Of the
three machine types, the VRM, IPM and SPM, in rank order, exhibited the most
tendency to excite driveline oscillations and noise. The IM was the most benign in
regard to exciting driveline oscillations and structure borne noise.
Figure 5.59 is a comparison of the peak power capability of each of these
machine types relative to vehicle axle speed (i.e. vehicle ground speed). The hybrid
propulsion is pre-transmission, parallel architecture with fixed gear ratio between
the motor and the wheels.
IM
IPM
SPM
100
90
80
70
60
50
40
30
20
10
0
VRM
0
200
400
600
800
1,000
1,200
1,400
Wheel speed (rpm)
Figure 5.59 Comparison of hybrid propulsion M/G technologies
It is clear from Figure 5.58 that all of the machines provide approximately
2.7:1 CPSR in the hybrid application. The induction and IPM appear most suited to
hybrid propulsion requirements based on peak torque, specific power density and
cost. There are further considerations for all hybrid applications relating to per-
formance at light loads and high speeds and conversely high loads at low speeds.
These extremes put additional burden on all machine types. No load spin losses in a
hybrid application are often a deciding factor in the choice of machine technology.
The assessment in this section is meant to offer a guide to hybrid propulsion system
designers. The last point to make on Figure 5.59 is that the theoretical CPSR range
of
>
5:1 for IPMs is often times not observed in practical systems, and in this figure
it was as limited as the IM.
