Electric drive system technologies - Propulsion Systems for Hybrid Vehicles - page 311

Figure 5.57 VRM prototype starter-alternator

The reality of a 5-phase stator in a bidirectional current drive inverter is that a
large bundle of stator leads are necessary (10 in total). This has the potential to be a
packaging concern unless the power electronics box is mounted in close proximity
to the high phase order VRM.

5.5.2 Synchronous reluctance
The synchronous reluctance, SyncRel, machine is more directly analysed using d - q
theory, and in fact the torque of this machine is given by

T av ¼ mp ð L d L q Þ I d I q ð Nm Þ ð 5 : 35 Þ

where I d and I q are rms amps. The number of pole pairs is given by p .
It is very interesting to compare the torque production of the SyncRel relative
to the IM. In the IM the average torque is

3
2

P
2

L m
L r ð L m i ds Þ i qs

T av i ¼ ð Nm Þ ð 5 : 36 Þ

where i ds and i qs are in peak amps, and L m and L r are IM inductances.
Taking the ratio of (5.35) for the SyncRel machine to (5.36) for the IM results in

T i ¼ ð

1 ð L mq = L md ÞÞð L md = L m Þ

T r

ð 5 : 37 Þ

L m = L r

Taking representative ratios for inductance in the SyncRel of ~8:1, the expres-
sion in parentheses in the numerator is (1 1/8). The second numerator inductance