
6-36 Power Electronics and Motor Drives
with
χ ξ ξ ξ= − + − +
3 1 9 1 4
2
( ) ( )
(6.48)
It is worth noticing that f(ξ) in (6.47) is a function of the saliency ratio ξ = L
q
/L
d
only. Its behavior is
reported in Figure 6.40. In the range between ξ = 2 and ξ = 6, such a function can be approximated by
the straight line f(ξ) ≈ ξ − 1, that is, shown in the same Figure 6.40 by a dashed line.
6.8.2 Decoupling between the Phases
In designing fault-tolerant PM motors, it is imperative to consider that any fault does not propagate from
a faulty phase to the other healthy phases. en, a complete decoupling among the phases is proposed
[34], includi ...