
Permanent Magnet Synchronous Motors 6-31
Figure 6.34 shows a graphical representation of the control strategies presented above, in the (i
d
, i
q
)
plane. In such a plane, the constant current loci are circles, the constant ux linkage loci are ellipses, and
the constant torque loci are hyperbolae. e critical conditions are respectively shown by the current-
limit circle and the voltage-limit ellipse in the (i
d
, i
q
) plane. e current vector satisfying both constraints
of voltage and current must be inside of both the current-limit circle and the voltage-limit ellipse.
According to both voltage and current constraints, the optimum current vector ...