Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...
Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...
Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...
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Introduction<br />
Generally, the permanent magnet AC machines can be classified into two types (Fig.1.1):<br />
trapezoidal type called “brushless DC machine” (BLDCM) and sinusoidal type called<br />
permanent magnet synchronous machine (PMSM). The BLDC machines operate <strong>with</strong><br />
trapezoidal back electromagnetic force (EMF) and require rectangular stator phase current.<br />
The PMSM’s generate sinusoidal EMF and operate <strong>with</strong> sinusoidal stator phase current.<br />
The PMSM can be further divided into two main groups in respect how the magnet bars have<br />
mounted in the rotor [6,7]. In the first group magnets are mounted in the rotor (Fig. 1.2 c-d)<br />
and this type is called interior permanent magnet synchronous motors (IPMSM). The second<br />
group is represented by surface permanent magnet synchronous motors (SPMSM). In the<br />
SPMSM magnet bars are mounted on the rotor surface (Fig. 1.2 a-b).<br />
q<br />
q<br />
SPMSM<br />
S N<br />
S N d<br />
a )<br />
b)<br />
S<br />
N<br />
S<br />
N<br />
d<br />
q<br />
q<br />
IPMSM<br />
S<br />
N<br />
c )<br />
d)<br />
S<br />
N<br />
d<br />
d<br />
Fig. 1.2. The cross section <strong>of</strong> the PMSM rotor shaft and the magnet bars placements:<br />
a),b),c) axial field direction, d) radial field direction.<br />
The magnets can be placed in many ways on the rotor (Fig. 1.2). In radial field fashion the<br />
magnet bars are along the radius <strong>of</strong> the machine and this arrangement provides the highest air<br />
gap flux density, but it has the drawback <strong>of</strong> lower structural integrity and mechanical<br />
robustness. Machines <strong>with</strong> this arrangement <strong>of</strong> magnets are not preferred for high-speed<br />
applications (higher than 3000 rpm). In axial field manner the magnets are placed parallel to<br />
the rotor shaft. This arrangement <strong>of</strong> magnets is much more robust mechanically as compared<br />
2