Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...

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