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

Modeling and control modes of PM synchronous motor drives
For the PM synchronous motor the amplitude of stator flux
Ψ
s
is established by
permanent magnet. Operation with stator flux amplitude belong the nominal value of
rotor flux amplitude
Ψ
PM
increases the amplitude of stator phase current. Please note
that maximum amplitude of the stator current vector is calculated as:
higher value may damage the PM (complete demagnetization).
I
s
Ψ
≤
L
PM
d
, and
From the Fig. 2.8 it can be observed that rated torque is achieved for torque angle
0< < 25
electrical degree.
δ Ψ
e[ ] M Nm
M
er
[ Nm ]
M
es
[ Nm ]
δ Ψ
[deg]
Figure 2.8. Variation of synchronous torque M es
, reluctance torque M
er
and resultant
torque M as a function of torque angle (for constant stator flux equal value of PM).
e
2.1.3 Mechanical motion equation
The equation of rotor motion dynamics describes the mechanical equilibrium of a drive
system. Taking the moment of inertia to be constant ( J = const.
) and neglecting friction
and elastic torque we can write:
where,
M
e
= Ml + Md
(2.59)
Ml
is the external torque on the motor shaft, and
M
dΩ
dt
where: J is total moment of inertia,
M
d
the dynamic torque
m
d
= J
(2.60)
Ω
m
angular speed of the rotor.
22