System description 23
The rotor-side flux reference is chosen to achieve the desired power factor at the stator
terminals. The operating flux level of the stator flux is completely dependent on the grid
voltage and therefore the rotor flux reference is dependent on actual stator flux. The figure
below shows the vector diagram of stator voltage, current and flux and rotor flux at leading
and lagging power factors when the stator is regenerating to the electrical power network.
Using stator voltage (and therefore the stator flux) as reference axis, torque is proportional
to the product of
I
ds
and
. The magnitude and sign of
I
qs
determine the type of
reactive (lagging or leading) power drawn by the stator.
s
Ȍ
r
Ȍ
I
ds
U
s
I
s
I
qs
I
ds
I
s
I
qs
U
s
s
Ȍ
r
Ȍ
Lagging power factor
Leading power factor
Symbol
Description
U
s
stator voltage
rotor flux
stator flux
I
s
stator current
I
ds
d-axis current of the
I
s
I
qs
q-axis current of the
I
s
r
Ȍ
s
Ȍ
s
Ȍ
Содержание ACS800-67
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Страница 76: ...76 Start up with medium voltage stator ...
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