Delta Tau GEO BRICK LV Benutzerhandbuch
Turbo PMAC User Manual
128
Setting Up Turbo PMAC-Based Commutation and/or Current Loop
Example:
A 4-pole induction motor has a rated speed of 1740 rpm at a 60 Hz electrical frequency. It is being
controlled from a UMAC Turbo with default clock source and frequency. The electrical frequency is:
A 4-pole induction motor has a rated speed of 1740 rpm at a 60 Hz electrical frequency. It is being
controlled from a UMAC Turbo with default clock source and frequency. The electrical frequency is:
=
=
sec
rad
0
.
377
cyc
rad
2
*
sec
cyc
60
e
π
ω
The mechanical pole frequency is:
sec
rad
4
.
364
pole
cyc
2
1
*
rev
poles
4
*
cyc
rad
2
*
sec
min
60
1
*
min
rev
1740
sec
rad
m
=
=
π
ω
In a UMAC Turbo, the default clock source is Servo IC 2 (I19=7207). The default value for I7200 is
6527, and the default value for I7201 is 0. The phase update time can be calculated as:
6527, and the default value for I7201 is 0. The phase update time can be calculated as:
(
) (
)
sec
000111
.
0
117964800
1
0
*
3
6527
*
2
p
T
=
+
+
=
Ixx78 can now be calculated as:
(
)
000149
.
0
32768
3500
*
000111
.
0
*
4
.
364
0
.
377
78
Ixx
=
−
=
Calculating from Rotor Time Constant
Occasionally, the L/R electrical time constant of the induction motor’s squirrel-cage rotor can be obtained
from the manufacturer (this is distinct from, and much larger than, the L/R electrical time constant of the
stator windings). The Ixx78 slip constant can be calculated easily from this value by the equation:
from the manufacturer (this is distinct from, and much larger than, the L/R electrical time constant of the
stator windings). The Ixx78 slip constant can be calculated easily from this value by the equation:
r
T
p
T
78
Ixx
=
where T
p
is Turbo PMAC’s phase update time, and T
r
is the rotor’s electrical time constant. Remember to
use the same units for both times.
Example
If running with a phase update frequency of 8 kHz and there is a rotor time constant of 0.75 seconds,
calculate:
Example
If running with a phase update frequency of 8 kHz and there is a rotor time constant of 0.75 seconds,
calculate:
000167
.
0
75
.
0
000125
.
0
r
T
p
T
78
Ixx
=
=
=
Experimentally Optimizing Slip Constant
For a given magnetization current, the optimum slip constant will maximize the acceleration capabilities
of the motor. Changes from the optimum value of Ixx78 in either direction will degrade performance.
Simple tests employing data gathering while using a low-valued O-command (e.g. O10) to accelerate the
motor, permit easy optimization or verification of optimization of the Ixx78 value. If the best value of
Ixx77 magnetization current has not been selected, use a value of 3000 for these tests.
of the motor. Changes from the optimum value of Ixx78 in either direction will degrade performance.
Simple tests employing data gathering while using a low-valued O-command (e.g. O10) to accelerate the
motor, permit easy optimization or verification of optimization of the Ixx78 value. If the best value of
Ixx77 magnetization current has not been selected, use a value of 3000 for these tests.
Setting Ixx77 Magnetization Current
Once there is a good value for the Ixx78 slip constant, find the best value of the Ixx77 magnetization-
current parameter. Ixx77 sets the commanded value for the direct current component in commutation, the
component in phase with the rotor’s measured/estimated magnetic field orientation. Ixx77 determines the
rotor’s magnetic field strength and so the torque constant K
current parameter. Ixx77 sets the commanded value for the direct current component in commutation, the
component in phase with the rotor’s measured/estimated magnetic field orientation. Ixx77 determines the
rotor’s magnetic field strength and so the torque constant K
t
and back-EMF constant K
e
for the motor. If
Ixx77 is not so high that it magnetically saturates the rotor, torque and back-EMF constants will be
proportional to Ixx77.
proportional to Ixx77.